Blake wrote:
Loose the V-belts and go with a Poly chain. Interesting to
see the mounting of the 90 degree drive, and the cooling air to it.

Paul, I still wonder if you could somehow get vertical
operation of a rotary.... Hmmmm.

How much is lost in a 90 degree drive in percentage of total power?

Blake, the V belts trouble me too.  Every single certified
piston engine helicopter uses them for the tail rotor as far as I
can tell.  The best kit heli (the Safari formerly known as the Baby
Belle) does NOT use belts in its drive train at all.

 > >

 > Interestingly, the mechanics I talk to say that the V belt TR

drives are trouble free and very low maintainence.  Therefore I'm
keeping an open mind on the Belt drive, but my gut instinct says no
to the belts.

 Hans Conser

 > And they absorb torsional vibration. Hard to beat IMHO.
 > Paul Lamar

  The Police department Hughs choppers had a "V" belt drive. It had
what looked like a gang of roller skate wheels to tension the belts
and act as a clutch for autorotation.
 Lynn E. Hanover

  From Ken Welter
As for Poly Chain they are very expensive and the pulleys  are
patented so you have to by them from Gates. You cannot even get gear
hobs for them. Also they are very heavy. The Pirelli RPP Panther
however will drop into the standard HTD groove and take the same
horse power as the Poly Chain. If you need any custom pulleys I can
make them for you as I make the pulleys for redrive that I sell. The
12 inch pully that I use on mine weighs 10 lbs it is made from 6061-T6
and hard anodized. Check out my web site at
http://homepage.mac.com/rotarycoot/

Not the same thing Ken. The helicopter guys like the V belts as they
can loosen them and let them  slip when it comes time to disconnected
the engine from the rotor system and auto rotate to the ground as mentioned
by Lynn above.

Also I suspect the torsional isolation is better than the Poly Chain
as the V belts can slip a bit on the torque pulse peaks.

The down side is they are a bit heavier than the Poly Chain system.
Paul Lamar

I believe that the toothed belts do dampen torsionals to some extent. Not as much as
V-belts, because it would shear the teeth, but an amount that is not insignificant.

Less weight id think, and less friction.... doing a search.... hmmm...

http://members.aol.com/flyapro/mainrotordrive.html

Seems to replace the main drive chain reduction from the engine on the Rotarway
helicopters.
Blake

The weight reduction claim of 22 pounds over a chain drive is impressive.
the Rotorway Exec must disconnect the rotor system from the engine some other way.
Perhaps a one way clutch?

Paul Lamar
 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.
ACRE NL web site.
http://home.earthlink.net/~rotaryeng/            http://www.linux.org