Here is a drawing of the Ross gear box.

2. is the front oil seal.

4. are the roughly 45 MM inside diameter prop gyro load needle

bearings.

These are part of the reason the Ross gear box is so light weight.
The other reason is the prop shaft is made from thick wall relatively

large

diameter chrome molly seamless tubing. A good feature of the Ross.

5. is the race for the large diameter needle bearing that takes all the

prop

thrust loads.

6. is the the large diameter needle bearing that takes the prop
thrust loads. This bearing to my knowledge has never given problems.
Part of the reason for this is it is running only about 2700 RPM
unlike the Mazda 13B thrust bearing running at 6000 or so RPM.

Tracy Crook wrote:

Just for a data point,

The last failure I had on my Ross drive was a failure of the prop thrust
bearing along with some spalling of the sun gear.  The thrust bearing
absorbs all of the combined thrust of the prop AND the ring gear thrust
(which is much higher).  Ring gear thrust is around 850 pounds at max engine
torque (13B). My drive has a spline between prop shaft and ring gear so
separate bearings carry the thrust.  Not sure why the bearing gave up on my
Ross since the specs indicate it should have easily handled the total
thrust.

Tracy Crook
rws@altavista.net
www.rotaryaviation.com

I think the reason might be once the end play in the system built up it just started 
pounding back and fourth and destroyed both the front needle and the prop thrust needle
from impact loads.

Paul Lamar
 
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