Freelance 3/4” traction engine

[Team ricky]

Hi all,

Here’s an interesting project part built and re-built !!

I do want to make a traction engine but at a cost I can do !
Brought partbuilt here’s the good :

Rear wheel rims ready for spokes
Main cab all built minus a water tank
Boiler parts individually ok
Parts made so far are scale
Several valves were made to a good standard

Bad bits :

The boiler was lashed up with soft solder and the front of the throat plate was slot milled to clear the horn plates and was very dangerous indeed….

No plans or drawings

No engine castings No n this scale available

So the way I’m tackling this is to come up with a sensible spec, stick to it , discard any bad bits and do over!

Silver solder the boiler

My spec as I see it going in is:

3/4” scale parts only
Engine casting set is from a Revees Trojan
Silver soldered boiler
Gas or meths (I thought about coal )
Engine reverse gear
Simple 1 speed gears with a neutral setting
Traditional crank and rods
Water pump (either axle or manual


I think so far I’m on the right track…

I have fully stripped the boiler and removed all traces of soft solder (big job)
And silver soldered the bushes back in and fire hole , Hopefully more pics soon

[propforward]

Heck of a project - look forward to seeing it take shape. Sounds like a readonable recovery plan - would be wise to cross reference the boiler to an established design, or else go through the design against a model boiler design reference and check to make sure it’s up to the task. Not knowing your background I don’t know how comfortable you are with either approach. Assuming you are in the UK it would be wise to engage the help of a model engineering club before you go far, as I think you’ll need to have it inspected in some manner if you wish to show it.

[Jasonb]

Rather than a freelance the tender/hornplates you show suggest it is built to or very closely base on the design "Modular" that was published in Model Engineer Magazine in the early 80s

With the cylinder, valve gear and crank on it's own platform it could be removed from the traction engine and used as a stand alone steam engine hence the name "Modular"

[Team ricky]

Small world !!

Yes I think you are onto something there…. The give away is the two entrance cut outs and the steam turret design… both features I have matching the one picture on the net !


I wonder what overall design/type I should go for ? Manufacturer’s?

I’m pretty sure I’m just going off piste with this one and probably will enjoy that alot more than hunting/following drawings- Famous last words !

I did forget to picture the smoke box end and chimney as they are complete

[Team ricky]

As for the boiler …..

A drawing for that would go a long way , However I’m pretty confident it’s to a general design up to this point and research and books I’ve brought pretty much show the overall design is sound just the soldering was terrible!!

The boiler design is a wet back front sides like a larger scale would be, Therfore stays will added which are not drilled for yet as you would expect, the doubler I’ve added allows for the fire box sides to be extended as normal- this will get fixture rivets for soldering.. I also extended the doubler to fix the mill slot a rank amateur did , Very dangerous as it was ….

I’m going for 80psi test and 30 psi on the relief valve , If it fails I’ll do what’s needed to fix or make a new one which isn’t too tricky looking at the build so far..

[propforward]

Good deal. Hope to see pics of it at some point. 👍👍

[Jasonb]

General arrangement and boiler.

There is mention of testing to 150psi so that would suggest a working pressure of 75psi.

[Team ricky]

Brilliant find thanks !!

Looks like the same design as my parts would suggest

16g copper throughout

Same fire box design

Only big question I have is it shows no stays….
Would not be detrimental to add and at those pressures mad not to …!

I’m definitely not going over 100 psi test 40 psi WP , that’s a good amount of power especially with the low gearing traction engines run !

[Team ricky]

A little soldier done ✅

I made up the crown sheet and soldered the tubes to the fire box and the front half of the crown sheet,

All went well but borderline on heat so I’ve ordered a 30 jet torch to finish the boiler ,

Offering up the parts inside the shell it all looks good and on drawing, To finish the fire box I will solder inside joints too just before soldering the fire box in the shell!

One other feature missing is the crown sheet gussets….. I don’t think it’s necessary but maybe at the higher pressures mentioned…

[Jasonb]

I think as the crown is arched rather than flat you should be OK without staying that.

Text does mention that it is about on the borderline for needing stays to the firebox but designer felt that provided you stuck with 16swg it was OK.

[Team ricky]

Interesting…..

I guess heat cycle the fresh made boiler before pressing test to harden the copper to nominal (half annealed) is a must

And I guess two stays per flat side would not hurt ?? Or just reduce the pressure to be on the safe side …. Many options all I think are ok

[Team ricky]

Here’s a bit more done ✅

Cylinder bored
Ported
Valve face lapped in

I’ve gone for 1/2” bore 3/4” stroke and the piston will be 8mm deep/thick

That’s pretty much the same as the Basset and lowke 3/4”

[propforward]

Interesting…..

I guess heat cycle the fresh made boiler before pressing test to harden the copper to nominal (half annealed) is a must

And I guess two stays per flat side would not hurt ?? Or just reduce the pressure to be on the safe side …. Many options all I think are ok

What heat cycling will you do that will harden copper? I know there are some exotic copper alloys around but I wouldn’t think you have one of those here. Copper can be work hardened but when heated enough it anneals. Heating it to anywhere below its annealing temperature is not going to harden it.

I know that some of the actual alloys like Cr-Cu, some bronzes, probably Be-Cu and I expect brasses (some of them maybe - haven't checked) among others can be precipitation hardened, and that there are heat and quench cycles for hardening (some of) them. Do you have one of those? (Unlikely - readily available copper sheet is just high purity copper around 99.9% or so depending on which one you have). If it’s just one of the high purity coppers then I am pretty sure it won’t be hardened by heating, quenched or otherwise. I did read something once about bulk oxidation of copper for hardness - but it also embrittles the material. Not good for boilers.

Reducing pressure / adding stays makes sense if the design is “close to the edge” which is never a good place to be with a boiler or pressure vessel.

[crueby]

Heat cycling will not harden copper or brass, it will only be hardened by working it.

[propforward]

As usual I dive in too deep and start thinking about all the exotic materials, none of which apply. They are all very fun to work with, though, by the way. Thanks, Chris, for the succinct answer.