PSRU design advantages

George wrote:
Richard Lamb wrote:

ADK wrote:

IF you had to design a PSRU, to drive a pusher propellor via shaft,
what would your experience dictate? Thinking along the lines of a
gearbelt, chain or gear. Please, I would appreciate the collective
experience available on this group. I have decided on the aircraft,
but want to make it the most reliable and safest it can be.

"ADK" wrote in message
news:X6TXf.28774$%H.11944@clgrps13...

This is probably going to open old wounds. What I would like is
experienced input on the advantages, for economic, efficiency and
longevity etc. of different types of redrives.

I am leaning towards a cog-belt reducer in a 6 cylinder, liquid
cooled, configuration driving a long drive shaft to the prop.




The collective experience is zilch = nada = squat = undefined.

THAT is what everybody had been trying to tell you.

Wait a second. Look around the airport.

How many shaft driven propellers do you see?

Have you ever seen?

If you are heart set on doing it, I sincerely wish you luck.

But I can't offer any further advice - 'cuz they ain't none...



Richard


Richard,

Didn't the military do this once?? Seems there was the P-39 Aircobra,
shaft driven from a rear mounted engine?? Are the gray cells working
that far back??

Not that it would be applicable to an experimental, but at least It was
once done?

George

Wasn't the gub'ment, George, but Bell Aircraft.
P-39 not only had a drive shaft but a cannon firing thru the psru gearbox.

layout of engine, gearbox and cannon at:
http://www.home.earthlink.net/~tp-1/p392.jpg


So it *can* be done.
(The cannon firing thru the prop! )

I was curious to see if Bell had reduced the shaft RPM between the engine
and gearbox, but it looks like 1:1 there.

That might have been of interest to the OP, since his setup will likely
drive the shaft at prop rpm (after the psru).

Gonna take one tough (probably spelled h.e.a.v.y) shaft for that service...


Are there any others?


Richard

-----------snip------------

Wasn't the gub'ment, George, but Bell Aircraft.
P-39 not only had a drive shaft but a cannon firing thru the psru gearbox.

layout of engine, gearbox and cannon at:
http://www.home.earthlink.net/~tp-1/p392.jpg


So it *can* be done.
(The cannon firing thru the prop! )

-------------snip-----------

IIRC, the Messerschmidt ME-109 (a/k/a BF-109) was similar--except that the
long driveshaft was omitted, the engine was in the "normal" location, and
the canon was located in the valley area of the engine.

Peter

"Richard Lamb" wrote

So it *can* be done.
(The cannon firing thru the prop! )

I was curious to see if Bell had reduced the shaft RPM between the engine
and gearbox, but it looks like 1:1 there.

Yep. The normal speed reduction unit for the prop is taken off, and put at
the end of the shaft.

That might have been of interest to the OP, since his setup will likely
drive the shaft at prop rpm (after the psru).

Gonna take one tough (probably spelled h.e.a.v.y) shaft for that
service...


Are there any others?

There are numerous dual rotar sling wings that have an interconnected rotor
shaft, but they are usually turbine engines. One example is the Osprey.

The normal Allison AC engine also had an active fluid torsional resonance
reducer at the non driven end of the crankshaft on the engine, and a
torsional reducer coupling (rubber) on the drive end. I could not find
that info about the aircobra, but I'll bet they are there on that
application, also.
--
Jim in NC

"Morgans" kirjoitti
...

"Richard Lamb" wrote

So it *can* be done.
(The cannon firing thru the prop! )

I was curious to see if Bell had reduced the shaft RPM between the engine
and gearbox, but it looks like 1:1 there.

Yep. The normal speed reduction unit for the prop is taken off, and put
at the end of the shaft.

That might have been of interest to the OP, since his setup will likely
drive the shaft at prop rpm (after the psru).

Gonna take one tough (probably spelled h.e.a.v.y) shaft for that
service...


Are there any others?

There are numerous dual rotar sling wings that have an interconnected
rotor shaft, but they are usually turbine engines. One example is the
Osprey.

The normal Allison AC engine also had an active fluid torsional resonance
reducer at the non driven end of the crankshaft on the engine, and a
torsional reducer coupling (rubber) on the drive end. I could not find
that info about the aircobra, but I'll bet they are there on that
application, also.
--
Jim in NC

The Bell P-39 Airacobra V-1710 engine does have a direct drive from the
crankshaft to the 8 foot extension-shaft. This coupling certainly may have
some kind of a damper unit? The rotation speed reduction is done in the nose
section PSRU unit. The extension-shaft does have a support bearing unit in
the middle of the shaft.

Here's some nice pictures about the powerplant/driveline combo
http://www.aviation-history.com/engines/allison.htm

"However, there were problems with the complex nose-mounted reduction gear,
which caused reliability problems and resulted in fairly low serviceability
rates as compared with other fighters"
(http://home.att.net/~jbaugher1/p39_1.html).

JP

"Morgans" wrote in message
...

"Richard Lamb" wrote

So it *can* be done.
(The cannon firing thru the prop! )

I was curious to see if Bell had reduced the shaft RPM between the
engine
and gearbox, but it looks like 1:1 there.

Yep. The normal speed reduction unit for the prop is taken off, and put
at
the end of the shaft.

That might have been of interest to the OP, since his setup will likely
drive the shaft at prop rpm (after the psru).

Gonna take one tough (probably spelled h.e.a.v.y) shaft for that
service...


Are there any others?

There are numerous dual rotar sling wings that have an interconnected
rotor
shaft, but they are usually turbine engines. One example is the Osprey.

The normal Allison AC engine also had an active fluid torsional resonance
reducer at the non driven end of the crankshaft on the engine, and a
torsional reducer coupling (rubber) on the drive end. I could not find
that info about the aircobra, but I'll bet they are there on that
application, also.
--
Jim in NC

Sounds like a pretty sure bet to me. BTW, Thanks--I had wondered what
Allison did to eliminate resonance.

Peter