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Post by tdaharvey on Oct 2, 2020 21:27:30 GMT
I am working on a part completed 3 1/2 Britannia and have bought the Kennion drawings to aid completion. In the drawings piping schematic it shows a hand pump feed and reference to a back head clack valve but elsewhere there is a schematic of the backhead with no clack valve. The loco came with a finished tender which does not have a hand pump. Also the boiler does not have a union for a clack valve on the backhead which is consistent with the drawings. So it would appear I have an engine which was not planned to have a hand pump and there may be a inconsistency in the drawings???
I want to add a hand pump and am thinking that I can feed water through the axle pumps to the boiler fead clack valve on the boiler barrel with suitable clack valves on the axle pump feed to support parrallel water sources. I am just wondering if I am missing something about the Kennion drawings and also if my plan for a manual water pump configuration / boiler injection sound reasonable?
Any advice is welcome.
regards
Trevor
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Post by dhamblin on Oct 8, 2020 21:35:07 GMT
Hi Trevor,
My Granddad's Britannia has a hand pump in the tender and feeds through a backhead clack as per LBSC's design.
The clack bush should be to the right of the firehole, towards the outer wrapper.
You might have more luck with this question in the General section of the forum as this bit is aimed at the 5" gauge kit builders.
Regards,
Dan
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Post by tdaharvey on Oct 11, 2020 10:00:26 GMT
Hi Dan, thanks for responding.
I have been looking at your posts about your grandad's engine rebuild. I see the clack you are talking about on the photo showing the cab layout, mine doesn't have this clack. It has the blower union, a smaller union probably 1/4" just to the right of it (both top right near the wrapper) for the pressure gauge and of course the two for the water guage. The tender is finished and without a pump, the boiler professionally made so I guess it was specified that way and there was no intention to provide a manual water pump.
I am not particularly happy to rely on a single steam injector for water refilling. I suppose I could fit two injectors or In theory a hand pump and run it in parallel with the axle pump to one of the boiler barrel mounted clacks.
Kind regards
Trevor
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Post by dhamblin on Oct 11, 2020 10:25:31 GMT
Perhaps that is what the original builder intended, although the lack of hand pump in the tender is strange and makes me wonder how they intended to fill the boiler ready to light up.
The idea of using the axle pump clack as a dual feed for hand pump and axle pump should work. In theory it is better for the boiler because if you have to resort to the hand pump while running this means cold water is being injected into the less sensitive barrel rather than the hot firebox water jacket.
Looking at the layouts the axle pump top ball should remain seated if the hand pump supply is fed in between the axle pump and boiler feed clack. The hand pump feed clack (mounted on drag beam) will help reduce the risk of back feeding anyway, but a further one nearer the join shouldn't do any harm. There are though many more people on this forum with better expertise on the subject!
Regards,
Dan
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