Paul,

Thanks for the gear box/speed reducer pics - Interesting - A few questions -

1 - Good lifetime on the needle bearings ??

2 - Looked like uncaged bearings ??

3 - Presume the 10 lb heavier unit used some other type of bearings ??

4 - What provisions for lubrication ??

5 - The drawings have all the appearance of a multi-thousand dollar
product - Price range ??

6 - Cooling problems - I would think that there might be some with uncaged
needles ??

7 - Doesn't look like a particularly difficult project from a machining
perspective -

8 - Presuming outer housings are aluminum castings - Patterns exist ??

Roland Friestad



You must keep the RPM on the  needle bearings down. Particularly on
the thrust needle bearings. Those tiny needles are really zinging around
in there. We have a lot of experience on this. Some people have worn them
out. That is the reason for three back to back. The RPM on any one is one third
of the total.

The shaft, surprisingly, does not get any load on the bearings
until the aircraft stalls or spins. Characteristic of planetary gear sets as all side
load is canceled out. Hard to imagine but true. Those give no problem and they
are much lighter, as is the housing, if they were ball or tapered rollers.
Win win situation not to mention much lower cost all around.

Note the extended point set screws are better and easier to machine than
splines. All back lash is eliminated.

I have an account set up with a local wholesaler of tranny parts.
I make no money on them I just charge cost plus shipping.
The 3.17 gear set is just under $200.

The box can be built for under 5 or 6 hundred in parts.
It all depends on what the NC shop charges.

Shares synthetic oil with the engine. BTW the oil stays clean in a rotary.
 Uses the engine oil cooler.

Here is some more stuff on the subject from 16 years exp. :)

There will be more on the rubber coupling with the engine.

Paul Lamar

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