Loco boiler pressure

[Martin Murray 2Participant @martinmurray2]

Hello I would appreciate your experience. I want to build a garden track 31/2" to run a couple of loco,s- one a tank loco and the other a tender loco- I am not into passenger hauling but building a realistic scenic set. This means the locomotive will run light with very little load as the trucks are no weight at all. My question is — given that the loco is well maintained what boiler pressure would be required to set and keep the loco in motion. Track will be virtually level– the only resistance will be basically the weight of the engine and the friction against the track. Depending on the pressure required will govern the boiler parameters -have two chassis minus boilers and would get or construct boilers to suit. I thought of converting them to an electric set up but steam would be more realistic.

[Martin Murray 2Participant @martinmurray2]

[Neil WyattModerator @neilwyatt]

Hi Martin,

I'm not sure you would gain much by designing a lower pressure boiler, except perhaps a few £s by being able to use a thinner boiler shell.

I would just use standard boilers as one day someone else will own them, and (1) you don't want them to have an accident and (2) locos capable of running at normal pressures and therefore hauling someone will have greater value.

Neil

[IanTParticipant @iant]

Hi Martin,

In Gauge '3' (2.5" at 1:22.6) I would say that most live steam engines are run at around 80psi even though they are being used in a "scenic" setting (e.g. not passenger hauling). You could most certainly run a steam engine at a lower pressure and there might be reasons to do so in G3, one of which would be the 3 bar/litre boundary.

Essentially the boiler test certificate requirements (required at G3 GTGs and at any MES Rally) are less onerous if the boiler is <3BL. The bar/litre is a combination of the total water capacity of the boiler x the normal operating pressure, so reducing the operating pressure can bring some engines below this 3B/L boundary (at least in G3).

However, assuming you will be running on your own track – formal boiler testing may not be an immediate concern for you, although I would still recommend you familiarise yourself with the general requirements and make your own safety checks. You can find more info at the Southern Fed website.

Overall though, I think Neil probably has the best advice for you.

Get the boiler built as originally specified for the engine design (again assuming they have been built to an existing design – LBSC/Evans etc.) and run it at the recommended pressure. If you have a boiler built for you make sure you get the maker to provide you with a hydraulic shell test certificate too. You are going to either spend quite a lot of time building these boilers/engines yourself – or paying someone else (a lot) to do it for you. So it makes sense to end up with an engine/boiler combination that is saleable for a fair price should the need arise.

Regards,

 

IanT

Edited By IanT on 11/03/2015 11:26:22

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