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There is no reason for a boiler inspector to reject thicker-walled tube or firebox plates for the same designed working-pressure, if that overcomes material-availability problems. (Using thinner than specified would obviously be a no-no, at least not without careful analysis proving no significant reduction in safety.)

Beware though – although thicker-walled tube would take higher internal pressure, it is not a reason for raising the working pressure for a particular boiler, without reviewing the entire design to assess that proposal.

Such changes might need dimensional revisions elsewhere on a traction-engine, as the boiler is also the engine-frame, transmission-casing and vehicle chassis – but note my point above about strength. The boiler on a loco and many steam-wagons is supported individually on a separate, strong chassis; but a TE boiler is the chassis, and subject to large bending-stresses.

Separating the feeds from the manifold and putting their bronze or gun-metal bushes in the normal places in the barrel, should please rather than upset a boiler inspector, too.

Whether as Jason says, the Julius design is not mechanically practical, is another matter, but his questioning its boiler design having ever been "approved" is interesting. Outside of the requirements placed on commercial boiler-makers, have any of even our best-known and long-standing, published designs been "approved"? I would say so, but by accumulated experience and proven repeatability.

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The imperial 2.5" tube which is the correct size for the imperial 1" minnie is available from most of the usual ME suppliers. Julius design for the metric one had a stock metric size picked off a chart somewhere with little thought to availability as table Y is not used that much.

Has anyone been able to find a working pressure specified anywhere on Julius' drawings?

As I said in my first reply I don't know if any boilers made to the metric design have been made and presented to a boiler inspector, it is in effect a new design yet with not even a working pressure on the drawings it's hard to say what it's design is to be tested to. So anyone contemplating this design should seek the advice of their inspector before buying metal.

I don't think many UK inspectors would take too kindly to the stainless steel spacers used for the firebox stays and the threaded firebox stay method is dated now, the bolts shown retaining the cylinder are an impossibility, etc

Gear sizes are also seem interesting being a rounded up metric PCD and OD of DP sizes rather than converted to MOD1.25 and if you bend all the rear spokes the same as shown you will get a nasty looking wheel as can be seen in the GA drawings.

Edited By JasonB on 25/12/2020 20:51:55

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Hello you can please your self .just as long as you are happy with the hydraulic test you will be fine.Its hardly likely you are going to be using it for public use is it ? There’s to many experts !who worry about everything. It’s just a metric version of the original and yes I do know what I’m talking about have built a Minne as well as 6 loco boilers (southern fed tested ) and at least 50 simple pot boilers . The only reason to get a certificate is if you want to sell it puts your profit up !