Need advise on electric trailer brake repair...

[NM_Shooter]

Took my old camper in to two different shops and neither fixed the problem.  I crawled under my trailer and found that the last owner apparently thought an adequate wire splice was twisting two wires together and wrapping them with electrical tape.  None of the "pros" found this problem.

Anyway, I now have new friction and turned drums on all four trailer wheels. 

All brakes are engaging, but I have one that is providing way too much braking and is heating up too much.  I have a non-contact thermometer that I shoot at it.  A typical 4 wheel measurement is:  125, 410, 195,177 degrees.

When I re-wired the brakes, I measured each magnet's impedance, all were around 3.3Ohms. 

I am heading out next to pull the drums, and clean the magnet and the drum with brake cleaner to make sure that there is not any grease between the magnet and the drum.  BTW.. I have Alko 10"X2.25" brakes.

Some questions...

I can adjust the drag setting for the brakes with the star wheel adjuster.  Does this also change the braking force or does it just set the drag amount when the brake is not engaged? I've fiddled with it a bit this morning and have not seen much in the way of results.

Is it possible that the magnets can become mis-matched?  I know that they can just open up and fail, but is it possible that they just weaken over time?  If cleaning the drums does not help, I am considering purchasing 4 new, matched magnets for the brakes.

Arrrggghhhh!!!!  I hate paying people to fix my stuff and then they do a half a$$ed job.

-f-

[NM_Shooter]

Went back in and cleaned up the magnet surfaces and the inside of the drums.  I also fiddled with the star adjuster.  Neither seems to have any impact on the braking force.

I think I'm going to order four new magnets, and possibly have the magnet bearing surfaces cleaned up on a lathe too. 

Yee ha.

-f-

[glenn kangiser]

Frank, not sure if I can help but, the star wheel should cut back on the aomunt of breaking effectiveness if it is shortened on a standard vehicle - not sure about electric brakes, also, there is a primary shoe short lining -  and a secondary shoe - long lining, usually.  Have you checked to see that they are in their proper places - primary to the front.

How about one of the variable resistors in that line if all else fails - I have seen them for the old brake systems - .

[NM_Shooter]

Good thoughts Glenn... I'll for sure check out the primary shoe thing.

-f-

[peternap]

I like Glenn's idea about the variable resistor. A good heavy 0-100 12V POT should work.

[glenn kangiser]

Let us know how you fair... looks like typing dyslexia struck me and I didn't catch it above.

[NM_Shooter]

I ordered 4 new magnets at $22 each. 

I've learned a bunch about electric brakes..  it looks as though the star wheel does not help braking force.  It appears to only be used for setting the initial gap on the brake assy.

When the electric magnet is energized, it sticks to the inside face of the brake drum.  The magnet is held in the assembly by a pin that is attached to a lever arm.  When the magnet sticks, the rotation of the drum pulls the magnet and the lever arm which in turn spreads the brake shoes out. 

The magnet actually "slips" on the face of the inside of the drum.  As more energy is applied to the magnet, it sticks harder, which presses harder on the lever arm.  It is actually a pretty cool design.

Looks like a few different things actually control the force of the braking.  The strength of the magnet, and the surface between the magnet and the drum. 

I've got the new magnets coming, and will see about resurfacing the magnet surface on the drums.  Hopefully this will fix the issue.

[MountainDon]

G/L   

[diyfrank]

I have some I need to work on.  I may be asking you some questions. 

[glenn kangiser]

I ordered 4 new magnets at $22 each. 

I've learned a bunch about electric brakes..  it looks as though the star wheel does not help braking force.  It appears to only be used for setting the initial gap on the brake assy.

When the electric magnet is energized, it sticks to the inside face of the brake drum.  The magnet is held in the assembly by a pin that is attached to a lever arm.  When the magnet sticks, the rotation of the drum pulls the magnet and the lever arm which in turn spreads the brake shoes out. 

The magnet actually "slips" on the face of the inside of the drum.  As more energy is applied to the magnet, it sticks harder, which presses harder on the lever arm.  It is actually a pretty cool design.

Looks like a few different things actually control the force of the braking.  The strength of the magnet, and the surface between the magnet and the drum. 

I've got the new magnets coming, and will see about resurfacing the magnet surface on the drums.  Hopefully this will fix the issue.

If that doesn't fix it I would maybe change the drum.  Is it different from the rest - More mass - thicker?