# troubleshooting axel pump



## Joel779 (Jan 2, 2008)

My Duchess has decided not to feed herself while running. I'm looking for hints on what to look for to analyze this problem. Here are the symptoms:

1. I always 'prime' the system - open bypass, hand pump until I get a good stream back into the tender, close bypass, and fill boiler.
2. When under steam, I have no problem topping boiler with hand pump.
3. When bypass valve is open and engine running, I see a steady stream out the bypass pipe in tender.
4. When bypass valve is closed and engine is running, there is no water coming out the bypass valve, but the water level does not change and boiler will not fill.
5. When bypass valve is closed and engine running, I use the hand pump, and get the normal 'pulsating' of the hand pump. Not a good idea, just checking that the pump is doing 'something', just not pushing water into the boiler.

I replaced the ball, and confirmed that it is not stuck. I lightly tapped on a spare ball on the banjo bolt (this seems to be the seat for the ball).

Any ideas? Other things I should check? 

Joel


----------



## John Allman (Jan 2, 2008)

#1 says there is no air in the system (but I suspect there may be) 
#2 says the tender pump works and does not mean the clack valve is not stuck. 
#3 says there is no blockage in the pipes and the axle pump works. But under pressure, the clack valve may stick. 

#4 says the pump does not work under pressure. Is any water leaking? It needs to go somewhere. If it is not leaking then either water is getting in the boiler or there is air in the pump which is compressing, and making the axle pump inefficient. 

#5 - do you mean the handle moves while the engine is moving? That is a sign the clack valve is stuck.


----------



## Joel779 (Jan 2, 2008)

Thanks for the response.

Re air in system, how would I check to make sure this was not the case? What can be done (other than priming) to avoid air in the system. It was my understanding that if you hand pump with the bypass open first, then closed, and fill the boiler, than you have removed air from the system. Is there a technique I am missing? I haven't had this problem in the past with the engine/pump and my Berk seems to work with this method.

Re stuck clack valve, If the clack valve was stuck, either under steam or when cold, how would I be able to pump water into the boiler with the hand pump?

no water leaking at all. I'm running this on rollers and I checked the pump carefully for leaks. The rollers remain dry as well. Also, if the water level in the tender was going down, but the sight glass was not filling, I would say leakage. But I checked the level in the tender with bypass closed and engine running at speed for several min and no change to water level.

Re #5, the handle does not move when the engine is running. If I stop the engine (close throttle, open blower), and use hand pump, the boiler fills with fine. When I pump the hand pump when the engine is running I get the normal back pulses in the pump that the axel pump produces when you hand pump when the axel pump is also running. This is the same as I experience with the Berk.



I'm thinking #4, and maybe the check valve in the axel pump is leaking. 

Joel


----------



## JEFF RUNGE (Jan 2, 2008)

As John said, It sounds like the clack valve is not closing properly. To check, with the engine up to pressure loosen the hose fitting between the engine and tender and see if you have hot water or steam. If so service the clack calve. 
Let us know what you find.


----------



## David Leech (Dec 9, 2008)

4. When bypass valve is closed and engine is running, there is no water coming out the bypass valve, but the water level does not change and boiler will not fill.


Joel,
Just need to clarify something here.
IF you are running, AND the water level does not change, then it must be pumping!
It is just that it is perhaps designed to be the correct size pump and you are replenishing exactly the amount of water being converted into steam.
I have always felt that it is a badly designed axle pump if you have to keep fiddling with the bypass to keep the boiler 'just right'.
Of course, this will vary depending on the weight of your train, and on the track being run on, but you get my point.
IF you mean that the water level continues to drop, then perhaps the pump is unable to pump sufficient water, or there is another problem.
As I have written about my Accucraft Royal Hudson, when I run too fast, the axle pump seems to NOT work, but at a nice scale 60 mph, it pumps just fine.
One day I will have to solve that one. Something to do with a restriction somewhere, 
All the best,
David Leech, Delta, Canada


----------



## David Leech (Dec 9, 2008)

But I checked the level in the tender with bypass closed and engine running at speed for several min and no change to water level.



Hi Joel,
Sorry, just read your later posting.
Obviously NOT pumping then.
Did you try that at different speeds? 
Or just fast?
As I said, my problem seems to be connected to speed. 
All the best,
David Leech, Delta, Canada


----------



## Joel779 (Jan 2, 2008)

Ok, thanks again for the responses,


David, by water level not changing, this is ref to the tender water level. I used the cross screws on the hand pump to provide a fairly accuracte indication of tender water level. When running the axel pump the tender water level does not go down.

I def understand what you are ref to re speed vs pumping. I found that the Duchess at a healthy speed could keep up with the boiler very nicely in the past.


Now for the debug report - I fired it up again and after I had run th engine for a bit I stopped it, opened the blower and got a full head of steam. Then I went and disconnected the high pressure feed line. The fitting was cold, so I was not surprised when there was no steam or water leakage at this point. This would seem to indicate that the clack valve is working as designed. I checked this with the bypass open and closed.

Ideas?


----------



## Semper Vaporo (Jan 2, 2008)

In the water circuit there are five automatic one-way valves and one manual valve (the Bypass). Tracing the water circuit from the Tender and back... Starting at the tender there is the Inlet Valve on the Hand Pump in the Tender, then the Outlet Valve on that pump. Pipes then lead to the Inlet Valve on the Axle Pump. The next valve is the Outlet Valve on the Axle Pump. Then there is a wye fitting with two valves leading from it. One is the Clack Valve on the Boiler and the other is the manually controlled Bypass Valve leading back to the tender.

If the Clack Valve is stuck open and the Bypass Valve is open you will get steam passing back to the Tender in the return line. If the Bypass Valve is closed then there are the other 4 one-way valves keeping the pressure from pushing water back to the Tender in through the two pumps in the Supply line.

If all 5 of the one-way valves leak you will see bubbles in the Tender water around the Inlet pipe of the Hand Pump and the Tender water will get hot. (I have seen it happen!)

If the Clack Valve is stuck closed and the Bypass Valve is closed then there has to be some sort of pressure release in the circuit or the Axle Pump would lock up on the compression stroke (or even any movement!) and the engine would stop. Either that or the pressure the pump is capable of producing could separate pipe joints, rupture pipes or bend the piston rod or the axle it is running from if the engine continued to run!

If the Inlet Valve on the Axle Pump is faulty, then the other two Valves before it in the circuit should take its place acting to hold the pressure the Pump is producing and overcome the Clack Valve to put water in the tender, (but like I said, I have seen all 5 of the valves leak and let steam back into the tender).

I bet you have a rubber hose from the Tender to the engine and it is ballooning to relieve the pressure and only the Inlet Valve of the Axle Pump is leaky at high pressure. The Axle pump does not move much water per stroke so you might not even notice the hose ballooning.

Either that or all three Valves between the Tender and the Axle Pump are leaky and in need of repair (either just a cleaning to remove grit or what ever is keeping the ball from seating or re-lap the seat surface to improve the seal, or replace the ball).


----------



## SalM (Jan 2, 2008)

Check the pressure side (output to axel pump) hose on the tender. You should be able to "suck" air from the tender but not be able to blow air back into the tender........good luck


----------



## Joel779 (Jan 2, 2008)

so, both balls show a lot of junk on them, and the banjo bolt looks like the seat for the ball is not shaped even around the hole where the ball sits. I will order a new banjo bold and new o-rings, and try to rebuild the axel pump. Should be good to go. I had forgotten about the ball that mounts from the side of the pump, and this ball looks pretty gungy. Really wondering what got into my water supply?!? 

Any good hints on how to re-lap the seat? I need to do this on the inside seat, because it is part of the pump body.


----------



## Semper Vaporo (Jan 2, 2008)

Do not poke something hard (metal) at the valve seat). You could scar the seat that way. I'd recommend first just a good cleaning with a cotton swab (Q-Tip) with some alcohol. Then rinse it well to remove any fuzz from the swab. Use a small magnifying glass to inspect the seat for fuzz, or grunge and clean again if there is any.

These small valves are often just a drilled and counter sunk hole that the ball sits over/falls in.

Kozo Hiraoka (famed for his construction articles in Live Steam Magazine (and his books)) is much more elaborate in his design. He uses a "D" bit to give the rim of the seat an inverted cone shape (volcano shape) which initially gives a sharp pointed shape to the seat, then he puts a ball in and taps it hard (well, not so hard) to deform the pointed ring to fit the shape of the ball. Lapping one of these is a bit of a problem and what is usually done is to put another ball in and tap it again... also note, he recommends to throw away the ball that is used for the tap shaping action and use a new ball for the one in the valve; tapping on it will deform the ball making it unsuitable to use in the valve.

But, doing this to a flat or counter sunk valve seat (or doing any good with it) is difficult, as you will have a lot more metal to move/deform to form a smooth seat. You might damage the part before you smoothed the seat very much.

I don't know what the valve seats are like on the Duchess so I am not sure what to recommend. If you see a lot of scaring or can detect that the seat is deformed such that the spherical ball would not seal with it, then you may need to do some grinding... scary!!!! Get help from someone if you have never done this before! You don't want to remove very much metal! There really isn't much available!)

I have "helped" a leaky valve by using the end of a wood dowel that fit the seat well, chucked in a slow speed drill. I dipped the end in some jewelers rouge/fine valve polishing compound to "sand" the seat. It didn't take long to remove the scratches I was concerned with... but I am still not convinced the scratches were deep enough to be the problem that valve was having (I did several "fixes" at once and didn't test each one, one at a time, to see what the problem really was). BE SURE to clean all the polishing compound out of the valve parts, you really don't want it to get anywhere else!

Some people recommend that you replace the steel balls with "Nitrile" (a kind of synthetic rubber) as they will seal better with the flat/countersunk seats on most of these valves and will seal better on a mildly scarred seat. Several places sell them and I am sure someone here can recommend a vendor to you.


----------



## zephyra (Jan 2, 2008)

I know this is an old thread but did it ever reach conclusion. I have exactly the same symptoms with an Aster Berkshire. 

1. Engine not running:

a. Bypass closed and hand pumping causes water to go into the boiler
b. Bypass open and hand pumping causes water to be pumped back to tender

2. Engine running:

a. Bypass open and water can be seen streaming back into the tender
b. Bypass closed - no water returns to tender but boiler does not fill and water level in tender remains unchanged.

I have disassembled and cleanied all valves and am running out of ideas!

What this tells me is the axle pump works fine with no back pressure but cannot overcome the boiler pressure. Given water is incompressible, this means that there must be air in the system but I'm darned if I can find it!

Robert


----------



## jgallaway81 (Jan 5, 2009)

If you aren't finding any indication of a leak, their are only three ways to NOT blow the axle pump apart or deform some component there-of... 1) the check-valve supplying water to the axle pump is leaking, and under steam the water is being forced back into the feedline from the tender 2) the water IS being pumped, but the by-pass valve is leaking and the water is being sent back to the tender 3) there is a bit of air that is taking up just enough pressure from the pump to reduce the pump's output to below the boiler pressure.


----------



## Michael Glavin (Jan 2, 2009)

Sounds like the pump is worn out to me... Is the pump serviceable, are the clearances within specification? 

Michael


----------



## Semper Vaporo (Jan 2, 2008)

If you are not seeing water return to the tender with the bypass valve closed, then it is one of these things: 

1) The inlet valve on the pump itself is not sealing... water is being pulled into the pump cylinder on the intake stroke, and expelled through the same pipe on the compression stroke. 

2) Some engines have such a short stroke to the pump and the parts are flexible enough that if all the valves are closing properly and the boiler check valve won't open, then the pump parts just flex and no water moves. You should notice a definite "loping" in operation of the engine when this happens, as the compression stroke results in bending of parts far enough for the pump drive eccentric to continue rotating... either the connecting rod bends sideways or the pump mount flexes. 

3) It could be the pump drive eccentric is not tight on the axle shaft. The set screws might be tight enough to move the eccentric with little or no pressure, but when there is pressure they might slip and allow the axle to continue turning, but not push the connecting rod to the piston. You might loosen it enough to slide it to the side and look for scoring of the shaft where the set screws are slipping. Reposition the eccentric and re-tighten the set screws.


----------



## Semper Vaporo (Jan 2, 2008)

Oops! Two more possibilities:

4) These pumps are not like the piston and cylinder in the power cylinders of the engine (or like a automobile). They are not a larger diameter "head" on the end of a smaller diameter rod... the piston is the rod and the rod is the piston. When the piston/rod is withdrawn from the pump cavity then the cavity volume is large due the absence of the piston/rod and the resultant vacuum draws water in. When the piston/rod is pushed in, it takes up all the available cavity (or nearly so, depending on the relative diameters of the piston/rod and the cavity) and the volume of the piston/rod must displace the present content of the cavity; i.e.: and the water in there must go someplace. If it cannot exit via the valves, then either the piston stops moving or the water might travel along the gap between the cylinder wall and the piston/rod and then exit via the gland (seal where the rod enters the cavity). Look for water leaks there.

5) It is possible that the checkvalve has leaked a lot of steam back into the system and steam IS compressible. Thus the pump is just working water into steam filled pipes. I would not expect this to last long, as the steam would eventually condense and there would no longer be any compressible media in the pipes... the water would still have to go someplace, and the pump's outlet valve would have to be leaking such that the pump is not drawing water in the inlet, but withdrawing if from the output pipes.


----------



## Taperpin (Jan 6, 2008)

Robert , 
I have had several Berkshires with Axle pump problems..the Ram /piston on some can be under sizeon the diameter. this cause insufficient water delivery to the boiler under steam pressure..but it will move water with "no Steam" inthe loco. 

check the fit of the ram in the pump bore..if its very loose thats probably your problem. you may find it best to make up anew ram in S/Steel sized to suit the bore less say .002" on the diameter and fit new Oring [6mm] od..i have aslo fitted aPTFE tip to the ram which carries the O ring and this gave good results , 

Gordon.


----------



## Charles (Jan 2, 2008)

Robet
Check with Hans, Aster has an update for the situation at hand. We installed it and all is fine.


----------



## zephyra (Jan 2, 2008)

Posted By Taperpin on 06 Aug 2010 05:28 AM 
Robert , 
I have had several Berkshires with Axle pump problems..the Ram /piston on some can be under sizeon the diameter. this cause insufficient water delivery to the boiler under steam pressure..but it will move water with "no Steam" inthe loco. 

check the fit of the ram in the pump bore..if its very loose thats probably your problem. you may find it best to make up anew ram in S/Steel sized to suit the bore less say .002" on the diameter and fit new Oring [6mm] od..i have aslo fitted aPTFE tip to the ram which carries the O ring and this gave good results , 

Gordon. 


I measured the diameter of the ram - it is 5.08mm and seems a reasonably good fit. I had expected the diameter to measure very slightly wider over the two o-rings, but it is exactly the same. I'm wondering if the groove in which the o-rings sit was cut very slightly too deep. In any event, Hans, reliable as ever, has offered to provide a update.


----------

