Wheel Pant Movement

During a recent pre-flight inspection I noted that the tail end of both main wheel pants had some vertical movement. Since it was time to re-pad the brakes, I figured I'd look into the issue further.



I suspected that the three bolts that hold the wheel pant bracket to the axel flange where loose. I was surprised to find the whole axel flange having a slight rotating movement on the axel.



I disassembled the axel bracket form the axel to see where the movement originated.





There was no one part that appeared out of tolerance, but each had a very slight amount of movement on the bolt. A new bolt was no different. So I re-assembled the unit using Loctite in increase the holding area of the bracket to the axel. Here's the assembled unit and the Loctite used:





Both axel brackets were loctited. The axel flanges can still be removed, but they will have to be heated to break the Loctite bond on the axel.

If you do this fix, just be sure not to get any Loctite on the bolt (infact, leave the bolt well oiled when you assemble the unit) as it would be VERY dificult to remove the bolt if it were bonded into the axel...

(Sorry for the fuzzy pictures. It's the first time I've used this camera and I'm still getting used to it...)

Nice pictures and well documented. Have you reassembled it and looked at the movement again?

Wheel Pant movement

All assembled with no movement. I suspect any movement now will be loose mounting screws, and/or the axel nut bolt being loose (but that's wire tied, so the chances are very low...).

jay.pearlman said:

Nice pictures and well documented. Have you reassembled it and looked at the movement again?

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Nice job but I suspect a firm application of the brakes will likely break the bond.

Maybe.. I thought of that when I re-assembled and preset the rotational movement in the direction braking would try to move it. So far, after only a few landings, there isn't any sign of movement. I've used the same bonding technique on the front gear leg mount and not seen any movement there after several years of flying... So time and use will tell......

Walt said:

Nice job but I suspect a firm application of the brakes will likely break the bond.

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Would a tapered pin through the axle work?

Since there didn't appear to be any significant wear on the acel flange fittingbolt holes, or the bolt, I'm not convinced that a tapered pin would be any better than a closer tolerence bolt. In any case, the extra holding area advantage of the Loctite is significantly more than either a close tolerence bolt of tapered pin could offer. Time and use will be the best test. Let's see what happens.

wilddog said:

Would a tapered pin through the axle work?

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Added a washer

At 450 hours, I noticed the same issue.

The nut bottoms out on the thread/shank before the assembly has the correct torque/clamping pressure. Refer to DWG C2; the stack up is a 5/16-20x1 1/2 screw, AN960-516 under the socket head, AN960-516 and -416 under the 1/4 - 20 locking nut.

I added an AN960-516L under the socket head, and I was able tighten the nut down sufficiently.

Your mileage may vary.

b

Added a washer


What I did when I built the plane was put washers onto the head and tail of the bolt then a washer on the shank under the nut. This allowed the nut to torqued properly without it bottoming out against the bolt shank. Even with this method, the fitting eventually began to move due the tolerance buildups of all the components. A similar issue happens with the front gear leg/motor mount fitting on -A models. Even properly torqued, there isn't enough holding power with just the properly torqued bolt to prevent eventual movement. Adding the holding power of the Loctite eliminates the problem....

bjdecker said:

At 450 hours, I noticed the same issue.

The nut bottoms out on the thread/shank before the assembly has the correct torque/clamping pressure. Refer to DWG C2; the stack up is a 5/16-20x1 1/2 screw, AN960-516 under the socket head, AN960-516 and -416 under the 1/4 - 20 locking nut.

I added an AN960-516L under the socket head, and I was able tighten the nut down sufficiently.

Your mileage may vary.

b

Click to expand...