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Need help with brake chambers

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by gkmissingca, Jul 16, 2017.

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  1. Jul 16, 2017 #1
    gkmissingca

    gkmissingca Light Load Member

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    To start, my background is in cars so I'm still learning air brakes.
    I'm converting a truck to single axle and the donor axle only has service brakes...oops. The travel at the clevis pin is only about 1.5" and the rod at rest only has about 1.75" sticking out. Most parking brake chambers I see have really long rods and aren't threaded far enough down. Could I buy this : www.oreillyauto.com/detail/brakebest-hd-2911/agriculture-hd-parts---accessories-19818/fleet---heavy-duty-20088/air-brake-compressor-valves---products-20110/hd-truck-brake-chambers---accessories-20251/piggyback-kit/bps3030/2543576

    And make the service brake a parking brake? The old service brake is an MGM 30 67-1.
    Thanks in advance.
     
    gkmissingca, Jul 16, 2017
    gkmissingca, Jul 16, 2017
    #1
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  3. Jul 16, 2017 #2
    AModelCat

    AModelCat Road Train Member

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    That isn't the pushrod in the picture of the park chamber you posted. That is a caging bolt that compresses the big park spring. That is only the park half of the chamber and gets installed in place of the back half of the service chambers you already have on the axle.
     
    AModelCat, Jul 16, 2017
    AModelCat, Jul 16, 2017
    #2
  4. Jul 16, 2017 #3
    gkmissingca

    gkmissingca Light Load Member

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    Ok, I understand that's the caging bolt. So in theory, I should be able to take apart my service brake and add this piggy back?

    Edit: oh duh, that's what you just said.
     
    gkmissingca, Jul 16, 2017
    gkmissingca, Jul 16, 2017
    #3
  5. Jul 16, 2017 #4
    x1Heavy

    x1Heavy Road Train Member

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    Caging bolt, aka maxi bolt is designed specifically to DISABLE the parking portion (The spring) when installed. It compresses your spring on that side of the brakes so you cannot have it locked down and roll during towing etc.

    There is nothing there for you with that bolt. It is made for that exact purpose and wont help you at all.

    What I think you are about needing to do is to find a complete assembly that has both the service brake side and a parking brake side for that axle. I don't know enough about axles but think they should make replacement brake assemblies for specific axles.

    I don't know if I want that donor axle that only has service braking on it. You need a axle with a complete braking, both parking and service already on it.
     
    x1Heavy, Jul 16, 2017
    x1Heavy, Jul 16, 2017
    #4
  7. Jul 16, 2017 #5
    AModelCat

    AModelCat Road Train Member

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    The complete chambers (service and park) are cheap. Just bought 2 Bendix MGM style 3030 chambers for $60 each plus $30 for 2 clevis kits. Just gotta cut the pushrod to the correct length as per mfg. instructions.
     
    AModelCat, Jul 16, 2017
    AModelCat, Jul 16, 2017
    #5
  8. Jul 16, 2017 #6
    gkmissingca

    gkmissingca Light Load Member

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    Ok thanks. I just wasn't sure on cross compatability on these chambers. I took apart my old service chambers and diaphragms were heavily cracked too so into the junk pile. Did get the clevis off though. Thanks for your help
     
    gkmissingca, Jul 16, 2017
    gkmissingca, Jul 16, 2017
    #6
  9. Jul 16, 2017 #7
    RET423

    RET423 Medium Load Member

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    Just put 2 new piggy backs on where the service pots are currently installed, cut the rods to length and plumb the new pots off of your original triple valve the same way they were plumbed as a tandem.

    Service pots actuate when air pressure is applied, spring brake/maxi brake pots actuate when air pressure is cut off; they are different beasts entirely.
     
    RET423, Jul 16, 2017
    RET423, Jul 16, 2017
    #7
  10. Jul 16, 2017 #8
    gkmissingca

    gkmissingca Light Load Member

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    I ended up finding two brake chambers on ebay. The main problem I had was finding the rod with enough threads cut down close enough to the chamber. The bracket and lever are very close to one another. Most of the inexpensive ones I found had a couple of inches of uncut rod which would be too long for my application.....I think.
     
    gkmissingca, Jul 16, 2017
    gkmissingca, Jul 16, 2017
    #8
  11. Jul 16, 2017 #9
    stayinback

    stayinback Road Train Member

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    Hey Northern Mechanic....Do You buy chambers with OUR Flag on them??
     
    stayinback, Jul 16, 2017
    stayinback, Jul 16, 2017
    #9
  12. Jul 17, 2017 #10
    Professional Passenger

    Professional Passenger Bobtail Member

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    Diaphragms never go into the junk pile. They're free tools...

    They make great bolt/part trays when working on stuff.
    I think I have 40 or so of them. And the best part, unlike those pesky fancy magnetic ones, they're easier to clean after the job is done...
     
    Professional Passenger, Jul 17, 2017
    Professional Passenger, Jul 17, 2017
    #10
    stayinback Thanks this.
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