design tip for tractor designer/builders

chuter

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original design tractor gyro
I came across some info this weekend I though I should share here on the conference. I don’t remember seeing it here before, but I could’ve missed it.

Basically, with a tractor design it is good to check the % of fuselage before and aft of the rotor. To do this, put the fuselage in flight attitude (level), drop a vertical line from the rotor head (I’m really not sure if it should be the teter bolt or the pitch pivot), then measure in front of the line to the prop, and behind the line to the front edge of the rudder. The ratio should be about 60/40, with 60% behind the vertical line from the rotorhead. The further away from 50/50 the better.

I was told that a few tractors have gotten into flat spins while in a power climb at low airspeeds; the p factor will start to yaw the fuselage and if you don’t have enough moment arm for the tail it will turn into a flat spin. At least one of the tractors that it occurred to had been flying for several years without incident, and I believe the front to back ratio on them was close to 50/50.

These were not any tractors designs that are currently flying as far as I know: definitely not a LittleWing.

Just a heads-up for anyone tinkering with tractor designs, I wasn’t aware of it when I was building mine. Turns out mine is very close to 60/40, but it’s still good to know and watch out for it. :cool:
 
Hi Victor, I like how well you could see, but the drive and cooling seem a little complicated. I was wondering what is the angle you need to rotate and what your thinking was on that? Thank You, Vance
 
firstly i thought we could mount a car fan onthe engine shaft , then always ducting an airflow exhausted behind the engine where an intercooler could be located.
about drives, i agree it is not the simpliest way.

whitch angle do you mean, i may misunderstand your question... :( tell me more please..

victor
 
Hi Victor, The angle that it sits on the ground compared to the angle it flys. My friends refer to rotating in order to fly. This usualy happens before the main gear leaves the ground. There is some controversy about how much is desirable. I am sorry that I did not express my self more clearly. Thank You, Vance
 
okay vance !!

in the drawing you can see quite the fight attitude , the on-ground angle is about 20 degrees in this drawing, i thought it for a 1m60 propeller and tried to keep some ground clearance for it .... i see what you try to point.... a such take off posture could be bad ?? you wonder if the gyro willget enough ground speed to rise the tail ... depends on the rotor rpm, prerotated ? not ? dont really have satisfying answers..

consider my drawing as a general layout, i just wanted it to look a little "sexy" ... it certainly could (will) be refined if i would plan to seriously build it.. i only try to plant a seed in some brains .... and let some one grow it up.. why not?

i am actually on helicopter data.... ;)

victor
 
Michael Guard said:

"I was told that a few tractors have gotten into flat spins while in a power climb at low airspeeds; the p factor will start to yaw the fuselage and if you don’t have enough moment arm for the tail it will turn into a flat spin. At least one of the tractors that it occurred to had been flying for several years without incident, and I believe the front to back ratio on them was close to 50/50."

That was a Jim Eich JE-2, Michael.

Floyd Brown, using a metal prop, got one in a flat spin from which he couldn't recover. Spun all the way to the ground. Floyd walked away with a few bruises and scratches but the gyro didn't survive.

I once flew a gyro in California that belonged to a person by the name of Royce Tanner (I think) that had a long nose pod on a Bensen airframe and standard Bensen tail. I put it down at the end of the runway without going around because it felt like it would rather fly backward than frontward.
 
Thanks Chuck,

I guess in a flat spin it would descend at the same rate as a regular vertical descent? Maybe the rotating motion of the fuselage would actually help lessen the impact when it hits the ground?
 
Here's a pic of the JE-2; if you hold your little ruler up to the screen to measure, you can see it is pretty close to 50/50.
 

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Jim Eich was a good friend of mine, Michael so I hate to be critical with him no longer around, but his JE-2 could have greatly benefited from a longer tail cone.

Jim was somewhat of a disciple of Arless Riggs; you may have seen his name mentioned in older issues of "Pop Flying."

Arless was an old desert rat who used to build tractor gyros from Taiwan door skins and carve rotor blades from planks with a stick of rebar embedded in the nose for chordwise balance. Everything tied together with a layer or two of fiberglass and polyester resin.

Arless was actually quite a clever gyro designer. His machines were always 2-place and he and his wife flew all over the California desert country in them, never with a serious crash. He probably couldn't have flown any better had he been legal.
 
Swapping Ends

Swapping Ends

I seem to remember Helicopter Ed getting into trouble with his tractor design. It had a Rotorway body on it. It got into spin that almost ate his lunch.
 
The bottom line is to remove the rotor, tie a rope to the teeter bolt and hang it from an oak tree limb.

If it doesn't weathercock the right way, you're likely to be in serious trouble.
 
Hello,

The gyro does not fly better when it is legal, on the contrary.


JOS
 
Thanks Chuter. Littlewing Booster Rich.

Thanks Chuter. Littlewing Booster Rich.

:) :) It was nice of you to post an informative note on how to check the percentage of airframe before and aft of the rotor mast. I am along with my associates building three littlewing two place units, and I might add, having a great time at it. May I ask what you are building ? I hope it is a tractor type unit. Thanks Rich.
 
experimenting with the tractor design

experimenting with the tractor design

Good afternoo;n all,
My name is Tony Stiles and I have been a gyro enthusiast for some time,(PRA#17081) and have enjoyed the organization and it's expertise plus the invaluable helpand assistance from a multitude of it's msmbers.

My interest in gyros came about as a result of seeing a number of gyros at early EAA conventions, which led me to join the PRA. I have had the privilege and honor pf knowing and talking with some of the greatest and most knowledgeable people in the present gyro comunity and some who are sadly no l;onger with us.

Whaat I know toda;y is totally attributable to the help and advice which recieved from them. Having attended over 19 EAA co;nventions in a row and eventually deciding that I would never own a P-51 Mustang or a $100,000 kit plane or for that matter a high dollar antique airplane, I eventually confined my activities to alternate engine forums and the gyros in the ultralight area.

Over the past 15 or so years I have even narrowed my interest in the gyros down to the tractor design only. In this time pleriod I have "crashed"probably at least a dozenor more gyros, I used the term"crashed" loosely to mean as in crashed in the waste basket ,or as in an unfinished scale model or in a few cased an unfinished prototype. All off the so called "crashes"were the result of the help andexpertise and advisefrom the wonderful and caring efforts of the people to whom I went for there input and I am proud to say everyone of them was a membera of the PRA. It is because of this advice and help that I am praobably alive and well today because my ignorance and sometimes stupidity was very large then. I would say that I got a whole lot more than just my membership m;oneys worth. I never went to a Bensen Day gathering or a Regional fly-in or definitely the National(where ever it was ) that I did not come away with somuch advice and information that I was still working on it in December, especially regarding the tractor design.

This brings me to the point of why I have chosen to join this forum, I amstill seeking all the desigh information on tractors that I can find. I will be looking foward to Andy Keech's talk at Mentone and his Forum on Tuesday ( the second day a Oshkosh )and as always, talking with Ron Herron (the man with the Plan) and any oth;er individuals who have interest in the tractor design.

Great strides have recently been made in the pusher design leading to safer flying and I think there needs to be a extended effort, to be as vigilant and cautious in the experimenting with the tractor design lest it produce some of t;he same results as the early pusher designs. ddDI feel there is just as much to learn regardign the tractor design as there was waith the pusher, there will definitely be a lot or "do ,do this and don't do that " in the new tractor designs.

Hope to see many of you at Mentone this year and will also be at the PRA tent at Oshkosh.

Tony
 
is it safe ?

is it safe ?

Howdy all
I am courious as to what you folks think of this machine.
is it safe.... will it fly , etc.etc.

it was at one time a Bumble Bee... but sense the bee was so unstable on the ground I modified it...
the best idea I could come up with was a tail dragger design to stop the thing from wanting to flop over on the front right or front left ... the extreamily fast steering of the tricycle landing gear was mostly to blame no doubt... and the entire craft was of the Loosie-goosie feel to it.

Now its rock solid on the ground, i have even done 18 to 20 mph brod-slides on the pavement ( due to an unwanted sharp left hand turn that i think i have solved now )
it is a Pusher, not a tractor( obviously ) Yes its ugly...
but personally i could care less what it looks like as long as it flys SAFELY!
that theory obviously holds true in my workmenship, it may be ugly but its strong as heck ! <grin>
so I was hopeing for your critisum , to point out flaws i may have over looked.
your help is greatly appreachated.
thank ya !

Bob.....
 

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Bob,
could you post some larger, detailed photos from different angles and zoom in on details like connection points, linkages, etc? I think that would help those here in answering some of your questions.

Thanks,
Brian Jackson
 
G'day Bob. In my opinion the gyro would be extremely unstable as soon as the tail wheel gets light. The C of G is so far behind the mainwheels that it would try to swap ends at the first excuse. I am not suprised that it has done broadsides with you on the pavement. With this undercarriage setup it would only have to get a few degrees off line and you would be along for a hairy ride and couldn't do anything about it. This is the reason why most modern aircraft are tricycle undercarriage.
Most tail draggers try to get the main wheels back as close as practicable to the C of G as possible.
If you could keep the tailwheel planted as firmly as possible you may get away with a take-off, but an aborted take-off will definately see you sitting in a tangled wreck. Not trying to discourage you but rather trying to save you from big expense and possible injury.
Your origonal Bumblebee must have had a something badly wrong to behave like it did.
 
Ah ! thats interesting Tim ! and it makes sense !
it would explane the problem i have been having indeed !
if i can get this site to let me up load a few pics I'll show some more pics....
Your right about the mains on most tail draggers i have seen their just behind the engine , where i expect the cog is ! ... hummm , not a darn thing i can do about that eather.... my design is flawed ! bummer!
... that is something i had over looked.... as close as i can tell the cog is about 16" up the mast inside the gastank .... that puts it way behind the mains like you say !
as far as the Original bumble bee goes , I checked the plans over and over again and everything was fine , the only thing that could have been some of the problem was the decoupleing springs on the front wheel being too small and me takeing it on a dirt feild instead of a paved landing strip... the rear suspension bungie cords were replaced by heavier springs, and they may not have been strong enough in looking back ...
add it all up and ya get a loosie goosie craft....
well, heck ! ..... i was hopeing someone would have a REASON it does what it does.... i think you nailed it Tim I thank you ! very much
even if it isn't what i wanted to hear , it probly saved me alot of repair again ! because i would'a kept trying to get it off the ground and sooner or later i'ed have gotten that dredded sharp left turn again !

heres a pic if i can up load it
THANK YOU !
Bob.
 

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