Spring compression question...

Discussion in '40- & 55-Series Tech' started by 72tlcnelson, Jun 28, 2005.

  1. 72tlcnelson

    72tlcnelson

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    When mounting a leaf spring under any rig, should it be mounted "uncompressed" where ever the eyes touch the frame? I have heard that the shackle should be at a 45* angle at ride height... What about the front with the weight of the motor? Should I set the weight of the truck down on the leafs to see how much they slide and then mount them there? I want to swap the stock leaf springs to F150s to give me more flex and WB, but I cant find info on mounting them compressed or not. hope this makes sense...
     
  2. dgangle

    dgangle total rice

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    I would locate the fixed end of the spring to set your tire centered in the wheel well. Then set the weight to compress the spring and locate the other end to provide 'good' shackel angle. You will have to define 'good' but usually for a better ride it will have some angle to it, not vertical as this is sure to be a kidney buster. See:

    http://store1.yimg.com/I/coolfj40_1852_32665733
     
  3. mr_manny

    mr_manny

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    I believe a fellow cruiser utilized a piece of wood between the springs and frame with the springs COMPRESSED.
    With the weight of your truck, you will be able to more accurately determine the location of the upper shackle mount for desired shackle angle.

    Have you tried performing a search on this? I would imagine this has been covered before...
    manny
     
  4. 72tlcnelson

    72tlcnelson

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    I have searched but as always, just not the info I'm looking for. But thanks for the info!
     
  5. mr_manny

    mr_manny

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    Shoot Dustin (on the board) a PM, he just finished a SOA and had to calculate where to locate the upper shackle mounts.

    Dustin, are U out there?

    manny
     
  6. dustin

    dustin

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    present.

    I tacked the front hanger on with the springs attached (and bushings in the springs) so that I knew I wasnt welding the hanger on crooked. Dont weld them up just yet Do that very last thing. Then I put a 1" piece of wood between the rear of the spring and the frame. I am running stock length shackles, so you might put 2" if youre running long shackles up front. I then put a tie down around the spring and cinched it up until the spring was fully compressed. I put the shackle on the spring and found where the frame side could mount given the length of the shackle. I put the frame sleeve as low on the frame as I could get it, which also allowed more shackle angle than if I pulled the shackle up higher into the frame. Longer shackles would have allowed more options with placement ofcourse. Were I to do this again, I might consider 4" or 5" shackles to get more lift and angle on the hanger, but I am still very happy with how this turned out. Anyway, the reason I figured out placement was so that I would be certain that the shackle A) didnt allow the shackle to somehow invert (unlikely on the front with a SR, but..), B) to also make sure I was getting the maximum amount of droop and compression from the spring.
    Looking at my set up compared to how the pros did it, mine looks identical.
    I measured the distance the center of the sleeve would be from the center of the front hanger and made a jig. I used that jig to make sure the holes on both sides of the Cruiser were the same distance. That distance turned out to be 42". The angle of my front hanger is steeper than 45*, since I am running such a short front hanger - something like 3" between pins, they were too short to do 45*. Also, the spring looks like it is really close to hitting the frame, but it hasent yet since my springs are pretty flat already. Looking around at others SOA with stock springs, my set up is very similar, if not exactly like theirs done by the pros.

    Once I had the sleeves installed and the springs in, I was able to put the axle under the springs and begin figuring out placement of the perches, pinion angle, etc. I was sure to have all the weight of the Cruiser on the axles, with the winch, body panels, motor, and even some extra for fluids, battery, etc, before doing the pinion angle, etc- since that weight compresses the springs, changing the angles..

    Theres pics at http://www.pirate4x4.com/forum/showthread.php?t=337337&page=2&pp=25

    -Dustin
     
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