Axle pump clacks - what am I doing wrong...

[JonL]

I've got some issues with my axle pump, it's a long story, so those with a short attention span skip ahead....

1. On the track I found the pump was squirting water out of the rear tank overflow, almost looking like it was running in reverse. I've stripped the water pump down and found the balls were grotty. I've since replaced them and buffed them to freshly cut seats. I should state it worked well at first.

2. On rebuild I've found its still happening on the bench. I've double checked and the pump balls are piped up in the correct sense, but still I'm getting back flow with no water going into the boiler. I don't think it's draining the boiler, I suspect its sucking water in and then sucking it back out the way it came.

3. In desperation I fitted a commercially made one way (clack style ball bearing style) valve to the inlet, figuring even if the output valve from the pump wasn't seating I've still got the boiler clack in place (which seams to hold steam pressure very well). The result is still the same, but I suspect the commercially made clack doesn't seal very quickly so is barely getting time to seat before its under suction again.

I'm feeling like a real simpleton, what am I missing? Making the rather large assumption that all the one way valves are now working on my pump I've got two on the inlet, two on the outlet and it still doesn't pump in the right direction! I've checked and checked again, the valves are fitted in the correct sense. 

As another point the axle pump spat out its seals as a result of this abuse, so I am waiting on fresh material for those.

As I type this one thing springs to mind, could the boiler entry clack be stuck shut?

Thanks to any that assist with a problem that I suspect will turn out to be a real clanger....

[cplmickey]

The one thing you haven't mentioned is the bypass valve. It sounds to me like it's fully open so allowing the pump to return water to the bypass rather than the boiler. If you close the bypass valve it should stop water going to the bypass so the only other place it can go is the boiler. Hope that helps. Ian

[JonL]

I have tried the bypass both open and shut, and water seems to squirt back into the tank in a hit or miss fashion, it sometimes takes a few revolutions to get going then squirts water back to the tank fine. I think tomorrow after work I might investigate the final valve into the boiler. This all helps, thanks for your assistance, I appreciate it. Helps get the little grey cells going!

[manofkent]

Hi.
I had this problem once - a piece of gunk (presumably from the axle pump) had got lodged in the bypass valve so it couldn't be closed. It was a small , tiny, bit of stuff which I didn't notice for a long time.
I cleaned out the bypass and hey presto all worked again.

Worth a try.

John

[smallbrother]

Maybe see if the axle pump fills the boiler when cold. Close the bypass and run the loco back and fore for a minute. Open the blowdown valve and see if any water got in. At least you would know the water is moving in the right direction.

Apologies if you have done this already.

Pete.

[Roger]

I'm not sure what you mean by "the rear tank overflow", do you mean the return from the bypass valve? I wouldn't imagine you could see the water returning from the feed to the pump. If it's coming from the bypass return, I'd agree with John that the bypass valve isn't closing.

Be aware that the balls don't need a lot of lift, and when they do, they must not block the outlet.

[JonL]

The William design has three tanks, two on the side and one lower at the rear under the coal bunker. The rear tank acts as a manifold for all three tanks. I put an overflow pipe on there to let air out to allow it to completely fill, the overflow output is higher than the top level of the side tanks.

I have found that despite the pipes being quite large diameter it does take a little while for the levels to all balance out.

Thanks for all the tips, I'll be giving these a crack tomorrow. So far all testing of the pump has been carried out under air pressure to run the motion, I don't have enough space to roll it sadly

[Cro]

A video may speak a thousand words here to make sure no wires are crossed.

Adam

[smallbrother]

I seem to recall problems with the axle-pump on my Polly 1 loco some years back. Sticky balls may have been the issue but I simply disconnected the boiler feed pipe from the pump, pushed the loco about a foot to see if it was feeding, which it wasn't. I remember wondering how on earth I could get at the thing and was thinking a major strip-down, but a bit of fiddling got the balls out. Good clean up and it has since worked very well.

I know a lot don't like them but if, like me, your main priority is sitting behind a reasonably reliable loco chuffing around the track on a nice afternoon in a daydream, then they are great.

Pete.

[nonort]

Having found something similar in the past check if the boiler clack ball is free? I have had a boiler that inexplicably stopped getting it's feed from an axle pump after a hydraulic test. I found after much rattling of the brain cells that a rubber ball had been extruded down into the feed pipe! Whilst you have the cap off the clack try pushing the engine up and down a bit you will only need half a turn to prove feed or not feed. Don't ever worry about not getting it right every time in no time at all you will become one of the go to people to solve problems as you will have solved most of the usual ones during your learning curve. Best of luck and many burnt fingers in the future.

[JonL]

I shall have a look this afternoon. Just cooling down after work!

[JonL]

The final clack into the boiler was fine. However it has occurred to me that the valve on the outlet of the pump may be misbehaving. If its letting water through in both directions it could be that its actually sucking in air through the bypass valve when its open, or not locking up enough to pump water when its not.

I'm clutching at many straws here, but the number of straws to choose from has at least been reduced by your kind inputs, thank you.

[Roger]

Aug 11, 2020 17:21:07 GMT JonL said:

The final clack into the boiler was fine. However it has occurred to me that the valve on the outlet of the pump may be misbehaving. If its letting water through in both directions it could be that its actually sucking in air through the bypass valve when its open, or not locking up enough to pump water when its not.

I'm clutching at many straws here, but the number of straws to choose from has at least been reduced by your kind inputs, thank you.

If the bypass valve is fully closed, there should be no flow coming out of the return to the tank, the delivery must all go to the boiler. If you're getting water coming out of there with the valve closed, the valve can't be working.

If the bypass valve if fully open, you should get all of the flow back to the tank each time the pump cycles.

Can you take the feed pipe off the delivery clack and put your finger over the pipe while it's pumping? You won't be able to stop the water coming out when the bypass is closed and you cycle the pump when it's working properly, and there should be nothing coming back to the tank. Do you have a rolling road you can sit this on while turning the wheels?

[stevep]

Nobby,

All the descriptions don't make sense, so can I check that you have the plumbing the right way round?

The suction side of the pump should be connected to the tank - normally at the bottom, to collect the water.

The delivery side of the pump should branch in two directions - one to the delivery clack, and the other to the bypass valve, which then leads on to the overflow in the tank.

As Roger says, with the bypass closed, all the water will go to the boiler. With it open, it should come out of the overflow.

[nonort]

Could it be something simple like the pump volume is more than the return feed back to the side tanks being restricted by the balance pipes. The Greenly Halton Tank as drawn has this problem it will quiet quickly pump one tank empty whilst over flowing the other i.e. the balance pipe work is to small. In an earlier post I seem to remember you saying that the tank levels took a while to settle out? Can you fill the tanks from one filler and the opposite tank fill and balance pretty quickly?

[JonL]

I think I've been doing the classic thing of changing more than one perceived error before checking on the results. I have a few things to try later this evening if it cools down enough in the workshop. I will report back with as many details as possible.

[JonL]

I disconnected the clack into the boiler and it is sealing and unsealing correctly. I then connected some windscreen washer hose to the pipe to the clack and sucked; I got very bubbly water through. I then applied pressure to the same hose and found water frothing at the ram on the pump. I will repack the gland and see what happens.

One thing at a time Jon....

[smallbrother]

Aug 12, 2020 17:08:29 GMT JonL said:

I disconnected the clack into the boiler and it is sealing and unsealing correctly. I then connected some windscreen washer hose to the pipe to the clack and sucked; I got very bubbly water through. I then applied pressure to the same hose and found water frothing at the ram on the pump. I will repack the gland and see what happens.

One thing at a time Jon....

I think you need to get the pump, pumping. Even if you roll the loco back and for just 6-9" it should want to squirt some water up that pipe to the boiler clack-valve, if the by-pass is closed.

Pete.

[JonL]

I agree completely. However I am now waiting for the graphited string I need to repack the pump gland. Otherwise I've now been through the whole thing with the pump on the bench. The top ball was letting through almost everything, so I suspect that was the issue. Problem is you can't get to it without either taking the stretcher out or the boiler. All clacks now seal properly from the start to the end of the system. When I reassemble it (hopefully the string will arrive in the next couple of days) I should be able to run it on my rolling road and get her pumping, but I can't do that until I repack the gland. The gland had made mush of its original packing material and it wasn't sealing until it was clamped right down, which I didn't like doing.

[stevep]

An option instead of waiting for graphited string is to use some PTFE tape like plumbers use. Tear off a length, and then 'twiddle' the ends in opposite directions, and you will end up with something looking a bit like a string. Pack that round the gland, and you should be good to go.