jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on May 1, 2016 22:15:56 GMT
Hi Alan,
Thank you for the further details.
I must admit I am rather at a loss to provide a solution without examining the pump myself.
Thay are not difficult to make.
John has made hundreds if not thousands!
As you have examined the seatings carefully and tested the pump off the loco I can only assume there is a problem with the eccentric rod length, though you did not provide ball lift figures that I requested.
Cheers, Julian
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Post by steamingmess on May 1, 2016 22:17:47 GMT
Hi Alan. You could always bring it to the island when your next over and could have a look at it at work. Dan
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johnthepump
Part of the e-furniture
Building 7 1/4"G Edward Thomas
Posts: 494
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Post by johnthepump on May 6, 2016 21:10:19 GMT
Alan's axle pump made it to the Pumphouse last Tuesday evening. Dan did the honours with the transport. I had set up my Sweet pea across two benches and connected up to the airline which is set below the working pressure of the Loco. I had fitted the little test point Tee piece in the delivery line just by the by pass valve. With the saddle tank full of water and an old 2 1/2" pressure gauge fitted to the test point. I was able to demonstrate that with the engine running that the pump was able to deliver into the boiler, the water level in the top of the tank went down rapidly, all the time the test point pressure was just above boiler pressure. The bypass valve was slowly opened thus making the pump inefficient, it was interesting to see the metering effect that the bypass can achieve. So onto Alan's pump, we found severe restrictions in the inlet and outlet valve chambers. To stop the ball rising and blocking the inlet to the pump chamber a cross pin is fitted, in this case the pin almost blocked the hole, this was opened up using a needle file. When we made pumps at Aptule works, instead of the pin, a clearance cross was pressed in, similar to the crossing milled into the delivery part, speaking of which on this pump they where minute, these were open up on the mill. The pump was hand tested on my pressure test rig and even when moving the ram as little as a quarter of an inch stroke in made plenty of pressure. I hope to hear from Alan when he has the pump refitted.
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Post by newington on May 10, 2016 10:07:00 GMT
John, Refitted the water pump and took it to the track last Friday night. Steamed up and went for a run. The pump just managed to maintain the water level in the bottom of the sight glass. I did not set off with a 3/4 full glass like would normally do as I wanted to see if the water would rise. I came back with roughly what I started , I would have expected it to be much higher. Withdrew the fire a discovered a leaking boiler seam right in the top of the marine firebox. I guess that did not help with the water level! Must thank John and Dan for a very interesting evening and Johns explanation of what was wrong with the pump was most enlightening. Alan
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johnthepump
Part of the e-furniture
Building 7 1/4"G Edward Thomas
Posts: 494
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Post by johnthepump on May 10, 2016 13:17:54 GMT
Hi Alan, Two Sweet pea's ran at Broadfields on Saturday afternoon for 3 hours along with a Simplex & a GWR Pannier tank. My Sweet pea did a couple of laps with the test point pressure gauge fitted, this demonstrated the control that the bypass valve has on the feed. The gauge was removed when one of the others stopped for water. As the Secretary's son was looking bored I put a trolley on behind the driving truck and let him drive for over an hour while I rode behind, he managed the loco well. We used the axle pump to keep the water level, The pump can supply more than is required by a little. My colleague had a 1/2" ram on his pump but had to reduce it to 7/16" as he found it drowned the boiler. If you feel your pump is still lacking don't hesitate to bring it back and I will remake the valve chambers with better clearances. Regards John.
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Post by newington on May 10, 2016 17:24:19 GMT
John, That's very kind. I think I need to sort this boiler leak out before I can really say if the pump is up to it or not.Maybe I should start a new thread about how to repair this leak. Back to work now so hobby to the back seat!
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Post by doubletop on May 11, 2016 5:44:20 GMT
Maybe the pump needs some load for it to function. It may well have been suggested already but when I test pumps I run them on a length of pipe on the outlet through a safety valve set to the max boiler pressure. Then at least the pump is working against a typical load and any leaks will be obvious. If the loco is run on air it won't need full boiler pressure to get the pump working. A bucket of water at the inlet and the safety in another container and some idea of the throughput can be obtained.
Pete
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