Serious problem ?

gyroplanes

FAA DAR Gyropilot
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I found this condition and would like some opinions on it. I'll try to word this as descriptivley as I can..

You have a heavy gyro with the requisite heavy, long rotor system.
When you move your joystick forward, off the rear stop, and set the massive rotorhead and rotorblades in motion and suddenly stop the stick, would you expect the inertia of the head/blades to bend the joystick?
Would you tolerate the flexing of the stick metal?
What do you think would eventually happen?

I don't know if the above scenario has ever happened to anyone.
But I found an even scarier one exists, in a large percentage of the fleet.

RAF & GBA gyroplanes have the "cross over" tube (the "tube" that connects the rotorhead torque tube to the pushrods) I quote "tube" because, unlike other gyros, the RAF & GBA use a solid aluminum bar, i believe they call it a gimble actuation arm.

The next time you go out to your RAF or GBA SH, move your joystick to neutral. Wait for the teetering to stabilize.

Now, with some vigor, pump the stick back and forth about 4 inches watching your torque (tube) bar.

The center of the bar and tips of the cross over bar will move in different directions. This movement, viewed from the front or back, will resemble a bird flapping it's wings.

I realize that we don't often pump our joysticks in flight, but every taxi out or exaggerated movement of the stick can cause a flex in the crossover and those flexations cause metal fatigue.

I believe it's just a matter of cycles before failure.
 

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Mark Sanders

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I found this condition and would like some opinions on it. I'll try to word this as descriptivley as I can..

You have a heavy gyro with the requisite heavy, long rotor system.
When you move your joystick forward, off the rear stop, and set the massive rotorhead and rotorblades in motion and suddenly stop the stick, would you expect the inertia of the head/blades to bend the joystick?
Would you tolerate the flexing of the stick metal?
What do you think would eventually happen?

I don't know if the above scenario has ever happened to anyone.
But I found an even scarier one exists, in a large percentage of the fleet.

RAF & GBA gyroplanes have the "cross over" tube (the "tube" that connects the rotorhead torque tube to the pushrods) I quote "tube" because, unlike other gyros, the RAF & GBA use a solid aluminum bar, i believe they call it a gimble actuation arm.

The next time you go out to your RAF or GBA SH, move your joystick to neutral. Wait for the teetering to stabilize.

Now, with some vigor, pump the stick back and forth about 4 inches watching your torque (tube) bar.

The center of the bar and tips of the cross over bar will move in different directions. This movement, viewed from the front or back, will resemble a bird flapping it's wings.

I realize that we don't often pump our joysticks in flight, but every taxi out or exaggerated movement of the stick can cause a flex in the crossover and those flexations cause metal fatigue.

I believe it's just a matter of cycles before failure.
My sparrow hawk has that set up and in flight every movment is very sudle and when I am making a full stop landing after the nose wheel touches the ground then the stick is brought full forward on the stop and the blades are still over 100mph and no sign of a problem so far and I have not herd of any yet. the rotor brake is not engaged until the blades are at or below 75 mph.
 
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gyroplanes

FAA DAR Gyropilot
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I guess I'm not very good at getting my point across. I tried to elaborate on my concerns in the GBA thread above. I will consolidate my answers there instead of running two separate threads. (see GBA thread above)
 

gyroplanes

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I hope you all note the "?" in the thread title. I'm not an aeronautical engineer or metallurgist, but I do know, that if any part of my control system flexes, it WILL lead to fatigue failure at some point. "When" is the only unknown.
 

LASsociety

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Many hombuilts (i speak of fixed wing experience) have people add things that they think will make the aircraft stronger and end up with a heavy, over-built aircraft. Gyrocopters are probably the exception for me. The extra weight of a triangular piece or reinforced brace wouldn't adversly affect anything, and would certainly help me sleep at night.
 

tomhall

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Torque tube

Torque tube

Anyone know a source ( other than RAF in Africa ) for that new & improved torque tube ? Tom T. Hall in MN
 

tomhall

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Sportcopter Blades

Sportcopter Blades

Steve, Thanks for asking. I had only 3 flights with the new blades last Nov. before weather and darkness arrived. On each flight I had to apply significant back pressure on the stick to remain level. I thought my mast may have shifted, but it had not. Ther answer, from Ron Menzie, is quite simple: the Sportcopter blades are " cleaner " than the RAF blades, which offered more drag. I was trimmed to the RAF blades; I changed " wings " , the cleaner wing would by nature put me nose down a bit. Last week I switched from mast position # 3 to #4 ( more verticle ). I still have to apply some back stick to keep level. I would still like to level the gyro without a lot of trim spring pressure, but I may try 2 springs on each side ( not 1 stronger one ) in case 1 breaks. I was hoping I could simply put on the new blades and fly into the sunset; but everything is inter-dependent. It was suggested I make a new torque tube with the offset 1/8" closer together; that seems a bit dramatic. Anyone else with Sportcopter experience ? Thanks Tom
 

CLS447

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Tom, I see that you got no response to the SC blade question.

I would do a forum search.....at least a few guys switched to the SC blades with great results.

Stan Foster, Tim O conner & others. Good Luck
 

giro5

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Steve, post 6, the picture. Those lightning holes in the horizontal bar look too big ie, not enough metal left on the top and bottom of the bar. That bar is scary to me.
 

earthbnd misfit

Biggles
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Even the 4 x 6 mm bolts that hold on the piller posts seem weak. It doesn't take much to strip the threads.
 

Hognose

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Steve, post 6, the picture. Those lightning holes in the horizontal bar
LightEning holes. Lightning holes were made by lightning.

look too big ie, not enough metal left on the top and bottom of the bar. That bar is scary to me.
The material in the middle of the bar carries relatively little of the load. So one might as well cut it away; it's dead weight. The details require a little bit of book learnin' -- for the layman interested in experimental aircraft I'd recommend Dan Raymer's book on homebuilt aircraft conceptual design.

Most of the strength in a bar is around the outside. The mass in the middle helps in compression, and a little in shear, but mostly it's just mass you have to carry.

If one is concerned about the possibility of fatigue failure, a steel tube might be a better choice, but there are tradeoffs there also. (Steel is more vulnerable to corrosion, and corrosion can lead to cracking, for one).

I understand Tom's concern, and I know that RAF redesigned this bar at least once (there's a thread here about why and showing examples of the old and replacement bar). I do believe that no mishap was due to failure of this bar in the field, and these aircraft have flown thousands of hours.

I'd feel better about it if the aircraft had been designed by an aeronautical or structural engineer, but it wasn't. But while the RAF may have some issues, this isn't one that punches pilots' styx tickets.

cheers

-=K=-
 

davreich

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Hi,
The aeronautical engineers at Sparrowhawk copied (oops) engineered them the same as the RAF 2000 original. I believe the parts are interchangeable for some reason.
 

Harry_S.

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Wayne Hubbs' New Torque Bar.

Wayne Hubbs' New Torque Bar.

This looks like a really nice job as evidenced by these photos.

Wayne asked me to submit these fotos for him...no easy task as I'm now with a new 'puter, with Vista at that. A big ole jump for me.

Maybe Wayne can come in here and give you more info.


Cheers :)
 

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WHUBBS

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Harry, i traced around my original torque RAF bar and added some of my own design to it, machined it out of 6061-t6 material and now looking for a place to get it, Anodized the same color to match the rest of my machine. although i have never heard of a failure of this part, i just feel better with the extra beef. i have over 160 hours on my RAF and the original part shows no sign of deterioration.

Wayne
 
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