Perry Mick wrote:

Now for the news that everyone has been waiting for!

Well, actually, maybe only a few have been waiting for.

My plane is down for annual so I took the engine off for the
first time in 2.5 years.  Took the front cover off and inspected
the thrust bearings this morning.  They look completely normal.
There is no noticable wear on the thrust plate.  123 hours.

Could it be that the Ross redrive is somehow harder on these
bearings than a prop is?

I'm thinking of reassembling it and measuring the end play so
we have some numbers.  Then replacing the bearings anyway since
the set is only $50, then send the old one's to you to inspect.

Based on this encouraging news, I'm offering the flywheel to prop
adaptor for sale.  Not produced by me of course, but Saber
Manufacturing.  The price is rather high because it's based on
a production quantity of one.  The price will come down if more
are made at one time.  If you use the starter in the stock position
you need a prop extension.  Might want one anyway for streamlining.
It's only been tested in pusher configuration.

--
Perry J. Mick
Duckt N7XR
http://www.ductedfan.com

Tracy Crook wrote:

Yes, there is an enormous diference between your direct drive and the forces
imposed by the helical gears in the Ross drive.  I don't have the exact
formula in front of me right now but the force from the gear is something
like Max engine torque (in foot pounds) divided by input gear radius (in
feet) times cosign of the gear helix angle (22 degrees).  This calculates
out to about 800 pounds.  At 200 mph and assuming 200 HP, the prop thrust is
far less than 300 pounds.  Running direct drive, the horsepower (and thrust)
would be even less.

Tracy Crook
rws@altavista.net

Applying our HP formula... if the prop efficiency is 80% the thrust at 200 MPH is
is 160 HP net out of the prop times 550 divided by FPS or 293 FPS or 300 pounds. 
Very good guess Tracy.

The worst case is full throttle climb at 100 MPH (146 FPS) or below where 160 net HP 
out of the prop translates into at least 600 pounds of thrust assuming the engine 
is running at max HP RPM.


Paul Lamar
 
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