Here is Bud's opinion on planetary gears the rotaries have been
flying with for the last 38 years.

The truth is the planetary has six times the critical line contact
length of any spur gear of the same width and that is
why they have been used in all size aircraft engines for
the last 100 years.

Just because you can rebuild a racing engine does not mean
you are a competent engine designer or gear box designer let alone
aircraft engine designer. I know a lot of race engine builders :)
Just about every SCCA racer builds his own engines.


Paul Lamar


"What about planetary gears in a PSRU?
I choose to use the best for safety and dependability in the Geared
Drive. For this reason, I am against the use of planetary gears in a
PSRU. Consider what they were designed for; to change an automatic
transmission from one gear and into another. They were designed to work
at high RPM for only short periods of service. They are very small and
turn at ultra high RPM when in continuous use, and from twenty plus
years of personal experience in professional auto racing, my personal
opinion is that there is any way that planetary gears can possibly hold
up long term. The strongest and most dependable kind of gear is a
straight cut spur, which is what I chose to use in the Geared Drive PSRU. "


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Just a question.  Has anyone ever made a PSRU using quick cjange gears? I see them on all sorts of race cars and I've not heard of them failing eeven with the high hp enignes.  If you look at a supplier like Speedway, they have all sorts of ratios availalble off the shelf.

Vince Homer

At 15 minutes per race once a week how long would it take to get 2000 hours on them ? :)

The other problem is: how do you get 3:1? I think you need at least
two sets and that adds a lot of weight to the housing.

Paul Lamar