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OK Guy's My Turn !

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

  1. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Hey all,
    We have a tandem axle goose neck for our larger rental equipment. The driver has been complaining about the brakes not working properly.

    It has two 10,000 lb. axles, The first things I checked was the controller and made sure I was getting power to all electro magnetic pads which were fine. Then I pulled the drums to inspect the linings which wear wise looks like they just came out of the box.

    Here is my questions using the picture below;


    When the brake is applied the electro magnetic pad grabs the disc inside the drum and moves the arm to the left to spread the shoes to apply the brakes since there is a stop tab keeping the arm from moving to the right.

    Is this the proper function of these brakes ?
    If not could you explain ?

    Thanks For Any/All Input....
  2. fly-4-fun

    fly-4-fun LawnSite Member
    Messages: 0

    Did the problem just start or has it been a gradual decrease in the trailer brakes?
    If it is a gradual decline, then I'd say to adjust the shoes out. Trailer brakes are not self adjusting like on a car and if they aren't adjusted ever so often the shoes can't expand enough to grab the drums.
  3. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Sorry fly-4-fun,
    I failed to mention we do keep the shoes adjusted and the adjustment was fine today before tear-down.

    I just need to know if they function as I figured they do in my above post.

  4. tomo

    tomo LawnSite Senior Member
    Messages: 660

    hello it would appear to be the correct method of operation for that brake set up .As u can assume this is over the web so i cannot see in detail the mechanisms to evaluate properly .
    As u may be aware u can have the shoes radius ground ,to the exact fit to the drum . Even when u think it will be ok radius grinding shoes ensures 100% contact to drum .
    New drums?? if not are the drums past there max limit for machining max diameter]
    The contact surface 4 the magnet is it grooved etc ?? replace magnet and either machine surface or replace drum
    U may be aware that braking systems can have a leading and trailing brake shoes [depending upon design] when they are reversed performance can suffer . Eg a pickup truck range at a dealer required the shoes to be reversed so to decrease max braking and to avoid locking of brakes when unladen .


    ps short linning to front ,picture seems back to front ,rotation of wheel is clockwise so short is trailing ,this raises questions ??

    ps2 Rob did u receive the pm with model type chassis etc??
  5. fly-4-fun

    fly-4-fun LawnSite Member
    Messages: 0

    Electric brakes are actuated electrically through a magnet rather than hydraulically through a wheel cylinder. The magnet is positioned so its poles are close to an armature surface, which is machined or bolted inside the brake drum. When the magnet is energized, it is attracted to the armature surface causing a frictional force that pivots the lever arm and slipper block. This forces the primary shoe against the drum which energizes the secondary shoe.
  6. fly-4-fun

    fly-4-fun LawnSite Member
    Messages: 0

  7. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Thanks fly-4-fun, That's what I was looking for.....

    Also read below;

    tomo, You didn't get my PM I sent at 8:47 ?

    The drums show no sign of a wear lip where the shoes don't touch and the E/M disc looks fine.

    The shoe length is only one of the questions......

    Here is a paste, I have this posted elsewhere also.

    This trailer never really stopped well from day one, We have had it around 10 yrs. and I don't recall ever putting shoes on.

    If these brakes function as I posted above and the E/M pad moves the arm to the left to spread the shoes with the tire rotating clockwise that would mean the above brake assembly would need to be on the right side correct ?

    Here is what I'm getting at;
    The brake assembly above (pic) is on the left (driver's side of the trailer). Therefore when the E/M pad is activated it grabs the disc inside the drum but can't spread the shoes because the arm is against the stop tab.

    So my theory is the guy that put the axles under this trailer had a couple six's too many the night before and put them in back-wards. If this is so all we've had is what little braking the E/M pads were doing. This could explain 4
    brake jobs on two trucks.

    When the manual lever on the controller is slid all the way over to engage shouldn't it Lock the wheels up tight ?

    When doing this I can pull off without hardly any drag.....

  8. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    I just seen this after posting, Boy am I confused now !

    The arms on our trailer don't move like the little animation but the other direction :confused:

    Guess I'll take a closer look tomorrow and see what the heck is going on.....

  9. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    Maybe the brakes and backing plates were installed on the wrong sides? Also the larger lined shoe goes to the front. The front shoes are thrown into a binding action and need the extra lining.
  10. tomo

    tomo LawnSite Senior Member
    Messages: 660

    Rob , as i mentioned earlier the shoes seem not correct at first at the start of the story .

    As we continue the plot thickens .If u notice on the backing plate there seems to be a brand maybe eg """"DEXTER""", well what ever it may be find the maker and make a few calls . Another theory is the original installer had both sides dissasembled and mixed the parts some LH and some RH together on same side . Seen all this b4:hammerhead:

    Check controller install as per maker they all have there own install particulars .Please donot make any general assumptions . Some controllers are fairly poor and seem to have a troubled history . Others like the prodigy and the better one again the P3 seem to be state of the art . Another valid point is the P3 can have the initial setup be at a certain percentage of brakeing eg 10--30 % .This applies as the trailer becomes large in comparison to tow vehicle .

    All this came after investigating brakes for my new trailer .
    HaHa ,i went down the road of hydraulic disc activated by over ride coupling with max legal gross weight of 4500lbs ,simple setup .
    Over 4500lbs i must be electric or air all wheels


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