Re: starting a steam loco

Andrew Robert Breen wrote:
In article <e07189da1570c5123160b2022bb00f91@xxxxxxxxxxxxxxxxxxxxxxx>,
Roger T. <rogertra@xxxxxxxxxxxxxxxxx> wrote:
get a steam loco to start moving if the piston is left in the top dead
centre position.

paul the pedant

No such thing as "TDC" in steam locomotive.

Catch Me Who Can?

Single vertical cylinder..

Not to mention the locomotive used at Penydarran, which had a single horizontal cylinder and large flywheel. That said, both of these machines probably count as "experimental". Certainly for static applications, the single cylinder seems to have generally been regarded as reasonable.

I was fascinated to visit the Kew museum, and later the Crofton pumping station on the Kennet and Avon Cannal, both of which operate early beam engines (in both cases they have, amongst more modern machines, Boulton and Watt engines, converted to work on a positive pressure cycle). It is interesting to watch the starting proceedure for these engines, as the driver has to work the valve gear by hand until sufficient condenser vacuum can be established for automatic running. What I could not fathom is how a purely "atmospheric" engine would have been started, the engines I saw seemed to rely on the positive steam pressure for the first couple of strokes, in order to get steam into the condenser and so build up a condenser vacuum. Perhaps some sort of starting valve to admit live steam directly to the condenser? An interesting feature of watching these engines work is that it gave insight into the reason that my thermodynamics lecturers always described "work" as "something that could be used to lift a weight", as the workign strokes of these engines lift a large weight, which then descends, doing the work on the load (pumping in this case). Thermodynamics - the science invented to explain why steam engines work.

Robin
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