counter rotating props

[ivyandmcpherson]

Hi! I'm trying to get some information on counter rotating props. My questions are:
1. how is the pitch changed on the inner (center shafted) prop?
2. If one prop were allowed to freewheel. would it deteriorate the other props performance by more than 25 percent?
3. If the props are not perfectly in synch, (in reference mostly to rpm's ) will the harmonics become dangerously amplified as so to create a physically destructive resonance (like conventional twins when the props are not perfectly at the same rpm)


Obviously , from my questions you can guess that each prop is driven by a seperate engine. the props are three bladed, composite and 84 inches in diameter each. Max rpm is 2780.
Thanks, Ivy and Mcpherson

 

[ornerynorsk]

Just stumbled across this post and it's WAY out of my field, but if my memory serves me correctly there is a Russian Turbo-prop bomber that employs CR propulsion. Jane's handbooks might be able to give some info, though probably not any engineering data. Just a thought.

 

[dooshanks]

Try the system used on R-R Griffon engines as used on the Avro Shackleton.
It is a long time since I worked on these, so I would not like to give wrong gen, but they worked very well.