If you think there is 10 lbs to save in Tracy's PSRU, that's huge
  considering CG and all...If someone is willing to get the necessary
  components that can be whittled and you direct in the ares to be
  machined, I would be willing to do this for a very small sum to cover
  the tooling and possibly the fixture material, about $200.  NO other
  machine shop would touch something like this for under $1000
  .................

  thanks

  jeff

 Hi Paul;

 I had a few questions regarding Tracy's PSRU.
 IIRC, the original RD-1 used the Ford C6 gear set.  Do later versions
 use the Ford E40D gearset or something else?

 Are the prop shaft and flange still from a drag (or sprint) car rear
 axle and flange - any idea which companies produce off the shelf parts
 like this?

 Also, do you know if the female splined flange in the damper plate (see
 attached pic) is based off stock transmission parts?

 Thanks
 Cary


 Yes the gear set are from the latter versions of the C6 called E4OD.

 Yes on the prop shaft and flange. Supposedly a AA Fuel dragster rear axle.

 Yes the damper plate is based on stock parts. I have not figured
 out what make of transmission they come from yet.

 Sluson Transmission parts has a catalog showing a lot of
 auto transmission parts.

 http://www.slauson.com/


 Paul Lamar

Hi Paul,
You have mentioned several times over the years that Tracey's PSRU is NOT
suitable to handle the loads imposed by heavy constant speed props.
If Tracey's prop shaft is from a dragster rear axle, what part of the
overall assembly do you think is the weak link? The prop shaft appears to
have good bearing support and good bearing spacing. Is the weak link within
the gearbox or is it the flex the gearbox  could impose upon the aluminum
adapter plate? Thanx,  Dave M


Well Tracy will tell you the same thing. I think the 1 3/8th" shaft is a bit
undersized compared to an aircraft engine  over 2 inch diameter crankshaft.
That does not sound like much but the bending moment of inertia is diameter
to the fourth power as I recall.

The other thing about the design that makes it heavy is the front ball
bearing takes both radial load and thrust load. In a two inch size it would
weigh well over 5 pounds I am guessing. Ross did the smart thing and used
needles in that application as well as needle thrust bearings on a two inch
hollow shaft.
Not only are they much lighter in weight they are much cheaper. The original
Ross gear box was ten pound lighter than Tracy's. Some of them are still
flying 30 years later. True they had a few minor problems like no thrust
bearing for the helical sun gear but that problem was fixed near the end of
the company.
A copy with the six pinion gear set and Tracy's torque isolator design would
be great.

Paul Lamar

Is it the weight of the CS prop itself that is the problem with Traceys
PSRU? I was planning on CS with vari-prop, it actually weighs less than the
fixed pitch Zenith spec'ed for my 640.
C. Smith

Yes it is the weight of the 50 pound metal prop.
More specifically its rotating inertia.

Paul Lamar