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


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.

These bearings are made in China. Unfortunately almost everything
is now a days.

More info. Try getting them direct to save money.


Paul Lamar


I would like a heads up when you area ready to have your planet pins
lazed,
I will get my 2.85 planet to you. Similarly, I will need the 7075 T73
material for the tube shaft. If you would like me to get the stuff and
send
you the length you need out of my order, we'll arrange it. I can easily
cut
it to your length on my chop saw. Don't know the cost yet. I am ready to
get
all this stuff including the bearings. If the 100x125x13 bearings are our
best option, I'll order those too. Two per shaft I presume.

I received the Creavey seals today. These things are really slick. I did
not
expect them to have a see through teflon coating.

Supposed to rain tomorrow, so I'll pay my favorite trans shop a visit and
ask about a pilot shaft with a 1.5" dia at the back end, and about an
accompanying disc center for the damper.

Ed Carver

Great Ed. This box is going to be the cat's meow.
It will be much lower cost too.

I will have planet carrier back by Thursday. It is in
the EDM shop right now. If you want yours done ship it to me
and I will put it in the EDM shop for you if mine works.
I'll know more on Thursday.

I need to do a bit more checking on the bearings. We may
be able to use steel balls and cut the $89 each price.

Another advantage of this design is it does away with the output shaft
spline to the planet carrier. That is another source of backlash in
Tracy's box.
We may even be able to lower the chatter RPM because of it.

I intend using the bell housing you got for me. I am going to use
something like this to mount it in the bell housing. It will be a very
cosmetic looking device. Something I cannot say about the current
boxes. IMHO under the cowl cosmetics are extremely important
when it comes to the acceptance of the rotary. It cannot look
like something you made with a hack saw, drill press and a
large hammer :)

In your pusher case I think you might benefit from a longer box
so you will need a longer input shaft. I am stuck with 14.5" over
all from iron to prop flange. No way do I have enough time
to build a new cowl so I will need a stock length input shaft.

Paul Lamar

I would'nt mind paying the $90 each for a sealed bearing that would last.
According to the spec, they are good for nearly twice our max speed, even
more with gear lube which requires a sump.
Having a really clean forged housing would be nice. No idea the cost. All
I
know about prop shaft length is that the current design is what is used,
as
shown in Buly's setup. I did read about possibility of setting the prop
back
further, don't know how to determine how much further.
I will try to get my planet sent tomorrow to your beach address. Did you
cut the output extension off first?
Ed Carver


I stopped in at a couple transmission shops to look at input shafts. One
shop had hundreds of short input shafts, they handed me a caliper and
told
me to go look on their shelves.
There are a few with our preferred 1.5" dimension, but have a minimum 3.5
inches from where the 1.5 ends, to where the splines begin. That is a
couple
inches longer than the current design. The spline is approx. 1.1" 10

Another possibility is using a 3rd member pinion shaft. The same shop has
as
many of those as they have input shafts. The pinion shafts all have a
spline
within an inch of the 1.5 dimension, and a threaded end that can be
ground
down for pilot use. Usually they can be fitted with a flange for mounting
our adapter plate.

Ed Carver

Take some pictures Ed.

Here is what the inside of a clutch disk looks like.
It could be used as is but Ken Welter has destroyed a few.
Early Ross boxes used them as is. I would take them apart
and tig weld the female spline part to 4130 sheet.

The female splines are square cut so it would be rather easy to
make custom splined input shafts Larry can do that using a straight tooth
woodruff key slotting cutter. The disk I have has .175 wide slots. About
11/64th as key cutters go. There are only ten splines.
Is that doable Larry?

Also this is the six pinion front planet carrier that gives 2.85:1.
The output female spline is still there and needs to be cut off.
The pinion shafts are smaller in diameter (.4375) so only a 5/16 (.3125)
bolt
will work.  However there are six 1/4 inch diameter holes for dowel pins
if necessary.

That would add .29 square inches to the shear area taking
about 14,500 pounds to shear them off at a conservative 50,000 psi
max stress for steel. Probably not needed.

The torque load at 600 foot pounds prop torque is 7200 inch pounds so
in theory the shear load is only 2400 pounds at a 3 inch bolt circle.
IMHO easily taken by six 5/16th bolts that have a total shear area of
.46 square inches. At 50,000 psi that is a max shear load of 23,000
pounds.
IMHO all and all a rather conservative design.

Check my arithmetic and numbers.

Paul Lamar


I have welded female splined disc centers the way you are suggesting. and
eliminated the springs to make solid discs by welding together the spring
rectangles.

It looks to me like the extra holes in the planet are for oil. I guess
new
pins could be installed through them if we lazed them together with the
pinion shafts. it just looks very close to the pinions. The pinion shafts
measure .417 on the planet I have.

The input shafts I saw today had square splines. Is that a ford thing? If
we
can live with the extra 2.5 inches or so in length, then these shafts
will
work. In my case probably no problem; your RV needs something shorter,
and
these shafts can't be that short due to the depth of the clutch assembly.

I measure about 4" from the back of the bell to the back of the female
splines of the modified forward drum. This dimension includes our 1"
damper
on top of the counter balance. The square splined input shafts should
work
fine for me since there is extra length on the shaft splines. All I need
to
do is have the pilot reduced to the RX dia., and of course, turn the big
end
down to our sun gear id.

Do you want some dimensions for an apparently adequate third member
pinion
shaft? They will probably let me photo one.

Next up for me is purchasing the 4.125"od 7075 T73 for the shaft, and
also
the material for the housing. I just need dimensions for both materials.
My
ring gear is roughly 5" dia

Ed Carver

.417 Yes not .4375 My mistake.

If you use the 100 mm (.3937 inch ID) bearings the shaft can be 4 inches
OD.
I don't think you will be able to buy 4.125" OD  7075 T73 shaft material.
I could be wrong.

The OD of the bearings is 125 MM or .492 so you will need at least 3/4
wall maybe 1 inch wall. 3/4 wall 6" OD tubing would be 4.5inch ID.

For the housing look for 6 inch OD 3/4 wall or 1 inch wall aluminum
tubing.
Or 6 inch aluminum bar stock. We have a shop at SZP that can quickly bore
really big
holes in really big bar stock with a really big and powerful lathe :)

Paul Lamar



That is simple enough, one 10" long 6"od 3/4 wall tube for the full
length
of the housing. The opening in the back of the bell is approx 6.2"
Do you thnk the 4" od will give us enough step to keep the 100mm bearing
in
place?

Ed Carver

Yes.

Paul Lamar

--  Flange type joints are a friction drive. The bolts are there to
provide the clamping pressure, they should see little or no shear loads.
One of the problems (there are some) with the aircooled VW is the dowel
pins and the single big nut to hold the flywheel on.  Getting enough
clamping pressure is the problem.  Doubling the no. of pins helps and
some
companies do wedge mating, a matching taper on the crank and flywheel to
increase friction and area.  The shear strength calcs should be
conservative as long as there is enough surface area in contact.


Murry I Rozansky


Hi Murry!
Hope to see you at Whiteman this month, been too busy the past couple
to get
there.

I'm not certain to what you are referring with "flange type joints".
Is it
the modified forward drum with the rivets? Or fastening mating surfaces
between the planet housing and the new 4 inch prop shaft? The 13b has a
tapered crank with a big nut holding the balancer/flywheel.

Ed Carver


Paul,
Is not that size of 125mm equal to 4.92"? I have looked at a
couple of times, thinking there was something wrong with the numbers, I
have not done a conversion but 125mm is aprox. 5"long!
John Burey

Yes. One inch is 25.4 mm.

Yes! The bearing OD is about 5 inches! That is what is so spectacular
about this gear box design. This is a classic example of how a major
technical
improvement in one field can affect a radical improvement in another.
The silicon nitride balls can allow this large OD thin section bearing to
rotate at high speeds with tiny balls that are really zinging along.

This is not your grandfather's PSRU let alone your father's :)

Despite the bearing cost of $90 each this is a major reduction in
the over all cost of a PSRU.

The use of the thin section bearing allows a drastic reduction in the
torsional stress applied to the prop shaft by doubling it's diameter. This
in turn
allows the use of 7075 T73 aluminum for prop shaft material. That in turn
does
away with some very expensive machining, heat treating and grinding
required of steel prop shafts with large diameter flanges.
In some cases forgings would not be required.

There is also a possibility that silicon nitride roller bearings can be used
as rotor bearings allowing low cost charge cooled and lubricated
Wankel engines, like the AIXRO, to rev higher and make more continuous HP.

Paul Lamar

Paul

How are you going to space the planet pins flush with the carrier?  I also
recommend using a washer under the bolt head for belt-and-suspenders
to hold the planet carrier to the shaft. Loctite and wire secure the bolts?
Are you going to include the torque meter? Design is looking really good!

Dan F

Space the planet pins?

The torque meter is so simple someone can add it if they
wish. Nobody is going into production on this as far as I know.
It is DIY.

Paul Lamar

The pins are not flush with the planet case, so any torque on the
bolts will put shear stress on the 1/8" spring pins.  Look at the pic
or better yet the planet assembly when you get it back.  What is
the cost to have the bolt holes EDMed?

Dan F

The planet carrier I have is flush. If it is only a few thou proud
a  little shear stress on the 1/8th pins won't hurt. Probably
shear them off. Put a thick washer under the bolt head to transfer
the tension load to the planet carrier.

Don't know the cost yet. Should be done this morning.

Paul Lamar