Main Gear wheel lock

B

BPQ

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Indiana
I had a clicking sound on my left Main wheel when I applied braking while taxing turning right. Jacked up left Main and spun wheel by hand, no issue. Applied slight braking ( hand brakes and drum brakes} and the wheel would turn freely to a point then solidly and suddenly lock. Turn the wheel in reverse direction 1/4 turn then turn in forward direction and it soildly locks again, as though something was hitting the brake shoes. Removed the wheel and saw absolutely no damage, marks or other clues as to to what's going on. Bearings were well lubed an no damage. Brake shoes had no signs of nicks or scares, drum was clean, smooth and damage free. I have no clue what's going on nor did my A&P who saw the same result as I did.

Anyone else ever have this problem??
 
I had to do some work on my brakes to get them up to par several years ago, so I'll point to a few areas of importance. You said clicking sound showed up when turning right, suggesting the side loading on the left wheel had something to do with the clicking sound manifesting then.

First area to inspect is the drum cooling ring. Is it loose and wobbling? It may be making some noise if it isn't rigidly attached to the drum. I had to epoxy my drum rings to the drums.

Second, look at the 3 bolt heads that hold the rim and drum assembly together. I'd inspect and re-torque them as there's not much clearance between the bolt heads and the shoes. Note the washers go under the nuts on the outside rim, not under the bolt heads on the inside of the rim.

If that doesn't fix it, I'd check the tightness of the main axle nut. Too loose and the conical bearing can allow the wheel to "lean" and the bolt heads hit the shoes. If the axle nut is torqued correctly but the bearings are worn, the wheel can also lean under side load. New bearings fixes it.
 
I have a friend with an early PA22 whose left drum brake would lock up. We discovered that the pivot hole in one shoe was slightly egged allowing it to cock on the pivot bolt and wedge in the drum. Then discovered that the nut on the pivot bolt would bottom on the threads before the axial clearance was removed. Installed an AN washer to take up the clearance and the problem was solved. He probably should have replaced the shoe with one that had a round hole but I couldn’t convince him to do it.
 
Thanks for the help. There was absolutely no marks, nicks or any signs of anything hitting anything. The wheel locked as though it was hitting something very solid. I tried to pull the drum cooling ring, but could only pull out aprox 3/8 ". So I reseated with a rubber mallet. I retorqued the 3 bolts that hold the drum and wheel halves per tag attached with the washers on the nut side as they were before I started. I've now reinstalled, hand checked by turning by hand, taxied applying Brakes several times both straight ahead and in a turn with no clicking or locking. I also flew a few trips in the pattern with touch and go and full stop landings. No clicks. Don't have any idea what I changed, but all seems good.
 
Re: elongated holes for the cams...Yep, that'll do it too. Very good point.

Have to say tho', The fact you could move your heat sink ring at all, tells me something. And, re-torqued bolts. Either one could have had an effect. But I suspect the fact you could move the aluminum ring at all, is an indicator of what was clicking. The clicking is not necessarily an indication of what was locking the brake. Moving rings don't generally create locking, in my limited experience. So I am inclined to give the nod to the loose bolts holding it all together. Glad you're back landing safely.
 
Mine did that (clicking/scraping noise) as well, and it was caused by loose cooling rings. (Didn’t know that’s what they're called!) I had a machine shop weld a small bead on the inside of the rings, then turn them down on a lathe for —IIRC— an .005 interference fit. That means the ring has to be heated in an oven to expand it, then re-attached to the drum; as Subsonic said, when it cools, there should be NO movement of that aluminum ring. You might want to look more closely at those rings.
 
Thanks for your thoughts about the cooling ring. They are tight to the drum, but was miss aligned on the left gear buy about 1/16th of an inch. I was able to reposition it with a rubber mallet. My only quandary is that it should not have locked the wheel every 1/2 turn of rotation. I did retorque the bolts that hold the 2 halves of the wheel together and that seems to have stopped the locking. The bolts were not suspect at the beginning as they seemed tight when I removed them and there was no marks, nicks or broken shoe particles anywhere. I'm puzzled.
 
Subsonic said:
....If that doesn't fix it, I'd check the tightness of the main axle nut. Too loose and the conical bearing can allow the wheel to "lean" and the bolt heads hit the shoes. If the axle nut is torqued correctly but the bearings are worn, the wheel can also lean under side load. New bearings fixes it.
Click to expand...

Can anyone confirm what the torque spec/procedure is for the main axle nut on a PA-22? I've sourced manuals for all other wheel/brake-related torque specs, but this one seems elusive. Any input (spec or manuals) is greatly appreciated!
 
Hi,

I don't think there is a specified torque value on those. Most users wiggle the wheel and feel out any play in top to bottom or side to side wiggling. Find the nearest slot, tighter usually, then put in the cotter pin. Too loose or too tight can cause the roller bearings to chatter or get hot and then run dry.

If there's a better way, I'm interested in learning too.
 
Nope, you're right. The "system" used here ("tapered" or "conical" bearings) is the same as it's been since I started wrenching in the 60s (and I know it goes back a LOT further). This is how I was taught to do it:

1) with wheel being hand-spun/wiggled to feel for any play, tighten axle nut with fingers until there is no vertical/horizontal play
2) while continuing to wiggle/spin wheel, continue tightening by hand until any further tightening results in additional drag on the wheel when it's spun
3) back off axle nut just enough to eliminate drag (wheel should spin easily, continuing a bit after hand-spinning)
4) check again that there's no wiggling of wheel - no (or very little) play; use your ears as well as your hands.
5) select nearest point where cotter pin hole lines up with nut or nut cover; a tiny bit of "play" is fine
6) insert cotter pin, bend pin over, replace dust cap.

Then on to brake shoe adjustment....

When I was a kid, I cleaned and re-packed some bearings on a '61 Oldsmobile -- hey, it's a nut, right? Tighten 'er up!
Car didn't make it more than a 1/4 mile before the bearing started smoking.... oops....

One of my first lessons.
 
Here is the paragraph from the J3 manual:

WHEELS: Cast aluminum wheels with Timken tapered roller bearings are lubricated at the factory and should not require additional lubrication for several hundred hours. When removing wheels, dust and dirt should be kept out of the bearings. When reinstalling wheels or to remove end play in wheel on axle, do not tighten axle nut enough to cause binding of the roller bearings as this will result in excessive wear. The proper procedure in adjusting the axle nut is to tighten nut while rotating wheel until a slight drag is felt, then back nut off one castellation and cotter.
 
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