Fray Car Tuning
By Tim Leppert
Rear End Gearing
OK,
For this episode we will need a few new things:
1: a supply of VERY small washers. I get these at the local hardware store, or
the train store. These need to be around .010 thick and .065 I.D. It would be
great to find a few that were different in thickness, so you could mix and
match.
2: Rear axles.
This depends on your track. For sectional, I would go with a Tyco. They are .059
and have a spline. Good for rough tracks.
If you run a lot of routed tracks, I would go with a drill blank. .063-.065 dia.
Any smaller and the crown will be loose.
You can try a super g-plus axle. Splined and .0625 dia. good for all around
stuff. just be SURE it is straight.
If you want top of the line, then go for a tungsten/carbide axle. These put the
weight back on the wheels and plants the rear end. They can be found at welding
supply stores, in the TIG isle. They are expensive, but you can get three axles
from one blank.
Also, you will need the RT gear removal tool and the gear press. Also some of
your 9 tooth gears still on the shafts, all of your rear driven gears and of
course ALL of your crown gears (only stock t-jet for this project).
And as an assembly aid, a spare Tyco axle (color the spline with a sharpie so
you don't get it mixed up with your good ones.
Here we go:
First off grab your good chassis, and strip her down. remove the arm, mags and
brushes.
Get your .059 axle and a crown, place the crown in the chassis and slip in the
axle. Then place one of the 9 tooth gear and the shaft in the plate you want to
use.
Now assemble the plate and the chassis and note the amount of left to right
movement you have on your axle. This is the endplay.
Endplay is critical in meshing gears. You need to have some but not too much.
Too much and it effects the pressure angles, too little and there is bind
induced.
With a t-jet, you want as little as possible. The more endplay the more the rear
end can move laterally. For anyone who has raced 1/24th cars, you know how
important this is. It can GREATLY effect the handling of a slot car.
Now, you need to start playing with the washers you have and get rid of the
endplay. Luckily, the folks at Aurora did us all a favor, they made the gears
pretty good. You should only need spacers on the inside of the gear, That is the
side toward the 9 tooth shaft. usually around .020 is a good start. This does
vary greatly.
As you rotate the crown gear slowly, watch the teeth for a wobble. If weebles
wobble, they need to go. Replace and move on to the next one.
Get this close with your slip-in shaft, then try a pre-fit with the good one. You
will probably be a little tight. Try to determine if the gear mesh is the
culprit or if it is the axle holes.
If it is the gears, you can loosen up by a good run-in with a Dremmel, or you
can try a lapping compound.
When you have this where you want it, protect it, 'cause you are that much closer
to a good Fray car.
Next installment:
The rest of the drive train......Choooo-Chooooooooo
Previous Installment: Brushes and Tensioners