Peter Cowan/Lexi Cameron wrote:
 >
 > >My impression is it is well engineered for an internal spur gear

drive.

 > >It is also true that internal spur gear drives are heavier than a
 > >planetary drive of the same torque capacity and cost more.
 > >They also have an undesirable thrust line offset for most aircraft
 > >installations. They lower the engine relative to the thrust line

taking

 > >up valuable room needed for a cooling radiator. I don't see the

advantage.

 > >Why bother?
 >
 > 1: 2.4 reduction. Some slow planes need big props
 > 2: Same rotation as other aircraft engines so more access to props
 > 3: Offset shaft also gives more room for the longer prop mentioned

above

 > 4: Weight and price differences are not a significant percentage.
 > 5: Made in CANADA.
 >
 > Don't get me wrong. I like and respect Tracy and his drive and would

buy one

 > in a minute but for these factors.
 > Peter.

 1: 2.4:1 is a slight advantage over 2.17:1 but if we can get Tracy to
 build 2.85:1 that is even better.

 2: OK

 3: I don't see this. The engine can be mounted anywhere.  If you mount
 the engine higher the prop will be higher and you will have just as much
 trouble seeing over the cowl. There is no visibility advantage to
 a internal spur gear box with the thrust line higher than the Mazda
 engine center line because the gear box itself sticks up above the

engine.

 4: OK If a 10 pounds or 15 pounds does not bother you.

 5: AhHa! Now I understand! Got to keep them Canucks employed :-)

 Good thing most Americans are willing to buy Canadian products :-)

 Paul Lamar

The situation is different than that for a pusher. Even if I position my
e-shaft at Rutan's recommended thrustline position, I will have to have some
warts on the cowling top to accomodate the alternator and waterpump fitting.
Raising the engine for prop clearance is not an option. With Tracy's redrive
my prop will 2 inches aft of the previous O320 position, which will put it
closer to the ground on rotation and flare. Prop clearance can be a real
problem in a pusher (except for Perry's ducted fan). Visibility over the
gearbox, on the other hand, is not an issue. The extra weight might be an
issue depending on where my final cg ends up.

Dick Gregory
LongEZ N613NC

Ten or fifteen pounds extra weight is a bad trade off for a two inch higher
thrust line. Why don't you cut off the water pump and move the alternator
to the AC mount on the left side of the engine with a small chunk of angle iron?

Paul Lamar
 
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