Anybody know the tooth contact ratio for Tracy's RD-1C?  Tracy?  Powersports
is over 2:1 according to their website.  Just wondering.  Been doing some
research on Powersport's package.  I am planning on doing it myself through
Tracy, but just wanted a comparison.

Chad
KBMI

In the latest Ford A4OD planetary you have at least six teeth or line contacts
assuming one per planet gear. Probably more as the gears are helical
instead of straight cut like the Power Sport. All the torque goes through
those sun gear planet gear line contacts in the form of compressive stress.

Total line contact length (bottom line stress wise) is there fore
about 12 inches for the A4OD planetary set up assuming a 2 inch gear width.
Assuming the Power Sport internal gear is 4 inches wide
that would give the A4OD planetary a 3:1 edge or one third the stress,
all other thinks being equal, over the Power Sport internal gear arrangement.
Despite this the complete A4OD planetary set weighs less than 11 pounds
and cost about $150 new. The Ford A4OD box is used in the F250 Power
Stroke 250 HP turbo diesel. This engine has close to 600 foot pounds of torque.

These are the facts. Not my opinion.

IMHO if you are going to pay $6,500 for a gear box I recommend
the Mistral with hydraulic prop governor drive. Hydraulic props
are much more readily available, cheaper and more efficient than
the current crop of composite (mostly wood) electric constant speed props.

As shown in these pictures Robin and I took at OSH and at the Paris airshow.
The red arrow points to the Mistral PSRU governor mounting pad.

Paul Lamar