OK Guy's My Turn !

Discussion in 'Mechanic and Repair' started by Restrorob, Aug 7, 2007.

  1. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Well olyman,

    They don't.....I just got the new ones this evening, I did have time to do a little test before leaving.

    I had left one of the old pads off when I put the trailer all back together.

    I performed a resistance (ohms) test and the old pad was 3.8 and the new one was 3.7 .....I thought aw crap they still are not going to work after spending 400 bux.

    Whipped out my jumper battery and putty knife again and re-tested the old one holding it in my hand and pulled the knife off, Did the same with the new one but it was a little harder to pull off. I really wasn't satisfied that these new pads were going to solve the problem.

    I just sat there a minute thinking about it then decided to see if they were any stronger on a piece of metal that covered the full pad surface (which the putty knife didn't).

    I hooked the old pad up and stuck it to the leg on my air table (I was sitting right there while testing) and was able to pull it back off with my hand, A little hard but could, Stuck the new pad on and well....That bulldozer would of came in handy, I couldn't get it to move.

    I told my boss of this and he asked how one can be stronger than the other with such close resistance readings, All I could do is shrug my shoulders.

    Can you or anybody else give some insight as to why/how ?

    I spent some time on "How stuff works" but didn't find a answer.

  2. DiyDave

    DiyDave LawnSite Bronze Member
    Messages: 1,695

    I don't know the physics behind it, but a thin ferrous metal object will never give you the hold capacity that a thick piece of iron will. I have an electromagnetic drill press that is used for drilling through truck frames. It says right on the side of it not to try to drill through any iron less than 1/4" thick, as the e.m. won't hold on thin metal. You were right to test it on a thicker piece of metal that likely mimics the thickness of the brake drum.:waving:
  3. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    Maybe it's your flux capacitor! :laugh:
  4. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    [​IMG] [​IMG]
  5. fixer67

    fixer67 LawnSite Silver Member
    Messages: 2,098

    How many amps does the new ones pull? How many amps does the olds ones pull? Maybe heat damage to the old ones is the reason they are not as efficient at turning the power into magnetism. Just guessing.
  6. olyman

    olyman LawnSite Gold Member
    Messages: 3,649

    also--think of it this way--you have windings inside for the magnet----if theres very little resistance to begin with--if a wire shorts across inside--so that instead of having 300 windings--you now have 150--how much diff in holding power???? right---a whole lot less---same thing will happen in a winding for the charge circuit inside the flywheel---sometimes will short across----because some yo yo that made the wire--didnt get enough varnish on the wire--and it eventually shorts thru--:) :)--also--theres a diff in the composition of metals--putty knife not withstanding--and they all have diff magnetic properties---
  7. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 964

    Your putty knife may be some version of stainless steel, which has varying degrees less magnetism than iron.
  8. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    OK Guy's,

    After more inspecting this morning this is what I came up with.

    Here is the exact brake set-up I'm dealing with, It's made by Warner Electric.


    The center core (in red) runs all the way through the pad and is flush on the back, The windings I'm guessing are wrapped on a plastic sleeve then this center core is bonded in place.

    On the old pad this center core has pulled it's self (guess became un-bonded) to the outside and wore this core smaller. The core is up inside the back of the pad by 3/8".

    With a smaller core in the center that would give less material to magnetize so would create a weaker pull ?

    Doe's this sound feasible ?

    Oh, The trailer is booked until next Thursday so that's when I may get a chance to install the new pads. The driver has been cautioned and is driving much slower with the weak brakes until we can down it again.

    Thanks to everyone who has helped enlighten me on these electric brakes. [​IMG]
  9. rockytopp

    rockytopp LawnSite Member
    Messages: 120

    I have a 24 foot roll back and it has the same dexter set up. I can skid all four wheels with 15 thousand lbs. on it. so you do have something not working. I have had to replace the electro magnets on two wheels. they do break down and lose their ability to function. this could be the problem, I have put brake shoes on mine once and I cannot recall the position of the parts. If you don't get a true picture as they should be installed I can pull a wheel and take a pic and post it for you. Rocky
  10. olyman

    olyman LawnSite Gold Member
    Messages: 3,649

    that core should not have come loose--junk for that one--when you get it back together--should be fine--oly

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