I mentioned last month that I'd detected metal particles in my oil.

Since

then I've traced the problem to a broken Sun-gear tooth, which tore up

the

Planetary pinion gears.  Only one tooth was slightly damaged in the

Ring

gear, but there were several gouges inside the ring-gear bulkhead.

See

attached photos.

Notice that the Sun-gear tooth failure began at the oil lubrication

hole.

Notice also the apparent galling of the sun gear teeth.  I don't know

if the

tooth failure caused some of this galling, or if it occurred previous

to the

tooth failure.

I had hoped to repair the redrive and replace the 4-pinion planetary

with a

six-pinion unit, but with the galling of sun-gear teeth I am wondering

if

the effort would be worthwhile.  A couple local mechanical engineering
retirees tell me that the tooth failure appears to be a high-cycle

fatigue

failure, although it may have been damaged during the manufacturing or
assembly process.

My next step is to dissassemble the forward housing to inspect for

further

damage and see if the prop shaft and bearings are usable.  More on

that

later.

Tom Parkes

Looks like you will need a whole new set of six pinion gears from
Slauson Transmission.
First hard data that the turbo three rotor is too much for the C6 four
pinion
version. Any sign of overheating in the gears Tom?

Paul Lamar

Al Gietzen wrote:

Paul;

In the few hours that Chuck Harbert ran and flew his turbo 20B, there
was a clear problem with the Ross drive.  Early indications were
excessively high oil temps exiting the drive and signs of high temps and
stress on the gears.  He worked on mods to the oil system, and other
changes I don't recall now.  It wasn't clear that the problems got
resolved.

Al

Yes too little info. 


On the other hand Tom has about  100 hours on his.
I agree with his consultants. The tooth failed from low cycle fatigue which
indicates high tooth loading. The crack started in the classic place.
Right around the small drilled hole at the base of the gear tooth.

The 2.85:1 sun gear does not have that hole. Also the tooth loads
will be 50% less on the six pinion as six sun gear teeth are
involved rather than only four.

Also I think Tracy's method of torque isolation using rubber bushings
is easier on the teeth rather than the clutch disk Ross used.

I know this is bad for Tom but I am rather relived that we finally found
the limits of the Ford C6 planetary. I was starting to worry it
was WAY OVER designed for our use :)

Paul Lamar
 
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