Friday, 21 December 2012

Remote Control - 1927 Style

Starting from cold, Sentinel 7109, like any other steam loco, has many cold parts which cause the passing steam to condense until warmed-up. There are automatic drain cocks at top and bottom of each cylinder that open to release collected water. However, 7109 has pipework between the boiler and engines which also accumulate condensation.
Exhaust Condensate Valve
The picture above shows a white insulated pipe underneath the water tank that feeds the steam to the engines at the front from the boiler behind in the cab. Either side of it are two very dark coloured pipes which take the exhaust steam from each engine to the blast nozzles in the chimneys.

Running across the white pipe is another pipe which links the two exhaust pipes and includes a valve for releasing the condensate. If the condensate is left in the exhaust pipes, it has to go somewhere so every time there is a decent chuff from the chimneys, there is an accompanying decent hot shower for anyone nearby! So it's a good idea to keep the exhaust dry.

As the condensate valve is underneath the water tank, it's not very accessible for the driver in the cab. So a remote control mechanism is required.
Restored Condensate Valve
The above photo shows that the valve is spring-closed. Pulling on the handle on the right opens the valve against the spring compression.

The top photo shows a wire cable going off upwards to the right that is used to operate the valve. It has to pass around a couple of pulleys to a friction-loaded operating handle.
Pulley and handle mounts darkened
The handle is mounted on the cab's right hand side using two bolts. From the handle, the cable extends downwards to a pulley mounted below on the cab floor and then diagonally to another pulley just by the cross member (used for linking the sander operating levers from the right to left hand side).

I'm having to remake one of the pulley mounts as the original has been lost; the other and the operating handle have now been restored.
Pulley (not rocket science!)
The handle assembled with hardwood mounting block (1)
The handle assembled with hardwood mounting block (2)
I had to take this handle mechanism apart to find out how it worked and clean it up. Effectively, it is a sticky movement which, if set correctly, will hold the condensate valve open itself rather than the driver having to hold it.

In the above photo, there is a dark layer between the top of the base plate and the handle's cable drum. It is a friction pad made of either hardened leather or 1927-style plastic (which I guess would be Bakelite). There is a spring in the centre of the handle which holds the handle against the pad. For it to work effectively, the spring has to be tensioned correctly. I wonder if I've got it right? Time will tell.
Component parts
The friction can be set by tightening the bolt to compress the tapered spring.
DG Sentinel Waggon Parts Manual diagram
The above diagram is is from a DG (Double-Geared) waggon parts manual. Sentinel used standard parts all over the place.

It would be nice to be able to show the whole mechanism in place; however, it's not helpful to have a trip wire in the cab whilst there is still so much to do there! I'll include a final photo later.

Monday, 3 December 2012

How to complete an Ashpan (7)!

In the previous Ashpan article, I'd managed to tack-weld the fixing brackets into place in preparation for adding reinforcement webs.

So here are the reinforcing webs:
More life-like than expected!
The eye-sockets are to help lifting it into place (with rope).
Magnetic clamp for holding the web in place for welding
Each web had to be ground to shape to fit the brackets. This was no surprise bearing in mind how they had been tack-welded in position.
Welding complete - I doubt if they will fall off in a hurry!
And finally:
In black...
...with a bit missed in the eye-socket.
(Nobody's perfect!)
I wonder if the ashpan will actually fit? (Because these brackets are staying where they are, come what may!).

Wednesday, 28 November 2012

Water Filter Valves

On the left hand side of Sentinel 7109's water tank, there is a pair of water filter valves. These valves are in line with the pair of pipes feeding the two engine-borne boiler feed pumps.
The pair of water filter valves (not a recent photo!)
There is a flange plate at the back of each valve which fits over a hole in the tank side. When the valve is opened, water is able to pass upwards through the filter and out through the pipe on the left hand side.
Filter valve section drawing
(from S-Type Waggon Parts Manual)
The above is the best drawing I've been able to find although this is a type made for mounting horizontally on a S-Type Sentinel Waggon. Just pretend the bung numbered '7' is at the bottom below the valve spindle!

An unusual feature of the valve is that it has two seats (10). The obvious one closes the water inlet to the right; less obvious is the seat to the left which closes when the valve is fully opened. This is to stop the water from seeping out through the valve threads. I guess this is a simple, low-maintenance alternative to gland-packing the valve spindle.

The filter element and other component parts are shown below.
Component parts showing the filter mesh
As I've described in a previous article, the assembled valve has a black cap to its right. This seals an outlet which formerly supplied an injector before the cab mounted boiler feed pump was installed.
Drain plug shown highlighted
There is a drain plug at the bottom of each valve which serves two purposes: firstly to drain the filter valve to prevent frost damage and secondly to allow rubbish to be emptied from the filter. Looking back at the drawing, the detritus collected by the filter will inevitably sink to the bottom of the valve housing. So, for a vertically mounted valve, this should work quite effectively.

However, Sentinel 6515, Isebrook, which usually lives at Quainton Road, has its filter valves inverted as in the photo below!
Isebrook's inverted valves
When I examined 7109's valves, one clearly had a frangible stud which has been drilled out and replaced with a nice shiny new one.
Stud frangibility...
... and the brand new replacement
Gasket material for these will be rubberised cork sheet as there is no high temperature to contend with and only low pressure from the height of the water in the tank.

Saturday, 17 November 2012

A Sound Surround

In an earlier article, a comment questioned what might have been originally fixed to the edges of the large hole in Sentinel 7109's cab roof from which the chimneys protruded.

At the time, I did not know the answer although Norman thought he had seen something that had come from the old cab roof. Despite much searching, I'd not found anything but then on Sunday 11th Nov. 2012, I spotted something amongst 7109's bits and pieces that was obviously the right item. (Had someone been hiding it as I'm sure it wasn't there before?)!
Chimney Surround plate
Judging from the fixing holes around the edge which match those on the old cab roof, this is the correct original item. But why have an extra sheet to reduce the size of the hole at all?
The hole matches the chimney unit size
When looking at the hole size relative to the size of the twin chimney units, it becomes clearer.
Easily takes the two chimney units (1)
With the chimney surround also in place, there will be a fairly close fit to reduce rain coming in.
Easily takes the two chimney units (2)
The main reason for doing it this way is that when the surround plate is removed, there is space to remove the chimney units without having to take the whole roof off (not that this is difficult, of course!).

A second reason is that if the hole in the cab roof does not match the position of the chimneys mounted on the top of the boiler, it is a lot easier to reposition a small plate like this than to move the whole roof.

Another mystery solved! Now how many years did that take?

Monday, 5 November 2012

Defying Gravity - Raising the Roof

[To all loyal readers - an apology. Since originally publishing this article, I have been asked to revise the content. I hope that what remains is still of interest. I do try to present things exactly as they happened; Midsomer Norton's engineering facilities are not always as one would like and considerable ingenuity and determination are often needed to overcome challenges - that is what makes life interesting!].

5th November 2012, was a demonstration of how well the Midsomer Norton Monday Gang work together to overcome a difficult problem. Firstly, a picture of the end result!
Nigel's party trick!
Hmm, a bit like a spot the ball competition?
If you've followed the 'blog for some time, you'll know that Joyce had a new hat some time ago. The bright blue tarpaulin 'hat' has not lasted well and has been in urgent need of replacement by the metal cab roof itself for quite some time.
Ready for fitting
I'd made the cab roof ready for fitting in June 2012 but there it remained in the MSN goods' shed waiting to be manhandled into place. Being made of 3mm mild steel, it generally needed four people to lift it but to lift it from the ground to the top of the loco was never going to be easy. With no operational or accessible lifting machinery to hand, it really was going to be to hand!

Despite the rare good weather, I'd concluded that the roof was going to be in the shed at the end of the day yet again. However, I hadn't bargained for the determination of the Monday gang pulling together to take up the challenge. After a while, the original plan of sliding the roof up slanting ladders was looking a lot more feasible than I'd thought - and the weather was still beaming down!
Tools for the job!
Strapping the ladders to the loco cab side and attaching ropes to prevent them sliding away from the loco was an essential outcome of risk assessment. Likewise, pulling up by multiple straps as well as pushing up from below with plenty of hands was going to ensure that a single problem would not cause any undesired result.
And there you have it! Just like that!
The clue to Nigel's party trick!
I'd like to thank all the Monday gang who helped today, not forgetting Norman without whom many things would never happen!

Tuesday, 23 October 2012

Sentinel 8805 Update (2)

I visited the Midlands Model Engineering Exhibition on 19th October 2012. Norman Smedley had Emailed me to say he was exhibiting his completed 7.25 inch gauge model of the unique Doble Sentinel shunter. I've described the model before in a previous article so here are some pictures of the completed item. Click pictures to enlarge.
Interesting coal-bunker feature in the cab!
Well done to Norman for producing such a superb, rare model of this Sentinel locomotive. A model to be proud of.

Sunday, 14 October 2012

Engine Testing

I discovered a simple answer to a question that won't occur to many Sentinel owners: On a double-engined loco such as 7109, how to you test one of the pair of engines without the other one loading it?

I was surprised but relieved to find that I wasn't the only one to have thought about this and that a vital feature had been already included by Sentinel in 7109's design.

In order to use one engine only, the steam to the other needs to be isolated. However this is not sufficient as air has to be allowed in instead to prevent the isolated engine from drawing a vacuum when the valve timing dictates that steam should be entering its cylinders.

This is how it works.
White insulated main steam feed pipe
The main steam feed pipe, from the boiler at the rear to the engines at the front, runs underneath the central water tank. It then splits into two smaller pipes, one to each engine, using a 'Y' splitter. The 'Y' splitter component makes it easier to insert a blanking plate in one or other engine's steam supply.
'Y' splitter highlighted bottom right
(Click the picture to enlarge it)
The vital feature I mentioned above is a bolt head which can be removed to open an air vent.
Vital feature highlighted to the left
Thus, by putting a blanking plate in the steam feed at the 'Y' splitter and removing the respective vent bolt, one engine can be disabled without loading with the other.

Tuesday, 9 October 2012

Appeal for help

I've been struggling to find suitable replacements for the four 15 inch diameter, circular, 'spectacle' cab windows for Sentinel 7109's restoration.
Front pair of 'spectacles' from an old photo
Ideally, I would like genuine Sentinel windows as used on many of their early locomotives but alternatives may be suitable. They pivot about a vertical centre line as shown in the right of the picture.

The original windows were lost during transfers between previous owners and have never been found.

Can anybody help please?

My Email address can be found as the Steam Locomotive Officer here:

Tuesday, 25 September 2012

Sentinel 8590 'Elizabeth'

On Monday 3rd September 2012, I did something I'd wanted to do for a long time: to have a ride on the Sentinel Steam Bus at Whitby, Yorkshire, on the east coast of England.
Elizabeth (1)
Possibly the only Sentinel Steam waggon still earning a regular income for its owners, 'Elizabeth', Sentinel Works Number 8590, departs for a trip around Whitby about every 20 minutes or so from near the eastern end of the northern quayside. (She is easy to find).
Elizabeth (2)
Built in 1931, Elizabeth is a Sentinel DG6P (Double Geared, 6-wheeled vehicle with Pneumatic tyres). But I mustn't steel the thunder here - have a look at Elizabeth's own website for more detail; it's a fascinating story.
Elizabeth (3)
There is also a facebook page on Elizabeth.
Elizabeth (4)
From the terminus, Elizabeth starts a steep climb from the quayside up to Whitby's higher levels. Not my best video but you get the idea. (Also on YouTube).

If you ever get the chance to visit Whitby, firstly beware of any vampires and secondly, make sure you seek out a ride on Elizabeth; you won't regret it.

Many thanks to Vernon, Viv and Andy for a brilliant Steam Bus experience!

Thursday, 20 September 2012

Bressingham Days

When Sentinel 7109 left Croydon Gas Works in 1968, it spent some time at Bressingham Steam & Gardens at Diss, Norfolk. Whilst there, it was still in its original working livery of bright green.
Original Livery at Croydon Gas Works
I visited Bressingham in Summer 2009 to see if anyone remembered 7109 and if they still had some of the missing parts. One or two people did remember it saying that it had not spent long there as some visitors had remarked unflatteringly that it 'looked like a diesel'! Seemingly it never steamed at Bressingham and hence it's understandable why it might be thought of as resembling a diesel. Believe me, underneath its skin, it's not a diesel! Also, despite being made very welcome, the missing parts were also missing there.

Whilst many pictures exist of Sentinel 7109, most of them are in monochrome and very few in colour. However, on Sunday 16th September 2012, I spent an afternoon at the Bedfordshire Steam & Country fayre somewhere not far from Biggleswade.

It was the annual big outing for the Sentinel Drivers' Club to show off their road waggons together and there was an impressive turnout.
Sentinel Waggons at Bedford (1). (Click picture to enlarge).
Sentinel Waggons at Bedford (2)
Amongst the Sentinel exhibitors, I met Neil Matlock, the Sentinel Drivers' Club's diesel waggons officer. In conversation, he mentioned that he had a small number of colour photos of 7109 in 1973 and the he could email them to me. This he did kindly and, with his permission, they are here below.
7109 at Bressingham (1)
7109 at Bressingham (2)
7109 at Bressingham (3)
7109 at Bressingham (4)
From the above, it would seem that 7109 had not steamed for some time. Bearing in mind that its new boiler was installed in 1951 and that it was taken out of service around 1960 and then not moved to Bressingham until 1968, five years later in 1973, it does not look like it had had a recent overhaul.

So, should it have red highlights to its lower features? Hmm.

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