Pattern Making Made Cheap!

As mentioned before, we have a problem with the #1 truck on the 309.  The bearing surfaces on both axles were turned down at some point, which would require thicker bearings.  But none of the bearings we have available are thick enough, so there's too much play between the axles and the motor mounts.  This needs to be corrected.

Here's what an axle bearing looks like.  It's in two halves: the one on the left I'll call the inner half.  It fits up against the motor casting and has no holes, but is completely solid.  The other half is the outer half, and is held in place by the axle cap, which is bolted to the motor.  There's a large oval hole where the waste rubs oil onto the bearing surfaces.  There are also holes for pins to keep the bearings from rotating relative to the motor.  There are four holes, but only two pins, so that the bearings are the same for either left or right.  The thicker end of the bearing, which is sitting on the table in this picture, butts up against the wheel or the gear and takes the stress of lateral movement by the motor.

For this particular motor, the GE 66B, the outer surface of the bearing has a diameter of 7 1/4".  The nominal axle diameter, and therefore the inner diameter of the bearing, is 6 1/2", but on this truck we're talking about, that's been turned down to as little as 6 1/8".   Therefore, we need to make two patterns for new brass castings that will be thicker.  After casting, they can then be machined to the correct diameter for each axle.  And the spare brass castings are an excellent basis for patterns.

Tim Peters pointed out that we had some leftover pieces of 6" PVC pipe.   The inner diameter is 6", of course, and it's 1/4" thick, so the outer diameter is 6 1/2".   That means it fits almost perfectly into a spare bearing.  So I took it home and started to cut it to size in an obvious fashion.

I prefer to use an ordinary hand-held hacksaw.  It won't get away from you like power tools can.

The next step will be to attach the PVC with contact cement, and carefully smooth the edges flush with the brass, using a rasp.   First, though, I want to check with the experts in the car shop before going any farther.

In any case, we should have usable patterns at basically no expense.  Pattern making is often a large part of the expense of casting, and if we didn't have these spare bearings available, it would be an extremely challenging task to make them out of wood, or whatever.

Once the patterns are done, we will get quotes on casting new bearings, then start passing the hat.  I promise to do my best to make you feel guilty.   It's the least I can do.