Neil Ungar had a great idea. He welded a section of square tubing on a plate and filled the empty volume with liquid  polyurethane. Polyurethane is a very tough flexible plastic used in race car suspension bushings.

I incorporated it into a 1.5 inch diameter hollow gear box input shaft.
Now one piece.

The aluminum spacer Neil used is made longer and a star shaped cavity is NC milled into it. Since you MUST use six metric screws to bolt to the counter weight a star instead of a square shape can be larger in diameter reducing the stress on the Polyurethane. The input shaft is made from a bar of steel machined on a lathe and then the small star is NC milled on it.

Most input shafts are one inch in diameter. The advantage of the
1.5 diameter shaft is it is easier to assemble the large  gear box adapter plate and the sun gear fixing to the shaft is much, much stronger. Dave Leonard had trouble with the sun gear pins shearing off. This uses 10 extended point set screws instead which Chris Hoskins is using.

Of course all this is hindsight based on 17 years of the news letter.
If it can be failed some one on here will fail it :-)
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I forgot to show the essential helical sun gear thrust bearing.

Here it is

Ross, Tracy, Perry Mick and others  failed the built in Mazda e-shaft thrust bearing by not accommodating this force in the gear box.

Two are used back to back to reduce the RPM the thrust bearing is subject to.
Each bearing rotates at half e-shaft speed. Needle bearings do not like RPM.

Again the reason for the extended point set screws is you need a way to assemble this with a one piece input shaft. Other wise it won't fit through the oil seal located in the large adapter plate.

The other larger thrust bearing is for the prop thrust.

The devil is in the details.

Paul Lamar




Hi Neil,
   How do you hold the ring gear into the housing ? is it a press fit ?
do you use any loctite ? 648 retaining compound or something ?
       Cheers Chris Hoskins.



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