Re: Pre-Rotator Powered by Compressed Air?

[nuke]

"...Liquified nitrogen gas can store a lot of energy, pressure-wise..."

Not so. The reason people store N2 in the liquid phase is that the density
is high so you store a lot of mass for little volume. Also if you keep it
liquified you can store it in a lightweight thin wall tank. To keep it
liquified you have to allow it to boil slightly and vent off the gaseous
component, to remove the heat coming in through the insulation. So the tank
and the liquid is at a LOW pressure, and a LOW temperature of course. If
you don't vent it, it will just continue to boil & pressurize as the heat
keeps coming in. Eventually you will have a tank of pressurized gaseous N2
if you're lucky, or an empty tank because it's all gone out of the safety
valve, or a ruptured tank if you're unlucky.

If you try to use pressurized N2 [vs liquid] to power your a/c you will need
a heavy tank to withstand the pressure. The energy you will get out of
expanding the gas through a turbine or recip engine probably won't drag it
into the air, and it will be all gone before you know it.

Now with a tank of LH2 and a tank of LOX, you could.... but that's another
story :)

nuke
"sanman" > wrote in message
om...
> Hi,
>
<snip>

[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.
>
>

[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!!!