Cladding

Cylinder block cladding.

I am using 24 swg brass fo the cladding and to make the cladding for the cylinder blocks I first made a paper template by cutting the paper to width and then wrapping the paper over the cylinder block and marking out the fixing holes and drain cock holes by rubbing a pecil over the paper which leaves an impression of where the holes are. The paper is then glued to the brass sheet already cut to width and the holes drilled.

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Paper template stuck to the brass sheet.

Two cut outs are required one at the bottom to clear the draincock operating lever and one at the top to clear the steam pipe flange. The top cut out in the template has been marked but not yet cut.

Once all the holes are drilled the brass sheet has to be bent to fit the curves of the block. I used a steel bar of similar diameter to put the curves in by hand pressure. Then its a case of offering up the cladding and checking the hole positions and the curves. So it’s on and off like the proverbial yo-yo ( I know that’s up and down) until a good fit is obtained and the holes all lined up with a little bit if filing here and there.

Once happy with the fit the cladding is still a bit springy so once all the fixing screws were in place for the bottom part of the cladding I used a gentle flame to reduce the springiness and get the cladding to lay flat on the front of the block. Then fitted the remaining screws and also reduced the springing at the top curve.

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The fitted cladding

All fixing screws have washers and are small head 8 BA.

Once done the draincocks are fitted and secured in place with thread locker.

Before fitting them I painted the cladding. The brass was first etch primed followed by a grey primer. Then satin black top coat was applied. This is same process used for all other painted areas but this time a problem arose as the black wrinkled. So I rubbed the cladding down applied another coat of grey primer and tried again. It still wrinkled but not as much. A bit of research on the web provided advice that wrinkling is usually due to the underlying layers of paint still releasing solvent from the drying process. I had left 24 hrs between coates which I thought sufficent but obviously not. So I repeated the process leaving it longer and achieved a better result although there was some evidence of wrinkling but in areas that were not visible. I left it at that.

Another cladding task that can be done with progress as it is the cover around the steam pipe exiting from the smoke box.

An awkward shape to determin so a template was made from card.

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How to make the template though? Well I used plastacine. I moulded plastacine around the pipe and shaped it the smoke box and to give the angled shape down to the running board. With this mould to hand I carefully rolled the mould onto card tracing the line as I went.. The card was then cut and with a few minor adjustments to true it up on the job used to cut the brass sheet.

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The card was glued to the brass sheet to enable the sheet to be cut and filed to the card template and trial fitted as seen above.

Satisfied that the cover fitted OK the flanges were cut by marking the sheet from the now available cover and soft soldered in place.

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Soft solderinga flange in place

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The finished article.

The cover is held in place with three 12 BA cheese head screws tapped into the running board. There is no fixing to the smoke box.

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The finished fitted cover

Before finally fitting the cover the pipe was lagged with 1/8″ thick  sheet lagging wrapped around and a small bit of wool lagging needed around the steam oil lubrication non return valve.

Barrel and firebox cladding

One of the first things to sort out on the barrel cladding is where does the taper start and finish. The barrel has a taper from front to back rising towards the back. At the fire box the firebox wrapper then tapers back down to the cab. The taper is not great, about 1/2″. However it is not clear from where at the front the taper starts. The GA drawing shows it starting from the smokebox and indeed a copy of the works GA drawing which I have in reduced form appears to confirm this. However looking at othe models and pictures of the full size it would appear that the first part of the barrel up to the dome or just before is parallel.

The boiler design has the barrel stepped which provides a 1/2″ difference in diameters of the front of the barrel to the rear of the barrel. This is the reason for the taper.

Another factor to have in mind is the clearance between the running boards and the cladding, there is not a lot of room. Also my boiler manufacture has a strap over its rolled barrel join underneath which interferes with the cladding going underneath. The boiler supports have a gap to allow some insulation between the support and the boiler, but the cladding has to be cut out to clear them. (They are not really supporting the boiler!).

Lastly there is the small matter of how to support the cladding as there are no crinolin rings in the design.

After much thought and chats with a fellow club member that has an A1 to a different design, I am thinking to have the taper start at the third boiler band from the front which is before the dome. This will give a parallel section at the front which can be done in one piece. The tapered section can also be done in one piece, and then the fire box wrapper with its rather difficult mating with the throat plate cladding and boiler barell taper.

One thing that came to light from thinking about the cladding and eyeing up the position was that the dummy sandbox fillers are too close to the cladding, not by much, but they will have to be relocated once the cladding is fitted.

All that remains is then the backhead cladding. This has its own problems of how to mate it with the fire box wrapper and how to get a nice rounded finish to the edges.

As a piece of cladding I chose to make the backhead piece first.

This involves lots of cut outs to clear all the fittings and a paper pressing was used to make a former by rubbing a pencil around all the bosses etc. This paper former was then glued to the brass sheeting and the cutout outs drilled (with sheet cutters) or sawn in the case of the rectangular cut outs and firebox hole.

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Paper former for backhead stuck to brass sheet …fire hole door looks a bit wonky! Also the right hand blow down bush did not have enough paper! I did not have the paper square on the backhead when doing the rubbing.

When doing the cut outs I did them undersize initially and then with many fittings on and off the loco with adjustments made by filing or opening out holes either just on the diameter or moving them slightly one way or another the basic backhead was finally fitted around all the fittings.

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The basic backhead cladding ….. the outside edge still to be profiled

An update on the cladding thinking while I am awaiting some materials. I have a book on the Peppercorn A1’s by Peter Tuffrey which has photos and descriptions of, I think, all the A1’s built. Looking at those photos that have a resonable side elevation view it is clear to me that the boiler taper starts at the smoke box. So that settles my mind on how I will tackle the cladding on the barrel.

In order to stiffen up the backhead cladding and to provide a nice rounded edge to the firebox wrapper a 1/4″ dia anneald copper pipe was soft soldered to the periphery of the cladding.

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Soft soldering the copper pipe

I used the highest temperature soft solder I had which is 170 degrees melting point.

With the pipe in place the cladding was finished to size by cutting off the surplus sheet and then filing the joint to give a rounded edge.

The copper pipe also has affixed to it tabs which will be used to screw the firebox wrapper to. The tabs are set back on the pipe so the firebox wrapper abuts the pipe to give a smooth edge.

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The tabs were put on with a lower melting point solder, 140 degrees melting point, to avoid disturbing the joint to the cladding.

Behind the claadding goes the insulation and this was cut from 3mm ceramic blanket. The required holes were punched out and the other rectangular cut outs and fire hole door cut with a model knife.

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The insulation was trial fitted and then removed to fit inside the cladding piped frame.

The backhead cladding was then primed and painted with heat proof paint.

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In the picture above the cab floor and reversing stand are not yet in their fixed position but the blowdown valves have been fitted.

Also in the picture can be seen cork bands around the barrel and firebox. As there as no crinolin rings as on the full size the cork bands act as a reasonably firm support for the cladding. The cork is under each of the boiler band positions.

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The cork bands are built up to the required thickness, they are glued in place with superglue, and then sanded down to match the required taper for the front barrel and rear firebox.

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The first bit of cladding being trial fitted.

The cladding is made from 27g brass sheet that I was able to source in 1 x 0.5 mtr size. It has a protective film on one side in green as can be seen. 27g is nice and flexible but also sufficiently strong so as take the rolling and be quite rigid in its rolled form.

Boiler inspection plates

On the cladding there are six inspection plates that need to be mimiced. There is no drawing for them so I had to make my own design by looking at fullsize pictures. There are three to mount on the rear firebox section and three on the section of cladding immediately in front of it.

I judged them to be about 5/8″ in diameter with a tapered side and having a bar and bolt holding them in place. In order for them to be clear of the boiler the depth could only be 0.140″ When fitted they would be soft soldered in place.

To make them I used 5/8″ dia. brass and turned down a 0.140 length to 1.2″ dia and then parted off to give a 1/32″ lip.The item was then reversed in the chuck and counter bored with a 1/4″ slot drill for 5/32″ and with a 3/8″ endmill ground with a 20 degree angle bored again to give the finished shape of a tapered side. Finally a 10 BA clearance hole was drilled in the centre.

To mimic the bar and bolt a piece of 16g brass was cut 5/16″ long by 3/32″ deep with a 10 BA clearance hole in the centre. A 10 BA c/s screw was then inserted from behind the plate to hold the bar in place with a nut.

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The finished inspection plate.

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trial fit

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Three fitted inspection plates

In the above photo the cover that fits over the reversing rod is marked out. The full size cover has very many fixing bolts along its top and bottom. I intend to use 10 BA fixings by soft soldering nuts on the inside of the cladding but only every other fixing position, the inbetween ones being dummy.

In case anyone wonders why I have a +3/8 taper note at the bottom of the cladding its because I cut the cladding square and forgot about the taper of the boiler. I will add a piece on the bottom which will cover that small bit of cork that can be seen which is just above the bottom of where the taper should start.