What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Wheel Pant Bracket Failure and Brake Failure

M

mmcmanus

Active Member
8


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
 
Last edited:
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.
 
bracket

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.
 
Last edited:
17vgih.jpg
2w36fk3.jpg


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

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

349bi1f.jpg


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.
 
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.

1289711480564208972753.jpeg


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.
 
DanH said:
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.

349bi1f.jpg


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.
Click to expand...

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?
 
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.
 
Dan hit it on the head.
As mentioned, the bracket runs very close to the brake disk. I discovered some minor scoring on my brackets very early on. I had to adjust the spacers to give the bracket more clearance.
I would do a run out check on your brake disks. There is a possibility of warping due to the excessive heat build up from the friction.

Wheel pant brackets, brake lines, brake disk, calipers, etc... should be inspected every time you take your wheel pants off. This probably didn't happen over night.
 
While my setup is slightly different (Sam James Wheelpants attached with the Van's bracket), I noticed a lot of play in the wheelpants bracket that I wasn't happy with. My solution was to rivet a piece of 0.090" 4130 steel to reinforce the wheelpants bracket:

DSCN3115.JPG
 
JonJay said:
Dan hit it on the head.
As mentioned, the bracket runs very close to the brake disk. I discovered some minor scoring on my brackets very early on. I had to adjust the spacers to give the bracket more clearance.
I would do a run out check on your brake disks. There is a possibility of warping due to the excessive heat build up from the friction.

Wheel pant brackets, brake lines, brake disk, calipers, etc... should be inspected every time you take your wheel pants off. This probably didn't happen over night.
Click to expand...

Yes, wonder what the tire pressure was?
 
How much clearance between wheel pant and tire? I have 7/8". Check tire pressure as often as possible to prevent contact from a not so greaser of a landing. I try to check mine every three months. I also inflate 5 psi over Van's numbers. Not saying that is proper, just what I do on my -10. It takes about 90 min for me to disassemble, inspect everything, reinflate and reassemble. It makes it easier to move too.
 
Also, the way the brake hose is connected, leaves little room for flexing. I believe if not using a flexible hose, one need to put a full turn/circle to make the line flexible enough for all the movement.
 
Bavafa said:
Also, the way the brake hose is connected, leaves little room for flexing. I believe if not using a flexible hose, one need to put a full turn/circle to make the line flexible enough for all the movement.
Click to expand...

Correct - which is exactly how the plans have always shown. It does not appear these lines where ran per plans. Good catch.
 
Last edited:
DanH said:
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.

349bi1f.jpg


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.
Click to expand...

Yep, from the fracture pattern on the other picture, I bet it broke loose first then drooped to the disk. The missing tube loop is already noted, and the caliper bolts are missing safety wire.

I will be mounting brakes next few days, so this is good information. Thanks for sharing.
 
Thanks to everyone who looked at this and for your ideas. The caliper and all have already been fixed and reinstalled. We did not do the safety ties since we're waiting for the new bracket to come in. The brake line IS steel braided, flexible line.

I think the suggestions about something getting into the bracket, forcing it into the rotor, and that causing the failure are probably correct. And, the idea that the caliper and O-ring got hot (and hard) and allowed the brake fluid to escape makes sense too.

Also, I was remiss and did let the tire pressure get low. I didn't have time before I left on this trip and planned to take care of the tire pressure this weekend when I returned. Maybe my own procrastination bit me this time :)

Thanks again for your ideas and help.
 
Brakes

During phase 1 and taxi testing I had a similar failure.
In my experience a dragging brake and numerous hi speed taxiing, heated up the rotor. The rotor heated the middle area of the pant bracket, causing it to warp and physically contact the brake rotor and wear a groove. I had to replace all of the seals, flex lines and pads due to overheating. I suggest that a dragging brake maybe the initial cause of your problems. Since you indicated you were going to add a flex loop, consider using a rubber flex hose, either automotive based or from a grease gun.
 
Note: brake pucks have sometimes been put in backwards. O ring is then closer to edge and subject to blowing the 5606 on hard braking.
 
great forensic analysis

OK, I think we all just got our $25 worth! I've noticed a brake drag after a flight, never before.... This makes me want to go out and address all the possible issues! When running in winter with pants off, the backing plate sure vibrates!....I like the stiffener idea.
Kudos to everyone for the analysis.
 
Just as an FYI I find MANY loose bolts at the backing plate to axle attachment, they should be checked whenever the wheels are removed.
 
Just a quick follow up. As I said in an earlier post, I appreciate all the ideas. The suggestion that something pushed the bracket into the rotor, causing the failure, causing heat, causing a heat hardened o-ring that caused the fluid loss and subsequent brake failure....all makes sense.

As followup to posts about the pucks in backwards. That was not an issue here.

I received the bracket from Vans on Friday and we installed it on Saturday. The old bracket, now removed, shows additional signs (a round arc scratched into the sheet metal) where it rubbed into the rotor.

Everything is back in order now. The brakes with new nuts (and safety ties), with the new bracket...all installed and air worthy now.

I plan to include a quick check up inside the wheel pants to my preflight. Plus I'm gonna' be a lot better about tire pressure going forward.

Thanks again to everyone who provided insights.
 
You must log in or register to reply here.
Back
Top