question to Paul

I am Pascal from France and have the following question:

I received the data sheet of the gear reduction drive of the Ford E40D.
But there are 3 planetary systems in it:

1) The over drive planetary

2) The front planetary (I think this is the right one)

3) The rear planetary.

I intend to build my PSRU for an RX8 engine with the ration 2.85, a
kind of a copy of tracy’s design who unfortunately doesn’t produce it
anymore as he retired.

Then I try to solve my problem by myself.

Which one is the good one??

Thanks for your help.

Best regards

Pascal

Pascal Virlouvet Project Engineering Manager, GMT Packaging Operations

.....................................................................................

Is kind of confusing. The very front planet set is the overdrive planet set.

They don't call it the front planet set because the second planet set
was called the front planet set for years and years long before there
was an over drive version :)

The front planet or middle planet set is the one to use for 2.85.

So far nobody has used the over drive planet to my knowledge.

The rear planet is used for 3.12 and it is the strongest.

Now we can add France to the list of many countries making gear boxes
for the Mazda rotary engines used in air planes :)

BTW I might add Tracy's was not the best design.

Paul Lamar

Thanks Paul

I got the details of a FORD E40D gear box and completely understand what
you mean by the front being the overdrive and the front installed in the
middle

Question: the 6 pinions one (middle or front) is capable of which max
power (I need 200 HP ). The rear one, strongest would surely absorb a
300 HP BUT 3.12 ratio is too low.

I will design a gear box "copying" mistral one by doubling the bearings
(rolls and balls) to support axial and longitudinal loads

I need to wait to receive my E40D to make measurement to draw around the
box (except if you already have those dimensions)
And yes you can add France :)

Best regards
Pascal

The max power is a function of how cool you keep the gear box oil.
Max torque and torque fluctuations are important parameters.
Rubber couplings mitigate the shock of the torque fluctuations
on the gear contact lines and damp some resonance problems.

The 3.12 is not too low if you want to get the most power from a stock Mazda
RX8 engine. The stock RX8 red line is 9000 RPM and the most RPM you will
see
with a 2.85 and a 70 inch prop is 6500 to 7000. The prop tips are transonic
at that RPM. Intake manifold runner length is critical for what ever max
RPM you choose..

Paul Lamar

BTW IMHO Lew Ross did a better job of gear box design in 1973 than Mistral
did with a larger diameter prop shaft, lighter weight and super light weight
(and lower cost) needle bearings. Ball bearings are HEAVY.
The Ford planet sets have a zillion needle bearings.
Not only that there are thousands of hours on Ross gear boxes.

Here is a P&W recent design.

Paul Lamar

I just did a quick search on Lou Ross PRSU's I can not find an example of it. Anyone have a set of drawings for it ?

George Curtice

This is what I have that Ross published.

However it is so simple that anyone can make dwgs of it.
Once you know the hollow shaft diameter, you have the SAE prop flange
dwg and you have the planet set there is only one way or dwg that will work.
It weighed only 35 pounds. Ten pounds lighter than Tracy's design that
used a Chevy rear axle and a large rear axle ball bearing.

It just needs two minor improvements. A way to get the prop flange
on and off for maintenance and a thrust bearing for the helical sun gear.
Ross pinned and tack welded the prop flange to the hollow shaft.
Extended point set screws where not invented yet.

BTW set up a folder named PSRU so you can save all these attachments
on the same subjects. That way I will not have to keep uploading them.

Paul Lamar

Paul,

Thanks for the wealth of information in your newsletters and on your website. The PSRU design is starting to make a lot more sense to me, your solid works drawings are very helpful. I can see the benefits of the hollow shaft as most the torsional load is applied at the outside of a solid shaft anyway.

Two questions:

1) Is the aluminum housing that attaches to the bell housing and contains the planetary gears a custom made piece, or can it be bought off the shelf?

2) In your other post I saw a prototype for a silicon torsional damper. Is this design tested, or would I be better off going with a clutch damper plate for now?

Thanks,
Clark Brinton

In the case of the Ross it was a custom casting.
Now we use spacers and a combination adapter plate and motor mounts.

The clutch damper does not hold up.

Go with the rubber damper. It is over designed for the job.

Paul Lamar

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