"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