Wheel Pant Bracket Failure and Brake Failure

mmcmanus · #1 03-20-2014, 06:59 PM

Here's the story. Perhaps someone has an idea about what might have caused this or if you've heard of it before.

I did my run up in Greenville, Tx and the engine was running a little rough. It had rained hard over the weekend. So I did a full power run up to about 2200 RPM. I heard what sounded like a screech on the right brake but the brake held. The engine ran smoothly in the runup so I took off and flew about 1.5 hours to Claremore OK. When I landed I discovered I had no right brake. I was able to get it stopped with only one, slow, 360 as I made the left turn onto the taxi way. I killed the engine and then walked the airplane to the A&P on the field with the tow bar.

When we pulled the wheel pant off, the inside wheel pant bracket had failed (like it was ripped) into two parts. It had failed on a top to bottom line behind the caliper. The brake fluid had drained out but the line was not cut. The brake pad was chewed up. It was not worn out, it looked like someone chewed on it. The rotor was also grooved.

We think that maybe something got caught between the rotor and the pad and broke or cut the bracket, but we couldn't find anything. And maybe that same thing caused the brake puck to stay open and the fluid drained out.

I have some pictures of the failed bracket, but I can't figure out how to post them. Any thoughts on what might have caused it? Has this bracket failed on anyone else?

My RV-7A was completed in 2010 and it has about 305 (trouble free) hours.

http://i59.tinypic.com/17vgih.jpg

http://i57.tinypic.com/2w36fk3.jpg

AlexPeterson · #2 03-20-2014, 09:06 PM

The picture seems to show a fatigue failure, as opposed to single event (i.e., there appears to be no bends at the fracture). Something has been vibrating or otherwise moving it would seem. One possibility is that the bracket has been fractured for a while, and then a hunk of it got into the brake, causing that problem.

Vansrv7arob · #3 03-21-2014, 01:12 AM

Are these not the brakets that have been know to crack for some time? (sorry didnt mean to sound smart assed, maybe i was just lucky enough to know someone else that was unlucky) would have been about the same amount of hours also. I know guys with the 6s were replacing them with stainless ones? Im still building but i have ordered stainless ones to replace standard from the get go. Ill see if i can dig up the suplier info for you.

If you like.

Vansrv7arob · #4 03-21-2014, 01:31 AM

They are about $100 for a set. Stainless steel. Picture is on page 13 of this document from their website. http://fairings-etc.com/Manual_of_Instructions.html hope this helps.

There may be other suppliers as well.

turbo · #5 03-21-2014, 06:17 AM

this is unreal. never seen any thing like this before.

why wasn't the brake working? brake line looks intact.

Wayne Gillispie · #6 03-21-2014, 06:21 AM

While your brake system is open, install some braided SS lines down the gear legs. Contact Bonaco. Glad you and the majority of your plane are okay.

DanH · #7 03-21-2014, 06:30 AM

The bracket was pushed against the disk. The disk cut through the bracket. Note the perfect semi-circle, and what appears to be a chunk still hanging.

Now look at the other photo. See how much bracket material is missing?

The brake disk is blue, and the caliper label has been heated. Both have been quite hot, either due to brake use or because the disk was wearing through the bracket. Either way, there's a high probability that the standard nitrile caliper o-rings are baked hard, thus the fluid leak.

rleffler · #8 03-21-2014, 07:22 AM

This may be a solution for a different issue, but on the RV-10s there were starting to have reports of the wheel pant bracket cracking.

Sean @ planearound.com came up with a solution that more effectively dampens vibrations and secures the bracket better than the default bushings.

I suspect that the RV-10 part may not work on other models, but I would contact Sean to see if he's willing to make the parts for the other models.

bret · #9 03-21-2014, 08:01 AM

Quote:

Originally Posted by DanH

The bracket was pushed against the disk. The disk cut through the bracket. Note the perfect semi-circle, and what appears to be a chunk still hanging.

Now look at the other photo. See how much bracket material is missing?

The brake disk is blue, and the caliper label has been heated. Both have been quite hot, either due to brake use or because the disk was wearing through the bracket. Either way, there's a high probability that the standard nitrile caliper o-rings are baked hard, thus the fluid leak.

You have a sharp eye Dan, Just finished mine a bit ago, the plans have you fab the shim spacer so that the bracket is very close to the rotor, could the pant-bracket been bent or damaged before this wore through?

Ironflight · #10 03-21-2014, 08:26 AM

I think Dan nailed it - there is normally very little clearance between the bracket and the rotor. If the axle spacer gets left out when mounting the wheel on the axle, you loose a quarter inch or so - and those spacers DO fall out and roll under work benches. Since they aren't a standard Cleveland part, many buyer's don't know they are are supposed to be there - something to check at least.