Twin Engine Gyro's [Archive] - Rotary Wing Forum

Screw

11-05-2003, 01:30 PM

Hi All, Out of curiosity, I haven't seen any twin engine gyro's.  Why? I know in an airplane, a twin offers a certain amount of comfort knowing you have enough power combined with a certain amount of safety in the event of an engine failure. Is there a stabuility problem designing a twin pusher 2 or 4 place gyro? Is there a stabuility problem designing a twin tractor 2 or 4 place gyro. When I say twin tractor, I'm refering to a twin engine configured near the nose like a hammerhead shark.  I believe there was an airplane made by Helio that did something similar in a STOL bushplane?

ToddP

11-05-2003, 02:56 PM

John, I don't think its just a gyro thing.  You'll notice there are very few if any experimental twin designs.  Only speaking for myself, just getting one tempermental 2 stroke engine to run right is tough enough, much less two.   :-[ I had a guy explain twin engine planes to me once.  Unless you really train well, and continue practicing single engine, engine out operations with a twin that second engine only helps you get to the crash site faster. Todd

Udi

11-06-2003, 01:05 AM

Someone mentioned on Norm's forum that they were working on a two-engine gyro. *I don't remember if it was Don Pharham or maybe D. Degraw??? *I think they wanted to have both a pusher and a tractor. Tandem engine aircraft don’t have the yaw control problem mentioned by Todd. Udi

PW_Plack

11-06-2003, 04:22 AM

I believe the main reason for going to twin engines in fixed-wing planes was not redundancy, but performance. The extra safety margin is a bonus, but only if you train and practice for single-engine emergencies. The horizontal thrustline offset of a typical twin with one engine out makes the aircraft a real handful. One advantage of twin engines in pusher gyros might be the ability to get much cleaner air to the props. In a gyro that's going to weigh under 1,000 pounds empty, it's hard to imagine a net advantage, given the increased weight and complexity.

r.coplen

11-06-2003, 01:24 PM

John, Do an Internet search for "Fairey Rotodyne".  You'll be pleasantly surprised to find a very large twin gyro.  It actually used tip-jets for hover, but cruised as a gyroplane while carrying up to 60 passengers. Also, check the Groen Brothers Aviation webpage (www.gbagyros.com).  You will see some more examples of multi-engine gyros. Randy Coplen

Screw

11-06-2003, 01:42 PM

I've seen tractor configured twins (Large) like the Rotodyne before.  I've never seen anything small experimental style 2 or 4 place. I'm wondering if a twin pusher would create more occilation problems than it worth? Udi?

rfi

11-07-2003, 12:12 AM

A friend of mine and I are designing a push/pull twin engine gyroplane.  In fact, I am working on an article on twin engine gyros for Homebuilt Rotorcraft magazine which I publish each month. There are several advantages to a well designed push/pull twin engine gyroplane.  First, the torque roll is cancelled because the props are counter-rotating when the engines are back to back. Second, if one engine fails the ship does not go down like a lawn dart---if one can not maintain altitude on one engine they can at least stretch their glide quite a ways. Third, a push/pull twin makes a side-by-side two place configuration simpler in that there is very little if any CG change between one or two persons on board. A twin engine ship with a couple of Rotax 503 engines would have good performance.  The 503 is a simple engine and probably one of the most reliable in the Rotax line. There was an enclosed twin engine gyro design about a decade ago---the Aerotech model 200.  It had twin 503 or 532 pusher engines turning 60 inch props.  I think eight or ten kits were built before the designer/builder Jack Craft ceased production.

ToddP

11-07-2003, 01:19 AM

Don, Tell us more about your monthly magazine.  I haven't heard about this before. Todd

Udi

11-07-2003, 07:09 AM

Don, I would like to subscribe to your magazine!  Never heard of it... I agree with all the advantage you've mentioned for a twin engine gyro, but will the cost be worth the benefits?  Gyroplanes suffer from any non-CLT engine configuration. *If I were to design a 2-engine gyro, I would install the two engines side by side or one on top of the other, and then use gears, shafts or belts to rotate two inline props in opposite directions. *There will be no rolling moment and no twisting air stream.  From a structural point of view this may be easier than a push-pull configuration. *It can be done in either pusher or tractor design. I don't know if harmonic oscillations are more of a problem with two engines. Udi

rfi

11-08-2003, 03:37 AM

The push/pull twin will be centerline thrust. *There shouldn't be any adverse *torque roll if one engine quits since it will have a tall tail. *There will not be any yaw problems. * The cost with a couple of direct drive engines shouldn't be any more than a single engine gyro of the same power. *The direct drive engines are inexpensive as compared to a higher Hp engine with reduction drive. You can read more details in Homebuilt Rotorcraft which has been in constant circulation since October 1988. *It is a monthly publication of typically 24 pages--strictly black and white--not fancy like the PRA. *It was designed to cover experimental gyroplanes and helicopters but lately the helicopter info has been skimpy. Cost is $24/year in the USA, $30US in Canada and Mexico, and 38US elsewhere for surface, $50US for airmail. *We accept Visa and MasterCard, checks, Money Orders and indian wampum. *You can email us at rfi@oklatel.net, call at 918- 823-4610 or fax at 918- 823-4690. We only advertise in Kitplanes and don't have a website. *It has been fairly low profile since its beginning and we never intended to get too big. *We have our own printing equipment so our overhead is relatively low. *Circulation is about half what the PRA magazine is although we have subscribers in most countries--a lot in Canada. *

GeneWeber

11-08-2003, 11:48 AM

Hi Don, In your first email you said: A twin engine ship with a couple of Rotax 503 engines would have good performance.  The 503 is a simple engine and probably one of the most reliable in the Rotax line. In your second email you said: The cost with a couple of direct drive engines shouldn't be any more than a single engine gyro of the same power.  The direct drive engines are inexpensive as compared to a higher Hp engine with reduction drive. Are you proposing to run 503’s with no reduction drive? That would require using very small diameter props, which would be very inefficient. Regards, Gene

Brent_Brown

11-08-2003, 09:42 PM

I have the old homebuildt mag. of Don's with the push / pull twin in it. someone was working on it almost ten years ago put they never got it done, maybe this time they will. Don is saying the use of two VW DD motors or Subs would work as well as the 503 rotax. I have a frame started that is intented to be use as a push pull gyro. It is like a KB with two mast a motor on each one. I'm not sure of the motor yet.

Brent_Brown

11-08-2003, 09:52 PM

I would like to have the front mast split like a two place Dominator front mast so you wont have trouble see around the mast. But to get one in teh air a 2x2 front mast will be on this one. I cant get the image to post.

Screw

11-08-2003, 11:27 PM

Brent Baby, Where ya been? ;D

rfi

11-09-2003, 01:27 AM

Gene, What I meant was that two direct drive EA81 engines are less expensive than a single EJ22 or EJ25 with a reduction drive.  I was not recommending that a 503 dould be used without a reduction drive. A 503 probably costs around $3600 with a gearbox and a 582 is on the order of $4500.  Two direct drive EA81s are less expensive than a single 582---that is what I was getting at. Yes, one could use a couple of VW engines also but they are more expensive than  EA81 engines. On a ship like Brent was talking about you could probably get by with a couple of 40 Hp engines but the ship would come down if one quit.  A couple of half VW engines would even work at 36-37 Hp each that would be enough to fly a single place gyro. I have been waiting for someone to build a simple push pull twin based on a Bensen style fuselage but it hasn't been done yet.  Maybe I will build one myself if I can get a medical certificate again. A front engine and windshield configuration similar to the open frame Airbike fixed wing would work okay. I have had physical problems that make getting a medical questionable with the picky FAA attitude.  I just had my second lens implant and got rid of cataracts, so I can at least see well enough to pass the eye test now. Twin engine aircraft/rotorcraft will not be allowed for Sport Pilots, so I may have to stick with a single engine configuration for my personal machine.  If so, I am going to build a two place tractor configuration based on the bolt-together aluminum angle and gusset plate BD-4 airframe.

GeneWeber

11-09-2003, 06:19 AM

Hi Don, OK, thanks for the clarification. Regards, Gene

Screw

11-12-2003, 12:19 AM

This was kinda the twin engin configuation I was wondering would work.  Any noted problems in the configuration?

Brent_Brown

11-12-2003, 02:52 AM

This can be made with a pusher motor added on. I will make one for us to see fly.

Brent_Brown

11-12-2003, 02:59 AM

yes it will have a tall tail. I guess it wil have a empty weight of 400 pounds and fly at  700 to 750 pounds this is not gross just me and 12 gal of gas about an hour flight time. two motors that pull 300+ pounds of thrust will be rocket climbout time.

rehler

11-12-2003, 03:44 AM

John, The configuation you illustrated was done several years ago.  The owner (I can't remember his name - Kraft I think) said it was difficult to keep the two engines pushing at the same rate, causing the gyro to yaw left and right and if one engine stuttered or failed the gyro tended to try to spin in a circle to the left or right depending on which engine stopped. I got the impression at the time that it was extremely dangerous - a bad idea.

Al_Hammer

11-12-2003, 06:10 AM

Here is a Ken Wallis  twin engine gyro (attached) Al Hammer

Brent_Brown

11-12-2003, 07:34 AM

Now that is cool. Any reports about it flying

Al_Hammer

11-12-2003, 08:18 AM

Sorry, a quick search didn't find any flight reports, but this site has info on most of the Wallis gyros including this one , G-BNDG. http://dspace.dial.pipex.com/town/square/rcy85/webdoc2.htm

Screw

11-12-2003, 10:58 AM

That Wallis design is cool. Ken, It seemed like a simple enough twin design, I though maybe someone would have tried it. The Wallis design looks like a very well thought out design.  Even looks like he attempted a Horizontal around the engines and props.  Appears to be CLT.   We got to try that one ;D Brent, can you build it?????  Will it be ready for next years ROC?????

Brent_Brown

11-12-2003, 10:34 PM

I can but that rear motor looks like it needs more support. if we make the arch of the twin mast go front and back of the motors it would be better

Screw

11-12-2003, 10:46 PM

Do it Brent, Hell, work it into a tall tail ;D

Udi

11-13-2003, 02:01 AM

Alright!  Make one for me too, Brent!  

mceagle

11-13-2003, 07:50 AM

I am a pessimistic bastard. It looks like a stunning exercise in irrelevant creativity to me. Are you sure Ken Wallis wasn't fishing for a few suckers! Could you imagine the hang test, let alone the fact that the propellers would collide with the slightest engine movement or keel flex. Is it a pusher or tractor?

Screw

11-13-2003, 07:59 AM

You could call it a "Tra-sher." ::) or how about a "Pu-ctor" if the "t" was silent. As far as hang testing. *If a single seat, move the pilot far enough forward, it should work out.

GyroRon

11-13-2003, 09:51 AM

It doesn't look like it would have been in the right range if a hang test was done. Those 582 rotax engines are light but not that light!

Whirlydog

11-14-2003, 12:53 AM

The "horizontal looks to be more of a propgaurd than any usefull horizontal  stabilization surface.   Also with the props facing each other and so close, wouldn't they counsel out each other.  It just looks like a strange machine to me. :-/

Al_Hammer

11-14-2003, 03:19 AM

John, I guess you're not familiar with the concept of counter -rotating props. Ducks fly in Vee formations so that the vortex from the wing tip of the leading ducks rotate in the opposite direction of the vortex from the wing tip of the trailing duck (e.g. Right wing tip behind left wing tip and vice versa). If the ducks fly close enough, (wing tip to wing tip), which they try to do, it is estimated that it takes 30 to 50 percent less energy for a duck to fly behind the lead duck. The lead duck has to use maximum energy to fly and this is why on occasion the lead duck will change position in the formation because the work of flying lead is much greater! Aircraft propeller tips also move at high radial velocity generating large trailing vortices. Counter-rotating propeller tips create vortices that rotate in opposite directions, clockwise and counter clockwise, which significantly reduces the net trailing vortices by cancellation. This increases propeller efficiency and reduces the workload on the engine, just as the trailing ducks have a reduced workload. A second benefit of counter- rotating propellers is that the net torque on the aircraft from the propellers is zeroed requiring less trim on the control surfaces to maintain level flight. This reduction in torque also makes multi-engine aircraft more controllable when engines have to be shut down while in flight. Adrian Popa, Directors Office, Hughes Research Laboratories Area of science: Engineering Al Hammer

Thumpernator

11-14-2003, 04:31 AM

And I'll bet you guys don't know why one side of the Vee formation is always bigger than the other side. Scroll down. . . . . . . . Keep going, it's worth it. . . . . . . . . . . It's because there are more birds on that side.   ;D Jeez, what did you think it was??!!

quadrirotor

11-16-2003, 11:53 PM

Here you have a two engines gyro!... http://www.rotorcraft.com/forums2/fileattachments/bensenrotor2.jpg

Screw

11-17-2003, 02:45 AM

Queetzal, No, I'm not familiar with counter-rotating props.  I had never seen the Walis configured twin gyro and it was, to me, a unique approach. Quadrirotor, I have seen that one.  But that wasn't a twin I had in mind. The question still remains:  Why aren't twin qyros being experimented with on a regular basis?  Until this post, I don't think I had ever seen one.  The benifit of twins seems to be worth it.

Brent_Brown

11-17-2003, 05:00 AM

John it has to do with the money

GyroRon

11-17-2003, 09:39 AM

Someone delete that post above that blew this thread out so damn wide!!!!!!!! >:(