Marc Wiese wrote:

Paul, I told him you wanted to talk to him about a planetary constant
speed high reduction model that they might consider making so don't
miss him!

I don't recall saying that.

Aren't we all always on the lookout for a lighter weight, higher power
cs unit? If I was there, I would talk to him about it myself. In any
case, it appears Marcotte has the tooling and production capacity for
such a venture. Do it for me, will you?
Marc Wiese

I don't think I will be able to talk him into a planetary if the
discussions I have had with Power Sport on this subject are any

indications.

I think he will try to sell me on the internal spur gear he
is using now.

Paul Lamar

Paul,
Sorry if this has been covered, but what are the disadvantages/advantages of
the spur gear redrive?
Thanks,
Ron Freier

Weight, weight and weight :) It is more than that. Gears tend to separate
themselves from each other with great force. With a planetary this is 
balanced by the ring gear which holds the whole works together
and keeps the gear teeth in optimum mesh. 

All gears transmit torque through line contact between the teeth. 
The amount of torque
that can be transmitted is directly proportional to the length
of this line. The next problem is the width of the gear is limited
by its diameter. One never sees a gear longer than its diameter.
This is due to torsional deflection in the gear mitigating
the line contact pressure on the outer end and enhancing it on the 
the power input end. Worse if the spur gear is cantilevered 
as is done with internal spur gears. The outer end of the gear is
less in proper mesh than the inner end due to deflection. Just 
because something is made out of steel does not mean it will not 
deflect. ANYTHING will deflect if enough force is applied.

All this means we are going to need a very large diameter and heavy bull
gear indeed to equal the line contact length we get in four or six
small pinion gears in a planetary. There is also a serious problem
with large diameter bull gears that can be over come with 
an internal spur gear and that is the growth of the gear
box with temperature. This affects greatly the tooth mesh
of a conventional spur gear box.

The bottom line is weight, weight and more weight.
The Ford planet set we use weighs only about 8 pounds.
It is widely used by Ford in F250 250 HP turbo diesel 
trucks with gobs of torque.

Paul Lamar
 
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