Scissors necessary?

[AirScooter]

On a larger machine, most have the mid point scissors on the control tubes. If you went with a double wall or thicker wall tube, would they still be needed? I have been told they will vibrate like a guitar string in the wind without the scissors. So just wondering...

[Penguin]

Scissors? Idler arms? Dog bones?

[AirScooter]

Yea, thats the ones. I didn't know the correct name.

[WHY]

HI Scott

Yes, they will vibrate like crazy. It's not that the tubes may fail, it's what the vibration does to the rod end bearings that is distructive. This applies to any long control tube whether on a heavy machine or ultra light, whether vertical rods or horizontal control rods .

Tony

[WHY]

Scissors, walking beam, dog bones, Idler arms, all the same.

It would be a good post if someone with a video camera could take some videos of some long tubes in flight, this would be the ultimate answer to any questions. If you want a good simple test of vibrations in your craft, anchor is down and have someone run the throttle up and down while you hold any location in question with just thumb and finger and you will get a little clue as to what kind of vibes you are getting, and they will be worse in flight. BE VERY CAREFUL OF THE PROPELLOR WHILE DOING THIS, (just thought I'd mention that )

You will be in for some real eye openers !!!!

Tony

[Penguin]

I have a Dom with the long control arms and no idler arms and I know they jump around in flight.
As soon as the weather improves, I'll put my camera on my helmet facing backwards and try to catch them jumping around.

[WHY]

Hey Larry

That would be great if you could get some videos like that, it would help builders to understand a lot about design.

Tony

[Boots]

Redbaron... posted this some time ago.
gyrobee reverse.wmv - YouTube

[hillberg]

teflon lined guides work on helocopter control rods that are several feet long
( 10 + feet in legenth)

[GaryMac]

How long is long enough to need the idler arms???

[WHY]

Hi Gary

I really can't think of a gyro that should not have the idler arm other than maybe an original Bensen, of course I'm a "vibration nut" when it comes to things like this because of a science demo I saw when I was in high school.

The place that I am concerned about most is on "ultralights" because they tend to use the "lightest tubing" to save weight and also no "scissors" to save weight and then the lightest rod end bearings. This situation can just beat the hell out of the bearings and produce a reasonant stress at the threads where the lock nut is on the bearing shank. You can "safety" the bearing with large washers on either side but there is not much you can do about the bearing shank other than make it sufficient size to start with.

Just my personal prefference, but if the control rod is going to be more than 4 or 5 feet, I want a idler arm.

Tony

[AirScooter]

Thanks for all of the replies and information guys, keep it coming.