Deformed foot support bracket for Wilhelmson electric nose lift

[DouglasHolub]

I put a Wilhelmson electric nose lift on my Velocity. I'm 34 hours into Phase I flight testing, and today I noticed that the bracket that clamps the nose wheel assembly to the nose strut was deformed (picture attached), and in fact was not clamping anymore. The only thing holding the wheel assembly up was the fiberglass nose strut fairing, and it was tearing. Another inch and the nose wheel would have fallen off.

 

Does this bracket often deform? My Velocity fully loaded can put 395 lbs on the nose wheel. I think the maximum a Cozy Mark IV ever sees is 295 lbs. I was testing full forward CG with 365 lbs on the nose wheel this week and I'm guessing that's when the trouble started. I don't recall any particularly hard landings. Up until this week, with just my weight in the front seat, the nose wheel only had about 250 lbs on it.

 

Last month I tested the gear with 900 static lbs on the nose wheel with no problems.

 

It would be an easy thing to add some steel angles under the bolt heads to beef up the clamp. I guess I'm a little concerned that if the clamp didn't deform, the strut might break. Should I be concerned?

 

Doug Holub

Irving, Texas

[TMann]

Doug,

You REALLY need to talk to Jack first on this one.

[David Clifford]

I didn't like they way the bracket bent just by tightening up the bolts. I solved it by using some 1/2" X 3/8" bar aluminum to fabricate a spacer and drilled it for the bolts to pass through. I also fabricated a 1/4" aluminum plate that goes between the strut and the foot plate also drilled for the bolts. Using longer bolts,,,this formed a solid aluminum pocket for the end of the strut to fit into. I ground out a small amount of material in the pocket in the bottom of the casting to form a pocket for flox,,,,so even if the caster assembly came loose it would not be able to fall off the strut. Waxed up the pocket and put it all together with flox. After cure,,disassembled. shaved .020" off the aluminum spacers,,,cleaned and roughed everything back up, and reassembled with runny flox. The .020 clearance allowed a controlled clamping pressure.

[NeilK]

Doug

 

I had the same thing happen on my Long-EZ within 20 hours. I made a duplicate part but 1/8" stainless. I made the part with the 4 mounting holes completely flat.

[DouglasHolub]

"You REALLY need to talk to Jack first on this one."

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I've worked closely with Jack from the beginning. He doubled the compression force of the spring in the lift mechanism so that the extra weight on the nose wouldn't compress it so much that the canard would have a negative angle of attack during take off. That part is working great. Of course I wrote Jack and explained what happened this week, mostly so that if anyone else is thinking about putting the Wilhelmson nose lift on a Velocity he would be able to tell them that there might be a problem. But Jack didn't design the nose wheel assembly or the fiberglass strut. If he did he would have been able to warn me two years ago about a potential weakness in the support foot bracket.

 

Is there another canard forum that might have some experience with over stressing that nose wheel assembly?

 

Doug

[DouglasHolub]

"Is there another canard forum that might have some experience with over stressing that nose wheel assembly?"

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I hadn't read Neil or David's replies yet. Thanks, guys. I'll beef it up.

 

Doug

[DouglasHolub]

And I think I'll safety wire the support foot to the strut so that if the clamp ever does get loose again, the wheel assembly won't fall off.

 

Doug

[TMann]

Good discussion!

I like the stainless solution. I don't have any time on mine so it's good to solve the problem prior to experiencing it.

Thanks all.

[Cozy Girrrl]

Seems like the clamping part needs to be twice as thick in your case.

...Chrissi

[Wayne Hicks]

Yep, you're supposed to use flox (or spacers) to take up the gap.