Travel trailer brakes - magnet question

I'll add my thoughts.

almot wrote:
I opened this one brake because it wouldn't spin after the hurricane with mud up to the axle. It turned out to be just mud inside. Bearings were fine, I repacked the front bearing since I opened it anyway. Could've lost some retaining ring from that "arm" that magnet is sitting on - while opening the drum, or some time earlier. So the magnet is now pushed by the spring from behind all the way to the inside surface of the drum. This is I think what happened. Sand is like water, you drop something and it's gone.

Q2: what this washer or ring might be?

I know you are thinking the magnet is the issue, however odds are high it is not the magnet.

The clip, yes the clip is in the middle of the magnet and the spring is behind the magnet pushing. However the clip really only comes into play when the drum is off so the spring does not push the magnet off the end of arm. See here

The brake before clean up. This is as it looks when the drum was just pulled off


Now cleaned up. As you can see the magnet is not flying off the pivot arm.


See here even better.


The spring creates light pressure to self feed the magnet up against the face of the drum. As wear comes, the magnet moves a little more. The magnet is kissing the inside of the drum all the time. Here you can see straight in. The magnet has room to move out on the arm as needed, just the clip comes into play when the drum is off. Think how fun it would be to put the drum on without the clip. The magnet would be falling off constantly.


There is one other thing about the magnet, it needs power to become a magnet. Unless you have power on the coil there is no magnet force attraction to the drum.

What you are describing points more to the brake shoes being forced to the drum by something other than the magnet. Did you take the adjuster apart to clean it? If so did you readjust the brakes after?

Is the pivot arm froze up? does it pivot? It may be froze, on.

If it is not those more common things, then be looking for something that is jamming the shoes outward.

As to how far and how fast, if the shoes are expanded to the point they stop spinning within an inch of moving, that is a lot of drag. Heat will build quick when moving at much any speed even 15 mph will create heat. Once the heat gets hot enough running a a level of speed, the lining can swell a little (thousands)and make the problem, even worse. At these temps you can start frying eggs on the drum.

Soon a brake fire, greases etc will set off if it runs like this long enough. And can affect the bearings and seals in time.

How long it takes to get to the real hot stage? That is a pure guess, but 1,000 feet with a brake locked on can create a lot of heat. Speed makes it accelerate rapidly. So how far do you have to limp? If this is miles, you need plan B. B = Short of a flat bed to haul the trailer, the drum has to come back off.

PS, By some odd reason, is the emergency break away switch pin pulled or partly pulled?

Hope this helps

John

Thanks guys.
The whole thing has been assembled already, and i would hate to go through this mess again - removing the wheel, drum, washing the 2-days old lubricant out, re-packing the bearing. There is nobody here to have them looked at. I have just learned that $$$ mechanic in town in inaccessible with trailer, small garage in back alley or a street like an alley, if you can imagine those Mex towns.

After some thinking, I "doubt" that the clip was lost, as the magnet didn't come off the cross-shaped pin completely.

Have just got an opinion from the camp neighbor, he says the shoes are out of alignment after my cleaning :), and magnet will eventually wear to where it should be. Says he always adjusts his drums so that there is some sound and some drag, and he likes it better this way. I realize that this is just an opinion, though he's got thousands miles under his belt as 8-wheeler driver. And, the word is, there is hole under the drum for adjusting with screwdriver if necessary - I don't know anything about this, and don't like doing something that I don't know.

Together with this neighbor, we "adjusted" it a little without taking drum off. I rotated the wheel and he pushed the brake pedal few times. It goes a little better now, spins a few inches when I let it go. Other 3 wheels spin like on a bicycle, and the guy says they are too loose, to his taste. The trailer has very little mileage, bearings are good.

Yes, I thought about loosening the bearing nut, but removing the dust cap and pin means re-packing the bearing, with all the sand and dust flying around.

Also check your wheel bearing

Both the bearing condition itself and the torque on the bearing nut...it could
be too tight

Old-Biscuit wrote:


Without clip spring will push magnet out against face of drum which will cause it to drag.....as it drags lever will move out causing shoes to drag.

The spring will always push the magnet out to the drum armature. This is normal and a slight amount of drag and noise will result. If the OP had an unusual amount of mud and rust, then there will be more drag and noise till it wears in.

Magnet is held in place by 'clip'
Spring goes on pivot arm stud then magnet then clip goes thru center of magnet and snaps in place onto end of stud.

Without clip spring will push magnet out against face of drum which will cause it to drag.....as it drags lever will move out causing shoes to drag.

I would remove the magnet....reassemble brake drum and get on down the road with just three brakes.
But that is me........

I would get them looked at they all need to be opened and cleaned. As for the one sticking if you lost the magnet clip I think the spring would push the magnet right off of the swing arm. If its stays on the clip is probably there. I would check the pin where the arm pivots on top for crude or rust causing it to freeze up. I had one do that without being mudded up and it would heat the brakes up on that wheel. To answer the question of how far and how fast I would be afraid to answer. With an inundation of water/sand/mud mixture there could be problems with the brakes working improperly or not at all. I know this may not be what you want to hear but I myself would be scared to death to trust them. They may work fine and may break down on the side of the road.