Sentinel Steam Loco 7109

'Ello, 'Ello, LO!

2012-02-18T03:00:00.003Z

Apologies for pinching this from the SDC Website!

On Saturday 11th Feb 2012, at the AGM of the Sentinel Drivers' Club in Liverpool, Tony Thomas (records officer) proposed and various members of the Goold family seconded me to take over the committee post of Locomotive Officer for both steam and diesel technologies. This I have gladly accepted and hope I can do the post justice.

The post has been held for many years by Martin Hawkins, uncle to Sentinel 7109's boiler inspector Peter Hawkins, a boiler maker in his own right and driver on the West Somerset Railway. So I have quite an act to follow.

To some extent, the task is a blank sheet for me to make of it what I can; the main object being to be the point of contact for anyone with queries about Sentinel locos. Where I don't know an answer, hopefully I can find someone who does!

Tony Thomas has kept records of locomotives still in existence for many years. I hope to make use of his existing information and to keep it up to date using a website, 'blog or such like.

Wish me luck!

Exhausting! (Extra, extra!)

2012-02-17T07:55:00.001Z

I've been asked in a comment on the 'Exhausting!' article about something that may have surrounded the chimney aperture.

Here's another photo.

(cropped from a Charlie Verrall photo)

Even clicking on the picture to zoom in does not make it clear.

Thus it will be a detail to be ignored unless reinforcement is needed in practice.

Exhausting!

2012-02-16T12:01:00.000Z

Unlike conventional steam locomotives, which have their boilers laid horizontally, Sentinel 7109 has its boiler the right way up (vertical) so that steam and smoke exhaust straight up and out of the top, in this case through a hole in the cab roof.

Roof top Chimneys

7109's original roof was clearly showing signs of rampant air-conditioning, nice in Summer but neither structurally nor aesthetically pleasing all the year round.

Air-conditioned original cab roof

A new 3mm thick mild steel cab roof was obtained some years ago and has been waiting its turn for attention.

It's substantial, 3mm thick and takes 4 people to lift it

Another day spent being 'jiggen' by a shake-saw cut the hole for the chimneys.

27" squarish chimney aperture
(the newly-restored, pristine S&D PMV is in the background)

The new baffle plate to support the boiler's superheater has now been cast, machined and fitted. A length of ceramic rope is needed to provide a seal between the assembly and main boiler superstructure. When this has arrived, the superheater assembly will be able to be lowered into place and fastened down - hopefully never to be removed again before steaming.

Then the roof can be put in place.

How to make an ashpan (3)

2012-02-07T15:17:00.001Z

Part 2 of this series covered the marking out and cutting of the ashpan base plate. Now the the curved walls needed to be rolled to the right radius and welded in place.

Until now, I'd never seen, let alone used, a sheet metal rolling machine so this was a bit of an adventure.

Sheet metal rolling machine

The rolling machine is not difficult to use; the front two rollers are adjusted to be parallel and to grip the metal being rolled. A third roller at the rear is positioned using the handles at each end. To create a bend, the metal sheet is wound through using the handle on the right and progressively forced upwards by the rear roller. After a few passes with the rear roller being raised each time, the correct curve can be created.

One or two problems can arise; the sheet has to be put in exactly at right angles to the front rollers otherwise a twist is created in the sheet that is hard to correct; it is possible to create an uneven curve or too tight a curve. I found I had to feed the sheet back in to take some of the curve and twist out before re-rolling to the correct curve. Some twist did remain and so one of the walls is slightly angled in - not critical but I like to do better.

There is also a good deal of hammering to get the curve at the ends beyond where the rollers can reach - not pretty but effective!

Apologies for no video of this - it was pretty physical and not conducive to camera work! (Oh OK, I forgot!).

Skipping ahead to after the walls had been rolled and welded in two parts to the base plate.

Base and walls welded together (MIG for inside corner weld)

Right hand inside MIG weld

Left hand inside MIG weld (not quite so tidy!)

MIG welding was good for the inside weld because of the length involved and the need for filler to be used to build up the corner strength.

Left hand outside TIG weld

TIG welding was ideal for the small outside corner weld; two 3mm thick plates corner to corner don't want anything heavy duty and only a small amount of filler! The welds came out pretty tidily but certainly benefited from cleaning up with an angle grinder.

Joint in the two side-wall pieces

The two side-walls had a small gap to be filled between them. I used a MIG welder for this, filled the resulting holes with an oxy-acetylene torch and tidied it up finally with an angle grinder. MIG can be a beast at times!

Then I discovered I'd missed my vocation in life; rather than an ashpan, I seem to have created a simply amazing GONG! I'd left the ashpan leaning against the bookcase in my hall at home (I have a very tolerant wife!). On tapping it with a finger (or later a rubber mallet), I was greeted with a marvellously musical ringing tone. Try this (best on headphones, loud, or on a home cinema system!). (Also on YouTube).

After all the work finding and renovating a whistle, perhaps it won't be needed after all (although perhaps a gong is an unconventional method of locomotive greeting!).

To be continued!

How to make an ashpan (2)

2012-02-01T17:04:00.003Z

In the previous article, I documented some design decisions and was able to purchase the required metal sheeting. This article looks at the marking out and cutting to shape of the base plate.

I first painted the baseplate with white emulsion so that I could see my own markings. Then I had the challenge to draw a circle of 17.75" radius. Pairs of compasses simply don't come that big in my house!

17.75" Radius pair of compasses

A couple of screws 17.75" apart in a piece of dowelling did the trick. Diagonal lines from corner to corner found the centre of the sheet.

17.75" radius circle
(and that's why I painted it white!)

The flap was easiest to mark towards one corner using lines at right angles from the marked diagonal.

And then all that was needed was to cut it out!

I dismissed gas-torch cutting; it is quick and exotic but needs a template making beforehand to guide the torch and leaves rough edges which need a lot of tidying up with a grinder.

The only other method left to me was to use a jigsaw with hack-saw type metal cutting blades. In actual fact, I'm glad I chose this as it is surprisingly accurate (to about 0.5mm, and yes I can do metric when I choose!) and doesn't require other tools to be made beforehand and little cleaning up after the cutting.

Cut that out!

This is when I discovered my hair had gone grey!

Whilst the jigsaw proved accurate, fast is not a word I would use to describe it! (Also on YouTube).

Can you see any progress in 30 seconds?

It took most of a day to complete the cutting (but it was accurate!).

Nearly there,only the flap's cut-out to do

If the above photo looks a bit wobbly, try holding a camera still after a day of being jiggen by a shake-saw!

To be continued!

Sentinel 7109 - A 28-ton Mistress?

2012-01-28T11:28:00.000Z

I'm told (honest) that a mistress can take a lot of time, money and attention to keep happy. "Joyce" (Sentinel 7109) is certainly expertly fulfilling this role!

This week, 'blogging the restoration of Sentinel 7109 led me to a whole new aspect of the restoration that I had not really thought much about before.

No comment!

Nigel, co-owner of 7109, kindly volunteered me to give a talk to the 82D Model Engineering Society group in the Wiltshire town of Warminster. About 20 knowledgeable members attended the evening and, judging from conversations afterwards, seemed to have enjoyed the event.

Simon Bowditch, chairman, thanked me and commented that it was the most detailed description of the workings of a Sentinel locomotive that he had ever come across.

My content included 7109's history and reasons for being at Midsomer Norton; details of the Sentinel boiler, superheater, chimneys, engines, feedpumps and chains plus additonal material on other Sentinels and models. I interspersed a few video clips to provide variety from the pictures only. I also passed around some supplementary pictures and texts and brought a few of Joyce's renovated components for interest sake. The talk lasted about 1 hour 20 minutes including discussions on the way arising from audience questions.

So, having done it once, I have the basis to tailor the talk for other societies should they be interested. Please leave a comment with a phone contact number below if you would like to invite me to give a repeat performance.

Many thanks to the 82D society for inviting me.

Chains - Free at last!

2012-01-22T19:27:00.000Z

After about seven weeks, Sentinel 7109's pair of big-time bicycle chains have finally given in to the lengthy diesel dunking and manipulation with hammers and Stillson wrenches; now all rollers and links are free to move.

Flexible chain links ...

... wound round semi-sprockets

So the work is now complete to ensure there are at least two workable drive chain sets. A deep oiling will be required before use.

How to make an ashpan (1)

2012-01-20T19:36:00.001Z

Sentinel 7109, when originally brought to Midsomer Norton Station in December 2004, came without a few items, one of which was its ashpan for mounting below the boiler.

I looked at the design in a previous article but have now decided that I want to have a go at doing the fabrication myself. Another article had a look at the ashpan from Sentinel 9622 at Teifi Valley Railway so there is a fair amount of information to go on for the basis of a design.

This drawing shows the basic idea:

Ashpan Plan View

A side view also helps:

Side elevation

I also scrutinised many photos of 7109 and other Sentinels for what their ashpan looked like. For example: (Click the photo to enlarge it).

7109's Ashpan Highlighted in the centre
(Photo cropped from original provided by John Hutchings, ILS)

The photo shows that, unlike the drawings, there are no cut-outs around the sides of the ashpan - which makes it easier to make!

Another ashpan from a Sentinel tractor emphasises the point:

100HP Boiler ashpan on Sentinel 6426 (Two-speed tractor)

So, to begin, some design decisions:

How big? The circular inside of the firebox is 34.5" in diameter so the ashpan needs to be slightly larger so that ash will fall into it rather than down the outside if not large enough. It must not be too large to prevent mounting brackets to be fitted.

Mounting at the base of the firebox (looking upwards)

The picture shows that about 1 to 2 inches in additional diameter will be fine. So it will be made 35.5" in diameter.

How deep?
The drawing indicates 5.5" depth of side wall; however, 6" seems more like the picture of 7109's ashpan. So 6" will be the height of the sides.

What thickness of what material?
Mild steel, 3mm. 9622's ashpan may have been this thick at one time but it certainly isn't now! Using non-stainless steel, there is a trade off between material thickness and weight. The difficulty of manoeuvring it below the firebox emphasises minimising the weight. 3mm mild steel is a good compromise for the base and side wall.

Any cut-outs to allow air to the fire?
No cut-outs. By butting the top of the sides on to the bottom of the mountings, a gap is created for air anyway so no additional gap is required. Also, by using long studs from the mountings, some height and hence air-gap adjustment can be made for fine tuning the performance of the fire. The cut-outs are additional work but also makes the side wall more difficult to roll to the right curvature before fixing to the base.

How to fix the side wall to the base?
Welded inside and outside butted corners of the side wall and base. Metal Inert Gas (MIG) is preferable because there are long continuous welds. Manual Metal Arc (MMA or 'stick') could be used but would not be so tidy.

How to get the ash out of the pan?
The plan drawing shows a flap and this is present on the 9622 ashpan. The flap on 9622's is made from a single sheet of mild steel and bent at the edges to produce the triangular sides. 7109's flap will be made from the piece cut out of the main base with 2mm mild steel sides welded in place. Sentinel would have been making loads of ashpans and hence the flaps could have been made in quantity. 7109's is a one-off so this different approach wastes less material.

How long a 6" wide sheet is needed for the side wall?
This is where we have to go back to school! The length is about the circumference of a 35.5" diameter sheet minus the bit cut out for the flap. So that's Pi x diameter = 3.14159262(etc) x 35.5 = 9' 3.5".

So how big is the bit cut out for the flap? Now we have to go to big school for this one!
At first, I thought this was about chord-lengths of circles but it's easier than that. We know that the flap is 19.5" wide from the drawing and we know the radius of the base (35.5/2 = 17.75"). So this isosceles triangle can be bisected to give two right-angled triangles for which we can find the angle subtended by the arcsine of the opposite over hypotenuse!
This gives us an angle of 33.3 degrees which needs to be doubled to 66.6 degrees because there are two right-angled triangles in the isosceles.

So this gives us 66.6/360 x circumference = 66.6/360 x 111.5 = 20.64".
And thus the side wall length is the circumference minus the flap's bit which is 111.5 - 20.64 = 91".

On a practical note, a 91" thing won't fit in my car so two 45.5" pieces it is!

I'd often wondered what trigonometry was actually for but now I know!

And how big a piece of 2mm sheet is needed to make the sides of the flap? It depends on the offcuts in stock! No trig needed here!

When the sheet steel arrives, it looks like this:

For scale, the part-feet showing are about 8" long!

To be continued!

100 HP Sentinel Locos (Fry's Type)

2012-01-10T19:27:00.001Z

I've been asked for information about the Fry's Sentinel loco which was rescued and returned to its original home area in 2010. Avon Valley Railway are doing the restoration work.

As a late addendum to '100HP Pre-war Sentinel Locos' posted in 2011, the following pictures are taken from the 1931 Sentinel catalogue '"Sentinel" Patent Locomotives'. It includes the following details of the Fry's loco type (Click the pictures to enlarge):

The Fry's Loco

100HP Loco as used at Fry's in Keynsham

See page 53!

Old catalogues do come in handy sometimes!

The Power of the Double-Engined Sentinels

2012-01-08T18:16:00.000Z

What can you do with a Sentinel locomotive rated at 200 HP?

John Hutchings, of the Industrial Locomotive Society, kindly sent me a copy of a very interesting letter recently (September 2011).

Recall that Sentinel 7109 was the first of a series of fourteen pre-war double engined Sentinel locos with the unusual curvaceous profile. Being a first-off, its performance needed to be marketed to potential customers and so it was delivered to the LMS at Newton Heath, Manchester for evaluation.

The letter below describes the tests and shows how impressed the observers were with 7109 at the start of 1928. (Click the picture to enlarge it for reading).

Sentinel 7109 performance
(Letter courtesy of John Hutchings, Industrial Locomotive Society).
(Note: this was retyped by JH as the original is in poor condition).

So these are the results of the actual tests done on 7109 which inspired the S&DJR Co Ltd to purchase their two similar locos for use at Radstock.

Clearly, you can do quite a lot with a 200 HP loco so long as you don't want to do it too quickly!

To Inject or not to Inject?

2012-01-01T03:00:00.036Z

Happy new year to one and all!

Part of the fun of doing a loco restoration is trying to resolve mysterious features that aren't obvious as to their purpose or function.

Lately, whilst cleaning up and renovating the pair of water tank filter valves, I've been pondering the purpose of a small tube on the left hand side of Sentinel 7109's water tank that is there in some photos but not in others.

Have a look at this:

Sentinel 7109 at Shrewsbury prior to delivery, probably 1927
(Photo courtesy John Hutchings, Industrial Locomotive Society)

Just in front of the cab on the rear filter valve, there is a small tube:

7109 Tube and valve highlighted

But in this later photo, the tube has disappeared:

Missing 7109 Tube
(Photo cropped from C Verrall 1964 original)

Compare these to the similar Radstock Sentinel (7588) which has two tubes to 7109's disappearing one.

Radstock Sentinel 7191 (wks no. 7588) showing its twin tubes
(Photo cropped from R. G. Jarvis original, Richard Dagger collection)

So what was going on, I hear you ask?

Sentinel 7109 was originally supplied with an injector; however, it apparently did not work very well and was soon replaced by a Worthington Simpson type boiler feed pump mounted on the right hand driver's 'window ledge'. Hence the tube was there to feed the injector in the early photo but missing in the later photo.

So if an injector did not work for Sentinel 7109, why was one or more then fitted to the later Radstock Sentinels and left there?

That is the question!

Comments welcome!

Season's Greetings...

2011-12-13T15:24:00.000Z

...and thank you for being interested in the restoration of Sentinel 7109 "Joyce". I'll do my best to keep up the 'blog's standard in 2012!

At 83, young Joyce playing in the snow on Boxing Day 2010
(I must make some Xmas cards with this photo for next year)

When I began the 'blog in May this year, I wasn't sure how it would develop and how it might affect progress with the restoration activities. In actual fact, the restoration has fed the 'blog and the 'blog has fed the restoration giving each activity a feeling that it is complete when lodged in the blogosphere.

I've also found that visitors to Midsomer Norton Station are starting to ask me more informed and searching questions lately (who's leaking the information, I wonder?). I even get a few 'blog comments, some sensible, some humorous. I'll leave you to figure out which fall into which category!

There is probably not much more to blog in 2011 but you never know. The weather has decided to cool it emphatically and contact with cold metal drains body heat in no time through gloves, footwear and clothing; not a pleasant experience.

The arrival of the DMU at Midsomer Norton has left Joyce isolated in the platform opposite the maintenance facilities of the goods' shed. Much anticipated activity has had to take a back seat and, after three weeks, I'm still waiting to turn the engines on compressed air to splash the gloppy crankcase oil about in the lower gear cases. Hopefully, when Santa has been and gone, normality will return and more progress can be made.

2012 should see Sentinel 7109 in steam again for the first time since the 1960s. There's still a long way to go but most of the major subsystems' restoration has been sorted and, when circumstances allow, it will be more a matter of bolting all the bits together and lighting the fire than the endless grinding away at rust and debris ("How naive", did I hear someone say!).

Have a good break and hope to see some of you as visitors to Midsomer Norton Station in the new year.

PS If you find yourself bored over the break whilst waiting for the next posting, why not have a look at Douglas Self's 'Unusual Locomotives' web page. It's rather short on UK Sentinels at the moment, however, hopefully that won't always be the case!

Diesel Dunking for the Chains

2011-12-02T03:00:00.003Z

Here's Sentinel 7109's offering for submerging a celebrity in slime!

Is it a snake?

Eel maybe?

In actual fact, this is the recommended method for reconditioning rusty chains. As of 27th November 2011, two of the huge chains described in an earlier posting are now lying in a nice moisturising bath of diesel and thin oil.

After much searching for a suitable container large enough and strong enough to take a pair of chains, a S&DRHT volunteer, Dave Read, came up with the ideal thing, an agricultural style tank which may have done service in a dairy originally! It's always a good idea to explore other technologies for solutions to your own!

The chains will remain submerged for a couple of months before further examination.

One method of cleaning the chains I was recommended was to set fire to them to dry off the diesel. How ever good an idea it may be, the H&S police would probably have a heart attack at the thought!

Between the Lines

2011-11-29T12:15:00.000Z

Welcome to all who've found my Sentinel 7109 'blog from the link address on the back of the superb new S&DRHT newsletter 'Between the Lines'.

Well done, in particular as there is an extraneous '1' before the 7109 where it shouldn't be in the 'blog address! Oops Mr Proof-Reader!

Inter-Telegraphy: Lines, wires, poles (even Road possibly!)

I've accumulated quite a lot of information since May 2011 with the aim of recording the restoration work partly for my own reference and partly for anyone else interested in Sentinels or for anyone who's interested. I'm an engineer so no apologies for the postings being about Sentinel loco engineering and construction. No apologies also for drifting off-subject from time to time!

To find your way around, click on 'A Warm Welcome' to get started. Any text in blue is a link to either 'blog content or something else. Who knows what you might find?

Brazed Nuts and Gear Cases

2011-11-24T16:59:00.002Z

After many years of staring wonderously up into the portals under Sentinel 7109's lower gear cases, 23rd November 2011 finally saw them closed up and an oil bath created inside.

Under-frame view showing the nice pair of closed-up lower gear case portals

There are a number of requirements to be satisfied with these cover plates: they must not leak around the gasket; they must not leak around the screw threads (the holes are open inside to the oil bath); they must allow condensate to be drained off from below the oil (all of it if possible).

The gaskets are hand made from a rubberised cork material about 1/8th inch thick (3mm) using the two plates themselves as the respective templates.

Plate and cork gasket (two of each)

Preventing leakage down the screw thread is not so easy. At first, studs were tried but they were loose in the thread. These could have been secured with Loctite of an appropriate grade; however, I was concerned that the seal might not be maintained for the many years it will be required. Also, if either plate needed to be removed, undoing the nuts on the studs could loosen a stud and require it to be refitted and resealed. So I chose to use 5/16" BSW hex headed bolts with fibre washers.

[Note to me: 6 of the 24 bolts have been cut to 1/2" length for the holes which have been closed off with weld where presumably there was a problem with the gear case casting. The rest of the bolts are 1" but could be cut to 1/2" in future if wanted - unnecessary extra work!].

I'd also been recommended to use 'Dowty' washers instead of fibre; however, I had to dismiss this idea as some of the holes in the plates were not round and would allow leakage at the long end of the holes! (Offers for 25 M8 Dowty washers anyone?).

I devised a cheap method for draining the condensate using M12 nuts brazed to the underside of the plates and drilled and tapped so that a bolt could protrude right through. I milled a slot along the length of the bolts so that they could seal when tightened up but let fluid pass when loosened.

Slotted bolt and brazed nut

The key point here is that fluid needs to drain down to the surface of the plate and not allow a pool of condensate to remain that cannot be drained. One suggestion had been to use a drain cock; however, it would still need a brazed nut or threaded boss to mount it and £15 or so each is a lot more than the cost of stainless steel M12 bolts!

Use Crankcase Oil

Sentinel require Crankcase oil to be used to lubricate the gears as there can be seepage of crankcase oil through the crankshaft end bearings from the crankcase to the gear case. After some careful investigation, I selected Hallett Oils' SCC680 Crankcase oil which is designed specifically for Sentinel steam engines. It is a viscous, gloppy (onomatopoeic word) fluid that encourages any condensate to separate out and sink to the bottom (water being heavier than oil). It's this property that enables the condensate to be drained.

The gear cases needed to be filled to the second check level to suit the diameter of the gear wheel inside.

The one in the middle

At this point I realised that the gear cases were somewhat larger than I'd anticipated as they swallowed at least two gallons per side! So the plentiful stock of crankcase oil purchased for the engines is not now as plentiful as it needs to be!

Right hand Cover Plate

Left hand Cover Plate

So let's hope that I've thought of everything to prevent any leaks as draining out two gallons of gloppy oil to start again is not an appealing prospect!

The Midsomer Norton Station Bicycle - Big Time!

2011-11-21T03:00:00.003Z

Midsomer Norton Station visitors have been developing a curioius interest in evidence for the existence of a giant bicycle. I have to admit there certainly is some evidence. Have a look at these photos taken 20th November 2011:

Bicycle Chains?

Nothing in the above to show the size of the chains.

But hang on, 2 7/8 inches wide...

... and a pitch of 2 1/2 inches?

This must be some bike!

OK, not a serious article. These are of course Sentinel 7109's drive chains before cleaning up and freeing. Only 3 are needed but they are just a little larger than for your average bicycle, don't you think?

Sentinel 8805 Update (1)

2011-11-20T03:00:00.001Z

I spotted a familiar model of Sentinel 8805 at the Midlands' Model Engineering exhibition at Warwick on 15th October 2011.

Sentinel 8805 with its condenser vent at the front

The beading around the cab window looks identical to that on 7109
(from which the dimensions were taken!)

Norman Smedley has clearly been busy lately on his model of 7192 which I featured earlier in 2011. Click here to view. Keep up the good work Norman; I look forward to seeing it run!

Chuffing Nozzles - Now there's a thing or four!

2011-11-19T03:00:00.003Z

To turbo-charge Sentinel 7109's fire, exhaust steam is blasted up the chimneys to pull a draft of air through the coals in the firegrate. When stationary, steam is also directed up the chimneys using the blower for the same purpose. So how is this done?

Exhaust steam from the cylinders is pushed through a narrow aperture via a set of four nozzles, two in the base of each of the two chimneys.

The Four Nozzles

The nozzles sit in the base of each chimney
where the end of each of the curved exhaust pipes enters

When the nozzles were originally extracted, they were not in an operable state. There was a good amount of hardened coal-tar in the nozzle pathway and the blower rings were clogged-up so badly that only one or perhaps two holes could actually do any blowing.

Two nozzles as found after dismantling

Sentinel 7109 has its blower fed from the main superheated steam supply which contains cylinder oil. As a result, the blower has cylinder oil blown through its tiny holes; I can understand why the pathway and holes get blocked. I wonder if later Sentinels used wet steam for the blower?

The clogged blower passageway

Let's see how a nozzle is constructed:
The exhaust steam connects to the main nozzle inlet (the big hole in the flange in the picture below).

Main Nozzle casting

It then has to go through the narrower nozzle exit aperture and up the chimney.

Nozzle Exit Aperture

The exit aperture holds down a blower ring with four holes in it over a pathway to allow blower steam to be blown through the four holes.

Blower ring

Blower steam pathway with inlet showing

A separate steam supply connects to a narrower blower inlet pipe to the pathway.

Blower Inlet Pipe

It looks like this when all is assembled.

A complete nozzle assembly

And there are four of them in a double-engined loco.

The Four Nozzles again

Superheater - Baffling!

2011-11-18T03:00:00.000Z

On my visit to J R Goold Vintage Steam Restorations Ltd on 11th November 2011, Grant Goold showed me the pattern he had made for the superheater's supporting baffle plate from the drawings below.

The baffle plate is at the bottom of the central vertical shaft

The baffle plate itself

The bright orange saucer is not a Frisby (so I'm told) but the pattern to cast the baffle itself.

Upper face showing the strengthening webs

Lower face showing the cut-outs for the superheater support brackets

A quote for the final article to be cast in stainless or 'SG' steel is awaited.

Steam Brake Cylinder Completed

2011-11-17T11:20:00.001Z

On 11th November 2011, I visited our multi-talented subcontractor J R Goold Vintage Steam Restorations Ltd in Camerton to catch up on progress. Grant Goold showed me the end result of his father's superb work on the steam brake cylinder with its brand new piston. Click here to see how it started out.

When the brake cylinder was originally removed from Sentinel 7109, it was not in a good state and needed to be re-bored to a larger diameter. This meant that the piston would no longer be big enough even with new piston rings to work satisfactorily. Thus the old piston was wrapped in tape to make it slightly larger so that it could be used as a pattern for casting a new one. Work was also needed to de-clog a condensate drain valve which had clearly not been operable for some time!

"As New" Cylinder and Piston

There is still a retaining ring to be bolted to the face using the six bolt holes. This is a useful feature to prevent the piston ejecting every time the brake is applied!

Close-up of the re-bored cylinder

This picture shows where the cylinder is mounted on the near-side frame below the footplate.

The Brake Cylinder is top left

The shaft across the lower part of the picture is rotated by the steam brake pushing on the crank shown below it.

Steam brake crank with cylinder removed

There is a similar mechanism used for the handbrake.

Handbrake crank pulled upwards to apply the brake

The shaft then has other cranks which pull on the brake gear to apply the brakes.

Brake operating crank

Rear wheel brake shoe and link to the front wheel brake
(Fairly heavy duty mechanism!)

I'm feeling more confident now that not only will we be able to make Sentinel 7109 go but we will also be able to make her stop!

Sentinel Loco Boiler Replacement - Big Time!

2011-10-14T22:37:00.001+01:00

Friday 14th October 2011 was a beautiful, sunny, autumn day, ideal for picking up, transporting and reinstalling Sentinel 7109's big 200hp loco boiler.

Starting out at Mendip Steam Restorations Ltd, Paul (star of the day) of R J King first puts the boiler on the lorry. (Also on YouTube).

About here:

On the back of a lorry (from where it must not fall off)

Then out on the road:

Stoke St Michael's motorway

Through Stretton on the Fosse:

No boilers coming the other way

Then, crossing the road to Chilcompton, signs of the visible bit:

Summit to think about!

Finally arriving at Midsomer Norton Station for repatriation:

Not seen each other for a while!

Attach the chains for the lift...

...put it over here...

...through that hole in the cab roof...

...down a bit...

...to here

This is how it's really done: (Also on YouTube).

Followed by this: (Also on YouTube).

Finally 7109 ends up back on the level, parallel to the ground, for the first time in years.

Back on the level

I think this is classed as a project milestone!

Why you need a Pointy Hat

2011-10-13T15:27:00.000+01:00

As delivered, this elegant, Penberthy, displacement lubricator will flood the cab-mounted Worthington Simpson Boiler Feed Pump's (WS BFP's) steam chest every time it's topped up. Not good!

Looks good but hides a flaw

Let's see why.

Mounted on top of the WS BFP's Steam chest

The lubricator relies on being mounted vertically with steam oil filled to the top of a centrally located, internal tube.

Main pot removed to show the internal tube

In operation, some steam from the steam chest below is pushed up into the air gap at the top of the main pot where it condenses into water.

Being heavier than oil, the water sinks to the bottom and raises the level of the oil. The oil then spills over into the internal tube and back down into the steam chest below. So this is how the steam oil gets into the steam chest at the same pressure as the steam.

How does the oil get into the main pot? Well, you take off the filler cap and pour it in or so you expect until you actually have a look inside.

The top of the tube is open!

The tube has nothing to prevent oil being poured straight down it into the steam chest. Whilst this probably would not do any great damage, the steam chest would certainly get more oil than required!

I've concluded that there must be a missing part which blocks the hole but still allows the oil to spill over into the tube as intended.

I spent a lot of time figuring out how this part could block yet not block the tube top. Eventually I came up with a sort of castellated pointy hat thing!

Castellated, pointy, hat thing drilled from below to meet six holes and...

...which can sit on top of the tube like this

Now when you look in the top of the pot, it's like this:

Pointy hat top

So pouring oil into the filler will now put it into the pot and not straight into the steam chest!

I wonder if it will still work and what was there originally?

Many thanks ...

2011-10-08T19:25:00.002+01:00

... to all who kindly made donations to the Sentinel 7109 restoration project at the S&DRHT AGM on Saturday 8th October 2011. Much appreciated!

The queen definitely looks younger in this photo!

Boiler Lagged and Cladded

2011-10-06T11:50:00.001+01:00

Nigel Dickinson, Mike Colborne and myself spent Wednesday 5th October 2011 at Mendip Steam Restorations' workshop affixing Sentinel 7109's boiler lagging and outer cladding sheets. Previous articles (1, 2) have shown the preparation of the 'duvet' and outer cladding sheets ready for this day.

First of all, the boiler had to be brought inside from where it had lain for some months.

Tight manoeuvres in the yard...

...and a squeeze past obstacles in the doorway

Once set up inside, the two happy-chappies got to work with the lower 'duvet'...

Nigel and Mike clearly enjoying their work!

... followed by the upper 'duvet'.

Self-adhesive Aluminium tape fills the gaps...

... to hold it all together

The apertures in the finished 'duvet', thankfully, really did fit over the fittings as planned.

Snug fit

Then the cladding sheets needed to be fitted and pop-riveted together to hold them in place. The sheets also had to be riveted to a lower ring support on the boiler and an upper ring above. Whilst the 'duvet' had gone on easily, this was a more onerous task requiring the sheets to be attached and then squeezed over the 'duvet'.

Upper ring holes being drilled-out ready to take the rivets

Nigel clearly considering how to drill his left thumb joint!

Things got rather busy and strained in this process so the photographer had to take time out to do some real work!

So we got it done in a day! I have to admit to going home feeling rather smug and relieved that it was ready to install after really quite a long time in preparation.

The finished, painted article ready for installation in 7109

A date is now set for the boiler to be craned into 7109 and it's soon (but secret!).

Spending a day in Mendip Steam Restorations' workshop was an experience in itself. This is a place where real heavy-duty work takes place; I was immensely impressed at the scale of the activities and how things progressed quickly compared to the months we have taken on 7109's activities.

Here's a few photos to illustrate.

Andy Melrose clearly ready to attack the boiler to the right!
(Note the 100HP Sentinel fireboxes in the background)

Fitting the boiler front section with its owner close to hand

This is probably the biggest lathe I've seen. I don't know what the component was but it was about 5 feet in diameter.

Richard Philips (not posing) whilst doing a 'little' turning
(he was actually shoeing the pet dog away!)

Large-scale turning in action (also on YouTube)

Traction-engine boiler currently under construction (1)

Traction-engine boiler currently under construction (2)

Many thanks to MSR for all the help and advice over the months - keep up the good work!

Chuff-Synchronisation - Now what's that all about?

2011-10-04T14:56:00.001+01:00

Richard Nixon, drawings' custodian of the Sentinel Drivers' Club and Isebrook's carer, emailed me recently with a technical query about double-engined Sentinels.

His concern was that, with two engines, if they were not coupled together so that each chuffed up their respective chimneys at the same time, instead of air being drawn up through the fire, would each engine merely suck air back down the other engine's chimney?

To understand the point, a bit more needs to be known about how a double engined loco works. In particular, each engine has its own double chimney mounted immediately above the firebox.

Twin double chimneys

Plan view of boiler showing the twin double chimneys

Single exhaust pipe divides to feed two chimneys

Blasting exhaust steam through a nozzle in each chimney tube draws air upwards through the chimney. The air should be drawn up from below through the firegrate.

This all works fine if both engines chuff at the same time; however, if they don't then air can be drawn down the un-chuffed chimney instead of up through the fire (probably being the path of least resistance). The result would be a poorer fire in times of need.

So are 7109's two engines chuff-synchronised?

I had originally thought this was true and that the two engines on 7109 were gear locked together.

A gear case on the end of each engine crankshaft
with the larger gear case below

From the above picture, it looks as if there would be a gear for each engine in its upper gear case (black, like a pair of eyebrows) meshed with the larger gear in the rusty/grey gear case below. (There is the same situation on the other side). If all these gears were in place as described, then the two engines could have been chuff-synchronised together.

However; to my surprise, when I first undid the oil filler cap in the front engine's off side gear case (the one to the right in the photo), I found that the gear case was empty. On the near side, the rear engine's case was also empty.

At first, I thought we'd been diddled but then it dawned on me. There is a sprocket for a chain to drive the front axle from each lower gear; the two gears are not linked and rotate on a fixed, 'dead' axle. Thus the engines rely on the chains being set appropriately and tightly enough to achieve chuff-synchronisation.

Twin sprockets for chain drive to front axle

It's doubtful that chuff-synchronisation was achieved particularly well in both directions due to slack in the chains.

This situation evolved in later double geared locos such as Sentinel 9622.

Sentinel 9622's drive chains

9622's chains are double width, presumably for extra strength. These were most likely adopted because of the double gearing. Depending on whether low or high gear is selected, the drive will be transferred to the front axle by one chain or the other but not both. Hence all the driving force has to go via a single chain in contrast to 7109 where both are used at the same time.

To make the double gearing work, both engines are locked together at the end of the crankshaft where the gear is engaged. This happens by having a gear in each upper casing meshed with the gear in the lower casing.

However, there is still more to the picture: double geared engines have a neutral setting in which neither high nor low gear is engaged and the engines can be run with neither load nor locking together. This enables better warming through of the cylinders prior to loco movement.

Front view showing different sized gears at each side
(Diagram derived from 1930 A2 drawing, courtesy Richard Nixon)

Side view of upper and lower gear casings
(Diagram derived from 1930 A2 drawing, courtesy Richard Nixon)

Of course, the asynchronous rotation of the two engines in neutral means that when they are put into gear, they could be in any relative state of rotation. As such, sometimes they might be chuff synchronised and sometimes not in an unpredictable manner.

So Sentinel 7109, 9622 and other double engined locos have the same problem.

There is yet another consideration and that is to do with the resonant frequency of the chimney system. This may not be relevant if the chuffing frequency never gets high enough to reach resonance and I am sticking my neck out here due to lack of in-depth knowledge of this type of system. (Ask a designer of resonant, high-performance, car exhaust systems!).

Below resonance, a chuff up one pair of chimneys could easily pull air down the other pair if out of sync. At resonance, I do not know what happens. Above resonance, the chuffing will be so fast that sucking air back in won't take place and each chimney will behave as if sealed. (I'm assuming that the chimney system behaves like a ported loudspeaker enclosure).

So the conclusion to all this? I think we'd better just try it and hope for the best!

Appeal for 'JOYCE' & her maker's plates

2011-09-30T10:23:00.005+01:00

Amongst the Sentinel 7109 missing items are the 'JOYCE' nameplates and the Sentinel maker's plates specific to works number 7109. These were mounted on the side of the cab as in the photo below. I have no idea where these plates are but the chances are that since the loco survived, so did these plates; but where are they now?

Sentinel 7109 Near-side 'JOYCE' & Maker's Plate

Sentinel Waggon Works had various designs of maker's plates and the design specific to 7109 is shown below. With a lot of work, a new pair could be recreated from the design; however, I don't have those sorts of skills, nor the time with all the other restoration activities in progress.

Locomotive Maker's Plate Design

Another simpler approach is to make a mould from another actual plate such as the one below. The drawback is that the result always comes out slightly on the small side due to shrinkage of the cast metal when it cools. (Normally a pattern is made oversize to suit the shrinkage of the particular metal to be used).

Isebrook's (6515) Makers Plate

Peter Mitchell, owner of Isebrook (6515) at Quainton Road, has kindly offered to make one available should we decide to do it this way. Obviously, we would have to blank out the 6515 and replace it with 7109.

But I'm still wondering where the originals are. I'd be really glad to hear from anyone who can throw some light on their whereabouts. Please post a comment below if you can help.

Sentinel 7109's Lower Gear Housings

2011-09-27T10:24:00.003+01:00

Since July 2011 (now September), I've taken some better photos for this article so here's the new 'enhanced' version!

Three new inspection bolts have been made for the level check holes in the lower gear housings.

Inspection bolt with blind axial hole and linked radial aperture
for oil level checking

The bolt is partly removed to check if oil comes out of the radial aperture

View from above

So why three level check holes and not just one? Simply, it depends on the size of the gear wheel inside. Sentinel offered the ability to change the gear ratio to suit each customer's haulage and speed requirements.

7109 was set up for slow, heavy haulage (I'm guessing here but it will be obvious in due course); hence it will have a large gear in the lower gear case. As a result, it will not need such a deep oil bath as one set up for higher speed with a smaller gear in the same place. So the the check hole actually used will be to suit the expected oil level inside.

Going off-subject for a moment, the Teifi Valley Railway visit on 18th September 2011 revealed an interesting angle on this with the double geared Sentinel 9622 built in 1958. Have a look at the next two photos:

Near side lower gear casing (9622)

Off side lower gear casing (9622)

Note that the drain cock (posh way of doing it) on the near side is on the middle level whereas, on the off side, the drain cock is on the top level. At first, this seems to be a mistake; however, it is a double geared loco with different sized gears in the near and off side casings. Hence a different oil level is needed for each. (It's inevitable that however many photos are taken at the time, something else needs to be illustrated when the time comes. Anyway, hopefully these are just about good enough to illustrate the point).

Also noteworthy in the 9622 photos is that bolts rather than studs/nuts are used to fix the plate in place.

Does anybody know what that big nut-like thing is in the middle of each cover plate? I guess it's a means of draining condensate from the gear case but it was so covered in green slime and it was raining hard that day so I didn't feel much like crawling about underneath and cleaning it up to find out!

A final noteworthy point: in the bottom right of the off side photo can be seen a drive chain. 9622 has double width chains whereas 7109 has single. The double chains would have been used for extra strength as, with double gearing, the drive would be only via the left or right hand chain depending on whether high or low gear was selected. 7109 has one single width chain per engine.

Back to 7109: the new gear housing bottom plates are under construction in preparation for crankcase oil to be added. Hopefully the oil will dampen the unceremonious 'clanking' heard when running on compressed air without a load.

The bottom plate goes here

Crankcase oil is a special type designed for Sentinel steam engines. Its specific characteristic is that water condensate separates out and sinks to the bottom easily for draining off.

Definitely Crankcase oil required!

When fitting 7109's gear case bottom plates, a gasket will be required between the plate and the housing. Hexagonal headed screws will need to be used with fibre washers to hold it in place as some of the holes into the housing are open to the oil contained within; without fibre washers and fixed-head screws, the oil will be able to seep out via the thread in the housing and the thread in the nut and possibly also between the nut and the bottom plate.

What will the Ashpan look like?

2011-09-24T03:00:00.006+01:00

On 18th September 2011, I visited the Teifi Valley Railway (a round trip of 280 miles) to examine the only other double engined Sentinel loco in the UK.

Sentinel 9622 at Teifi Valley Railway 18th September 2011

Sentinel 9622 is looking a bit sorry for herself at the moment but is due to be put through a thorough 10 year overhaul and back into service before too long. It last ran on the Gwili railway around 2007.

A lot can be learned from examining other similar locos. 9622 is substantially different from 7109 as it benefits from 31 years of development. More perhaps in another article; however, one of the main reasons for the visit was to find out about the construction of an ashpan. Whilst drawings depict what is to be made, sight of the real thing really helps in understanding what's required.

Having said that, whilst 9622's ashpan matches the drawings, 7109's will have to be different as there are only four mounting points as opposed to the five shown here.

View from above

Cut-outs to allow air to the fire

This ashpan has clearly been used and the metal thickness is not as new.

View from underneath

Flap for emptying ash (1)

Flap for emptying ash (2)

A short chain is used to support the bracket so that the flap does not open too far.

Flap hinge close-up

Eagle-eyed observers will be wondering how the damper works. A fire is damped by reducing its air flow; this can be done either by stopping the air getting into the fire or stopping it from getting out. The Sentinel method is to place a flap over the top of the chimneys so there is no inlet damping.

7109's chimney flaps and operating handle

Back to Black

2011-09-23T03:00:00.004+01:00

Wednesday 21st September 2011 saw a coat of gloss black paint over the red oxide primer shown previously.

Lower front right hand corner of the boiler-free cab

Completion of the paintwork behind where the boiler will be located was the last (he said confidently!) preparatory task on the loco before the boiler can be refitted.

Lower front left hand corner of the boiler-free cab

I've been as thorough as possible in identifying all the things that would be rendered impossible once the boiler is in place. Looking at the photo, I'm wondering whether we ought to do the under-frame paintwork also.

Rear view of boiler-free cab

Nice blue hue, don't you think!

Joyce has a new hat!

2011-09-22T09:35:00.002+01:00

After trying for ages to find a way to put the new cab roof in place, I concluded that an interim measure was needed to make progress on the cab-interior paintwork prior to the boiler being repatriated with the loco. Hence a new blue hat to protect from the elements!

New blue cab cover

In a previous article, I showed the cab being painted with red oxide paint ready for a gloss top-coat. However, the red oxide was done on 10th August 2011 and then rain and other difficulties got in the way. In the end, it was about five weeks between coats so much work was required to clean up the red oxide before it could be painted over.

And from the rear

The lack of available undercover facilities at Midsomer Norton station is becoming a real problem and not just for this project. Sentinel 7109 really needs to be protected from the elements for many months to complete the restoration - so a major stumbling block is on the horizon - particularly as winter approaches.

Sentinel 8571 restored by the Salvage Squad

2011-09-19T03:00:00.001+01:00

Sentinel 8571 at the SDC 'Noggin & Natter' 25th April 2009

Some time ago, I heard about a program in the Salvage Squad series which featured Mendip Steam Restorations Ltd repairing a Sentinel Waggon boiler for Waggon 8571. This is the same company that has also done the repairs to Sentinel 7109's boiler. Tony Thomas, the records' officer of the Sentinel Drivers' Club, also appears.

To my great satisfaction, I recently found the program by accident on YouTube!

It's split into four parts which can be run from the links below. It's a fascinating program and includes many challenges in common with Sentinel 7109's restoration.

Part 1, Part 2, Part 3, Part 4.

Same day, same venue

Same day, same venue (same caption!)

Another Special Welcome...

2011-09-18T03:00:00.003+01:00

... to all you garden-geeks arriving from VegPlotting!

(NSW, Non-Steam Wife) is still clearly generating a lot of traffic to Sentinel 7109. So here's another little gem of a posting especially for you!

Midsomer Norton won many competitions for best kept station and particularly for its horticultural efforts. As well as the greenhouse, there was the 'Sun, Moon and Stars' astronomical garden creation between the station building and the roadway.

In this 1922 photo, the garden is clearly in good order.

Midsomer Norton Station 1922
(Courtesy Richard Dagger Collection)

However, at the start of 2002, the garden was in a very sorry state with the area only mapped-out and not seemingly too fertile!

1st Jan 2002

1st Jan 2002 again
Note the appropriate sign beyond the buffer stop!

By the middle of 2005, the garden had been put back in place creating a reasonably authentic reproduction of the original. (Note - when the Silver Street bridge was removed, the area for the Sun, Moon and Stars was also cut-off in its prime; hence the new garden is actually slightly smaller than it used to be - but that's progress!).

7th July 2005 has the garden in place
and a steamy thing inhabiting the background!

Jumping to 2011, the Sun, Moon and Stars are resplendent in bright colours and a credit to the volunteers who look after it.

30th August 2011

30th August 2011 again

Keep up the good work!

Shake, Rattle, Roll and Clank!

2011-09-17T03:00:00.008+01:00

On 14th September 2011, I decided that I would give Sentinel 7109's engines a little exercise on compressed air. They are still not connected to the front axle as the chains have not yet been fitted and so running them on air is quite easy.

For the first video, I set up a tripod on the Midsomer Norton Station platform and pointed it at the leading engine's open cover; the result follows: (Also on YouTube)

There are some interesting noises. The clanking is the knocking together of the substantial gear teeth without any load to hold them in contact. A creaking noise seems to be one of the valve springs compressing. The regular hisses are the four valve pairs opening in turn; the fact that the sound is consistent for all four is a good sign.

To get nearer to the engine sounds, I then set up the camera with two of the tripod legs on the nearside running board on the of the loco. Little did I know that the engine would shake everything in sight including the camera. So apologies for a little fuzziness but it hasn't spoiled the detail. Can you tell whether the inlet valves (LHS) open and close at the same time as the respective outlet valves (RHS)? (Also on YouTube)

I did say Shake, Rattle, Roll and Clank. Pretty close to the mark!

Radstock Sentinel Model is ready

2011-09-16T03:00:00.000+01:00

Roger Slade of CSP models has been beavering away on an etched brass model Radstock Sentinel loco and it has now come to fruition. It is a superb model as is obvious from the pictures.

CSP Radstock Sentinel Model

Roger's announcement (slightly edited for this context) is below:

S&DJR/LMS/BR. Sentinel 0-4-0T Steam Shunter.

Dorset based CSP Models in Dorchester have launched their long awaited 4mm etched brass kit for the Sentinel Shunter.

The project was started 2 years ago by CSP and Zenith Works. It was a challenge to produce an accurate and buildable kit for this quite complex locomotive. It wasn’t just to be a model but a lasting record of what these delightful little locos were.

With the priceless help of Andy Chapman and his long term lover “Joyce”, a set of somewhat doubtful works drawings, a fistful of photographic evidence and a great deal of optimism we set to work.

After a number of visits to MSN with a ruler and a camera we had our first set of drawings. A test etch was produced in November 2010 and a prototype produced. It looked OK but we found a number of inaccuracies. Andy let me see all the boiler fittings and with a set of drawings we decided to add a fully detailed boiler, ashpan, superheater and chimneys. How they went together was another matter but with the help of one of our most enthusiastic customers, Richard Roper of Emborough, who sketched a working model of the chimneys, we managed to get it right, we hope!!!!!

The chassis is driven by a “High Level” Gearbox through a series of spur gears to all 4 wheels. With the chassis weighted by the ballast in the boiler and ballast in the front chain box, yes it even has that and an etched chain! Maximum adhesion has been achieved.

The chassis, “00” or EM, with provision for compensation for P4, is Nickel Silver and the body a fusion of Nickel Silver and Brass. All the fittings are lost wax brass. The kit comes complete with wheels, gearbox, gears and motor. It also has etched number plates for both LMS and BR eras. All that is required to produce your own little masterpiece is hours of patience, some black spray and some decals.

There is a comprehensive, 16 page set of instructions with exploded diagrams of every stage of the construction. It is an eminently achievable project for people with average skills of kit construction. The cost of the complete kit is £135.00 + £5. 50 p&p; we can supply the basic kit for £95.00 for those that have their own ideas for motorising it.

We hope that it be well received by all S&D modellers. It has been a very difficult project to bring to fruition but we are happy with the outcome. We hope you are too.

A similar kit for “Joyce” in 4 & 7mm is nearly finished and will be available early in 2012.

It's very kind of Roger to acknowledge my assistance in the project. More so, I'm really pleased that he is working on a Joyce variation.

More pictures of this superb model are here below:

Incredible boiler detail!

Sentinel 7109's Superheater Assembled

2011-09-15T09:44:00.001+01:00

The previous superheater article showed it passing its hydraulic test. Now it has been reassembled with the boiler's top plate at J R Goold Vintage Steam Restorations Ltd and it's as good as ready to fit to the boiler.

Superheater and Boiler assembly drawing

The superheater consists of four coils of tubing sitting in the top of the boiler supported by the top plate. The top plate then sits on top of the boiler inside the outer shell casing and is clamped down in six places.

Plan view of the superheater in place

Wet steam feeds the superheater inlet via a one to four-way manifold (elbow); the superheater outlet then feeds the stop valve and regulator assembly.

View through the top plate chimney apertures
The central support 'dish' is under construction

Four holes are provided for cleaning out with a steam lance. Each has a 'bung' to close it off when not in use. The bungs had become stuck fast due to corrosion and needed to be removed forcefully! As a result, new bosses had to be welded in place and tapped for the bungs. The bung's thread doesn't look too good and a new bung will be required. Fortunately this is an off-the-shelf item with a one inch BSP thread or thereabouts.

Reconstructed clean-out hole

Assembled top plate and superheater

Having said above that 'it's as good as ready to fit to the boiler', I have one hesitation; the central support 'dish'.

The support 'Dish'

For this to be effective, (you guessed) the dish has to be a larger diameter than the inner ring of the superheater. Thus it's not a bad idea to include the dish in the assembly before putting it all into the boiler as the dish won't fit through the inner ring from above afterwards!

Sentinel 7109's Ashpan

2011-09-13T10:01:00.001+01:00

Amongst Sentinel 7109's missing items from when it first came to Midsomer Norton station in December 2004 was an ashpan to sit below the boiler's firebox and grate. This was never going to be an off-the-shelf item and would need to be fabricated anew.

So where do you start with something like this?

The Sentinel Drivers' Club (SDC) has a drawings' archive and drawings can be obtained via the SDC archive page for a nominal sum. It's not quite that straight forward as first you need to know the drawing number required. This can take some time to work out but is not too difficult if an assembly drawing is available.

As such, the ashpan assembly drawing number for Sentinel 7109's boiler is 11815 although there is a simpler type under drawing 10634. As 11815 is a design which makes emptying of the ashpan more straight forward and doesn't tend to empty itself wherever it likes, that is the one that will be used.

Ashpan 11815 Drawing
(Courtesy Sentinel Drivers' Club)

Various other part detail drawings are indicated which will need to be purchased from the SDC to enable them to be made.

Detail Drawing Numbers (1)

Detail Drawing Numbers (2)

I was talking to a gentleman welder and fabricator who was visiting Midsomer Norton Station for the Heritage open weekend (10th September 2011). He said he was interested in helping to sort out the ashpan. So keep an eye on this page as it will be added to as the ashpan comes into being (fingers crossed!).

Sentinel 7109's Mechanical Lubricator - A Mystery Solved!

2011-09-11T20:26:00.001+01:00

The previous posting about Sentinel 7109's Mechanical Lubricator left an unsolved mystery - namely why was there a piece of wire in three of the four pump barrels?

Wire lodged in the pump barrel...

...and extending down into the pump nozzle

Colin Evans, one of the last Somerset coal miners, provided the answer for me on 10th September 2011 at Midsomer Norton Station's Heritage open weekend event.

As the individual pumps are constructed at the moment, with brass barrels, the wires do not do anything at all and can be discarded. However, the pumps may have originally been constructed with glass barrels but with the glass later replaced by brass. Glass may even have been an option that was not chosen.

Brass barrels

The glass was intended to contain a quantity of water through which the droplets floated from the bottom to the top. As oil is lighter than water, when the pump injects a droplet of water, the droplet floats to the top and is pumped to its destination having displaced water from the top of the barrel.

The wire was to catch the droplet as it enters the barrel and guide it upwards along the wire. Without the wire, the droplet could follow any path and tend to deposit itself on the side of the glass so that neither could it be seen nor would it arrive at the top as a droplet. Hence water could be pumped instead of oil and flow monitoring rendered impossible.

With the lubricator mounted under the loco's engine covers, it could not be seen by the loco driver and certainly not able to be adjusted from the cab. Thus, while the loco was being driven, the ability to be able to monitor the oil droplets was of lesser importance.

Sentinel 7109's mechaniacl lubricator will be operated without water in its pump barrels and with opaque (brass) barrel material. Thus, it will operate blind but be able to be adjusted should more or less oil seem necessary.

The flow rate adjustment is made by shortening or lengthening the crank arm of the lubricator so that, for every driving stroke, the pump's camshaft is rotated less or more respectively.

Lubricator's crank arm length adjustment

Deep in my past...

2011-09-06T17:33:00.001+01:00

... I sometimes wonder how I got into restoring a steam loco in this day and age. There is, however, a clue from my family history.

My paternal grandfather, H. Albert Chapman, was at one time employed by W. H. Yeatman and sons Ltd of Poole, Dorset, England. Amongst his duties at the time was delivery of goods using the company's 'van' or, as appropriate to the 1920s, the Steam Wagon!

The wagon was a Garrett overtype and is listed in the comprehensive volume: Garrett Wagons, part 1, Pioneers & Overtypes by R. A. Whitehead (ISBN 0-9508298-5-4).

Stoker 'Tubby' Hibbs and Driver H Albert Chapman with BJ-1882
(Picture courtesy G M Chapman, date & location unknown)

The specification of the wagon was as follows:

Garrett works number 31925

Factory despatched 8th December 1913

3-tonner

Superheated

Piston valved

Non-tipper

Fixed sides

Hinged ends

Cast steel wheels

Rubber tyres

'Tubby' Hibbs and H Albert Chapman (seated) with BJ-1882
(Picture courtesy G M Chapman, date & location unknown)

I know nothing of 'Tubby' Hibbs from the pictures or his family. My grandfather lived his final 30 years with Disseminated Sclerosis. Undaunted by the affliction, he continued to work from his wheel-chair in his backyard workshop sharpening saws, mowers, shears and anything else that was blunt using mainly tools that he'd made himself! He died in 1975 at 84.

W. H. Yeatman & Sons Ltd, I have been stunned to find, still exist in Poole although their business has somewhat digressed from its activities 100 years ago.

There is an old family tale that H Albert Chapman was the first person ever to motorise a straw baler by mounting it on the back of an old Morris car chassis and driving the baler mechanism with a belt and pulleys from the prop-shaft. It was never patented but my dad went on to become a patent agent. I wonder if he was conscious of a connection!

So, with that lot in my past, I guess it was inevitable that H Albert Chapman's heritage was going to find me out one day and Sentinel 7109 just happened to be there at the right time!

Postscript

After I first posted this article, I was telephoned by Anthony Yeatman who was very pleased to see the photos again and for the reference to his company. He explained that W H Yeatman & sons Ltd is one of the country's oldest companies still run by its original family owners.

Meanwhile, G M Chapman, daughter of H Albert Chapman, my aunt and supplier of the photos, started to dig in her cupboards for any other related photos and came up with these two.

Tubby Hibbs (left) and H Albert Chapman (right) foreground
(Picture courtesy G M Chapman, date & location unknown)

And before the steam lorry...
(Picture courtesy G M Chapman, date & location unknown)

I had to work hard digitally with the original pictures to make them presentable. Hope you agree it was worth the effort.

How do I support the restoration?

2011-09-05T06:00:00.005+01:00

The easiest way to support the restoration of Sentinel 7109 is by using Paypal to donate. For this you will need a Paypal account which can be arranged through the Paypal website. All you need to do then is click the Donate button below and the rest is easy.

Another simple way to support the restoration of Sentinel 7109 is to donate to the project by writing a cheque made out to "Sentinel 7109" and either handing it to the Midsomer Norton station shop assistant or sending it by post to:

Sentinel 7109 Restoration project
c/o Midsomer Norton Station
Silver Street
Midsomer Norton
Radstock
Somerset
BA3 2EY

Don't forget to include a phone number, email or contact address so we can thank you.

Offers of engineering skills are of course welcome (please)! Just post a comment below and say how you would like to help.

And finally...

...there's always these (or the modern equivalent)!

Trailing Engine's Boiler Feed Pump Valve Regrinding

2011-08-25T11:11:00.003+01:00

The last episode left the inlet and outlet valves in need of a quick regrind. The process is simple and requires only a little fine grade grinding paste and a screwdriver to rotate the two halves together.

The rotation action is backwards and forwards in a two steps forward, one step back arrangement with the two rubbing surfaces never being allowed to stay in the same place for long. Otherwise the surfaces could stray from being flat and a good seal would only take place when the valve and seat had a particular position relative to each other. This would be clearly undesirable so hence the continual back and forth rotational movement.

Inlet Valve being reground.

After grinding, the remaining paste must be removed from all surfaces so that the paste does not get where it shouldn't during the pump's operation. I used Duck oil and a cloth to wipe away the residue. Paraffin is actually recommended but I didn't have any. However, there did not seem to be any residue remaining!

Inlet Valve

I did the inlet valve first and the result is below (apologies for slight lack of focus).

Inlet valve after the regrind
Deposits on the valve have gone and
the marks on the seat are lessened

At this point I spotted a problem which I had not previously noticed but was there all the time. The cap over the valve had clearly been over-tightened at some time sufficiently to break it apart.

Cap viewed from the side/below

Cap viewed from above

It had been tightened so much that it had pressed the centre section through so that the outer rim would seat but the whole piece would not seal. Whilst there would be little consequence to the pump operation because there is an outer cover to hold it in place, it has been remade to avoid any further trouble from it in future.
The original cap seems to have been made from gunmetal; however, a 1.5 inch diameter piece of brass rod has been machined for the new one.

Old and new

I decided to mill a groove across the top to enable the cap to be rotated. With valve grinding paste between the mating surfaces, it can now produce a good seal. At first I didn't think that water escaping into the cap cavity would be important; however, it could possibly act as an air bubble in the system and hence reduce the effectiveness of the pump (which was designed to work with an incompressible fluid). So I've convinced myself it will be better as a result!

Needless to say, the outer cover which holds the new cap in place should only be delicately 'nipped' tight to avoid further destruction!

New valve cap installed

Outlet Valve

The outlet valve was reground in a similar manner to the inlet valve.

Valve deposits removed compared to before

Seat deposits reduced

The outlet valve is now ready for action.

200HP Pre-war Sentinel Locos

2011-08-21T06:00:00.001+01:00

Sentinel 7109 is a 200 HP type; however, Sentinel also produced various other 200 HP types before they settled on the 7109 configuration. One such type proposed was the double centre-engined type shown below. However (see comments below the posting), this type was never apparently built although others were (but I don't have diagrams for them!).

Double Centre-engined 200 HP Locomotive

The front engine was intended to be linked to the front axle and the rear engine to the rear. Those specified to be low geared (and hence high torque) also had their engines locked together to prevent wheel-spin on one axle.

Compare this to Sentinel 7109 with its engines at the front (and check the comments below).

Sentinel 7109 - A balanced double-engined 200 HP locomotive

Both the types and others could be built with double gearing; however, 7109 is only single geared.

Cab Repaint

2011-08-20T06:00:00.001+01:00

Wednesday 10th August 2011 saw more work to tidy up the cab before parts become inaccessible with the boiler reinstated.

Red paint is now getting everywhere...

...Left....

...Right and...

...Centre!

And who's idea was it to do a 'Banksy' of a road railer on the RH window?

Progress continues!

Sentinel 8837

2011-08-19T06:00:00.001+01:00

I paid a swift visit to the Middleton Railway in Hunslet, Leeds on 14th August 2011 hoping to see their Sentinel (8837) in action. I was given a very warm welcome and, after a ride up the 1 in 37, was provided with a guide to show me around the workshops and in particular to the Sentinel.

Sentinel 8837 is not the priority restoration project at the moment and is unlikely to see steam for perhaps four years. The body and chassis are currently in the workshop with the boiler and engine stored away elsewhere safely.

Rear view...

...front view (or is it the other way round?)

Apologies for the camera shake. (There are two possible reasons for this: (1) I'd been to a party the previous night and was in need of restoration (2) I'd recently been shown how to use the manual controls on the camera to get the very best pictures. I'll leave you to figure out which was the dominant cause. Needless to say, being shown how to and knowing how to use a camera's manual mode when in a hurry are two different things. I'll stick to automatic in future!).

Many thanks to the Middleton Railway for their warm welcome and I look forward to seeing 8837 in action in the future.

100HP Pre-war Sentinel Locos

2011-08-18T06:00:00.004+01:00

I found a wonderful book recently named "Sentinel" Patent Locomotives that covers much more than just Sentinel 7109. Although it was reprinted in 1974, my copy was the genuine article published by the Sentinel Waggon Works in 1931 as a kind of technical marketing catalogue for pre-war locomotives.

For example, here's a LNER Y3 type in drawing format.

And the Y1 type; however, the difference is not apparent except to those who looked underneath.

The Y3 had a gearbox below its engine to enable two levels of capability whereas the Y1 drove directly from the engine's crankshaft. The Y3 was thus the more flexible locomotive.

Sadly, no Y3s have survived.

The little engine that could...or maybe could not?

2011-08-17T06:00:00.003+01:00

My OO gauge Sentinel Y3 model arrived from Model Rail Magazine (9th Aug 2011) as pictured.

MRM (Dapol) Y3
(with a distracting back-drop from another interesting book I've found lately)

The supplied instruction sheet set me wondering due to the comment that the model was produced from detail obtained from Isebrook at Quainton road.

Extract from instruction sheet

However, Isebrook is a single geared type as with the Y1!

Isebrook's chains drive from the crankshaft sprockets

So is the model actually a Y1 or Y3? I'll leave it to you to figure out; this posting might help. In reality, it's not important; it is a fine, tiny model which runs very nicely. For more information have a look at the Model Rail Magazine's website.

Here is a small video of Isebrook in preserved action on YouTube at the Buckinghamshire Railway Centre, Quainton Road. The occasion was the Sentinel Drivers' Club 'Noggin & Natter' held on 10th April 2011.

Leading Engine's Boiler Feed Pump and Valve Regrind

2011-08-16T12:27:00.001+01:00

Having said in the first episode that the leading and trailing engine-mounted pumps look the same, here's the leading one to compare with the trailing one.

Leading Engine's Feed Pump in situ

The regrinding process for improving the inlet and outlet valves was exactly the same as for the trailing engine's pump; these photos show the leading engine's pump valves' condition for comparison. Regrinding took place on Wednesday 10th August 2011.

Inlet Valve

Inlet valve on opening for view

Valve cap is intact

Deposits on valve...

...and on the seat...

...but flushed clean away after regrinding

I also decided to mill a slot across the top and regrind the valve cap as with the trailing engine's pump. Now it seats itself more positively and should perform better as a result.

Leading engine's pump valve cap cleaned, reground and in place
(11th Sept 2011)

Outlet Valve

Unlike the trailing engine's pump, there was no washer sitting on top of the valve. I don't know why this should be unless a botch was used on the trailing pump to reduce the maximum opening of the valve. Comments welcome.

Outlet valve and seat were fairly dirty on opening...

...but much improved after a good grind!

Mount Rainier Scenic Railroad

2011-08-11T19:48:00.003+01:00

So what has this to do with Sentinel 7109, I hear you ask! Well not an immediately obvious lot except that on my travels to Washington State USA in July 2011, I landed almost accidentally on the Mount Rainier Scenic Railroad. Not expecting too much to begin with, I was pleased to be cordially invited to visit the 'shops' and see the steam locos not in use at the time.

I was stunned to be presented there with a Heisler, a Climax and a Willamette - all in working order. A Shay under restoration was also there in the shed.

On returning home, the photos I'd taken in the 'shops'' shed (yes, the apostrophes are correct; a quote of a genitive plural!) were far from as good as I'd hoped. However, here are some of the best ones.

Willamette 34

Not a Shay

The less mechanical side

Leading drive-train

Trailing and tender drive-train

And finally, the Climax!

Having had a good look around the Mount Rainier Scenic Railroad website, I can't come close to their pictures. Try these:

Heisler, Climax, Willamette (On the right).

Have a look around the Gallery; it's a superb collection of photos of Steam Logging locos.

Meanwhile, Sentinel 7109's whistle has featured prominently during its refurbishment. Strange noises from my garage have kept the neighbours bemused for hours (well, minutes anyway). So if Midsomer Norton station can manage to replace its missing Silver Street bridge with a level crossing, how about if we upgrade 7109's whistle and blow it like this to frighten the traffic away! (Also on YouTube)

Whistling in the USA!

The culprit in the video: July 29th 2011,
MRSR's newly restored Baldwin 2-8-2 Rod Locomotive
No 70, Polson Logging, near Elbe, Washington State, USA.

And after all that, there is a connection with Sentinel 7109 - it is also a gear driven locomotive!

Sentinel 8843 - A different sound of steam

2011-07-17T11:49:00.003+01:00

Coming off the rails for a posting, the more I discover about Sentinels, the more interesting they get. In answer to a request earlier in the year, I was invited to spend Saturday 16th July 2011 at the Langport, Somerset, steam rally paying particular attention to John Goold's beautifully restored Sentinel Steam Waggon, works' number 8843.

Who's the happy-chappy in the passenger seat?

Built in 1933, it is a S4 type (meaning shaft-drive, 4-wheeler) with three-way tipping gear (left, right & centre).

Unlike Sentinel 7109, 8843 has a four cylinder, single acting steam engine (2-stroke) driving the rear wheels via a shaft and axle-mounted differential. Sentinel Super waggons before the 'S' type had two-cylinder, double-acting engines and were chain driven with the differential as an integral part of the engine's crank-shaft.

I was able to have good explore of 8843 during the day but what caught my attention was the engine ticking over in neutral gear. I'd always thought that steam engines were permanently linked to their driving wheels but here was not the case. I was also interested by the sound of the engine; having my camera with me, I used it to record the engine ticking over. Initially it is in late cut-off (starting), then shortly after it starts, the middle (intermediate speed) cut-off setting is selected then finally the late (fast) cut-off setting. Note how the sound changes before it finally stops. (Also on YouTube).

Listen rather than watch (the paint is already dry!)

Even more interesting is that this engine sounds far more like a diesel engine than a steam engine yet there is no internal combustion here!

Whilst out on an evening trip on the roads around Langport, I was sitting just behind the cab and able to catch the 'bark' from the chimney. This next video clip is of 8843 starting from rest and changing gear (cut-off) as it accelerates. (Also on YouTube).

Listen rather than watch (the paint is still dry!)

What also impressed me was the turn of speed. Although 8843 struggled a bit on the hills, on the flat it had no trouble getting to 40mph or so and apparently it can do quite a lot more! I always thought vehicle were pretty slow in the 1930s; clearly Sentinel had produced an advanced, modern vehicle but still propelled by steam!

Trailing Engine's Boiler Feed Pump

2011-07-15T06:00:00.003+01:00

Whilst I had first run Sentinel 7109's engines on compressed air on 26th July 2009 and on subsequent occasions, I had not checked whether the Boiler Feed Pump (BFP) attached to each engine was in working order. Having renovated the Worthington-Simpson BFP, I was now much better prepared as to what I would find.

Engine BFP in-situ

Both leading and trailing engine BFPs look the same.

Part cut-away drawing

The cut-away shows that the pump is a reciprocating type driven from the crankshaft (or geared from the crankshaft).

Inlet (RH) and outlet (Left centre)valves

Access to the pump piston was not attempted as it would involve breaking and damaging one or more gaskets. From the Worthington-Simpson BFP piston design, I expect a similar multi-ringed piston forced on to the cylinder wall by the pressure of the water being pumped. I may be proved wrong! I was more interested in the condition of the inlet and outlet valves and how they were constructed.

Inlet valve to the right
Outlet valve below the 'bulb'

Inlet Valve

Cap on inlet valve chamber

Cap removed to show inner valve cap

Inner valve cap removed to show the valve itself on its seat

Valve removed to show its seat

Valve itself showing a clean surface

Valve seat in reasonable condition but would benefit from regrinding

Outlet Valve

'Bulb' instead of cap on valve body

The bulb is initially filled with air and provides a cushion to the pulsations of the reciprocating pump. It is similar in effect to a smoothing capacitor in an electronic circuit power supply.

Base of 'bulb' (just about) showing valve internals

Valve on seat with washer on top

I'm not sure of the purpose of the washer; however, it must prevent the valve from fully lifting and thus restricting the maximum flow. To me, it seems as if this might put an extra load on the engine for no apparent good reason - unless somebody knows better? It might also prevent the valve from coming out of its location but Sentinel were better valve designers than that weren't they?

Valve on seat with washer removed

Valve removed with washer in place on top

Valve seat slightly corroded (green)
and needing improvement by regrinding

Cab repaint - A bit of a blow!

2011-07-14T08:16:00.003+01:00

Before the boiler is put back into the cab, the surrounding paintwork needs improvement particularly behind the boiler where it will eventually be inaccessible. This was expected to be a quick job but soon took on surprising proportions.

Initially, angle grinders and radial wire brushes were used to good effect on the cab floor. Also on YouTube

Bit of a grind

Then the cab wall revealed a strange effect. A compressed air jet was being used to disperse the settled dust but was found to be also particularly effective at blowing off the paint from the cab walls! (Also on YouTube).

Bit of a blow!

Whether this was due to the particular paint used previously or poor preparation of the underlying surface at the time is hard to say. However, the paint was clearly keener to come off than stay on!

Looking better already - all four boiler support areas are visible

By the end of the day, although not completed, the cab floor was beginning to look a lot better than at the start. To be continued.

Sentinel 7109's whistle valve and how does it work?

2011-07-13T06:53:00.000+01:00

A peculiar looking valve had been hanging around Sentinel 7109's stores looking for a use. Eventually, I was advised that it was a whistle valve.

Grubby looking thing!

Alternative view

With mounting flange and whistle-mounting elbow

Whistle valve roof-mounted in Isebrook

Whistle valve roof-mounted in William

Unlike Isebrook and William, Sentinel 7109 has the whistle and valve mounted vertically on the cab front.

Front-mounted whistle (the valve is inside)

So how does a whistle valve work and how does it enable the 'pop' action needed for the whistle?

Functional Parts

The main valve body allows steam in through the top right connection where the air-hose adaptor is shown here. The steam is held back by a conical valve pressed against a valve seat by a spring and also by the steam pressure.

Conical valve (not to scale!)

Valve seat inside end of valve body

Spring and retainer which screws into the end of the valve body

A rod passes through the valve body and rests against the conical valve's base. To sound the whistle, the conical valve is pushed off its seat by the operating lever's movement which pushes the rod against the conical valve's base.

Rod (not much more to say on this!)

Operating lever

The steam can then pass out to the whistle through an aperture in the valve body's flange.
The steam pressure holds the conical valve in place until the lever is used to push it open. This is a sudden action which is also terminated abruptly by the steam forcing the conical valve shut again. Hence the whistle valve enables a quick 'pop' to be achieved as well as the long 'poop'!

There is one more aperture in the valve body shown with a copper tube attached in the Isebrook valve picture (but, oddly, not on William).

Condensate drain

As a result of the whistle being sounded only occasionally (hopefully), the valve body will generally be cold when steam is admitted. Thus the copper drain tube is added to allow the resulting condensate to be drained away.

When it's all assembled, it looks like this.

Note the elegant MDF cab front substitute and supporting clothes' peg!

Finally, when I first took the valve apart originally for renovation, the conical valve seemed to have a leathery pad between it and the seat. As the pad was in an 'aged' condition, I discarded it wondering where to find a replacement. On subsequent closer examination, it looked as if the conical valve and seat were both in good condition and, after a small amount of regrinding, were clearly perfectly satisfactory. Thus I concluded that either the leathery pad was accumulated muck or was a misguided bodge from the past! Who knows? But it isn't there now!

Clean as a Whistle!

2011-07-12T15:58:00.002+01:00

When Sentinel 7109 was originally brought to Midsomer Norton Station in December 2004, its whistle was missing. From early pictures of 7109 in service, a tall thin item was required as a replacement.

Tall thin whistle 1

Tall thin whistle 2

Other Sentinel locos seem to have a variety of whistles such as William's but something more authentic to the original was wanted.

William's proud possession

Early July 2011, the ideal thing came up on Ebay and I was the only bidder! Although its fittings were not quite suitable, it seemed as good as was likely to be found (another was offered for £350 which was declined rapidly!).

On arrival, it was tarnished but in good working order and a definite possibility.

Clearly, it once had a sticky label attached

Gun-metal mounting and steam inlet to the left

It's such a simple, passive device, I'm sure I could have made one!

Cap machined from solid gun-metal

To clean off the tarnish, I used a phosphoric acid gel originally used for derusting car bodywork. Finally it was brightened-up by Brillo pad and a french polishing technique known as grisse d'elbeaux.

Shiny and clean as a whistle!

Some say (where've I heard that before?) that the whistle looks like one from an 08 diesel-electric shunter. I checked this out in Brian Haresnape's British Rail Fleet Survey "7 Diesel Shunters". It appears that 08s did have this type but they also had a number of others and horns too. As Sentinels also had this type and others, I'm sure this whistle will do just fine!

Despite many attempts at testing the whistle with compressed air, my neighbours are still talking to me. However, when I put the video below together, it frightened the hell out of the local cats and the next-door dog had a fit!

(Note: I've sometimes had trouble playing the video repeatedly. If this is the case, reload the window (F5 on PCs) and try again). Alternatively, it's here on YouTube.

Sentinel 7109's Boiler Mountings

2011-07-10T19:51:00.000+01:00

Sentinel 7109's boiler is supported in the cab on four brackets around the firebox.

Four Fixing brackets (there's another round the back)

Three fixing holes (rear set)

It is held in place with seven longish and three shortish bolts about one inch in diameter. The longer ones go through the footplate floor; the shorter ones through a thinner supporting bracket towards the cab front. In a pretty dilapidated state, I've cleaned them up using an electric drill and wire brush.

Before (LH) & after (RH) brushing-up

Judging by the state of the top ends, which presumably had the hole through to take a split pin and castellated nut, they required a certain amount of violent percussion to remove them when the boiler was taken out. Despite their state, they are probably adequate to reuse. Anybody seen the nuts?

Water Pump Pumps Water!

2011-07-07T10:05:00.083+01:00

Despite the original heading of the last WS BFP episode, I've used that heading here and corrected the previous one (owing to the fact that no water had actually been pumped at the time!).

I concluded that the water pump valves did need regrinding. Advised to use genuine valve grinding paste, I 'Googled' it and found that it is available from various manufacturers in a two part tin: coarse paste at one end and fine at the other. Chippenham is not an easy place to buy valve paste but KM Farms Parts had what I wanted.

Typical Coarse/Fine Valve Grinding Paste container
(Spot the product placement in the form of the Worthington Valve handle!)

I hadn't done anything like this before so it was a bit of an adventure working out the best way to use the paste. The fine type seemed to be all that was needed.

The valve seats are basically a pair of flat discs of which the moving one sits loosely around a supporting stem; as such the valve has to seal both at the outer edge and the inner edge for it to work. If the inner edge leaks, then water seeps back through the gap around the valve stem.

Mating parts of an upper chamber (outlet) valve

By inking the inner and outer seat surfaces and rubbing them together, it was clear that there was incomplete contact and scope for improvement. The outer seat needed to be ground down in all eight cases for the inner seat to come into contact. Coarse paste was needed initially as there was a fair amount of metal to be removed.

It seemed from the initial state of the valve seats that the inner seat could never have made contact unless it had eroded considerably during the pump's original working life. If this is the case, then there is much reliance on the boiler inlet 'clack' valve to prevent leakage back through the pump. Alternatively, the valves may rely on being flexed by back pressure to make contact at the inner seat. I had expected the pump piston rings and valves to need to be a tight fit but I'm not so sure now. Some leakage allows the pump to operate without seizing in one position. Time will tell!

Lower chamber (inlet) valve seat

The lower chamber (inlet) valves are of a different design and have indents between inner and outer seats. Again, both seats need to seal for the valve to work properly. As can be seen, the lower valve seats were not easy to get at but fortunately not impossible!

The valve grinding had clearly paid off as the characteristic 'raspberry' produced before was now much better pronounced. Also the inlet could be felt to suck and the outlet to blow.

Moving swiftly on to testing with water. Eat your heart out William Heath-Robinson, here's the test set-up. Recycling is a strong feature!

Complete with spurt!

The pump self primed at the first attempt with the reservoir (watering can) at the same height as the pump but it needed help when having to suck from a lower level. There is also a leaky weld in the inlet pipe which will need repairing.

And the video you've all been waiting for... (also on YouTube).

I'd noticed that the flow did not seem even; half the time it was steady and half a bit slower. At first I thought one pump cylinder was faulty but then realised that this is bound to happen as each pump cylinder has a piston-rod in one half with a consequent reduction in the cylinder capacity at that end! 'I-think-I-can,'I-think-I-can...' comes to mind as the typical two cylinder steam engine rhythm.

So the pump seems to work. I'm still slightly nervous that the pump valves don't seat well but they are probably better than they were when previously in operation.

The user manual (yes, believe it or not, there is a user manual for these pumps) makes no comment about valve seat geometry; however, it does mention the pump piston rings. The four hollow rings are intended to have 1/16 inch of total axial play which I guess is to allow them to fill out when pumping the water to make a seal. What is not mentioned is that the only way to check the play is to remove the piston and rod completely (including the steam end also) and have a look.

No! This is going to remain one of those assumptions that it was OK originally so it's OK now as taking it all apart again belongs in the 'too difficult pile'!

Sentinel 7109 gets a Duvet!

2011-07-06T00:01:00.019+01:00

Having passed its first hydraulic test, Sentinel 7109's boiler is now being prepared for repatriation with the loco. Before this can happen, its lagging and outer cladding sheets have to be fitted as they would be impossible to work on once the boiler is lodged within the bijou confines of the loco's cab.

With the boiler at Mendip Steam Restorations, the plan is to take the various bits and pieces to the boiler and assemble them prior to transporting the complete sub-assembly back to Midsomer Norton Station to be dropped straight into the loco. This enables a single crane hire to complete the job.

An earlier post showed the cladding sheets in preparation. The lagging also needed to be cut to size with apertures (in the right place) to fit around the boiler fittings. Fortunately, the cladding sheets can double as templates for locating the apertures.

The ticket office platform at Midsomer Norton station seemed an ideal large flat surface for the cutting out. However, the first problem to overcome was that the wagon containing the cladding was on the far track and there was a train in the way.

Wagon stuck behind 7109 on the far track

Manhandling large floppy sheets between (stationary) trains isn't the first subject I'd mention to a safety inspector but needs must so a ladder was put diagonally between the wagons and the sheets precariously carried across to the platform.

Midsomer Norton's Circus Tricks

The lagging material was laid out on the platform and cut to length. All edges were sealed over using self-adhesive Aluminium foil tape designed for the purpose.

Preparing the templates

The lagging material is a high-spec (expensive) version of the type used for loft insulation. It is Aluminium foil faced on each side and made from ceramic rather than glass fibres so as to handle the boiler's high temperatures. Its trade name is 'Superwool Ceramic Blanket' manufactured by Morgan Thermal Ceramics and supplied to us by Heritage Steam Supplies (HSS). The Aluminium foil is to help avoid condensation being held in contact with the boiler casing and also to reflect heat inwards to the boiler's outer surface. The Aluminium foil tape also came from HSS.

Apertures were cut in the lagging using the cladding sheet templates and a Stanley knife (Why are sharp knives always called Stanley?).

Cutting around a template aperture...

... and removing the waste

The aperture edges were sealed with foil tape to keep it all in place.

Completed Lagging sheets

A good day's work was made possible by the good weather but could have been easier and safer without the manhandling of cladding sheets across the gap between the wagons.
All that was left to do was put it all away again.

More of Midsomer Norton's Circus Tricks

There are one or two small preparation tasks remaining and then the boiler, lagging and cladding can be assembled ready for repatriation with Sentinel 7109.

Water Pump Won't Pump Water!

2011-07-04T07:39:00.008+01:00

The last episode of the Worthington-Simpson Boiler feed pump destined for the cab left a cliff-hanger: it was merrily allowing air to be blown through the pump section forwards or backwards. As such, the chances of it actually being much better when faced with pumping water were not good. And guess what? I was dead right; not a sausage of a spurt!

Up to this point, I'd looked fairly carefully at the steam end but ignored the water end of the pump assuming it would 'just work'. I should have known better; it's always the assumed bits (that make an 'ass' out of 'u' and 'me') that don't work.

I began with the section drawing.

WS BFP Pump Section

The inlet is the lower and the outlet the upper of the orifices on the right hand side. The inlet feeds up through the middle of the two cylinders to the lower of the two banks of four valves. As the pistons move back and forth, they suck water in through the lower set of valves and then blow out through the upper set; the valves enable water to pass one way against a spring pressure but lock themselves closed for the other way. Hence they are non-return valves (a bit like diodes if you are that way inclined).

Even though I'd previously suspected the piston rings, the fact that I could easily blow through would not be affected by the piston rings. Therefore it had to be the valves so I took them apart one by one. Fortunately, a large hex key worked well to undo them all.

Hex key removing the valves
(with a little help from me when needed but it sat there just nicely for the photo!)

Being a water pump, all fittings are brass and not corroded despite being 60 years old.

Top view (water is pumped up from below the valves)

All of the upper set of four outlet valves are clear and in good condition.

View of valve seats from underneath

The lower set which receives the incoming water was rather more interesting. Clearly a filter had not been used to sift out rubbish and something akin to pieces of a matchstick and other 'detritus' had got into the seats of three of the valves.

One of the offending pieces of matchstick...

... and where it was not very usefully lodged!

Detritus (bits of old sock to you and me) also in the works.

No socks-appeal here!

Having cleared all the bits and pieces and reassembled the valves and the pump section, it was clearly harder to blow any air through albeit that there was not a complete seal so perhaps the valve faces will need regrinding. So, the bit you've been waiting for, here's a little more video with the valves seated. (Also on YouTube).

As well as the view from the water end, there is also a very subtle acoustic difference to before in that there is a feint 'raspberry' in time with the pump strokes. But as with deep-seated raspberries, you'll probably need a good subwoofer with your speakers to hear it!

Just to complete the picture, some photos follow of other WS bits and pieces.

Valve components

Broken spring, later suitably 'bent' into shape and stretched to fit.

Now, how to ensure that it will pump into 275psi boiler pressure! Continued here.

Sentinel 8805

2011-06-29T17:38:00.006+01:00

In February 2011, I attended the Sentinel Drivers' Club AGM in Basingstoke. In conversation after the formalities, I met Norman Smedley who proclaimed that, in the boot of his car, he had a 7.25 inch gauge model of the unique LMS Sentinel-Doble shunter numbered 7192.

Not the normal car boot contents I thought (with raised eyebrows) and, at Norman's invitation, went to have a look.

Although 7109 is a 12 inch to the foot scale, I've long admired the amazing amount of time and effort that goes into model locos. This was another moment of admiration.

Car boot contents (1)

Car boot contents (2)

Amazing detail (and not just the boot catch!)

Right hand side

Norman sent me this photo recently of the model nearing completion and what a fantastic model it is! I'm very much looking forward to seeing it in action.

Nearing completion (June 2011)

The 'prototype' for Norman's model was the only true Doble loco built by Sentinel, works number 8805, and delivered to the LMS in 1933. It was driven by two 150 HP Doble engines, one for each axle, and had an oil-fired 1500psi boiler and condenser! Whilst it performed well, it was too complex to maintain and was withdrawn in 1943. (Norman's model will be battery powered!).

Sentinel 8805 (Photo Tony Thomas)

And again (Photo Tony Thomas)

As 7192 numerically follows Radstock's 7190 and 7191, this is the reason why 7109 will not carry the number 47192. See also 7109 Restoration.

Sentinel 7109's Superheater passes 550psi Hydraulic test

2011-06-27T20:46:00.002+01:00

After repairs, a boiler has to pass an initial hydraulic test (water) at 1.5 times working pressure to ensure that it is physically sound. The superheater, because it works at a higher temperature to produce dry steam, has to pass its initial hydraulic test at 2 times working pressure. For a Sentinel, this means 550 psi (~38 bar).

I'd thought that the hydraulic test would require some pretty sophisticated equipment; however, this is not the case.

First the far end of the tubes need to be blocked. The sealed ends can be slackened to let air out so that there is only incompressible water contained.

Blocked superheater tube-ends

Then an artistic arrangement of pipework is attached at the near end (the bicycle wheel is not essential).

Artistic pipework

The hydraulic pump is then connected to the artistic pipework and pressure applied.

Check the gauge reading...

...this one's easier to read.

About 565 psi (39 bar)

So how is the pressure applied, I hear you ask? (Note the video was shot by the owner). Starring Justin & Pete.

(Any suggestions for the owner to do the hard work are met fiercely by the camera lens!). Clearer video on YouTube.

The pressure has to be held for at least 30 minutes. If satisfactory, then the test is deemed passed and a certificate written on the spot and issued.

Al fresco computing

Many thanks to Justin Goold of J R Goold Vintage Steam Restorations Ltd and Peter Hawkins of Hawkins Inspection Services Ltd for their services.

Sentinel 7232 Ann

2011-06-26T08:00:00.003+01:00

As background to the restoration of Sentinel 7109, I've visited some other Sentinel locos and, in some cases, done a pretty thorough photo-reconnaissance of internal bits and pieces. My visit to the picturesque Embsay and Bolton Abbey Railway near Skipton, West Yorkshire, in June 2011 was not one of the thorough photo sessions but interesting all the same. Ian Douglas kindly showed me around.

Sentinel 7232 Ann (1)

Sentinel 7232 Ann (2)

Built in 1927, Ann is a single-engined balanced Sentinel steamer rated at 80hp. It spent its working life at British Tar Products Ltd, Irlam, Manchester UK. Now at Embsay, it has not run since 2007 due to safety valve problems and the boiler being out of ticket. Its operating future is uncertain (June 2011).

More details are available from the Embsay and Bolton Abbey Railway website.

Sentinel 7109's Blowdown Valve

2011-06-25T17:17:00.002+01:00

The blowdown valve is used for clearing out (blowing down) accumulated scale, rust and assorted particles from the bottom of the boiler. 7109 was missing this item on arrival and it has taken a long time to find one capable of handling the high 275psi boiler pressure. John Goold has obtained a new old-stock type as in the picture with 4.25 inch diameter undrilled flanges.

New Old-stock Blowdown Valve

It has to be fitted on to a flanged "drain-pipe" at the bottom of the boiler (it has been cleaned up and the snow has melted since this December 2010 picture was taken).

Blowdown valve "drain-pipe" flange

And then there is the spanner needed to operate the valve from a suitable distance. And the angle of attack to avoid the spanner operator from being steam-cleaned!

Sentinel 7109's Polished set of gauge glass valves

2011-06-25T16:31:00.001+01:00

All loco or waggon boilers use a gauge glass to enable the fireman to see the boiler's water level. A glass tube between an upper and lower gauge glass valve is where the actual water level can be seen. The upper and lower valves are used to ensure that the level is indicating correctly and that any doubtful muck can be jettisoned when required.

Luckily, 7109 came complete with gauge glass valves attached to the boiler although they were in an unknown condition at the time and looking fairly dull.

Gauge Glass Valves as arrived (with curved handles)

Gauge glass valves to fit Sentinel boilers are unusual in that they have to have a curved surface to match the cylindrical curvature of the boiler profile.

Gauge Glass Valves after a little cleaning
(and much improved in bright light!)

The internal moving parts of the valves, despite my initial (naive) attempts, were not in a good state. The curved handles indicated an old design that was famed for leaking badly.

"Klinger" Valves spindles (Photo Heritage Steam Supplies)

John Goold advised the rebuilding of the valves to the "Klinger" design and this has been completed.

Good as new and not so dull!

The almost as-new look has been achieved by 'pickling'. I never quite understood whether this was to do with an extended visit to the pub or a dip in an acid bath but the end result looks brilliant!

Sentinel 7109's Boiler ready for cladding

2011-06-24T20:38:00.003+01:00

Final preparation of the boiler has been completed at Mendip Steam Restorations so that the cladding can be added to hold in the ceramic insulating material.

'Lip' Highlighted

Around the lower edge of the wide upper section is a 'lip' which both supports the lagging and enables the cladding sheets to be attached with pop-rivets. This is how it was done previously however many of the remains of the rivets were still blocking the holes. These needed to be drilled out in preparation to fit the new rivets and cladding.

Drilling for drainage

Water had been prone to collecting in the 'lip' and promoting rust and required some holes to be drilled in the lip to improve drainage.

I enjoy visiting Mendip Steam Restorations as there is always something interesting happening and a friendly welcome (possibly influenced by the packet of chocolate digestives I took along!). Currently, three traction engine boilers are being worked on as shown. I hope to do an extensive article on MSR in the future.

MSR (1)

MSR (2)

MSR (3)

Until work began on Sentinel 7109, I'd been completely unaware that this type of industry still existed in the UK; however, I really am pleased to find that it does and what a wonderful and skilful bunch of guys these people are!

A special welcome...

2011-06-20T11:18:00.082+01:00

... to arrivals from VegPlotting.

(NSW, Non-Steam Wife) has clearly been generating a lot of traffic to Sentinel 7109. So here's a little posting especially for you!

2011 Greenhouse at Midsomer Norton Station

Sentinel 7109 lives at Midsomer Norton Station, near Radstock, Somerset, UK (BA3 2EY). This particular station was always characterised by its greenhouse which was situated next to the signal box. Station staff used it to cultivate all sorts of produce (which, in those more gentle 1950's days, there was time to do between trains).

1959 (Photo: Eric Rimmer (SDRT Collection)
from Alan Hammond's Heart of the Somerset & Dorset Railway)

The line was closed in 1966 and most of the station including the greenhouse was dismantled. In September 2003, the scene looked as in the picture below.

September 2003 wasteland

In 2005, work began to bring the signal box and greenhouse back to life.

October 2005

June 2006

January 2007 (with Graeme Mayes perched on the roof)

May 2007 (My name is on one of the roof-tiles as are many others
who sponsored the tiles at a pound a time)

June 2008 externally complete but no greenhouse

Magically stepping forward to 2011, the greenhouse is complete to accompany the signal box. Produce is being grown again and sold to raise funds for the project as a whole. So Garden Bloggers and all, do come and visit us at Midsomer Norton Station any Sunday and enjoy all the sights and sounds (and cake) that are on offer.

May 2011 Greenhouse and Signal box complete in all their glory