Limber Mast Question

skyguynca

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OK , so quite a few questions have been done on 2/rev shake and the stiffness of the mast and using a slider head.

If you were to do a tractor gyro, and wanted to use a round mast to prevent using a slider head, with the lower section of the mast (about equal to height of the seat) used for the main engine mount (about the same height of the engine mount on a pusher gyro) with the same approximate bracing between the mast and bottom frame and the engine mount uses a tube clamp to the mast. Also only using gang nut plates inside the mast for attachment to bottom airframe tubing. No triangulation above this area and approx 40 in of the mast is unsupported.

Would the following be acceptable mast material choices:

2020T3 2"x .065"
6061T6 2.25"x .065"
6061T6 2.5"x.065"
4130N 2"x.065"


David Mikesell
San Jose, CA
 
Going on the small amount that I have learnt from Chuck, The 4130 would be good but any of those aluminium should be more like 0.120 wall.
Hopefully others will confirm.

wolfy
 
I used 6061-T6 x .065 or .083 for the mast on my second ultralight gyro. I'll have to check my stock rack at the hangar to be sure. I should have a stick or 2 left from it. I've also used 2 1/4 x .058 Titanium.
 
Thanks John, I appreciate the info. Also thanks for checking on it and let me know. I want to build a tractor gyro this time and really don't want to build a slider head.

David
 
I'm looking at my stock rack right now and I have both 2 1/2 x .065 and 2 1/2 x .083 round tube. IIRC I used the .083 for the mast and the .065 for the front keel.
 
Awesome, thanks for the info.
 
John, how was the 2/rev? was the mast limber enough to help?
I don't want to build another square tube machine, hate the stick shake.

Thanks
David
 
I was thinking of going with 2 1/4 6061T6 with the mast at .083 and the frame at .065. My crude math says it should work, it is an ultralight and weight below 510lbs gross
 
I'm not sure how much the round limber mast helped. It felt like the stick shake was reasonable but I didn't feel it was so important that I never used a square mast again.
 
Thanks for the info John. That is something that helps with the decision. I am looking at less 2/rev, ease of construction, cost of materials. I am trying something new to me and hopefully with all things others will be too.

David
 
The square mast allows clamping that the round does not. You'll need to make at least one hole through it for the engine mount so it doesn't twist or slide. I ended up using a wide 2 piece clamp and a single bolt through it for the engine mount atachment as I recall. The ends can use gang nut plates or a series of rivits.
 
Thanks for the info John, I really appreciate Alot
 
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