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Thread: Spread axle turning

  1. #1
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    Spread axle turning

    I've got a 45' fixed spread axle air ride flatbed that I am using in and out of farm fields and yards, where it can get kind of tight, especially getting in and out of small field entrances or small yards. I was wondering if I can effectively make the wheel base shorter (and reduce scrubbing when turning) by plumbing the air bags on the trailer so that a switch on the dash of the tractor would dump the air to the rear bags only, so that it would pivot on the front axle. As soon as the turn was made, you'd flip the switch to return to normal suspension (probably have a red light to remind you).

    So do you think this is a wild, hair-brained idea???
    Most of the weight would be on that front axle- would that matter for just a short time at low speed? I don't know what weight rating the axles have- they are just "normal" axles, if there is such a thing!
    Also would the bags be able to handle the extra pressure for that short time as well?
    When you go over ridges and lumps, the weight transfers back and forth between axles anyway, so I would think that it would be okay, as long as a dumb operator doesn't forget to flip the switch again!

    My loads shouldn't exceed 40,000 lbs.

    Ever seen this done?

    Pb

  2. #2
    Senior Member Iron Horse's Avatar
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    Theres merrit in the idea , but i think the front bags would need upgrading to a larger diameter to take the weight . I have seen a large bag on top of the diff in a lazy axle prime mover . When the drive lost traction the operator flicked a switch which inflated the bag , forcing the drive down .

    I think if you fitted a raise/lower valve on the trailer so it could be lowered , and then have a solenoid valve/manual ball valve stopping the air back into the rear bags it would work . When you throw the raise/lower switch , the oversized front bags would take all the weight and the rear axle would just skim around untill the turn is made .
    Just my 2.02 cents including GST .

  3. #3
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    Good idea. Thanks!

  4. #4
    Senior Member Iron Horse's Avatar
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    You may want to check that your shockies have axle limiting bump stops that will carry the axle without over extending the air bags when going over driveway pipes etc. Either that or fit a pair of straps from the floor crossmember down around the axle and back to the crossmember , leaving a couple of inches of slack to allow for oscilation . Shockies will do the job , but you never know when an eye may break off and allow the airbag to be torn from over extension .
    Just my 2.02 cents including GST .

  5. #5
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    It's done more than you (or DOT) know. It'll work fine. Just need a free wire for power and an electrically opperated pilot valve.

    Note: It's not legal to control this from inside the cab of the truck. You might want to label the switch as something else, just in case.

  6. #6
    Senior Member tonka's Avatar
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    its called a dump valve, call mac trailer and order one.....
    Live the Low Life, Put it in the dirt!!

  7. #7
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    Thanks for the good info!

    I am always learning as I go...

  8. #8
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    All you want to do is dump the air in the bag in the rear axle. Like tonka said mac could hook you up with a kit for a reasonable price.

    You don't need a lift axle just to dump the air out of the rear so it will pivot on the front tandem.

  9. #9
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    You can call it a "dump" valve.... we all know what you're saying. However if get "rookie" parts person, they may not. The Neway pilot valve is what is most commonly used (there are other brands) but this is just about the least expensive and easiest to install that's out there. You can buy leveling valves with a "built-in" dump feature, but you'll be exhausting (dumping) all air springs, not just the rear axle.

    The pilot valve is very simple. Its noting more than a gate valve, It has 4 ports if air operated and 3 ports if it's electrically operated. Port 1 - normally open / 2 - normally closed / 3 - exhaust. The 4th port is for an air supply to activate the valve. Very easy to install.

  10. #10
    Senior Member tonka's Avatar
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    Quote Originally Posted by Jammar7 View Post
    You can call it a "dump" valve.... we all know what you're saying. However if get "rookie" parts person, they may not. The Neway pilot valve is what is most commonly used (there are other brands) but this is just about the least expensive and easiest to install that's out there. You can buy leveling valves with a "built-in" dump feature, but you'll be exhausting (dumping) all air springs, not just the rear axle.

    The pilot valve is very simple. Its noting more than a gate valve, It has 4 ports if air operated and 3 ports if it's electrically operated. Port 1 - normally open / 2 - normally closed / 3 - exhaust. The 4th port is for an air supply to activate the valve. Very easy to install.
    Ok, i told him to call MAC trailer, they have been building top notch trailers for years now. The parts deptment is sceond to none, these guys know what a dump valve is and what it does.

    www.mactrailer.com
    Live the Low Life, Put it in the dirt!!

  11. #11
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    also a thing to remember is if your going to try and pull this maneuver off with a full load 40,000lbs+ then your going to want put a muffler on the exhaust port to slow the bleed down so the front axle doesn't have to take twice the load it was rated for.

    just dumping and jacking around the trailer can be very hard on frames, suspensions and axles

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