Engines > Restoration of Model Engines

Completion of Allchin Traction Engine (hopefully)

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Twizseven:
I have obtained a partially built Allchin 1 1/2" traction engine.  This was started around 50 years ago by the grandfather of one of the ladies who lives in my village.

Current status:
All wheels built and assembled
Hornplates and tender all complete
All axles and bearings complete
Water pump complete
All gears complete
Crankshaft,flywheel, conrod and all eccentrics complete
Steering complete
Smokebox and door complete along with chimney apart from top ring.
Front axle, turntable, spudpan complete
Basic boiler complete but currently missing the side and front/rear stays.

Wheels and tender/hornplates and flywheel all painted but need stripping and repainting


50 years of dirt and very light rust to be removed from all parts.

This is going to be a long job, I guess over several years.  The final outcome really depends on the boiler

I have all the castings needed to complete other than the cylinder casting set, lubricator platform, cast grate and chimney top.

When I first saw it I was surprised to see the foundation ring all soldered up but no side and front/rear stays fitted.  Since reading the book and copies of Model Engineer from 1957 I see that this was the sequence recommended to follow.

The boiler is currently just loosely held in by the steering rack.  When i have it removed the first intention is to give it a good soak in citric acid to clean it up and check what threads have been done already.  Will then make suitable blanking plugs and get boiler low pressure tested by my clubs boiler testers.  What sort of pressure would you suggest.  This test will give me some indication as to how well the boiler has been built.  Looking at the quality of the work on the rest of the components my guess is that it will be perfectly okay.  If they are happy with the boiler I will continue with the work that remains on it.  This leads me on to several questions.

1.  The book suggests either soft soldering the stays or silver soldering them.  I would have thought silver solder but would like peoples thoughts. Personally I cannot see how soft solder does not melt when boiler is fired.

2.  The book says the stays can be copper or bronze, with bronze being the better option.  I see that there are various grades of bronze (depending on whether the copper is alloyed with tin, lead, aluminium, etc.)  What grade should I use, does it make a difference?

3. The stays are all threaded.  I  guess it is going to be easier to do these in four goes, side 1, side 2, front, back.  I have only ever silver soldered the crank for the Redwing I recently built so am not experienced with this this level of soldering.  All advice accepted.

Help.  Have I bitten off more than I can chew.

Merry Christmas to all,

Colin

redhouseluv:
Ah yes, soldering, I have only just succeeded in silver soldering some fittings last weekend with a lot of assistance from forum members. Sounds like you have some experience if you soldered a crank, but appreaciate this is a bigger task.

Good luck with your build and it's nice to think that after 50 years it may be finally completed - I'll be following along  :ThumbsUp:

Jasonb:
Probably best to clean up the boiler and then take it to whoever is likely to test it for their opinion. They will have the last says you whatever methods you use to complete it should be what they will approve. Although it is a heritage design methods have moved on and most new boilers have plain stays soldered in not threaded and caulked.

If you have only done a crank then get some more practice in with the various fabricated parts before tackling a boiler of this size and complexity.

If it is only going to be a show piece run on air then that is a different matter.

Twizseven:
Jason,
Yes my boiler inspectors will have a look.  I would like to run it on steam.
The book and magazine articles both have the stays soldered, either soft or silver.  I would have thought that silver soldered would be better.
Colin

internal_fire:

--- Quote from: Twizseven on December 17, 2024, 07:12:58 PM ---Personally I cannot see how soft solder does not melt when boiler is fired.

--- End quote ---

Soft solder melting temperature is considerably higher than the temperature of the water in the boiler, at least for "ordinary" solder and typical boiler pressures. Even though there is no water in the firebox (we hope!) the copper is so conductive that its temperature remains close to the water temperature outside the firebox.

If the water level gets too low on the crownsheet, for example, the soft solder will melt. This effect can be used as a safety device to make a fusable plug to prevent major damage if the water gets too low.

Gene

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