George G,
 Very interesting, you have put a lot of thought into this.  Does anyone
 know if the e-shafts are heat treated at the factory?  Would an older,
 and heavier, e-shaft for the engine section next to the PSRU be slightly
 stronger?
 Concerning the PSRU, look at the dampning to see if a more rugged
 connection is needed.  Then, will the alum housing take all that
 torque? A possible alternative would be to use an Allison trans
 gearset as they are straight cut to handle even more torque of a
 big diesel and maybe a double wall welded, steel rings and
 sheetmetal, housing.

 I remember Steve Beckman discussing their PSRU and how they made
 everything stiffer to eliminate the need for dampning.  An
 engineering analysis showed the improvements eliminated harmonic
 problems.  Don't know if this solution would work with a planetary gearset.
 Dan F

Dan, Torsional resonance as the name implies deals with resonance of
mechanical systems resulting from torque applied to rotate the shaft. This
can be calculated for rod and crank piston engines from known formulas. They
are complicated by anyone's definition, however they can predict the
resonant frequency throughout the range of operating RPM of the device.The
entire system including engine and gear train is analyzed. the lowest
frequency will reoccur  at all multiples of itself.One at 700 would repeat at
1400 2100 and 2800. Halfway between the resonant frequencies are the sweet
spot where you want to be operating.An accelerating system passes through
these frequencies  in most cases quickly enough that the resonance doesn't
build to catastrophic levels. Porsche spent 4 years getting their 928
gearbox built into their rear axle connected to the front mounted engine by
a driveshaft running at engine RPM. In a forum at sun-n-fun Tracy Crook
pointed out that his original ross  redrive had problems at low idle speeds
just off minimum idle. He operated his by passing through this speed as
quickly as possible but later dscovered that the original ross used the
small engine thrust bearing for propeller thrust.


The car thrust bearing is
only to keep the rotors from scrubbing ths side housings during
acceleration, braking and when the clutch is depressed and end loads the
shaft to 2800 pounds.Tracy just designed his own  to eliminate all known
problems. The financial success of the redrive was a surprise and the
production of parts has hampered his available time to finish his current
airplane project.His wife Laura does a lot of the logistics
now which is really helpfull.


If you can't avoid operating at a resonant
RPM  It can be changed by adding mass to one or more of the components. More
mass lowers the frquency and occasionally or often the second frequency is
above the operating RPM.The problem with added mass is the possibility of
increased point loading at some junction of parts due to the dampening of
the mass which causes fatigue related failures. The allison transmission
planetary gearsets extend beyond the deisel pick up truck into heavy truck
models, large taylor forklifts and others. The gear ratios available are of
prime importance and the 2.85 six pinion ford is an excellent choice.


The
planetary gearsets drive simultaneously with six gear teeth in contact and
are self centering. small manufacturing variations wear in or lapp
in quickly from new and all gears are loaded. The operation of the airplane
at other than cruise angle  of attack on the wing such as climb or
aerobatics puts the thrust line of the prop out of alignment with the
incoming airstream. This results in more prop bite top to bottom since the
prop is now at two different angles of attack top to bottom.This is called
P-factor and causes a bending of the propeller shaft. The direct drive
aircraft engines in certificated aircraft are pretty much model specific and
prop specific and they don't always get it perfect.

I remember a recall on
540 engines a few years back where there were sudden catastrophic failures of
the crankshaft. A large diameter tubular redrive shaft as Paul posted
yesterday is the bullet proof way to attach a prop to an airframe. I am
wondering if the thrust bearings might be able to be put inside the tube
diameter by mounting a 3 set stack off the back of the planetary just bigger
than the sun gear shaft on the same studs that hold the planetary cage.It
may not be lighter than the RD-1C but the strength to weight ratio would be
impressive.

As far a older 13-B e-shafts go  there are no real dimensional
differences or materials and the 4340 doesn't need heat treatment for
strength although hardening of the bearing surfaces could be done. The RX8
looks the same as RX7 but there is a very slight taper on the stationarry
gear bearings and also on the bearing shells The tapered e-shaft if used
with tapered bearing shells has been used by drifter car people mainly
because the e-shaft was then current production and half the price.I hope to
send a CD by mail Monday to Paul to the address shown on newsletter
postings, if there is a different desired address I need to know by then.
Well my wife needs the computer so I am out of business for a while.

george grimes

Well done George. That covers a lot of areas.

830 East Santa Maria St.
Suite 303
Santa Paula CA
93060

Will work.

How are you at building computers George? I have
some free old computer parts you can have like mother boards hard drives
and memory. Linux is free. It runs fine for email on old
hardware.

BTW if you build a six rotor engine what prop would you use?
a Multi blade prop is less efficient that a two blade prop except
for climb. Large prop diameters soon become a problem for landing gear
design. Here is a way to use two 3 rotor engines in a counter rotating
prop arrangement. Multiple V belt drive. The new small kind. Many of them :)

Here is the way GM took the power out of a four rotor.

Paul Lamar