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Technical My First Straight Axle

Discussion in 'Traditional Hot Rods' started by Al Peckenpaugh, Aug 21, 2019.

  1. Al Peckenpaugh
    Joined: Mar 30, 2018
    Posts: 19

    Al Peckenpaugh

    We bought a car with a straight axle.. It's set up on dual quarter elliptical springs. In short it needs "toe out" to prevent a death wobble situation. It also doesn't "return to center" very well.
    It has positive caster to (best I can read) about 8*. Camber is positive.. Scrub pad is affected by 5/8" spacers required to fit 1935 Ford rims on 1948 Ford F1 drums. Tough to measure at this point.
    I'm posting a few pictures, anything jump out at you? Thanks

    Attached Files:

    Tall t 26 and dana barlow like this.
  2. J. A. Miller
    Joined: Dec 30, 2010
    Posts: 1,291

    J. A. Miller
    from Central NY

    Back to the top for Al
  3. koolbeans
    Joined: Apr 12, 2015
    Posts: 427


    I'll jump in. Lots of mushy bushings. That always worries me. Too much compliance. Castor sounds good. Toe ok but not more than an eighth. Toe out with your castor will lead into a turn. Self return will be sluggish. But should track dead straight. If mine there would be a panhard with hard rod ends, not tie rod ends. Finally does the tire and wheel combination run true?

    Sent from my XT1710-02 using The H.A.M.B. mobile app
    alanp561 and dana barlow like this.
  4. 1ton
    Joined: Dec 3, 2010
    Posts: 357


    So you have upper and lower quarter elliptical springs. Upper ones are single leaf and the lowers have multiple leaves. And those springs are the only thing locating the axle? I have not seen that done before. I'm no expert on front end geometry but I'd question the rigidity of that setup. And FWIW, the tube axle does not bother me.
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  5. dana barlow
    Joined: May 30, 2006
    Posts: 3,686

    dana barlow
    from Miami Fla.

    Cool looking hot rod. Two things maybe at lest adding too shakes. Looking at photos,the spring bushings may be sliding some,it dose not take much to let axle shift side to side with that set up/even 1/4in. is enough to help start wobble. Friction shocks work if kept adjusted,but they get out fast,an when not adjusted are nothing helping. I like tube type my self. Check run out of tires side to side,I see they are balanced,but dynamic balance may not of been done,that is not the same as one plan balance as many think is all that is needed.
    alanp561 likes this.
  6. AmishMike
    Joined: Mar 27, 2014
    Posts: 413


    Signed up to watch this one. Love these suspension problems - hope experts jump in. Reads like you know you have to much camber, can you find/borrow another set of rims & tires to test? Think you need way to accurately measure caster - maybe a spacer fit parallel to spindle. Do each spindle have heard can be difference between them. Also suggest check your ackermann. Would also love to see picture of spring mounting to frame.
    alanp561 likes this.
  7. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,821

    from SW Wyoming

    You might also want to check the pre-load in the steering box, too tight can contribute to sluggish returnedness.
  8. gene-koning
    Joined: Oct 28, 2016
    Posts: 1,588


    I would like to see how the other end of the springs are mounted as well. I think expecting the ends of 4 leaf springs extending out forward from the frame to hold a front axle in place is expecting a lot. There is a lot of movement on the end of a leaf spring, and you are using 4 of them to locate your axle. I don't see that working well at all. Gene
  9. 1946caddy
    Joined: Dec 18, 2013
    Posts: 1,515

    from washington

    looks like ackermann is way off.
    Piewagn and Montana1 like this.
    Joined: May 5, 2015
    Posts: 607


    I would think that when you hit a bump the camber and caster will change, one spring will pull and the other will push.
  11. earlymopar
    Joined: Feb 26, 2007
    Posts: 1,098


    Your car has a "Dropped Axle"....

    Deuces likes this.
  12. Wheel offset/scrub radius is a factor. Also that single leaf/upper locator looks weak....
  13. Hard to tell...but I would think the length of the springs being used as radius rods (they appear to be pretty short) would introduce an exagerated axle arc compared to the much longer drag link. The axle moving through its travel arc would move fore and aft which would provide significant bump steer (and if it repeated could invoke death wobble). The soft spring bushings would exagerate similar movement.

    If it were mine, I would head back to the drawing board on the front suspension/axle retention approach.
    clem likes this.
  14. AmishMike
    Joined: Mar 27, 2014
    Posts: 413


    Love the comments so far. Agree panhard would help or at least not hurt. Agree with “anothercarhuy” about bump steer but change to cross steer might be easier. Stand on front frame & jump up & down see if steering wheel or front wheels move.
  15. Doublepumper
    Joined: Jun 26, 2016
    Posts: 558


    Here's two cents. To keep what is there and try to improve on it, I'd loose the rubber spring eye bushings and replace with solid. I'd try to improve the scrub radius, it's a bit much for easy wheel return. A panhard bar would be a very good idea to positively locate the axle. Ackerman is way off, but might be tolerable with the other modifications done. Sorry, that's all the change I have...:D
    alanp561 likes this.
  16. 1ton
    Joined: Dec 3, 2010
    Posts: 357


    While making monkey noises
  17. For those suggesting the need for a panhard bar...don't get me wrong, I like panhard bars, I just don't see how the lack of one on a fore and aft steering drag link equipped car will induce a death wobble. The tie rod is a fixed length (like the axle) so if they have a bit of side to side movement, the steering should remain in step with the axle. If the car were cross steered, I understand the benefit of the panhard.

    If it's simply to limit any unnecesary movement of the axle, I get it, but not sure it will reduce death wobble in this case. Perhaps someone that thinks otherwise could help me understand?
    King ford and Vic Walter like this.
  18. Al Peckenpaugh
    Joined: Mar 30, 2018
    Posts: 19

    Al Peckenpaugh

    Thanks guys,
    Good info.... First off I'll say the guy that built the car was looking at Harry Millers dual quarter elliptical spring set up on some of his Indy cars of the 20'-30's..... We've discussed the spring mount location points, a panhard bar, shocks need to be raised. Some solid bushings would definitely be an improvement. We just switched front tires to the truest wheels. They're not bad...
    Jumping up and down on the front of the car barely moves suspension, steering wheel and front tires don't move.
    We did check out the Ackermann. It is really off, as stated. Seems wheel base would have to be about 6 1/2' long for intersection to be at rear axle. How did that happen? Wrong spindles? The spindle arm is cast into the spindle. How could that work on anything but a 6 1/2' wheelbase...? Our wheelbase is over 9' Is this a case of needing to find spindles with steering arms that will create Ackermann effect on our wheelbase?
  19. chrisp
    Joined: Jan 27, 2007
    Posts: 799


    This kind of setup is very similar to Alfa's and other race cars of the 30's. I'm no specialist at all, not even a mechanic but the scrub line looks to be way off. The upper leaf looks very weak as do the friction shocks.
    When I drove classic cars with similar setup but not same as yours I can tell you that they act weird compared to more traditional setup, but no death wobble or sluggish or no return to center.
  20. Just heat them with a rose bud torch and move them to the correct location... then shorten the tie rod.

    As to the 1/4 elliptic suspension, Henry had it correct. :)
  21. Redrodguy
    Joined: Nov 18, 2016
    Posts: 85


    Hard to tell from the pics, but are the friction shocks coming in contact with the tie rod - they sure look close? Looks like marks on the rod. Don't think this would cause the wobble you're describing, but could certainly cause other steering problems.
    xsquiden likes this.
  22. RJP
    Joined: Oct 5, 2005
    Posts: 1,315

    from PNW

    I'd lay the kingpins back a bit, solid bush the springs, and bend the arms to get ackermann closer.
  23. Al Peckenpaugh
    Joined: Mar 30, 2018
    Posts: 19

    Al Peckenpaugh

    Well, I think we've come to the same conclusions. This summer we'll get some solid bushings in it, Ackermann in it by bending the arms and take it apart and refine it best we can this winter. Thanks for the input, helped bring it all together. This is the one we've acquired. It'a almost what we want.........
  24. AmishMike
    Joined: Mar 27, 2014
    Posts: 413


    Please follow up & report results. If possible one change at a time followed up with a test drive. Nice looking modified
  25. oj
    Joined: Jul 27, 2008
    Posts: 6,224


    The problem as I see it is the builder applied the concept of radius rods keeping a spring mounted axle located but now the spring is part of the location device. Can't do both, it is an either'or situation because as you go thru a bump/rebound the spring gets longer and shorter without a shackle to accomodate the movement. As you turn right into a parking lot the lower right spring/control rod will get shorter while the upper gets longer putting the axle into a torsional twist while the other tire has yet to make contact with the parking lot entrance ramp. This will happen very quickly but if you put a floor jack under just one spindle and raise it you should see it happening.
    Did you mispeak when you say toe-out will run straight?
  26. Al Peckenpaugh
    Joined: Mar 30, 2018
    Posts: 19

    Al Peckenpaugh

    We found a front drum that wasn't seating properly on the hub. Took some filing and scraping but that wheel is running much truer...... That was the wobble... We've ordered some delrin stock to turn some bushings, located a rosebud torch to bend the steering arms for Ackermann, and working on a plan to better locate springs to frame this winter. Not a perfect design but I think we can make it work well.
  27. Al, where are you in NY?
  28. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,581


    I have run toe-out on 4x4 rigs, to combat death wobble.
    OFT likes this.
  29. lamaison
    Joined: Oct 21, 2006
    Posts: 80

    from Canada

    Whole setup looks pretty shaky to me. Shock absorber link looks to be touching tie rod, or very close. Spindles appear to be 1946-48 Ford and it appears that the steering arm has been bent up already. Whole setup needs to re-thought and re-done would be my opinion. HAMB - front suspension.JPG
    clem likes this.
  30. Al Peckenpaugh
    Joined: Mar 30, 2018
    Posts: 19

    Al Peckenpaugh

    Yes lamaison, The system IS being rethought. The arms were bent up and possibly in. Bending them inboard may be what disturbs the Ackermann. The shocks will be raised so arms don't hit the tie rod. Maybe replaced.... We're trying to get through the rest of the summer determining how to attack this, and we'll take it apart this winter.... Thanks for the input.

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