Got the gears for my new super simple gear box
with the four inch diameter aluminum prop shaft.
This does away with half a dozen parts and the need
to heat treat and grind a steel prop shaft.

This is the back Ford  planet set with steel planet
carrier. Only about 7.5 pounds.

This will allow the p-port rotary engine to rev to about 9,000
for take off making close to 300 HP. Since Dave Leonard
went 230 MPH with his turbo rotary RV6 at Reno last week
my rotary RV4 ought to go about 240 MPH once I get the carbon
tail done.

It will be a while before I need it so I'll slowly gather
all the other needed parts together.

It will need a custom input shaft due to the large internal diameter
of the sun gear. I am not comfortable with a sleeve.

In effect the use of the stock planet carrier straddles the planet shafts.
I will have the current 1/2 inch planet shafts EDM-ed out to 3/8th while
they are still in the planet carrier. That way we will keep the stock
finish and hardness.

Six 3/8th inch diameter bolts on a 3.25" BC are over kill anyway.
There is room for six 1/4 inch dowel pins as well. The holes are
already in the planet carrier for those. I am not worried :)

BTW the planet carrier is not steel. Probably sintered powdered iron
alloy. We found that out today when we machined the teeth off.

John Lynch turned me on to high fatigue limit 7075 T73 for the prop shaft.
40K fatigue limit. The tensile is a bit down from regular 7075 T6.
He claims it is at least twice as good as 6061 T6.

He also says to chromic acid anodize. The one inch wall is way
over kill so I am thinking of machining it down where possible
to 1/2 inch to save a bit of weight.

Here is a good 7075 source. Sunshine Metals in Orange County
or Future Alloys in the San Fernando valley 818 701 1144

We used John's lathe today. He builds a lot of stuff for F16's.
He also did the 2nd landing gear design and build on the NXT.

Flying straight and level there is no radial load on the thin section
bearings with a planetary unlike a spur gear transmission.

This is so simple I should have figured it out years ago.
I had to get over my prejudice for using aluminum for a prop
shaft. Basically all it is; is a simple spacer between the planet
carrier and Warp-Drive/Sensenich type prop flange.
Sensenich is now making 50 HP blades for O-320 RV's.

This a a comparison with Tracy's box.

BTW rumor has it the stock Sensenich two blade hub cracks.

Paul Lamar


Good morning Paul,

You are up early. It must be before 4AM there.
I have sleep problem and then it is almost time to get going for work.
Which bearing do you have in mind? To me the one to use would be the 71822
CD/HCP4 as it has the highest load and fatigue ratings. Granted 1 lb each
but
a bit of weight with higher load and fatigue tolerance might be a good
trade.

Dale Davies

They are all pretty much overkill.


Paul Lamar


Paul,   I am trying to cross reference bearings for my PSRU to compare
prices (unsuccessfully so far) and I ran across something you might could
use.  They sell Torrington shafts used in planetary sets.  One common model
has the hollow drilled center you are looking for with softer ends for
staking into the planetary carrier. There are also different end
configurations such as snap rings  and different lengths.   Try
www.daltonbearing.com/torrington/torrington-planetary-gear-shafts.aspx

george grimes

I found a source for the thin section bearings. Apparently these are silicon nitride
balls so they are over kill for our purposes but are top quality. These
are good to 1000 F.  I am not sure the seals would live at that temp however.
Probably not.

BTW Tracy's front ball bearing is also sealed in case you were wondering.

You will need 2.

BTW this gear box design will work with the front planet and yield 2.85:1 for those
that just want to cruise.

Paul Lamar