When I went up to see Chuck's Velocity after the in-flight fire the subject of the
Ross PSRU came up. Chuck was noticing some unusually wear on one or two pinions and 
at first attributed to the higher HP of his turbo three rotor. He embarked on an
ambitious
program to change the Ross oiling system in part I suspect because of this wear.

Somewhere along the line between when Tracy got his Ross PSRU  and the time Chuck got
his Ross PSRU
...Ross changed the design! Instead of machining a bunch of slots in the housing to
locate 
the planet carrier Ross decided to bolt the planet carrier onto the bell housing
part. This probably
saved a lot of machining cost as those slots are very difficult and tedious  to
machine using 
a simple mill. See the enclosed drawing.

Properly designed planetary gear sets rely on the fact that the planet carrier is
self aligning 
if allowed to float. In other words the planet gears balance the load among
themselves automatically.

Tracy noticed a little wear in these slots after about 600 hours of use which by my
hindsight
was perfectly normal. Tracy was concerned about it and as I recall applied RTV to
help
cushion the backlash in these slots.

Chuck finally realized this problem and enlarged the bolt holes and minimized the
torque on the bolts to 
allow the planet carrier to self align. If you have such a Ross I would suggest doing
the same.

I think, but I am not sure, Tracy has the necessary slots milled in the PSRU housing
by someone
with an NC mill. This is the right way to do it.

If you have a three rotor you should be running a six pinion planet carrier. No
amount
of additional oil will compensate for the higher line contact loads on the pinion
gears.
The best thing to do is add two more pinion gears. You can buy such a planet carrier
or
machine your own out of a light duty three pinion version and add three more pinions.
Since the planet carrier, complete with pinion gears, can be bought from a automatic 
transmission parts house for about $20 you could cannibalize one of these for
additional 
pinions.
 
Paul Lamar
 
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