Heisler Outside Truck Gear Construction
Nelson Riedel, Nelson@NelsonsLocomotive.com
8/25/2005, last updated 04/08/2006

Recall that the gear design required more iterations than any other part of the design.    We'll see if all that work pays off.   Refer to the Outside Truck Gear Design page for design information.  

Gear Case: The first step was to make the gear case.  If I could accomplish that task, the rest should be straightforward.  

The specified gear case large tube is 3.5" OD and 3" ID.   The inside is to be bored to 3.1".  A cheaper 3" pipe was substituted for the tube.  The pipe has a 3.5" OD and 3.06" ID.  There was a protruding weld bead on the inside and the outside was not perfectly round.  The outside was turned down slightly to get a round surface and the inside was bored to 3.1" which removed the weld bead.   Photo at right shows tube and 0.5" thick end piece.
Next, the end piece was silver soldered to the tube and the combination was then mounted in the 3-jaw chuck and the bearing recess bored in the end.   The large tube with end was then mounted in the 4 jaw chuck as shown on the right.  A metal plate was positioned against the open end of the tube to enable the jaws to hold the tube.  A dial indicator was used to position the tube correctly (not as difficult as it might seem).       The hole for the small tube was drilled and then enlarged by boring.   This step would have went faster if the opening had been rough cut in the end and side before the two pieces were silver soldered together.
The gear case small tube is 2" OD-1.875" ID.  Seamless tube was purchased so that the pinion tube would slide  inside easily.   The tube was cut to length and the end piece soldered to the tube.  The end was then milled to mate with the end piece of the large tube.  The part of the small tube that extends into the large tube was only rough cut at this point.  Photo at right shows the two tubes.
This photo shows silver soldering the two tubes.  A small screw from the large tube into the small tube held the two pieces together during the soldering operation. See Shay  Line Shafts & Universal Fabrication  for a discussion of silver soldering.
Gear Case End Cap: The next step was to fabricate the end cap from 0.25" plate and a short length of 2.25" OD - 1.375" ID tube.  The tube and plate were soldered together first and then the bearing recess was bored in the tube part. The photo at right shows the gear case and cap with the bearings in place.
The back side of the gear case.
This is the cap side of the assembled gear case.  Four  6-32 screws hold the cap to the case.
Pinion Tube: The next step was to make the pinion tube from a length 1.75" OD - 1.25" ID tube.  The only machining required was boring the bearing recesses in the ends.  The stock tubing slid into the gear case small tube without additional machining.  The photo at right shows the gear case and pinion tube.   The initial plan was to slot the the small gear case tube and use a clamp around it to retain the pinion tube in position.   I've changed my mind and instead now plan to run the screws that attach the swivel pin through the gear case small tube into the pinion tube.
Axel: The next step was to turn the axel from 1" mild steel rod stock.  The big gear was bored to 1" ID and the hub length and diameter both reduced.  The gear was broached for a key and a mating slot was milled in the axel.  The photo shows the finished axel with gear, gear case bearings and axel bearings.  The key slots for the wheels haven't been milled (wheel quartering will be dealt with later).     The axel design information is in the  Truck Design I  page
This shows the axel installed in the gear case.  The end cap has been removed.  Everything fits as planned ---with no spare space.
Pinion Shaft: The next step was to cut the pinion shaft to length from  5/8" mild steel rod.  The key slots were then milled and the grove turned for the E retaining ring.  The pinion gear ID was increased to 0.625" and a key slot broached.  The hub was also shortened.  The photo shows the pinion shaft with pinion gear and bearings.
This photo shows the pinion shaft installed in the pinion tube.

The photo above shows the completed outside truck gear case.   The only thing remaining is to make and install the swivel shaft and the swivel block.   I'm deferring that until the truck castings are available to verify the swivel design.     The next step was to test the gear system with the truck patterns as shown in photo at right.
This is another view of the gears positioned with the truck patterns.  Everything seems to fit together properly.

The fabrication of the next two gear cases went much faster once I knew the design actually worked.  It's much easier to machine identical parts at the same time.   I purchased the bevel gears from Applied Industrial Technologies which has outlets throughout  the US (~ $300 for the six gears --- ouch!).   I purchased the ball bearings from Enco ---- they are Chinese but seem to be of good quality and the price was right.  

The gear case worked out more or less as planned.  The tubes make it easy to keep the shafts, bearings and gears all in alignment.  It's on to the middle truck gears next.