Mailing List flyrotary@lancaironline.net Message #30033
From: Richard Sohn <unicorn@gdsys.net>
Subject: Re: [FlyRotary] Re: Single rotor smooth as silk now
Date: Mon, 6 Feb 2006 22:06:44 -0800
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Message
 
----- Original Message -----
Sent: Monday, February 06, 2006 7:06 PM
Subject: [FlyRotary] Re: Single rotor smooth as silk now

 

Would a single with no dampers put the resonance
beyond the useful range?

Good question Ernest.  I thought about trying the RD-1C drive with a solid plug where the rubber dampeners normally live, but when I considered that all the normal gear lash play would still be there, I realized it was probably not going to be much of a test. 
 
How much gear lash is there on a typical Hirth, or Rotax gear box? 
 
Cheers,
Rusty
 
 

There are two issues to cope with, one is resonances and the other is transferring the torque pulses. The torque pulses are transferred completely in a indefinitly stiff system. We do not want that, because of the internal forces involved. That leaves the resonances created by coupling and element flexing properties. I believe the only way to stay out of the resonances is to keep them low. This is what ROTAX is doing, a 582 has gear rattling around idle. When you watch a ROTAX starting up it is very obvious when the rattling occurs. I have not observed any rattle on my C-Box with the SOOB.

My ROTAX C box has about 1/8" gear lash at the tip of th 72" prop. I have seen the same on others, seems to be normal.
 
Richard Sohn
N-2071U
 
Richard,
Do you have a photo of that donut type damper - is it similar to the BMW type? 
Have a look on the internet for Lord Dynaflex Couplings, that's what Don Dunbar is using and sounds like it is ideal for the single rotor, I prefer Tracy's set-up for the 2 rotor.
George ( down under)
 
George,
 yes, it is the same in principle as on a BMW. In Europe it is a GIUBO from Italy.
 
Richard Sohn
N-2071U
 
 


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