Gas fired engines

[HopperParticipant @hopper]

Posted by phillip gardiner on 20/03/2023 21:26:54:

Converting model locomotives to run on propane is really not that difficult all i changed was remove the grate and ash pan and replaced them with the burners fitted in the old ash pan ,i did not change anything in the smokebox . The gas lines were made large enough so you do not get freezing of the pipes , this system is used in the USA they seem to be less regulated than us and they have massive burners in there settups.

Yes the Yanks tend to go on and get stuff done while the rest of us are still discussing why it could not be done and then making red tape to prevent it as much as possible. There is a lot to be said for their "can do" mindset.

[noel shelleyParticipant @noelshelley55608]

Duncan, Gas Turbines – Kurt Schrecklings book on the subject tells how it's done and how to do it ! In small scale. Noel

[Nick Clarke 3Participant @nickclarke3]

In the 11/9/1958 edition of ME there is a design for a 5” gauge water tube boiler that it is suggested could work with the ‘tube with slits’ type of burner described above.

Food for thought?

Perhaps best redesign the asbestos lining to the casing though!

Edited By Nick Clarke 3 on 21/03/2023 15:11:57

[duncan webster 1Participant @duncanwebster1]

I've sent a pm to NC3 but no response. Anyone else got a copy of the article referred to above?

Noel, is this the book to which you refer?

[noel shelleyParticipant @noelshelley55608]

yes Duncan it is ! An interesting read. Noel

[duncan webster 1Participant @duncanwebster1]

Oh dear, hand in pocket time again. Fortunately it's my birthday soon.

[Nigel Graham 2Participant @nigelgraham2]

There seem two threads on one here, and neither are BSP.

One about burner design, the other on tests and certificates. I don't know gas-burner design, but it does seem well covered above.

The matter of insurance seems to have elicited misunderstandings, though. In the UK, club insurance normally relies on following the MELG system, whose requirements for gas-firing cover gas-tanks below 250ml capacity and made specifically for the models. It does not cover the fittings, pipes and burners – though obviously it would be sensible to bubble-test them for leaks while you are at it.

There is no "insurance" reason for not gas-firing locomotives in scales larger than the "garden gauges"; or equivalent road-steam and stationary-engine miniatures.

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Nothing to do with Gas Safe, either. Those cover building installations – and most Gas Safe registrees are trained in mains gas to homes, but less likely also to hold the separate approval for LPG installations, such as serving a house from a big tank. (You can't blame them – few would need it anyway, but despite many overlapping areas the Powers-That-Be decreed accreditation for either type of gas supply needs a separate course, which is very costly for self-employed gas-fitters by the course fees plus the week's lost earnings.)

The objections against gas-firing locomotives of 3.5" and larger gauges, would be technical ones and most are covered by other contributors here. In short:

– The likely fuel consumption may entail a regular gas cylinder and regulator that can only be hidden in a driving-trolley, not a scale tender.

– The cylinder may have to be upright, not on its side.

– Simply raising steam from cold, and maintaining pressure between runs, would use a lot of the gas available.

– The burner would need be designed for the task, especially in a boiler designed for burning coal.

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The MELG scheme covers only specially-constructed LPG tanks, own-made or bought as part of commercially-built locomotives, up to 250ml volume and refilled from standard cartridges such as you'd buy for a blowlamp. It explains that non-refillable cartridges used directly are neither tested nor banned; but does not say anything about the larger, standard, refillable cylinders of the types exchanged in a caravan-site shop.

The Boiler Test Code 2018 (orange print on white covers; the only edition to be used at present) probably assumes only small models with little tanks refilled from blowlamp cartridges. It does not say we cannot use such cartridges directly. It does not say we cannot gas-fire bigger engines from standard, exchangeable, trade-refilled cylinders.

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Finally it is not a matter of "club rules". If your club is affiliated to the MELG (via its own federal body), its Club Rule is simple: test boilers and gas-tanks to the current MELG rules, instructions and certificates. Not to some local idea of dubious provenance or use.

A boiler inspector can decline to test a boiler he or she feels beyond personal knowledge, and the book covers this diplomatic problem; but deviating from the regulations may take the lid off a big tin of wriggly Lumbricidae.

– Weakening or changing the requirements may invalidate the test hence the club's insurance – potentially a very serious matter even if some claim has nothing to do with boilers.

– On the other hand, gold-plating with invented "extras" or specious refusals is likely only to give your club very aggrieved owners unable to run perfectly sound models; and that could harm the club's reputation.

(Specious: Known boiler-test refusal "reasons" have included thicker (not thinner!) firebox plate, a rocking-grate, and feed check-valve locations differing from original drawing!)

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