Weird thought and question #4 - autorotators - Page 2

Bob · 17-09-2005, 01:34 AM

On the subject of pre rotators and Jump starts...
Igor Benson experimented alot with the system and I guess did fairly well with it ...
though I have never gotten even close to a jump start with my gyro its v-belt system works extreamily good ! getting the rotors well into flight speed if i so desire its power is taken from just behind the prop hub from a v-belt pully and goes into a 2:1 90degree gear box from there it goes to the rotor head via a swivel socket ( universal joint) and slip joint to a pully with a one way clutch in it that then drives the large pully on the rotor blades ...
its simple, light and works well,
however sense i don't have brakes on my gyro I have a hard time spinning the things up because it wants to go ! hehehehe but brakes are comeing soon to cure that problem.

here's a pic of it if anyone cares ...
C ya !
Bob.....

jonem · 23-09-2006, 08:28 PM

Greetings all,

I am also looking into a high performance prerotator, as I see it ,there are two options (I presently have a Wunderlich) A Poly v belt drive to deliver sufficient HP through a flexible shaft drive or a prop shaft with a spline and universals complete with a o degree pitch adjustment on the prop is one reasonable bet. Another option is a seperate motor, ie a tuned mini 2 stroke coupled through a shaft to the bendix, no problem with the prop! I saw a video of one in use and it was quite impressive. Has anyone in OZ tried it?

cheers...jonem

Brian · 24-09-2006, 12:42 PM

Anything that is used to pre rotate that gets the revs up around the 200/ 250 mark AND is simple and reliable as well as light is going to be a winner.
As yet, there doesnt seem to be anything that meets this requirement.

I question the real need to have a 'jump takeoff' for a gyro, is the complexity and the associated risks involved, really worth it ?? Most people that have a gyro, have a bit of ground to takeoff on and I know from personal experience, that having somthing to be able to spin the blades up to say 200 or 250 would be great and enable a very short takeoff roll.

Of course, you could wait till conditions like we have here today with the wind up around 30 knots, that should equate to around 200 revs, only need 10 knots forward airspeed and she's flying.

Scorpion · 10-11-2007, 01:21 PM

Hi there members,

I've read a lot of the threads about prerotor's and jump-takeoff, but haven't found anything that suggests the power required.

Can any one talk numbers to achieve the results needed.

I have a unit I'm looking at using which is 17 HP and weigh's in at 3.9kg. To that I have to add other bits and pieces which would probably double this weight, but it would certainly be under 10kg complete and should spin up to full flying RRPM.

Any ideas?

Graeme

Fencing Wire · 10-11-2007, 06:01 PM

Quote:

Originally Posted by Scorpion

Hi there members,

I've read a lot of the threads about prerotor's and jump-takeoff, but haven't found anything that suggests the power required.

Can any one talk numbers to achieve the results needed.

I have a unit I'm looking at using which is 17 HP and weigh's in at 3.9kg. To that I have to add other bits and pieces which would probably double this weight, but it would certainly be under 10kg complete and should spin up to full flying RRPM.

Any ideas?

Graeme

G'day Graeme,
I hadn't given it that much thought, BUT from a simple blokes perspective, If it takes me 75 hp to take off horizontal, why would I bother when I can take off vertically for 17 hp? I don't see any helicopters (which appear to specialize in this "jump take off" sort of thing) that use a 17hp motor. My suspicion is that you are going to be at least 50 horses short. But some-one (like young Nick) will have a formula that will allow you to calculate the power required for lift-off. If it's 7hp, then I'm going to sack my 75hp motor for bludging on me.

Cheers

Scorpion · 10-11-2007, 06:34 PM

Thanks, Fencing Wire.

I wasn't looking for VTO just a prerotor with a bit guts for VSTO (Very Short Take Off).

I have heard that around 12hp would be sufficeint but then there are others who have said much the same as you.

There are many who have already experimented with different types of pre-rotor, but no one seems to divulge the HP they needed to achieve it.

Hoping someone might enlighten us with the hard facts.

Graeme

rotor · 10-11-2007, 07:08 PM

Graeme,

take a look at this site -

Peroxide Propulsion :: Peroxide Propulsion

Power your rotors up with hydrogen peroxide rockets on the rotor tips

Mitch · 13-11-2007, 10:57 PM

Scorpion,

Have a look here at the Metro Launch System......

The Butterfly LLC

Mitch.