Heisler Axel Pump Construction
Nelson Riedel, Nelson@NelsonsLocomotive.com
9/215/2005, last updated 04/08/2006

A few days after finishing the the design of the axel pump I strained my shoulder.  This is the time of the year when she usually wants me to work in the yard.  However, with the sore shoulder I thought it best to rest and let it recover.   There was a constant mild pain so any distraction was welcome.  Building the axel pump turned out to be just the right distraction.  (She didn't buy it either).

The design details are at: Axel Pump Design .  I had obtained all the parts except the rear bearing  to verify the design.  So it was off to the storeroom to find suitable material for the inner and outer rings and cover plates.  I found a scrap sheet of 0.090" aluminum that would work for the retainers.  I had a short piece of 3" OD aluminum rod that could be turned down for the inner ring so I was ready to start.

 

Inner Ring:  I started by rough sawing the retaining plate, attaching it to the end of the 3" diameter rod with three 6-32 FH screws and then turning the outer edge of the plate to match the rod OD.  Next, the rod was mounted in the 4-jaw chuck and setup with an offset of 0.375"  using a dial indicator (0.75" total throw.)  The 0.75" axel hole was drilled undersize and then bored to the final size.  The photo shows the boring setup.  This approach rather than just drilling the axel hole was used to assure the hole was parallel to the sides of the ring.
The next step was to move the rod to the 3-jaw chuck, make sure it was mounted straight and then turn the outer surface of the ring.  After seeing the actual part I decided to reduce the width of the inner ring from 0.875" to 0.66".  The combined ring and retainer have a total width of 0.75"   I also increased the OD from 1.875" to 1.9"  Photo shows turning the OD.  The ring was sawed off the stock and the other face then turned flat.
This photo shows the inner ring parts with the bearing.   Forgot to mention that I also used a broach to cut the keyway.
The assembled inner ring.   This photos is several times actual size.   Those gouges in the retainer surface are barely visible scratches.
Outer Ring: The initial plan was to use steel for the outer ring  solder a stub to the ring for connecting the pump shaft.  However, the remaining end of 3" OD aluminum rod looked perfect for the ring.  I altered the design so that the OD was 3" to give plenty of threads for the pump shaft.  The ring plus retainer width was increased to .75" to match the inner ring.  Ring ID was reduced from 2.125" to 2.0"   Photo at right shows the finished outer ring pieces.
This photo shows the bearing positioned in the outer ring.
Bearing Housing:  The bearing housing was made per the design drawing except that the bearing will be retained by a plate similar to the eccentric bearing rather than by a retaining ring.  The housing width was reduced to 0.375" in accordance with that change.  The photo shows two 4-40 screws with washers. The retaining  plate will be made later.  A shallow slot was  milled in the tee to help hold the housing in alignment when the pieces were soldered together.

Mount Spacer:   I deferred making the mount spacer until the spacer length can be verified on an assembled truck. I'll make that mount bearing retainer at that time too. 

Assembled Pump:  The next photos show the assembled pump.

The pump worked out more or less as planned and I'm very satisfied.  It should run for years with no maintenance.  Looking at the photos above, the only issue is that the outer eccentric ring seems larger than it need be.  I could probably mill 3/8" off the top, bottom and rear which would make it look much smaller.   

I can put the pump away until the truck castings arrive.