> >  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

Thanks for the picture. It's the best one I have seen so far on mounting the
alternator in an alternate position. I think I can do it like that. What I
am not so sure of is my ability to cut apart the waterpump and weld it back
in another position. Even with pictures, I will need help from someone with
those skills.

BTW, I am still leaning heavily towards Tracy's redrive, as I always have
been. I was only playing the devils advocate with my above comments. Two
more inches of clearance would sure be nice though, since it would acutally
be 4 inches in the diameter measurement.

Dick Gregory

Bruce Frank can help you with the pump fab.
Bruce Frank <bafrank@worldnet.att.net>

Paul Lamar
 
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