Hangar Flying

Hangar Flying => Hangar Flying => Topic started by: N87dm on October 29, 2010, 04:25:16 PM

Title: heat gun to soften then twist composite gear leg
Post by: N87dm on October 29, 2010, 04:25:16 PM

Well guys, the nose gear on Long EZ N87DM has a new pivot fixture with roller bearings and shimmy dampener,,,,,, now it looks like the nose wheel axle is 3 -4 degrees off of level causing the tire to ride its edge. I'v read in CP about heating and bending composite structures to shape. Anybody heard of this or have an idea about heating the nose gear leg and giving it a slight twist to level that axle ???

Title: Re: heat gun to soften then twist composite gear leg
Post by: Bill James on October 29, 2010, 10:19:52 PM

Having reinstalled and aligned the nose fork on someone's Cozy, I believe it is much preferable and easier to pop it off of the strut and reinstall it. It is pretty straightforward to align using a level and understanding that the strut/spring will compress some, and that it should be installed so that the vertical pin is vertical when the aircraft is loaded and taxiing. Someone here might have the exact installation numbers...

Title: Re: heat gun to soften then twist composite gear leg
Post by: N87dm on October 30, 2010, 11:00:07 PM

Thx Bill........I do actually have some twist in the gear leg itself. Have you ever seen this ?  I guess before replacing it I should at least try to heat it and twist it straight............any thoughts on what that might do to the foam and glass strut structures???

Title: Re: heat gun to soften then twist composite gear leg
Post by: Bill James on October 31, 2010, 04:38:30 PM

No I have not seen a twisted nose strut. Try to get some other eyeballs on it, particularly eze types. Maybe it was home made. I don't know how one would get the strut hot enough to deform, which raises the question of whether the strut was bent while at normal temp, with the possible weakening. Of course there isn’t any foam in the strut, and if needed, only flox should be used in attaching it, not micro.
To your question, trying to re-twist it, enough heat could cause an epoxy void. Thus my thought is, if it is still totally sound, pop the fitting off and re-attach it.

Since I am rambling, on heating the strut, to elaborate a little on the one i fixed, the obvious problem to the owner was the constant need for right rudder while taxiing. He thought the right tire was not aligned correctly. Examination revealed that with the constant braking, even on takeoff, the right gear strut had overheated, with the combination of flexing, there was an epoxy void and the strut was weakened adjacent to the brake disc. He believed the problem was there before he bought the plane.
We tapered and rebuilt the lower strut to original shape. When we took the external wraps off of the lower strut it easily bent and came off at the top bolt holes. (The strut repair has been good now for about 10 years). After the repair he expected the plane to taxi straight. It didn’t. it had the same problem of turning left. I joked that it was a NASCAR airplane. He wasn’t interested in joking around.
To the rambling point. The problem was that the nose wheel fitting had been installed at a canted angle. I noticed it after we had fixed the strut and he was climbing in and out of the plane. If the airplane was wiggled the nose wheel would turn about 10 degrees to the left, which was its “natural neutral point.”
I popped it off and put it back on. He taxied it and came back in smiling big, wanting to know where I had hid the power steering pump. Effortless taxiing.
Installing the fitting striaight is straight forward. Holler if you want a walk through on that anyway :)

  

Title: Re: heat gun to soften then twist composite gear leg
Post by: N87dm on October 31, 2010, 04:55:38 PM

Thanks for the info Bill.........I spent a lot of time today looking and inspecting the leg and you're right . It's not flat on the cast alum. pivot fitting... I'll take it off and re-flox it on --- I'll just put it on straight this time---haha---I sure like that new alum. casting with roller bearings from Wilhelmson......