Grate Solution to a Problem

Not widely known but just before the press were due to arrive on a steaming day recently, Joyce's firebox centre firebar dropped into the ashpan - not really what's wanted with little time to put it right and in the middle of a raging furnace!

Complete Firegrate;

However, miracles can be performed when there is no choice and the fireman of the day managed to put it back in place and all was well.

It's easier to empty ash/clinker from the grate by removing a firebar but getting it back in isn't easy without crawling underneath (ideally with the ashpan removed)(decidedly not my favourite activity).

It's Grate

Although it won't be much help with replacing a dropped firebar under a hot fire, I've made a tool for putting them back through the firehole after emptying the grate when cold.

One end fits through a firebar slot and the curved end is for twisting the firebar into position.

How to fit an Ashpan (8)

I last wrote about Sentinel 7109's ashpan in December 2012. In that article, I showed the fixing brackets being processed. Since then, the whole ashpan has been languishing in my garage acting partly as a storage shelf and partly just getting in the way!

February 7th 2016, three years later, it is now actually fitted to the loco (bar a few missing nuts).

In place beneath the boiler

This photo shows how it was originally - not so different!

The original (other side view) 

There is a flap for raking out the ash.

Open for emptying

It can be closed when 7109 is in use.

Closed for use

Whether the flap is also for use as a fire-controlling damper, I don't know. I need to do some more reading on the subject.

I made a small change before the fitting in that I replaced the flap hinges with stainless steel ones. The previous mild steel ones struck me as incapable of withstanding the nasty environment.

In another Ashpan article, I showed the ashpan being jacked into place. At the time, 7109 was outside with track and sleeper ballast underneath. It was not an easy working environment.

In Midsomer Norton's shed, the floor is flat and can be traversed under 7109 using a creeper trolley. This enabled me to lie on my back with the ashpan sitting on my chest. I could then lift it into place and hold it there using a spare leg whilst doing up the nuts. Fortunately I was unable to take any photos of the process. Sometimes a selfie is just out of place for a situation!

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!).

How to fit an Ashpan (6)

Making an ashpan is one thing but actually fixing it in place is quite another. It's not just offering the ashpan up to the firebox, drilling a few holes and screwing up a few nuts and bolts. The ashpan is heavy, all my tools etc. are at Chippenham and the firebox is 25 miles away in Midsomer Norton! And what sort of brackets are needed?

In amongst many other things, I've been pondering how to do this for months. The ashpan is circular so angle iron brackets would have to be curved to just the right radius. I can't do angle iron bending and it would be too pricey to have four made. Even then, it still does not answer where to mount them!

Ear's the idea I came up with.

'Ears' (4)

I made these four ears with the inner radius ground to suit the ashpan curvature. The plan was to fix these in place then jack the ashpan up under the firebox, adjust the ears for best fit and finally tack-weld them to the ashpan wall.

Two of the four 'ears' in place

With the ears in place, the ashpan was put on a pair of wooden beams so it could be 'walked' along the rails to its location beneath the firebox.

Ready for 'walkies'
Spot the deliberate error here!

In position below the firebox
(Deliberate error corrected!).

Then the ashpan was jacked into the highest position abutting up against the brackets...

Highest position

... and ears tack-welded in place.

Tack welded

Bearing in mind that I'm almost six feet tall, not a natural contortionist and was at times wearing a welding helmet, getting into position to do the tack welds was not a trivial operation particularly for the ears towards the front of the loco. I confess there were a few flashes as the welding rod caught the wrong thing on the journey getting into position!

Why three nuts per fixing? The top one holds the studding in place; the other two can set and lock the ashpan height and hence the air-gap. I hate things being able to rattle!

Having brought the ashpan back to base, I have to complete welding the ears with a 'leg' support, increase the ears'-hole size (of these ears, not mine!), add some fresh smoke-box paint, assemble the flap and fix the complete ashpan in place. Hopefully this job will then be complete after about nine months duration!

Grate Stuff!

After all the work on the boiler, superheater and ashpan, there's the little matter of where to put the fire. Ages ago, I looked over the fire-grate parts and cleaned them up with the usual electric wire brush. What I had never done was to try to put the grate actually into the firebox - assuming that is was the right one and would fit!

When assembled, the grate looks like this:

Arranged fire-grate (boot toe-caps not included!)

It consists of two semi-circular rings, each with its own 90 degree segment of grate affixed. Two more 90 degree segments also sit on the semi-circular rings (the ones with the row of holes). There are then five slotted fire-grate sections laid across between the two fixed segments (the ones without the row of holes).

6th Aug 2012, Fire-grate in position (It did fit, thankfully!).

In-situ, the ends of the semi-circular rings sit on two of the four brackets which also provide the fixings for the ashpan.

Gap between halves of the rings

Near to each end of the semi-circular rings, there is a downward protruding lug which abuts against the bracket to prevents the grate from rotating.

An 'Open-Mouthed' view in through the fire-hole opening

So how does the grate assembly arrive in the bottom of the firebox I hear you ask? It has to be put in item by item from below starting with the semi-circular rings, the two segments and finally the five slotted grate sections. A tough job providing more stiffness in the joints next day!

Isebrook's 100 horsepower fire-grate

For readers familiar with 100 horsepower waggon and loco fireboxes, Sentinel 7109's 200 HP grate is quite different from the 100 HP type shown above.

How to make an ashpan (5)

In Ashpan part 4, I'd almost completed the ashpan's flap. I wanted to add a bracket to the angle iron cross-piece to attach a chain to for raising and lowering it. (Chain links can be hooked on using any link to set the length and hence the position of the flap when used to control the primary air entering the fire).

Chain bracket welded in place
(a simple fixing hole in the angle iron would have weakened it)

The completed flap with hinges

So how does the flap work in practice?

To minimise air to the fire (and prevent ash falling out!), it is held at the highest position.

Minimum air and ash-fallout

To control the primary air flow to the fire, it is set as required between extreme positions.

Mid position

To be able to draw out the ash, the flap is released to its lowest position, i.e. flat.

Fully open.

Sentinel 7109 could be driven with the flap fully down for maximum air but Hansel & Gretel would be jealous at the result!

If it is still not clear how the flap works, try this video clip: (Also on YouTube).

About all that's left is to fit the fixing brackets in place. This will entail spending quite some time buried beneath 7109 in a pit whilst holding the ashpan in place and marking out the hole positions. When I've figured out how to do this, another ashpan 'blog article will appear!

How to make an ashpan (4) - Getting in a flap!

In ashpan part 3, I'd got as far as making the pan section of the ashpan. Now there is a 'flap' to make which allows the ash to be emptied (hopefully only when intended!). It is an odd-shaped fabrication with a hinged panel and sides to prevent spillage when Sentinel 7109 is in motion. The picture of Sentinel 9622's below shows the general design idea.

9622's Ashpan Flap

I started with the flat sheet cut out from the pan base and welded 2mm mild steel sides shaped to fill the gap when the flap is raised.

Sides in place and ready to weld the cross-piece

I added an angle iron cross-piece to provide some reinforcement and prevent the flap from being raised too high when closed. A good exercise for the Tiggling Stick!

Cross-piece welded in place

Despite Sentinel 7109 being 28 tons, these welds are really quite small. I used TIG welding because it is much gentler where space is tight. Stick welding can be a sledgehammer adding extra metal where it isn't wanted.

I needed to add a pair of ears to prevent the flap dropping out when opened for ash clearing.

Ear clamped ready to weld (sounds painful!)

Pair of ears

At this stage, I concluded that, whilst adequate, the harsh environment that an ashpan lives in would soon cause it to fall apart and that extra reinforcement would be essential for it to have a long life.

Side reinforcement

I welded two rectangular pieces between the sides, the flap plate and the angle iron. Now it feels like a rigid structure capable of the abuse it will receive in service.

Nearly complete: Screwing it all together, add the fixing brackets and a raising and lowering mechanism and apply a coat of smoke-box paint (which I doubt will last very long in service but it makes me happier with the end result!).

To be continued.

How to make an ashpan (3)

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)

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!

How to make an ashpan (1)

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!

What will the Ashpan look like?

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