12 a

Paul, looking at the Ross PSRU pics, has there been any failures at the ring gear to
output shaft weldment ?

Steve Carlisle

Not that I have heard but the HP was quite limited. That was 20 years ago.

There was a Ford stock bulkhead  that was inserted into the ring gear and that had a
spline the prop shaft fit in. In those days it was not powdered metal.

I don't know how Ross fastened the prop shaft to that bulkhead. Unlikely he used a mating
spline. It would not surprise me if it were  welded. The prop shaft was larger in
diameter
than any Ford shaft being around 2 inches.

That was not the correct connection anyway. That limits the reduction to somewhere around
2 to 1 and rotate in the wrong direction.

The prop would then limit the engine RPM to around 5000 RPM and
that in turn would limit the HP to well under 180 HP. Probably around 150 HP.

Another factor is ....in those days P-ports were not common further limiting the HP.

Paul Lamar


As soon as people get the idea to do away with the old fashion steel SAE prop flange
and go with an aluminum ground adjustable hub gear boxes will get lighter
and lower cost to make.  Also their airplane will fly better as they can get just
the right prop pitch to suite their needs.

The expensive and heavy traditional  prop flange is so
implanted in people's mind that they don't think about it.
Probably they don't even see it.

Perhaps something will work better. Yes I think it will.

The trick is connect an aluminum ground adjustable prop hub directly to a steel
prop shaft on a gear box doing away with the expensive and heavy steel prop flange.

John Lynch came up with a TTC coupling that can replace splines. Splines are expensive to make
as they require an expensive machine tool dedicated to making splines  probably costing thousands.
It worked very very well as we got the record.

This pin couple can be done on any NC mill rather quickly. It will couple an aluminum prop
hub (adjustable pitch) to a steel prop shaft no problem. You mount the shaft vertically
and drill 18 precisely located small holes about 3/16 inch in diameter. Voila you have a replacement
for a spline.

Tell you gear box maker you want one.

Paul Lamar

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