Mr Lamar, I saw in one of the emails that someone (or you) had
said that the ford c9 planetary was better than the allison, having
better gear set up amd engagement? I'm sorry to bother you about it
nit for the life of me I can't find the discussion chain that has
it , I read it last night.

Rob Miller.

The Allison gear is four pinions but they are 1.4 inches wide and
the Ford is .9 inches wide.

The ring gear on the Ford is 4.6 inches in diameter and the
Allison is 6 inches in diameter. So line contact length is not
much different.t 4 X 1.4 is 5.6 inches for the Allison and 6 times
.9 is 5.4 inches for the Ford. Loads on the Allison teeth are a bit
lower due to the larger diameter.

The Allison however is much heavier but I don't know how much as I
never weighed it cut down. Kevin has a big lathe so maybe he will
cut one down and weigh it. It is too big for my lathe.

They both are about the same reduction Ratio. The formula is C / A
+ 1. C is the ID of the ring gear and A is the diameter of the sun
gear.


Paul Lamar

Ok thank you sir ! I thought that it said the c9 was stronger. I
know I've read that it would be better to get a 4:1 reduction, so
to achieve that would need to build a custom planetary? Would it
be possible to copy one of them just in the correct ratios?

Rob Miller

There is some Jeep Transfer case planetary that is hard to find
that will work. Not as strong as the Ford. Very expensive to make
one from scratch as strong as the Ford.

Speaking of gear boxes here is a ten to one for the turbo
compound. The input toque is limited to about 15 foot pounds at
100,000 RPM and the output torque is 150 foot pounds at 10,000 RPM.
The out put could be connected to the e-shaft with a multi V belt.
That ratio can be easily varied for tuning. This is much cheaper as
the gears are narrow 1/4 inch wide and are off the shelf more or
less. MacMaster Carr.

The ring gear is stationary and power is taken out by the planet
carrier.

It is a little over kill for a 2 rotor but would be about right for
a 3 rotor.

Another way of doing it is feed the output from the compressor
shaft into the starter ring gear on the flex plate. The pinion
would then be on the order of 1.5 inch in diameter. That is real
low cost and efficient. To get reasonable alignment the turbo
would have to go forward and in next to the prop gear box.

Paul Lamar


I am cutting down the Allison now, will let you know when I get it
done what it weighs.

Interesting thing. I have a 2.85:1 box on my rotary, and I have a
second one that was the 2:15 reverse one where the power was taken
from the ring. Playing with it I found that the ring gear is 4.25 ID,
and the sun gear is 2". That yields a ratio of 3.12 if I drive it
from the planet instead of the ring. That's coming next.

I am going to try to simplify it a bit.

Kevin Alderman

Anyone familiar with the d-drive by vrt innovations?
Could it be used between the rotary and propeller?

Matt Habez.

No advantage and much more cost.
No beating a planetary gear set mass produced and made in the millions.

Paul Lamar


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