|31 forum posts|
by scrollin through the web i've found partly build Britannia locomotive, 3.5" gauge, that was described in Model Engineer magazine. I believe in volumes 104 to 109. I've seen a few different builds of 3.5" Britannia locos and couple of things catched my attention: the boiler, regulator valve, superheater. The one i'm talkig about is here:
And it doesn't have holes on the top for the water feed valve like in this example the holes are marked 1 & 2 below:
And it doesn't have the element protruding from the boiler (RH side) - number 3 above. This element looks like a support/pivot for the linkage of the steam regulator valve located in the "cube" in front of the smokebox - number 4. Not mentioning about superheater (for sets of superheating pipes).
However in the loco in question (first two photos) the boiler is different, not many bushings for valves, etc. in the cabin. And boiler back head arrangement:
I found another example of Britannia in 3.5" gauge and here:
In the above example the superheater is simpler and there is no regulator valve in the smokebox. Boiler arrangement in the cabin is even more different. I'm confused. Were there different options described in Model Engineer magazine?
Another question: the offered boiler is naked: no fire door mounting holes, no regulator handle support holes and as per description it was proffesionally made, tested and have all the papers (though outdated). Does it mean it has to be drilled to mount all the necessary stuff? What about the certificate then? Is it normal practice that the boiler ws tested, certified and the some new holes are made? Much confused:/
Please share you thoughs on that. Is it worth to thing about that project?
|Paul Kemp||06/06/2020 21:03:32|
|485 forum posts|
with respect to a commercial boiler it will come with a shell test certificate only. This a 2x WP test to verify the basic structural integrity. Later when incorporated into a model it needs a 1.5 X WP test to verify any mods done to mount it and then a steam test verifying the safety valves do not allow more than 10% accumulation. So full boiler certification is a 3 stage process.
It is not unusual (take traction engines for example) where a number of holes need to be drilled in a commercially supplied boiler for cylinder studs, steam uptake etc. It will be up to the inspector taking the certification forward to judge if any of the work carried out since supply constitutes a material or significant structural change, in which case an additional 2 X WP pressure test will be required.
Hope that makes sense!
All the best,
|31 forum posts|
Paul, this is now clear. Much appreciated
At this point i think that any addition/modification to the boiler that require silver soldering, meaning high temperature treatment - is a real problem. I've read about "chasing the leaks" after subsequent silver soldering (in case of repairs or mods). So if any bushings are to be added it impose a problem. I can't see the place for regulator valve as well. Apparently, as i said earlier, there were two designs: main one is the smokebox mounted regulator valve block, and alternative design: internal regulator with the bushing and glad on the back head. I found this info here:
Boiler construction started in volume 107:
"Smokebox Regulator. Superheater, distance-piece, regulator block, details of regulator, poppet valves, regulator shaft, bottom cover, how to assemble the regulator, erection "
" Alternative Regulator of the Slide-Valve Type. Distance pieces, regulator body and valve, operating gear, how to assemble and erect, regulator rod and backhead gland "
Is the thing at the bottom left of the photo below a part of the regulator of the first type (smokebox mounted)?
The steel shaft looks like "regulator shaft" however the rest is mystery for me... It just doesn't much with the arrangemens i've seen on the internet.
Anyone have these ME volumes 107 and 108 for reference?
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