On May 18, 7:44*am, routund wrote:
wrote:
On May 16, 4:13 pm, bildan wrote:
Re. PSRU's

There is a gear reduction unit that handles massive torque and power
the size of a a one-pound coffee can - it's the planetary gearset from
an automatic transmission. *I have two in my Jeep Grand Cherokee
'airport car' transmission that have lasted 300,000 miles - so far.
These things are built to very tight tolerances and are VERY tough.

If you want still tougher, speed shops sell replacement planetaries
that can handle 1500HP or more. *Ask *one to handle only 100HP and
they should last forever. *You can specify just about any reduction
ratio you want.

All you have to do is machine a nose case from billet aluminum to hold
the planetary gearset and the thrust bearing.

* I wish it was so simple. Without a flywheel and/or torque converter
to damp the engine's power pulses, the engine's desire to run in a
vibratory fashion will conflict with the prop's desire to run
smoothly, and at some resonant RPM the gears can die. They need almost
zero lash, or some heavy flywheel on the engine, or the damping of a
torque converter.

Dan

I'm not sure that we can handle someone who knows what he is talking about, Dan.
Isn't this group about speculation and WAGs.

Seriously, Tracy Crook and others have done a lot of work on the planetary gear
redrive in conjunction with the Wankel rotary, which BTW is a much better
solution to the overall search for the optimal aircraft engine. *Their
conclusions are similar to the ones you pointed to.

I hear rumors of a Japanese motorcycle maker that will introduce a
500cc inline 4 with direct injection. If it lives up to its Japanese
reputation, it will produce about 50 very reliable HP.

Take 5 of these 4-cyl blocks and arrange them around a common case and
crank to make a 20 cylinder, 250HP liquid cooled radial. De-rate it
to 150HP for reliability. Since it uses direct injection, the
plumbing would be air in and exhaust out. Fuel lines would be 3mm
stainless tubing from a common rail to the cylinder heads.

20 cylinders would make the engine smooth enough that the crank itself
would be plenty of flywheel. (Ever see a flywheel on a geared
radial?) A planetary in the nose case would get the prop RPM down
below 2000 RPM.

BTW, I don't think casting has any place in prototyping. Design the
parts with SolidWorks, email the file to a CNC shop who will mill them
from billet and ship the parts in a week. Machined billet parts are
FAR better than castings - and cheaper.