Dog Star
Western Thunderer
No.... because I cannot clarify the vacuum pump on this loco (or the 1361 class) for myself. I shall try to explain in a day or so.
simond
Western Thunderer
Chris, Graham,
thanks both.
The “pot” on the most recent photos is in the same place as the curiously shaped pot on Dave’s earlier post, but is a different shape. I’m going to have a look through my books and see if I can find out more. Might get a chance tomorrow evening.
atb
Simon
thanks both.
The “pot” on the most recent photos is in the same place as the curiously shaped pot on Dave’s earlier post, but is a different shape. I’m going to have a look through my books and see if I can find out more. Might get a chance tomorrow evening.
atb
Simon
Dog Star
Western Thunderer
Simon,
This link... GWR locomotive lubrication in the 1930's | Model Engineering Clearing House ... includes a decent photo of a pepper pot, also known as a vacuum relief valve; there is going to be one of those in the vacuum system somewhere. Until I started looking for the pepper pot on a 1366 class I believed that the valve was screwed into the top of the vacuum pump.... I cannot see it in any photos of either 1361 or 1366 class locos.
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Rgds, Graham
This link... GWR locomotive lubrication in the 1930's | Model Engineering Clearing House ... includes a decent photo of a pepper pot, also known as a vacuum relief valve; there is going to be one of those in the vacuum system somewhere. Until I started looking for the pepper pot on a 1366 class I believed that the valve was screwed into the top of the vacuum pump.... I cannot see it in any photos of either 1361 or 1366 class locos.
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Rgds, Graham
James Spooner
Western Thunderer
Hi Simon,
Just had a quick look on Google and came across the attached, which, towards the bottom, has a sectioned drawing of a GW vacuum pump. One of the three pots on top is a vacuum relief valve.
cheers
Nigel
Just had a quick look on Google and came across the attached, which, towards the bottom, has a sectioned drawing of a GW vacuum pump. One of the three pots on top is a vacuum relief valve.
cheers
Nigel
Pencarrow
Western Thunderer
I should have added that both photo snips are preservation era.
Many thanks for that - it is a brilliant resource (particularly GWR Mechanical Institute Papers - K&ESR Virtual Mutual Improvement Class) The papers listed there by some real experts of their day are a real goldmine and the provide a real insight into what was really going on - and not only on the GW. I cannot understand how I missed it until now!
simond
Western Thunderer
Thanks Graham,
my understanding of that vacuum relief valve is that it is in the steam circuit to prevent the ingress of cinders etc through the blastpipe by the avoidance of a vacuum in the live steam supply when the regulator is closed. I'd have called it a snifting valve, but I rather thought they were much bigger - perhaps this one is used on the ejector supply? It looks rather like the valves that are fitted fore and aft on all standard GW cylinder end plates, which I took to be overpressure relief valves - if that is the case, it will make the engine rather freer running with regulator closed.
Putting one of these into the vacuum pipework would break the vacuum, as it allows air in through the holes in the cover, and the pressure differential across the valve head (which is hidden) pulls the valve open against the spring. This would not be helpful and I don't think it belongs on the vac pump.
We want something like this - the "bicycle dynamo" which is definitely a lubricator.
cropped from Dave's photo
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