Paul wrote:
It happened twice so far that I know about. Different results. It just
hit me why the engine accelerates so fast. It is because the stock auto
transmission engine has a heavy torque converted bolted to the
flex plate while we are running with flex plate only.

Paul, almost any engine will rev to destruction if you open the throttle
with no load on the engine whether it has a flywheel, or not. The trick

is

not to leave the throttle open when you start them up. I ran my turbo

20B

with a light weight aluminum flywheel (about 8-10 lbs, I think) and the
Ross gbox, but without the prop, for several hours. It sure would rev

fast,

but it's really no different than stepping on the gas of a manual tranny
(in neutral) car.

Chuck Harbert

There is a big difference in flywheel weight and rotational inertia.
The flex plate normally has a heavy torque converter bolted to it
and the rotary manual transmission flywheel and clutch
plate cover is 35 to 50 pounds. The rotary engine angular acceleration IS
much much faster than just about any engine.

This is not to be taken lightly. It could be fatal under the wrong
circumstances. PLEASE be careful!

Paul Lamar

I should comment further on the latest over-rev incident.  A builder using
an EC2 and and RD-1A (with no prop load) reported that he started the engine
(for the very first time) and let it idle for several minutes to warm up.
When warmed, he slowly advanced the throttle but the engine did not respond.
He eventually he got all the way to full throttle and the engine just sat
there and continued to idle normally.  Then suddenly the engine reved to a
very high speed whereupon the flywheel/damper assembly exploded ruining a
lot of hardware.

I can't say with any authority exactly what happened because I was 3000
miles away but I think part of the story is missing.  To my knowledge, it
should be impossible for an engine to idle normally with no load with the
throttle wide open.  The symptoms suggest that perhaps the throttle linkage
may have been binding and the throttle plates were not really opening as the
throttle quadrant was being moved, then whatever was binding up the linkage
broke loose and let the throttle go to WOT.  Only a guess.

In any case, the distruction revealed the weakest point in the
flywheel/damper interface and I came up with a design change to greatly
reduce the stress at the damper drive pin mounting point.  The parts to
retrofit this change were sent to all owners of the RD-1 & RD-1A at no cost
(after test flying the change on my plane).

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

I did a few calculations. At 12,000 RPM the broken parts were moving
at 628 feet per second or 428 MPH!.

Paul Lamar
 
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