Realistic pump testing – boiler simulator?

[SteveR]

I’ve built the Allen Consolidation axle pump and, mindful of the many Chaski threads discussing the pros and cons of axle pumps, want to bench test it at operating pressure (100psi). Currently I have the pump connected to a 12V gear motor and it puts out pretty decent pressure, but this is a far cry from actually making it work for long periods of time.

I envision a simple pipe-like vessel that I can pump up to 100psi that would have a pressure regulator and additional safety device which would let me run this and perhaps other pumps unattended for a week to try to simulate a year of (continuous) running. I’d like to try some different o-rings and an idea for a packing gland I’d like to test without actually installing it on an engine. The Allen consolidation doesn’t have an axle pump bypass – I’d like to test that concept as well.

Not sure if a simulator has been built previously but I couldn’t find anything on Chaski. Anyone have any experience building a test rig as I’ve described? Is there a better way to test pumps without a locomotive?

Thanks,
SteveR

[Marty_Knox]

Steve, I would put a bypass in the axle pump delivery line.

[amadlinger]

Hi Steve,

I would suggest you look at a backpressure regulator. The concept is exactly the same as a conventional (forward pressure) regulator, except - instead of holding the pressure constant downstream of (after) the regulator - the BPR will hold a constant pressure upstream of (before) the regulator. You would install the BPR on the discharge of the pump and can then dial in any pressure that you want to test it at. The water reservoir can then be just an open bucket.

Sincerely,
Adam

[SteveR]

Marty - I think it will be better too. There is a thread where it is suggested to put a notch in a check valve(?) to allow some water movement all the time, but I think this will be more controllable.

Amadlinger - I didn't know such things existed and I am going to get one straight away. Certainly seems like it will make things simpler. The pictures that I googled showed an adjustable spring loaded valve as shown here:
https://blog.lesman.com/2016/01/18/regu ... -pressure/

Thank you. Will post results when available.
SteveR

[Bill Shields]

just put a weight on the top of a vertical a plunger with a ball check on the bottom of it. connect the pump to the bottom of the plunger..

simple math can give you a psi number.

basically is is one of your pumps in reverse....

cost: shop scrap.

in reality, build the pump correctly and you don't have to worry about this....it will work for years and years....

[amadlinger]

Hi Steve,

Glad I could help! Please let us know how it works out.

Sincerely,
Adam

[ALCOSTEAM]

I built a couple axle pumps for one of the scotty mogals being built. Just testing seeing what they would do using my hands to push the plunger in I ruined a 250 psi gauge, two pumps on the engine, running on air and the engine barely slows down as you close the bypass and the water pressure crosses the 300 psi mark.

Axle pumps have their naysayers but properly constructed and plumbed are a worth while project and a nice addition to a steam engine.

[NP317]

I have had excellent performance from the stock axle pump on my Allen Ten Wheeler.
It has worked per design for 16 years and never missed a beat. (now that I stated that...)
I did plumb in a bypass valve which has allowed trouble-free operation maintaining 90% of the boiler water needs.
I also plumbed in the tender hand pump through the axle pump allowing pre-run testing and priming of that water feed system.

This design worked so well that I built a similar axle pump for the Mikado.
When we can return to the tracks I look forward to extensive running and testing.
RussN

[SteveR]

Thanks for all the responses! Very helpful.

Bill - I had to think about this and then realized it's probably what I will try first.

.

NP317 – Did you plumb in the bypass line separately? – Bill has written about using the bypass line as the same line as the tender hand pump. In bypass, the water flows backwards with the help of some extra valves. viewtopic.php?t=90334.

ALCOSTEAM -

properly constructed and plumbed

- I agree; Just trying to figure out exactly which way to skin this particular one (no cats were harmed in the writing of this thread!). On this engine, I think the easiest way to remove the pump for fixing things will be to pull the front frame and lead truck off. So I'd rather do a bit more work up front. And it's my first one so I don't mind wearing this one out on the bench to build a better second one. Already on my second piston using dimensions from the Parker book instead of the prints.

What about some way to disconnect the eccentric strap in an emergency? A cross bar to keep it from dragging?
Thanks again.
SteveR

[NP317]

Steve:
I plumbed a separate bypass return line to the tender.
A "T" is installed between the axel pump output and the boiler input check valve. That "T" connects back to the bypass control valve in the cab.
Because the pressure between the bypass valve outlet and the tender is near 0 psi, a simple rubber flex hose between the bypass valve and the tender works just fine.
Zero failures of this system in many years of operation.
RussN

[Bill Shields]

Sorry my description was not the clearest...but see you got there despite my poor efforts. In reality you may want an air chamber in the pressure side..

Follow?

[NP317]

With no air chamber in the pump output to smooth the pulses, there is a useful feedback to the Engineer:
With the bypass valve closed the valve handle makes a "bump" that can be felt!
So if I want to know if the pump is working, I just close the bypass valve to feel the pulses.

Normal operation on my locomotive usually has the bypass valve partly open to delver the required water to the boiler.
Note that I usually run with the valves hooked up 50% or so, so water consumption is lower than other similar locomotives that are run "in the corner."
I have seen model steam locomotives with just 3 slots in the Johnson bar quadrant: Center and in the corners.
I am always surprised when I find that situation, so I offer my full-sized steam locomotive operating experience...
Fun stuff.
RussN