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  1. #1
    Veteran Member
    Join Date
    Jul 2004
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    1,632
    Location
    Bancroft, Ontario
    Tractor
    JD4300

    Default Trailer spring shackle angles???

    Relocating the axle on an old trailer that I acquired. It came with one broken leaf spring and a bent tonque. The axle was too far back for my liking so I am moving it forward 6" and putting on a longer tonque.
    Its been 25 years since I have built a trailer with leaf springs and I've always liked to have the shackles vertical so thats what I was going to do, but looking around at a few others I notice they are all angled, but some are angled forwards, others to the rear....
    What does everyone suggest? (5000lb springs with axle under the springs)

  2. #2
    New Member
    Join Date
    Jul 2011
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    2
    Location
    Blaine, MN 55414
    Tractor
    ford

    Default Re: Trailer spring shackle angles???

    I am familiar with how a trailer is put together. I used to build Flat deck highway trailers and logger trailers. I am at the stage where i have the trailer upside down and i have the front spring hangers located and squared off the center of the hitch. Now I would like to know what the angle of the shackles should be. I know i shouldnt have them too steep so they flip over forwards lol, or too low so that they bottom out.

    its an 8 foot long trailer and the hole centers on the springs are 25 1/4". Any other info that is needed I will provide it. Thanks in advance!

  3. #3

  4. #4
    Veteran Member
    Join Date
    Jul 2004
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    1,632
    Location
    Bancroft, Ontario
    Tractor
    JD4300

    Default Re: Trailer spring shackle angles???

    Their diagram shows a slight rearward angle. This is about what I should have when the trailer weight comes on the springs.
    I read the question about trailer sway and he mentions "the rules for axle placement". I've always followed the TLAR (that looks about right) engineering principal and had no problems. Anyone know the actual rules?

  5. #5
    Bronze Member
    Join Date
    Jun 2011
    Posts
    97
    Location
    central,wi.
    Tractor
    TYM 350

    Default Re: Trailer spring shackle angles???

    One rule is to have 10-15 percent of the total weight on the tounge. A trailer with lumber evenly loaded will require an axle placement different than the same trailer hauling a tractor or car.

    Too much tounge weight can exceed the rating of the hitch or even effect the steering geometry of the tow vehicle.

  6. #6
    Silver Member
    Join Date
    Jul 2009
    Posts
    197
    Location
    La.
    Tractor
    Kubota L 3400DT

    Default Re: Trailer spring shackle angles???

    I have a a cd on how to build your own trailers.
    This is what it says.

    Measure the entire length of the trailer from the outer end of the coupler to the very back end of the trailer in inches. Multiply the length in inches by 0.68, this will give you the length from the end of the coupler to the center line of the axle. You can round the result up or down to the nearest inch.

    Now that you have marked the centerline on the outer frame pieces, you can determine where to mount the front spring hanger. First, measure the length between the eyes of the spring (center to center). Next, divide this measurement by 2, this will be the distance between the centerline mark on the frame and the center of the bolt hole of the front spring hanger. Weld the front hanger in place. The distance between the bolt hole centers of the front and rear hangers is simply one half of an inch shorter.

    For example, if the length 26 inches, half of 26 equals 13 inches. You would then mount the front hanger with its bolt hole centered 13 inches from the centerline mark on the frame. The center of the bolt hole of the rear hanger would then be aligned 25 1/2 inches from the center of the front hanger bolt hole.

  7. #7
    Gold Member
    Join Date
    Apr 2011
    Posts
    376
    Tractor
    none

    Default Re: Trailer spring shackle angles???

    Not to hijack this thread but,
    justbill, I just sat down after a shower and working on my dump trailer all day and just wanted to relax but, I was so facinated by your formula that I had to put on my slippers and go measure my axle centers. LOL I did the TLAR method when I built it! Using your formula, I came up with the "ideal" centerline of 122.2", my actual is 115.5". It's nice for me to know that I am at least pretty darn close Thanks for the info.
    On a side not, where did you get that CD?
    thanks,
    dave

  8. #8
    Veteran Member
    Join Date
    Jul 2004
    Posts
    1,632
    Location
    Bancroft, Ontario
    Tractor
    JD4300

    Default Re: Trailer spring shackle angles???

    Well, I haven't decided on the exact tongue length yet, got the spring hangers welded on and just flipped the frame over to finish chopping off the old tongue. Maybe I will work backwards and just see how the steel I bought for the tongue works out lengthwise.
    I think that this was an old landscaping trailer that had too much topsoil on it...Originally designed for a couple of lawnmowers then beefed up for heavier loads

  9. #9
    Silver Member
    Join Date
    Oct 2009
    Posts
    170
    Location
    land of living sky
    Tractor
    B434 ,V 700 and 1086

    Default Re: Trailer spring shackle angles???

    Just Bill ,my understanding would be for a tandem axle that using your formula would give the point where to mount the equalizer centre ,is that correct?

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