Question:

 Handpropping a rotary engine ... Possible?  Easy/Difficult?
Robin Berglund


 Difficult due to the gear box. One rotation of the prop is
 2.88 revs on the engine. A lot depends on the EFI tuning
 and the position of the fuel injector relative to the rotor
 housing.

 Also it is a function of prop inertia. A low inertia
 wood prop would not help.

 Paul Lamar


While the effort (perceived torque) to turn the engine with the prop
will be relatively high, swinging the prop a relatively short distance
will cause a comparatively large (and fast) rotation of the engine -
aiding in starting.  The rotary's relatively low compression ratio and
small displacement may make it possible.  In a way, isn't propping a
geared engine much like propping an engine with a large number of
cylinders?

Has anyone tried it?  It should be approached with great care as
propping any engine is potentially very hazardous.


Matt-



It is easy to turn the engine by advancing the prop by hand.  However,
Tracy's controller has a minimum speed and number of compression cycles
before it will trigger the injectors and ignition.  While that is a very
nice safety feature it makes hand proping impossible.  You could do it with
a different type of ignition system.

I have left my master switch on a couple of times.. easy enough to jump
start with a car.  But it is still important to run it on the ground long
enough for the battery to recover before attempting flight.