Weird thought and question #4 - autorotators

serverlan · 25-04-2004, 11:42 PM

Are

prerotators electric or hydraulic? (I presume that hydraulics would run from engine oil pump pressure? They don't seem to do much of a job, from what I've read. They reduce takeoff distances a bit, but no greatly. If they are hydraulic, is it possible to get decent shaft-drivedn hydraulic pumps capable of delivering real power? or would the weight be prohibitive?

Don

le-wardy · 13-06-2004, 05:38 PM

Don, the hydraulic prerotators used by some gyro pilots on their machines, are made up of components using a power steering pump from a car. As much as we'd all like to have gyros which could take off like a helicopter, the complexity involved rears its ugly head.
The weight factor involved between hydraulic or electric prerotators is negligible. Electric prerotators are limited by their designed output, whereas the hydraulic option is determined by the pumps oil flow rate, pulley wheel size on the pump, and the engine powering it.
As the rotor blades are fixed pitch. Trying to attempt to spin the rotor faster than the rpm's required in flight while on the ground, will have you dancing your machine across the paddock like a swaggering drunk. Not good !The best thing is to remember, although we still need a take-off run of some distance. It's still a hell of a lot shorter than a normal fixed-wing does.

rotor · 13-06-2004, 07:25 PM

The reason we use a pre-rotator is yes to shorten our take off roll

BUT

what it really does is help us get the blades rotating to about 80-100 rpm. When ground rolling in a zero wind situation without a pre-rotator it can sometimes take a bit of effort for an inexperienced pilot (even experienced pilots can have trouble) to get the blades to wind up to this point. You also lesson the risk of hinging your blades (or your trainers) if you try to go to fast to quick without waiting for the blades to wind up. Of course this can happen at any speed with some blades.

After the blades get past this point they are easy to get up to flying speed.

Yes, pre-rotators do the job they were designed for, and in my opinion do it well.

I hope this answers your question. I'm sure some one will let me know if I'm wrong

joey · 23-09-2004, 10:36 AM

How difficult is it to use the main driving engine with a gearing system to the main rotor that has some simple pitch control. The rudder then would need to use the downwind from the rotor to keep the craft 'straight'. Engine power is then 'transferred' to the rear prop while pitch is reduced or simply flattened.

Are there any craft built like this? It would reduce take-off distance and increase the risk factor. However wouldn't still have blade twist effect as helicopters do so will still be relatively safe if on engine failure blades are flattened and engine disenganged from rotor...

any info..

I am interested in building a gyro but my budget is very very limited so cost would need to be at a minimum. i can do some engineering myself though..

Aussie Blue · 03-07-2005, 10:22 PM

Saw at the Dubai Air Show a Jordanian gyro. The pre-rotator was a 'manually coupled idler wheel' that coupled to the flywheel. This was connected to a worm drive that spun the rotor. Coupling was done by a lever next to the seat. Oh, the gear on the rotor was also coupled in some way.

rotor · 05-07-2005, 06:04 AM

Did this gyro jump off like the Pitcairns and Ciera's or was it just a prerotator? They used a mechanical type similar to what your saying and ran the rotor up to flying speed getting off with next to no airspeed.

Echo 2 · 15-07-2005, 08:20 AM

Art Spink sent me a DVD he filmed while in the States , it includes a machine called the Gyrhino(?) , this thing is amazing - it is jump take off with no ground roll. I think it has mechanical drive up to a modified Hughes chopper rotor head , the pilot gets the blades up then pulls on pitch. ( there may be more to it than that ,but it sure is impressive)

rotor · 15-07-2005, 04:38 PM

When I first saw a picture of this machine I didn't realise it was so versatile. I didn't know what it was - thanks for the update

Linked to Gallery Pics:

Echo 2 · 15-07-2005, 06:08 PM

It looks a bit weird but once you see it flying you'll want one...thanks for the pics.

Bob · 17-09-2005, 01:21 AM

Joey :
You can build a gyro for next to nothing IF .. you scrounge up a good engine and are good at building stuff yourself....
I got my gyro in a bunch of pieces at a yardsale..for 900 bucks ... the engine was just gone over by a shop and still had the tag on it ... the rotor was dammaged and only one of the landing gear was there.... but the Assembly instruction book and instructions came with it ... within a month I had it ready to test out.... the gyro was ready but I was far from it ( un known to me at the time )
.... so yes you can do it cheeply... Dirt cheep if your realy carefull !
I am presently makeing my new set of rotor blades, prop and repairs because I flopped the silly thing over about 2 weeks ago....
the gyrobee is a great little Gyro and the instructions are available over the internet for free
though buying the metal is not cheep it isn't near as expensive as buying a kit ....
the most expensive part of your gyro will no doubt be the motor ... so start building your gyrobee and keep an ear to the ground for a good cheep motor ... in a year or so you'll have your bird ! .... you can do it if your willing to do everything if your broke ... I know because I'm broke and I have rebuilt this gyro 3 times now ! hehehehe
while there are those that will question my sanity in doing this and not buying all new pieces to repair with , I have no doubt my gyro will get me home ... if you don't have the skills ... get them ... its cheeper to learn how to build one than it is to buy one !
there is no reason your dream of flying should be held up because of cash when a gyro is so darn simple.... but plan on and do get qualified instructions... its expensive ! so plan on it !
and hopefully you won't be rebuilding your gyro as much as I

my 2 coppers !

Bob......