What's new
Van's Air Force

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

Slight Rotation of Brake Assemblies

T

twcroy

Active Member
Folks,

My A&P and I replaced a set of brake pads yesterday and he noticed the brake assembly on each wheel rotates slightly (I'd guess 1/16" each direction). Is this normal / ok? His concern is it will eventually wear through the bolt or elongate the hole necessitating a new axle. Also concerned if a brake malfunctions steering is lost.

Happy New Year and appreciate any guidance.
Tim
 
Not sure if it's normal, but you're unlikely to require a new axle. More likely, a new brake bracket. Probably not a safety issue (if I understand correctly what you are describing) at this point, but worth replacing the bracket at the next opportunity.

greg
 
twcroy said:
Folks,

My A&P and I replaced a set of brake pads yesterday and he noticed the brake assembly on each wheel rotates slightly (I'd guess 1/16" each direction). Is this normal / ok? His concern is it will eventually wear through the bolt or elongate the hole necessitating a new axle. Also concerned if a brake malfunctions steering is lost.
Click to expand...

Tim, I'm not sure I understand exactly what you are talking about, but there should be no slop in the assembly except where the caliper anchor pins go through the anti-rotation bracket (normal for the caliper to free float a bit).

The Anti-rotation bracket is bolted to the axel and there should be no slop in that hole. If that bolt is loose in the hole than you need to be looking to step it up to an oversize hole for a nice tight fit or perhaps replace the bracket like Greg mentioned above.
 
Thanks Greg and Walt,

Is the bracket you're referring to the sleeve that goes around the axel with the bolt going through it or another component?

Tim
 
twcroy said:
Thanks Greg and Walt,

Is the bracket you're referring to the sleeve that goes around the axel with the bolt going through it or another component?

Tim
Click to expand...

Yes, the one that the caliper pins go into.
 
In my experience, it's the Brake Flange (WD-4??) mounting holes that are becoming slightly elongated. You will see this on almost all mid-time RV's. It can be replaced with a new one and mounting bolts during your next brake pad/tire changeout.

Probably not a huge safety issue (unless you are seeing abnormal bolt wear), but it will result in a small amount of play in the brake assy and wheel fairing...
 
Brake Assembly Rotations

Thanks Walt and Joe. My A&P says it's definitely the axel / sleeve bolt and hole with the play. I'll call Vans tomorrow to see what size bolt we can go up to and put it up on stands to get a better look.

Tim
 
I noticed slight play - just enough to feel - at my second annual and around 70 hours. I'll see how it progresses at the next inspection. Thing is in an RV - unlike a car - you only brake going forwards so there is no reverse load cycling on the holes to open them up faster.

Sounds like a design mod to include a thicker walled axle sleeve is needed.

Jim Sharkey
RV-6
 
This attachment method is very common on this type of landing gear leg/axle. Because of the high torque loads and thermal cycles, it is really tough to keep the bolt from working the hole. This is one of those situations that requires a reamed (perfectly round) hole, and an interference fit fastener. If you can put the bolt in place without a hammer and drift, it's too loose.

You might be able to save it by reaming slightly oversize and going with a specialty fastener.
 
That's right!

LARCO said:
Tighten the bolt
Click to expand...

Mine has been like this since I bought it with 1300 hours and it's no worse now with 2500+ hours. I have inspected them and found they look fine; it does not take mush clearance to give you some play. Snug the bolt so it?s not sloppy loose and carry on;)
 
Remember that this is a fastener that's loaded in shear, not tension. If the hole is elongated enough to show movement of the assembly, tightening the bolt will only deform the bracket and mask the real problem. Properly installed, the nut is only there to keep the bolt from falling out.

All that said, plenty of airplanes are out there with sloppy bolt holes and aren't going off the end of the runway... So cranking down on the nut might work fine - it just isn't the right way to do it.
 
Just trying to save Tim fixing something that's not broke.

Toobuilder said:
Remember that this is a fastener that's loaded in shear, not tension. If the hole is elongated enough to show movement of the assembly, tightening the bolt will only deform the bracket and mask the real problem. Properly installed, the nut is only there to keep the bolt from falling out.

All that said, plenty of airplanes are out there with sloppy bolt holes and aren't going off the end of the runway... So cranking down on the nut might work fine - it just isn't the right way to do it.
Click to expand...

You are right however snugging the bolt does not just mask the problem, snugging the bolt does deform the brake anchor slightly causing it to hold to the axel so the assembly is not vibrating loose and slows its wear. It?s going to be like this on most of these airplanes that are flown, you can wear it out fixing it or you can pick your battles and go flying.
 
Thanks

Thanks folks. Put it up on the stands today. Play going through the axel was quite a bit less than through the flange. The A&P wants to replace the brake flange / bracket. So will fly it until I get that in and then do it with an oil change most likely.

One thing the tech at Vans mentioned was, ensure the different sized washers are stacked correctly so that the bolt is tightened correctly.

Appreciate all the help,
Tim
 
You must log in or register to reply here.
Back
Top