Re: Pre-Rotator Powered by Compressed Air?

[Gil G.]

On 27 Jul 2003 12:19:57 -0700, (sanman) wrote:

>Hi,
>
>I'd done some reading about pre-rotators for gyroplanes which can be
>used to give them a jump takeoff. I was wondering if any of them have
>tried using compressed gas to power the pre-rotator?
>
>I got the idea after reading these links:
>http://www.howstuffworks.com/question133.htm
>http://news.bbc.co.uk/1/hi/world/africa/988265.stm
>http://auto.howstuffworks.com/air-car.htm
>http://www.evworld.com/databases/shownews.cfm?pageid=news190503-04
>
>Gee, now that I think about it, why couldn't compressed air even be
>used to power the gyroplane pusher prop during regular flight?
>
>An onboard compressor could even be used to compress air into the
>cylinder in the first place. Liquified nitrogen gas can store a lot of
>energy, pressure-wise -- more so than what a battery could store. That
>compressor could be reversible as a motor.

Hello,

I think the tank would be too heavy to take along... However, I am
thinking that a scuba tank could be used with a regulator and quick
disconnect system to prerotate the rotor, then disconnect the air hose
and immediately start the take-off.

Still not very practical, since you don't get to take the tank with
you..

Gil.
--
http://planenews.com

[Rich S.]

"Gil G." > wrote in message
...
> I think the tank would be too heavy to take along... However, I am
> thinking that a scuba tank could be used with a regulator and quick
> disconnect system to prerotate the rotor, then disconnect the air hose
> and immediately start the take-off.

How about a catapult?

Rich "Cum catapultae proscriptae erunt tum soli proscripti catapultas
habebunt " S.

[G. A. Loeffler]

this one http://celag.free.fr/museum/tresor/us_so1220_1.htm
even hoovered with 'cool' gas exiting at the wingtips
-loef (www.loeff.de)


"Rich S." > wrote in message
...
> "Gil G." > wrote in message
> ...
> > I think the tank would be too heavy to take along... However, I am
> > thinking that a scuba tank could be used with a regulator and quick
> > disconnect system to prerotate the rotor, then disconnect the air hose
> > and immediately start the take-off.
>
> How about a catapult?
>
> Rich "Cum catapultae proscriptae erunt tum soli proscripti catapultas
> habebunt " S.
>
>

[Rhodesst]

>
>I believe that in order to have the capability for a jump take-off,
>the rotor blades would have to be depitched to zero, and then when a
>lot of rotor rpm is built up, the pitch has to be added in rather
>rapidly to achieve the jump.

>Ken J. - Sandy A. Gowe

Ken,

I've heard that they actually overspeed the rotor system relative to it's
normal autorotative rpm. The added inertia is what gets them airborne but it's
then critical to get some forward speed going so it can establish an
autorotative state when the rotor system slows back down to normal rpms.

I've also heard that they actually over pitch the rotor blades to make the jump
and that has to be let back down to a setting that will allow the rotor blades
to establish an autorotative state as the aircraft accelerates forward. This
part really makes me wonder. It sounds like it would be pretty critical to get
it right. Can confirm whether this is true or not?

Wondering!
Fly Safe,
Steve R.

[Stephen Austin]

>I've heard that they actually overspeed the rotor system relative to it's
>normal autorotative rpm. The added inertia is what gets them airborne but
>it's
>then critical to get some forward speed going so it can establish an
>autorotative state when the rotor system slows back down to normal rpms.
>

I've got some time in the Air & Space 18A and it uses this method for a jump
takeoff. I'd have to dig out the books, but it seems that the rotor is
oversped about 100 RPM. When the jump is commenced rotor RPM decays
immediately though.



>I've also heard that they actually over pitch the rotor blades to make the
>jump
>and that has to be let back down to a setting that will allow the rotor
>blades
>to establish an autorotative state as the aircraft accelerates forward. This
>part really makes me wonder. It sounds like it would be pretty critical to
>get
>it right. Can confirm whether this is true or not?

As far as the 18A goes, this is not the case. When the jump is began in the
18A the hydraulic pressure holding the blades at flat pitch is released
allowing them to pitch. Once pitch is introduced the rotors remain at that
pitch until the flight is ended. There is no mechanism for varying the pitch
in flight. Other aircraft may vary.





Stephen Austin
Austin Ag Aviation
Charleston, Missouri

[Red]

I like the idea of compressed gas for the pre-rotar! That might be do very
able...

"sanman" > wrote in message
om...
> Hi,
>
> I'd done some reading about pre-rotators for gyroplanes which can be
> used to give them a jump takeoff. I was wondering if any of them have
> tried using compressed gas to power the pre-rotator?
>
> I got the idea after reading these links:
> http://www.howstuffworks.com/question133.htm
> http://news.bbc.co.uk/1/hi/world/africa/988265.stm
> http://auto.howstuffworks.com/air-car.htm
> http://www.evworld.com/databases/shownews.cfm?pageid=news190503-04
>
> Gee, now that I think about it, why couldn't compressed air even be
> used to power the gyroplane pusher prop during regular flight?
>
> An onboard compressor could even be used to compress air into the
> cylinder in the first place. Liquified nitrogen gas can store a lot of
> energy, pressure-wise -- more so than what a battery could store. That
> compressor could be reversible as a motor.

[Ken Sandyeggo]

"Red" > wrote in message >...
> I like the idea of compressed gas for the pre-rotar! That might be do very
> able...

Where is the gas going to exit...at the tips of the blades, I'm
presuming? Now you have plumbing running through the blades plus a
lot of plumbing and complexity where the gas enters the roots of the
blades. Gyro blades are hard enough to balance as is, with a gram
added here and there via powdered lead or a tiny washer or 2.

I got a long ride in an Air & Space and the blades are depitched to
zero until about 300+ rpm, I believe. Then the blades are quickly
released to their normal pitch for the jump. I doubt you'll get
anywhere leaving them pitched and spinning them up, even to a high
number. Otherwise A & E would have skipped the complexity of being
able to depitch and repitch the blades rapidly if all it took was some
rpm. Then you'd have a "helicopter" spinning wildly out of control as
soon as it left the ground because it doesn't have any means to
counteract the torque. To those that think it's doable...do it and
then show us how you did it. We'll all be anxiously awaiting.

Ken J. - SDCAUSA



>
> "sanman" > wrote in message
> om...
> > Hi,
> >
> > I'd done some reading about pre-rotators for gyroplanes which can be
> > used to give them a jump takeoff. I was wondering if any of them have
> > tried using compressed gas to power the pre-rotator?
> >
> > I got the idea after reading these links:
> > http://www.howstuffworks.com/question133.htm
> > http://news.bbc.co.uk/1/hi/world/africa/988265.stm
> > http://auto.howstuffworks.com/air-car.htm
> > http://www.evworld.com/databases/shownews.cfm?pageid=news190503-04
> >
> > Gee, now that I think about it, why couldn't compressed air even be
> > used to power the gyroplane pusher prop during regular flight?
> >
> > An onboard compressor could even be used to compress air into the
> > cylinder in the first place. Liquified nitrogen gas can store a lot of
> > energy, pressure-wise -- more so than what a battery could store. That
> > compressor could be reversible as a motor.

[sanman]

Hmm, well what's happening with these newer elastomeric bearings,
these days?
How are they coming along, and where are they falling short?

I've heard that they are at the cutting edge of rotor hub technology,
and could be used to change the rotor pitch on a gyroplane, for jump
purposes.

[Ken Sandyeggo]

(sanman) wrote in message >...
> Hmm, well what's happening with these newer elastomeric bearings,
> these days?
> How are they coming along, and where are they falling short?
>
> I've heard that they are at the cutting edge of rotor hub technology,
> and could be used to change the rotor pitch on a gyroplane, for jump
> purposes.

Uh....O.K. The gyroplane market is so miniscule, one would have to be
an idiot to develop anything over a cost of a couple thou and 2 to 3
weeks in your basement or garage. Hardly any 2 gyros are alike.
Gyroheads are the "Kings of Modification." To make something that was
adaptable to the whole gyro market would be an exercise in futility.
Too many variations and little standardization. You lost me on the
elastomeric bearings. They are far from new and in about 6 years on a
very active gyro forum, I don't recall the subject ever coming up. No
one there is interested in jump take-offs. If they were, they'd be on
the heli forum. Gyros are meant for the simpler end of rotary flight.
Jump take-off adds a complexity that actual, flying gyroheads are
disinterested in. It's good for mental masturbation on NGs, but
that's about it.

Ken J. - Sandy, eh?.......GO!!!

[Jean-Paul Roy]

At last someone who stands up and tell the whole story
Thanks
"Ken Sandyeggo" > a écrit dans le message news:
...
> (sanman) wrote in message
>...
> > Hmm, well what's happening with these newer elastomeric bearings,
> > these days?
> > How are they coming along, and where are they falling short?
> >
> > I've heard that they are at the cutting edge of rotor hub technology,
> > and could be used to change the rotor pitch on a gyroplane, for jump
> > purposes.
>
> Uh....O.K. The gyroplane market is so miniscule, one would have to be
> an idiot to develop anything over a cost of a couple thou and 2 to 3
> weeks in your basement or garage. Hardly any 2 gyros are alike.
> Gyroheads are the "Kings of Modification." To make something that was
> adaptable to the whole gyro market would be an exercise in futility.
> Too many variations and little standardization. You lost me on the
> elastomeric bearings. They are far from new and in about 6 years on a
> very active gyro forum, I don't recall the subject ever coming up. No
> one there is interested in jump take-offs. If they were, they'd be on
> the heli forum. Gyros are meant for the simpler end of rotary flight.
> Jump take-off adds a complexity that actual, flying gyroheads are
> disinterested in. It's good for mental masturbation on NGs, but
> that's about it.
>
> Ken J. - Sandy, eh?.......GO!!!