Bent Onex main gear

[flyingbear]

I am curious why so many Onex gear are bending. When I instructed in Traumahawks years ago, we had students land so hard that there would be black tire marks on the wing bottoms....but those gear never deformed. hmmmmmm
Any ideas out there? Poor temper or material???? Something is wrong for sure. Sonex do not appear to have this same problem do they? I think 1.2 inch is too thin for gear but they should retain their shape.

[13brv3]

The Onex is the only Sonex model with flat gear legs, so there's really no comparison to other Sonex models. From all the rust I see on pictures of Tomahawk main gear legs I'd say they're steel, where the Onex is aluminum. The Piper was built as a trainer, with the expectation of constant student punishment, so heavy steel gear legs makes sense. The Onex is a sport plane aimed at more experienced pilots so I can certainly understand choosing a lighter material. I'd bet if you had steel gear legs you'd rip out the support structure on a really hard landing, which makes bent gear legs seem like a better option.

Rusty (hope I don't bend mine)

[flyingbear]

Good points Rusty. Do you know what type of alum the ONEX gear is made of?

[13brv3]

Good question. I don't see the material spec anywhere on the plans, or on their web shop. If anyone wants to ask them, I'd bet they'll tell us. Probably just didn't figure anyone is really going to be making their own gear.

I had considered getting taller gear made by O'Keefe, and they list theirs as 5/8" thick, 2024-T351. There's even a picture I'm sure you'll find familiar on their page :-) http://www.okeefeaero.com/-landing-gear.html

[sonex892.]

I had considered getting taller gear made by O'Keefe, and they list theirs as 5/8" thick, 2024-T351. There's even a picture I'm sure you'll find familiar on their page :-) http://www.okeefeaero.com/-landing-gear.html

Even though O'keefe do sell 5/8" thick gear the picture showing the dimensions of the Sonerai undercarraige is from the actual Sonerai plans and shown as 1/2" thick. Since the dimensions are shown it would not be hard to measure a onex gear to see if it's a direct swap.

I believe the Sonerai gear was upgraded to 5'8" because of the same bending issues. The Sonerai stretch I built had the 5/8" gear, I bought it from Great Plains, now O'keefe. I can guarantee it had some less than gentle landings and never deformed.

Steve
Sonex 892

[13brv3]

The Onex plans don't give enough detail to make your own landing gear from what I can find. They show 27" for the top flat dimension where it bolts to the fuselage. The max width is shown as 51-3/4", and the max height (no weight on it) is 16-7/8". They don't show any other detail, including thickness, or material.

I just measured SN-85 and the gear is 1/2" thick. It would be really interesting to know if they've changed that with the more recent kits. Anyone got a recent Onex to measure the gear thickness?

Rusty

[railer833]

I have kit 031 and before I ever made one landing, just after taxi testing I could see that the landing gear looked splayed out. I talked to Sonex and they said there was a known problem with the gear during the production of my kit and said they replaced many gear legs to the original buyers. They only offer me a new set of gear at a discounted price because I was not the original buyer. I have the new set of gear and it looks exactly the same as the original gear that came with the kit except it was bent the the correct angles. I personally don't have a lot of faith in Sonex spring gear but time will tell. I just know their is a lot of people having problems with this part of the aircraft.