Ok  Paul,

Sorry but I am going in circles again. I can understand the concerns of a
heavy flywheel going at 7,000 rpms. If it broke loose it would take out the
engine stand and sheet metal wall.

Wouldn't it be safer to remount the transmission and bellhousing and attach
a prop to the transmission output and engage  2nd gear.?  It will be a long
unit but they have been designed to work together:)

 Paul since you have seen the workshop I use, it would be much easier for me
to whip something up in metal.

How about this?  Two or three equally weighted 34 "long   3.2mm thick 1 "
diameter pipes with sheet metal paddles welded onto the last third. The
center hub would be made from a piece of 6 in. diameter 6mm thick pipe with
a  backing plate welded on with 4 holes drilled into it to attach to the
transmission outlet drive. Whole thing mass balanced of course.

In addition he central hub needs three bosses to reinforce each hole around
the prop shafts.  The props could be rotated and locked in place (rotation
only) with set screws.  To keep them from going into orbit a ring can be
welded to each pipe on the inside of the hub.


I tried to draw it but I got stuck. I could probably make it faster:)

Doug in Japan

Your pulling my leg right? This thing will do real damage when
it throws one tube/blade at 2700 RPM. Make sure my buddy Yutaro is not
within a mile from this thing when you fire it up.

Stick with the wood design.

Paul Lamar ...No rotor no motor.

Direct-drive at 7000 shouldn't be a big problem, I was turning mine at 5400.

Centrifugal acceleration at the tip is V^2/R, V is tangential velocity,
generally around 750 to 900 fps to keep it below the speed of sound.
The V^2 term then is constant as you increase RPM and decrease R.
Centrifugal acceleration is increasing only inversely proportional to R.

For 7000 RPM and a tip speed of  750 fps you would want a diameter of
about 20.2 inches. Use very strong but lightweight materials to keep the
mass to a mimimum, force = mass * acceleration.

Perry

I have an idea Perry. Got any of those old direct drive fans
and old direct drive fan extensions lying around you can sell/send to
Doug? Doug could cut some off the tips to get them up to 7000 RPM.


Paul Lamar ...No rotor no motor.

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