Heisler Wheel & Axel Construction
Nelson Riedel, Nelson@NelsonsLocomotive.com
3/26/2006, last updated 05/03/2006

The wheels are iron castings obtained from Allen Models.   The castings are a bit rough but clean up quite nicely.  The 40" wheel scales to 5.33".  The castings were intended to make a 5" wheel.  The goal is to make the wheel as close to 5.33" as possible.  I was able to get 5.25", which is close enough considering the alternative of making my own wheel castings.  The wheel and axel design information is at Heisler Truck Design I.  I started by completely machining one wheel and then doing the remaining eleven wheels in assembly line fashion.  The following describes the assembly line.   

Machining the back: The rough casting is about 1/4" too thick.  The first operation is to turn about 0.2" off the back and to drill and bore the center hole. The font of the casting has the counter weight that sticks out from the tire about 0.1" and the base for the rod pin that sticks out a bit more.  I cut three pieces of 1/8" X 1/2" bar stock about 2" long and placed them between the tire and the face of the (reversed) chuck jaw as shown on the right. This was an easy way to keep the front face perpendicular to the turning axis.
The next step was to dill and bore the center hole.  I made the hole 0.750".  It would have been best to use a reamer to get it exact --- but I didn't have a reamer so there is some small variation wheel to wheel.  Will deal with that later. The next step was to turn the back such that the remaining tire width was ~1.0"  I did this in two cuts of ~0.1" each running at 60 rpm. The final step was to turn the outside slightly such that the back quarter inch or so is flat.   The outside has a considerable taper so there was no problem doing this while keeping the tool from hitting the chuck jaws.   This operation was completed on all wheels before doing the next step.
Turning the front: The next step was to reverse the wheel and turn the front.  The tire is turned down to 15/16" width, the counterweight and crank pin base to 1" and the hub to 15/16".  I was able to do this in one pass at 60 rpm.  The tool was set for the 15/16" tire width, then moved out to 1" for the counterweight and crank pin base and then adjusted back to 15/16" for the hub.       The photo shows turning the counterweight and crank pin base.  This was taken before I figured out that I could do the front in one pass.
Fixture: Proper quartering will be insured by making the keyways at each end of each axel exactly 90 degrees apart and making the position of the of the crank pin relative to the keyway identical for all wheels.  The simple fixture shown on the right insures the wheel keyway-crankpin relationship.  The fixture is a piece of 1/2" X 1.25" aluminum bar stock and a 3/4" keyway broach bushing for the 3/16" keyway.   The small hole is 3/16" and offset from the bushing center by 1.875".  The keyway is aligned with the smaller hole ---- it doesn't have to be exact since the requirement is that all wheels be identical.    The surface of the fixture under the small hole is recessed 1/16" to match with the wheel crankpin base that extends 1/16" beyond the hub.
Keyway: The fixture is mounted on the wheel and the rotated such that the small hole is centered over the crank pin base.  The fixture is then clamped in place and a 3/16" shank center drill run though the small hole to mark the location of the crank pin.  The fixture  is then removed and the the mark used to drill a 3/16" hole about 1/2" deep --- this is a pilot hole for the crankpin.  The fixture is then put back on the wheel and a 3/16" pin inserted through the fixture into the hole in the wheel as shown on the right.  This keeps everything aligned for the next step of broaching the keyway.
This shows the finished keyway and the pilot hole for the crankpin ---- it's beginning to look like a wheel.
Mandrel: The mandrel shown on the right was made for turning the tires. It is simply a piece of 3/4' diameter CFS with a 3/16" X 3/32" keyway and a 3/8"-24 hole tapped in the end. The outside was turned down slightly (~.001")  to make the wheels a sliding fit.  The mandrel sticks out less than the wheel hub width so that the bolt forces the wheel against the collet face.
Turning the tires: The photo shows turning the tires.  The tool corner was ground to a 3/32" radius.  The cross slide was set for a 2 degree taper. The tire was turned in two passes at 60 rpm. After all the tires were turned, each was mounted on the mandrel again, the flange turned to the correct diameter and then a course file used to round the flange and the front edge of the tire.

Finishing the wheel: Many of the wheels had extra material around some of the spokes next to the hub or the tire. In many cases the material was coarse and crusty.  I used the Dremel and some inexpensive diamond cutters (points) from Harbor Freight to clean up these areas and also to round the inner edges of the counterweight and crank pin base.  About 10 or 15 minutes per wheel did the trick.  This was the first real test of the battery powered Dremel.  Don't know how I ever got along without it.  

Once the wheels were finished I completely cleaned the workshop to get rid of the iron dust and chips that the cat was dragging to other parts of the house.  (I later learned that residue from my jeans stained the inside of the washing machine.  Someone is very unhappy.) 

Crank Pin: The crank pin was turned from 3/8" diameter drill rod.   It is secured to the wheel by the flat head screw.  High temperature Loctite was used on both the part of the pin going through the wheel and on the retaining screw to make sure everything stayed in place.

Painting the Wheel:  The wheels were powder coated before they rusted.  They  were first soaked in hot pickling solution to remove the casting oxide.  They were then lightly bead blasted and then the crank pins were installed.  The pins were masked and the center hole plugged with reusable silicon plugs .  The outside wheel surfaces weren't masked ---- that paint will wear off in a few weeks of use. The photo at right shows the finished wheel.

Axel Keyways.  A 5C Collet Block Chuck was used to hold the axel when milling the keyways.  The clock is a perfect square so it is easy to rotate the axel 90 degrees.
This photo shows milling one of the non geared axel keyways.  The block chuck is held in the milling vise.  After this end was milled the block was reversed and rotated 90 degrees to mill the other keyway.  The keyways should be milled such that the right keyway leads the left by 90 degrees.  Confession ---- I milled the first axel wrong ---- and reversing it end for end didn't change anything.

The photo above shows a completed wheel set.  The HM203 spacers are visible between the bearings and the wheels. The spacers were cuts from a scrap piece of 3/4' pipe (~0.83" ID - ~1.05" OD).  This set used that first axel with the incorrect keyways.   The axel was later replaced.

The driven axel wheel sets are described in the Gears & Shafts section