Pusher vs Tractor - The old debate

Nuff_Sed

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Jul 16, 2007
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Location
Port Elizabeth, South Africa
Hi all..

I know this debate comes up every now and then, so my apologies if it seems boring as old leather, but I have to make the right decision..

I am considering building either a Dominator (Already have the plans) or a Little Wing.

Now, there's not much (on Youtube at least) that will provide a good comparison between the two types.. Ron Awad and others tearing up the sky in a Dominator vs a clip covering Little Wings Trans-continental flight.

And yes, pushers are more agile, but how much more, and is it worth the trade-off considering the tractor safety advantage etc.

Any and all comments will be appreciated..:suspicious:
 
One thing you should consider it that the Little Wing takes a lot more effort to build. Most people that start one never finish it.

I've got a tractor gyro; I enjoy it but I don't do a lot of extreme yank and bank. I haven't really pushed it so I don't know how capable it is compared to a pusher.
 
I have flown 5 different tractor gyros, including Ron Herrons nice radial powered White with red trim version. My opinion is get the tractor if your just wanting a cruiser ( might as well get a airplane if all you want to do is cruise ) Or get a pusher if you want to have a little fun as you cruise.
 
From the standpoint of agility and stability, it is irrelevant which end holds the propeller.

A tractor by nature spreads out the various masses which increases the polar moment of inertia and reduces agility.

The Pitcairn models AC-35 and PA-36 had front mounted propellers shaft driven by engines behind the pilot, giving moments of inertia similar to pushers.

A tractor by nature makes it difficult to misconfigure vertical CG to the extent of a pusher low rider.
 

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I don't think you would be disappointed with either configurations.

The allure of a pusher is that the noise and prop wash are behind you. Giving you the best view when your flying.

I like the classic look of a tractor though. Most seem to have more cargo room than a pusher.
 
The drive shaft concept is interesting, I noticed that Jukka Tervamaki designed a couple like this. jukka gyros
I hear about the torsional resonance issues, but why would an automotive type drive shaft with U joints, not work if it were balanced?
 
A flywheel or some other form of rotating mass at each end of a shaft is a resonant system, the shaft being the spring. Either damping is necessary or the natural frequency must be outside of the range of exciting frequencies; engine firing impulses, etc.

Boats, with propellers dipping in the water have pretty good damping. Fluid couplings in automobile transmission provide good damping. If manual transmission, the spring hub of the clutch supplies damping and lowers the frequency. Rubber donut couplings can lower the natural frequency enough to avoid resonance.

Of course shaft driven props can be made to work if properly engineered. It’s not something that can be bolted on without foresight.
 
Thanks for the comments ...
I was also wondering about the time issue with the Little Wing.. I also like the fact that there are so many Dominator fliers and owners out there with very little (reported anyway) incidents...

Someone here in South Africa is just completing a tractor - by all accounts it will be way affordable.. www.wagtail.co.za
 

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I think a "lovejoy" coupling at each end of the drive shaft would remove any Torsional resonance. That is if the shaft is inline. One could have the engine in the rear and the redrive in the front. Just a thought.

John K.
 
What fixed wing fuselage do you think that is ???? As others have pointed out, if you are thinking tractor be prepared to invest A LOT MORE TIME IN CONSTRUCTION.

We in the gyro world are not used to see post or announcements (like in EAA) where a project was finally completed after 3,4, or 5 years of labor.

Tony
 
As for the long propellor shaft, Molt Taylor spent years fighting that problem on his "Teal" and "Taylorbird" as did Jim Bede on the BD-5. "It just aint that easy to cure"

Tony
 
I particularly like my tandem open two place pusher gyroplane.

For me the feeling of openness enhances the feeling of freedom.

I love to smell the strawberries, the ocean, and the orange blossoms.

For me that is part of the joy of flying low and slow.

The prop blast in a tractor is typically twice your forward speed.

I would not want to deal with the prop blast in the open if it were a tractor.

Being inside is too much like a cage for me.

If I needed to fly in the rain or the snow I think I would prefer an enclosed gyroplane.

If I needed to go fast I feel an enclosed tractor would work better.

I don’t.

Thank you, Vance
 
Wagtail

Wagtail

I think Wagtail used a Bushbaby, however I'm not sure..

I'm raiding my old drives for some pics of tractors I found (possibly even on this forum) some time ago...

Vance, I like your comments along with GyroRon's..
 
Pusher Pics

Pusher Pics

Some Pushers

Most of these seem to be "under development", and I don't have the skills or the required titanium B@lls to attempt experimenting... I'll go with the numbers..
 

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Drive Setup

Drive Setup

Obvious drive setup on this one looking at the interior shot... Nice looking, but does she fly?

Also what looks liked a hacked up cropsprayer....
 

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There is no denying the fun factor of a pusher. Putting the noise, exhaust, slipstream and visual clutter of the powerplant behind you enhances the experience no end. With little structure in front of you, the flight sensation approaches dream flight.

BUT, you must have a talk with yourself if you are going to fly a pusher. You are about to make some safety compromises.

We just lost two people in the MT-03 crash in Germany, very possibly because a camera came adrift and took out the pusher prop. The same incident in a tractor gyro would have resulted only in a broken camera.

The nearest I've come to dying in an aircraft was when a BRS bridle cable made its way into the pusher prop of my Kolb U.L. plane, ripping the engine right out of its mounts and almost setting the engine free of the aircraft. I was lucky.

When a pusher aircraft crashes nose-down with forward speed, the engine becomes a cannonball aimed at the pilot's back. It's not possible in an aircraft (which needs to be light) to build a mount structure that will keep the engine away from the pilot on impact. Another way of saying the same thing is that the pilot serves as an airbag to protect the engine on impact. In a tractor, the engine arrives first and has its own direct encounter with the earth, without the pilot's getting the middle.

With the aft tilt of a gyro's rotor during the takoff run, and the (usually) minimal clearance between the rotor and the prop, it doesn't take too much rotor flapping to bring the rotor and the prop into contact with each other. If they merely graze each other, you may just hear a "chirp" and see some blemishes on one or the other, but solid contact will break things.

Pushers are noisy and, in the practical real world, less efficient than tractors, because the air flowing into the prop is mighty "dirty" by the time it has passed the cabin.

Again, though, pushers sure are fun.
 
drive shaft

drive shaft

I have used shaft drives on several machines and I have found that you will have less problems if you turn the shaft faster than the prop .
 
Chuk, I compared with Excel inertia of a pusher with my project of tractor (front engine): It has substantially the same inertia. The box which bears the tail is a very light body.
WHY, construction time is a bit longer. But it does not compare to the construction of the wings of an airplane consisted of thousands of pieces glued.
Vance, to 3 feet in front of or behind the propeller, the speed of airflow is not so different (20% ?) Only in stop that the difference is large
Nuff Sed, the gyro blue on your photo was destroyed on landing, because of a bad maneuver. No wound. only self-esteem. Until then, the pilot and friend was very happy.
I completely agree with Doug, but visual clutter of the powerplant behind can be significantly reduced with a engine inversed in line Rotax 503 and a small scoreboard .
Jean Claude
 
Jean Claude, the moment of inertia of an object is the summation of each particle of mass multiplied by the square of its distance from the rotational axis; I =mr². If the distance is increased by 2, the MOI is increased by 4.

The two primary masses are the pilot’s body and the engine.

With front engine, the pilot needs ~40” from seatback to firewall for legroom. The CG of a seated pilot is typically at his belly button, perhaps 6” from seatback. The engine CG is perhaps 6” in front of the firewall.

With pusher engine, the distance from belly button to engine CG is perhaps 15”. Reducing MOI by a factor of 7; (40/15)².

You’ll get the same ratios using centimeters.

Of course there’s lots of other stuff but none so important as engine and pilot.
 
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