Got the gears for my new gear box.
This is the back Ford  planet set with steel planet
carrier. Only about 7.5 pounds.

This will allow the p-port engine to rev to about 9,000
for take of making close to 300 HP.

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.

There are a couple of ways to get the torque out of
the rotating planet carrier.

1. EDM the roll pins holding the planet shafts in and replace
them with 1/2 inch shoulder bolts. The S-bolt hardness is only C32.

2. EDM a 7/16th hole in each shaft and use a regular 7/16th bolt.

Both methods have their good and bad points.

I'll probably try the first method  first.

What do you think Larry?

Paul Lamar

Paul,
Personally, I would remove the roll pins (by drilling on the
opposite side and punching out) and remove all the stock gears,
shafts, bearings and such. Reverse engineer the steel housing, then
I would machine one to fit my output shaft, reusing all the ford
shafts, pins...... the whole lot. It is the most machine work, but
the safe way to go. Ford already figured out how to make it last, so
don't change the core items. The ring gear can be done with a tight
press fit and a couple of roll pins to lock it. Sun gear can either
be done the way Tracy does it, or make a new shaft and have the sun
gear cut on it like the Ross drives. The Tracy method is fine unless
you are going to make lots of power. Larry

That is a good idea for getting the roll pins out. I did not think of
that. You did :)

On second thought those shoulder bolts have rather lax tolerance
at minus nothing plus .004. C32 is also marginal. Probably better to
make your own. What would a good shoulder bolt cost hardened to
Rockwell C50 or so and final ground?

Do you do your own splines or do you farm them out?

Paul Lamar

Paul,
I cut straight splines here, but farm out any involute splines. I
would stay away from using shoulder bolts as the load is applied in
single shear and any deflection in the pin changes gear tooth
loading. Whatever carrier you build, use the pins in double shear.
If I were making pins.... 300M tool steel Larry

In effect the use of the stock planet carrier straddles the planet shafts.
I will not use the shoulder bolt option. 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.

Paul Lamar

Paul

How about sandwiching the roller bearing at the planet interface end
of the shaft
and using thin needle bearing(s) at the prop end?  This could
simplify oiling and machining/assembly.  A design I was thinking
about had the input shaft under pressure with spray jets to lube the
planet gears.  Do we still want to have the HP indicator?  I had
sent a sketch on 12/16/10 with these ideas.

For those of us wanting to reduce weight for a single rotor, is it practical
to
"swiss cheese" the planet carrier?  I was able to take 3/4 lb off the
carrier and
another bunch of weight on the ring gear by maching the OD, and then
parting off the not needed smooth ID section.  Strength should be
maintained because of shrink fit the ring gear into the housing.

Dan F

Paul

Thanks for posting the sketch.  For the most failsafe design should
the roller bearing be on the prop end?  Then if there is a failure
the prop shaft would most likely stay in.  To the thrust component
of the prop we have to add the thrust component of the gear assembly
which is additive to the prop thrust.  The planetary thrust bearings
will be eliminated with your design, reducing part count.

Dan F

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

Paul Lamar

The ring gear is locked into the housing; the planet carrier is located fore
and aft on the prop shaft. That leaves the sun gear on the input to need to
have thrust bearings to control end play.

Dale Davies