Turbo Optima mid SE

[radioactivity]

The installation of the rwracing.co.uk acetal gear did not go as smoothly as possible.
But I believe it is partly due to my usage of the ball diff vs using a gear diff.

The rwracing gear is much wider than the Kyosho OT85 style gear. Approximately 9.1mm for the rwracing gear vs 7.7mm for the Kyosho and about 8mm for the pargu aluminum 32p OT-85 variant.

This extra width caused interference with both the gear diff and the OT-86 main gear pinion.
For the most part, trimming the rwracing gear width to 8.8mm tended to solve the interference problems.
Then shimming the bearings properly and adjusting the main gear shaft a little got the gear in place without any interference.
It is a very tight fit even with the ( now thinned ) gear. Clearances of approximately .004" to .010 side play all around.

Chuck

[radioactivity]

A portion of the interference at the ball differential was caused by the integral shoulder on the gear. Ball diff on right.
It is a little difficult to see in the pic but the 2 piece design of the gear diff, on the left of the pic, gave a little more clearance.
The diff cannot really be shifted side to side and spacing the full size ( 9.1mm ) idler to clear the ball diff caused the idler to contact the inside of the gear box.
That is why the rwracing idler gear needed to be thinned to 8.8mm.

Chuck

[radioactivity]

Now with all the clearance issues aside, on to the benefits.

15% wider contact area vs the Kyosho idler gear. More face contact = more strength.
The Kyosho idler gear, by all appearances, is quite soft and not very durable.
Conversely a Derlin/acetal/POM gear is beautiful to machine, very durable and a known high quality plastic for gear manufacturing.
The gear train is now back to all .8mod. The slightly larger OD of .8mod vs 32p has removed all unnecessary slop between the gears.
The gear train feels buttery smooth when rotated.
Really quiet when spinning.

Overall very happy with results, well worth the effort.


The final "breaking in" of the gears is accomplished with compressed air blown across the spur gear. Spin the heck out of it.
After 3-5 minutes of high speed break in I feel the case, out drives, etc to feel for any warm/hot areas that could potentially show binding or friction.

That blow gun is a favorite tool for breaking in gear boxes.


Chuck