Axle Pump Revisited

[ccvstmr]

At the end of August I posted a request for info and assistance regarding axle pumps. Even if you don't have an axle pump on your loco...consider this perspective from a materials selection viewpoint. Thought I would provide board readers and contributors with an update on what happened and what I found. 1st...many thanx to the various people from this forum that offered ideas, suggestions and more...even from afar! Invaluable experience.

The Rutland is now 19 years old and still going (built by the late Pete Bialecki of the Buckingham Central RR). It's been a great little Allen 10 wheeler providing miles of fun, enjoyment...and on occasion, some frustration. During those years, the Rutland racked up 2000+ miles of service while the axle pump inlet and outlet stainless steel check valve balls cycled at least...5.2 million times. Note...pump is typically used when newbies are running around the club training circle...OR...to put ambient temperature water in the boiler when the safety valves have lifted. In use or not, the check balls get cycled with rev of the drivers. The water either goes to the boiler or back to the tender. It's a positive displacement pump...the water has got to go somewhere! Btw...the pump moves some 0.2 cu. in. of water with each cycle.

Find attached a series of photos that show what was discovered and what was done...

#1...pump outlet screw in fitting shows Allen Models suggested 9/32" diam hole "squared off" to allow water to pass when the ram extends to push water out of the pump. Note the rounding of the square hole edges from stainless steel check ball. The ball made a seat for itself on the 9/32" round hole. The ball "hammered" the brass fitting to the point where it closed off the outlet port.

#2...1st repair attempt...machined the worn seat off and soft solder a wafer in place. It was thought the wafer was a piece of bronze. Instead of drilling a 9/32" hole, the hole size was reduced to 1/4". Used an 1/8" end mill to machine an "X" or "+" pattern to allow the water to bypass the check valve ball. Thought the problem was resolved.

#3...still having problems, the screw in fitting was removed. This is how the fitting (with new seat) looked like after only 11 miles of operation (another 30,000 pump cycles). You can see where the points have been beaten into a spherical pattern.

#4...back to the drawing board. A wafer of bronze was soft soldered to the screw in fitting. Drilled a 1/4" hole and had to consider the best way to allow water bypass while maximizing the surface to support the stainless check ball. Decided several slots would best fulfill this criteria. However, didn't have mill tooling to do this...until I thought of the Dremel kit with its various disks. The screw in fitting hex config provides the "indexing" in a mill vise. Just run the abrasive tool in (slowly) the same distance for each of the (3) pairs of slots. The cross sectional area of the (3) pairs of slots had to be equal to or greater than the original square hole.

#5...finished outlet axle pump screw in fitting. The pump was put back in service and provided a good stream of water back to the tender after another 10-15 miles of service. [make note...check the screw in fitting in the year 2030].

No doubt, there are many ways to get to the same destination. If this helps others with axle pump issues...great. If not, remember material selection is critical parameter for machine component longevity. Looking forward to continue "testing" next year when warmer weather returns to the upper Midwest. Hope this helps. Carl B.

[NP317]

Very useful solution. Thanks for sharing.
Some years from now I will expect to perform the same rebuild on my Allen Ten Wheeler!
~Russ

[ccvstmr]

Russ...you're welcome.

All I can say is the builder took certain liberties with the loco design and fabrication. In some instances, it's been a matter of 1 step backwards to go 2 steps forward. The axle pump was one such deviation. While the general "flavor" of the Allen Models design is there, the ram size is larger and more than likely, the builder used materials he was able to put his hands on at work (haven't we all done that at one time or another?)...which might not have been the best choice. So it became of matter of; 1) what was the original design? ...and then 2) why was there a change? ..and then 3) how does one go about correcting the matter?

I'm not complaining...but when something doesn't work...a little detective work is necessary figure how I got to where I am. That's one of the aspects I enjoy about this hobby. And once again...this has been a great info exchange media to be able to learn and share. Thanks again guys! Carl B.