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Technical Split Wisbones

Discussion in 'Traditional Hot Rods' started by DJ909au, Nov 22, 2015.

  1. DJ909au
    Joined: Apr 14, 2015
    Posts: 25

    DJ909au
    Member
    from Sydney

    Just a question regarding my 32 Ford rear suspension, Its a 9" diff with split wishbones (about 10" apart) using threaded in rubber bush type joints up front (not heim joints) , at the back of the wishbone appears to be an original style forged perch attached to the wishbone. The diff housing has a flat steel piece welded to it that wraps 1/2 way around the diff almost and has 2 mounting holes drilled in it. The perch has a slot or recess in it that the flat steel fits into and is bolted through with two 1/2" bolts. Because the perch is forged it doesnt squeeze in tight onto the diff mounting steel piece, so there is some movement where the perches attach to the diff. At first I was thinking of drilling out one side of the perch and using a cap screw so the head was supported by one side of the perch and the other side is bolted up tightly to the diff mount. But then i had second thoughts about creating a bind because the wishbone is split, and I had also noticed that when my rear buggy spring was removed the suspension had no bind and would rock easily side to side when supported in the centre (because the looseness of the perch attachments) My question is what is the normal way of attaching split wishbone perches to the diff, is there normally any movement left in the mounts or is it to be tightened up tight ? Perch mount.JPG

    Perchbolts.jpg
     
  2. I did that on my A pick up initially, they will break at the weld where the forged end meets the tube. They only were meant to keep the original axle housing perpendicular to the torque tube but did not have any axle torque forces applied to them. They were not designed to handle that load.
     
  3. Please do a search here for threads about using 35/6 rear radius rods. There are several threads discussing it.

    BTW what you have there simulates the stock 35/6 diff mounting. As Pocket Nick says, the original radius rods were to brace the diff tubes to the torque tube (which did all the work.) People like to use the 35/6 rods as suspension arms because they conveniently also incorporate the spring hangers.

    Basically the join in question should be tight and you should have at least one additional bar from the top of the diff to a forward mounting point where the radius rods are mounted (to deal with torque reaction etc.) You could even attach it to a tab welded to the front of one of the radius rods.
     
  4. DJ909au
    Joined: Apr 14, 2015
    Posts: 25

    DJ909au
    Member
    from Sydney

    Hi Pocket Nick, so did yours end up breaking off or did you change them just to be sure. I have read quite a bit about them but not read of any first hand experience of them failing and I do realise that the torque tube was there to handle most of the load on acceleration.
    X38 so this join should be tight, I have never seen an original wishbone and how it connects to the axle, but I am assuming that is very similar to my set up but because of the function of the torque tube they didn't need to be real tight. If they were real tight then the diff brackets must have been an almost interference fit (or very snug) into the wishbone perch, and then tightened up with the two bolts. Apparently many people actually do use this type of system without a torque tube or additional upper bar, do you have any idea how they get this to be a tight joint between the perches and the diff, Or any comment on my thought of drilling out one side of the perch to take the head of the cap screw so it can be cinched up tight.. its the only way I can think of to make it a tight joint.
     

  5. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 8,625

    mgtstumpy
    Member

    This is how Ryan did his 32 roadster. 121.jpg
     
    dana barlow likes this.
  6. Odd looking brackets; don't look much like '35-'36 bones; but anyway on your original question, I would drop them off and either drill the holes out to the next size, or of there is not enough material, weld them up and re-drill to the original size. While it is apart, build up the thickness of the axle plates with weld and grind them back to a tight fit between the ears on the 'bones. Then use a bolt where the unthreaded shank passes thru the whole assembly.

    On the other issue brought up in the tread; looking at your picture, it appears your bones are spread enough they are under the frame rail. This would preclude running an additional bar directly over the 'bone as in the picture posted by mgtstumpy. If you decide you want to add an additional bar while you have it apart; look around on the net, you can probably find some pictures where the rear of the bar is mounted inboard on the axle housing enough to clear the frame. Maybe not as strong as directly above but still reinforces the stress point of where the wishbone tube meets the end forging.
     
  7. original:

    [​IMG]

    Bones with diff brackets replicating factory ones:
    [​IMG]


    And being attached to an 8":

    [​IMG]

    Another version with modified bones attached to stock axle bells and brackets:

    [​IMG]

    One version of an additional torque rod:
    [​IMG]
     
    Texas Webb and dana barlow like this.
  8. el Scotto
    Joined: Mar 3, 2004
    Posts: 4,357

    el Scotto
    Member
    from Tracy, CA

    Excellent pictures X38!
     
  9. DJ909au
    Joined: Apr 14, 2015
    Posts: 25

    DJ909au
    Member
    from Sydney

    Thanks X38 they are some good pics, and I can see that as Rich B says, mine aren't really 35/6 bones but something vaguely similar . I think I will build up the thickness of the axle plates and grind them back to an interference fit into the ears on the bones next time I'm doing something back there then. Anyone know what the other holes between the axle mounts and the spring perches are for, mine have these too but you just cant see them in my pic. 00036wishboneholes - Copy.jpg
     
  10. 117harv
    Joined: Nov 12, 2009
    Posts: 6,590

    117harv
    Member

    Shock link ball mounts there.

    DCP_2822.jpg
     
    Last edited: Nov 23, 2015
  11. They were hanging on by a thread, the u joints went out phase and resulting vibration was what alerted me to check for something that failed.
     
  12. von Dyck
    Joined: Apr 12, 2007
    Posts: 678

    von Dyck
    Member

    Just a clarification: "wishbones" were used from 1908 to 1948 Fords (and Mercs) to position the front axle. Radius rods were used to keep the rear axle perpendicular to the centerline of the car. The '35/'36 rods when properly installed are the toughest of the bunch and they come with the spring hangers. Yeh, Ford assembly line workers made those four 1/2" bolts and nuts really tight! You should too.
     
    clem likes this.
  13. DJ909au
    Joined: Apr 14, 2015
    Posts: 25

    DJ909au
    Member
    from Sydney

    Thanks for that Von Dyck, I had thought they were both called 'wishbones' front or back, learning a lot here and fast too.
     
  14. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,903

    gimpyshotrods
    ALLIANCE MEMBER

    If you are running without the original torque tube, you absolutely must add something that duplicates its function. Be that a torque arm, or making the radius rods into ladder bars.

    Without doing so, it is only a matter of time until you have a catastrophic failure.

    Some people get away with it. Just because they didn't shoot themselves playing Russian Roulette does not make it safe.

    Never use luck as your survival strategy.
     
  15. 55willys
    Joined: Dec 7, 2012
    Posts: 1,615

    55willys
    Member

    Instead of splitting the radius rods one could use the yoke off of a front wish bone. The Model A has a wide yoke while the 35-48 have a narrow yoke. I like to use the pivot set up from the bell housing of a Model A. Here is one I did recently on a Model A using a 37 front wish bone. It is best to have the pivot close to the front u-joint so that you don't have extreme travel on the slip yoke. I reinforced the bones with a 1/4" thick flat bar running the full length of the bone. IMG_20150921_181654954.jpg IMG_20150921_181708850.jpg IMG_20150921_181716027.jpg IMG_20150921_181723353.jpg IMG_20150921_181737846.jpg IMG_20150921_181745122_HDR.jpg
     
  16. 27troadster
    Joined: Mar 14, 2013
    Posts: 105

    27troadster
    Member

    To answer your question about radius rods breaking; yes. My '35 radius rods snapped at the welds where the tubes are welded to the forged part. In my case it was because I split the radius rods to the frame rails, not torque that caused the breakage (80Hp flathead, not worried about too much torque!)

    All the above are great examples of how to do it right. Tighten up the clearance with weld, shims, completely new plates, what ever. Then figure out how to put an upper bar on. The setup shown by 55willys works in the same manner as the stock Ford with respect to axle movement (not torque) the more you spread the front of the radius rods, the more binding that will be introduced. This doesn't become significant until the rods get near the rails. Since your rods are 10" apart the only thing you should need is an upper link going to the front of the radius rods to absorb the torque, essentially turning the rods into ladder bars.

    On mine, because I wanted the look of the radius rods split to the rails, I turned the rear suspension into a 4 link, where the lower links are the radius rods with tie rod ends at both the frame and at the axle and the upper links are tucked up between the frame rails - works great.

    Kipp
     
  17. pooch2
    Joined: Jun 5, 2012
    Posts: 110

    pooch2
    Member
    from Australia

    Kipp, how about some pics ?

    That is exactly what I want to do.

    Show the lower radius rods at frame with movable joints at both ends, and tuck some upper links just inside chassis out of sight .

    What type of panhard bar did you use ?

    edit, I found the pics in another thread .
     
    Last edited: Nov 25, 2015
  18. 27troadster
    Joined: Mar 14, 2013
    Posts: 105

    27troadster
    Member

    pooch2,

    I made the rear suspension into a "4-bar" using the radius rods as the lower links and fabricated the upper links from 3/4" black pipe. I used 3/4 ton Chevy tie rod ends on the rear of the radius rods and on either end of the upper arms. The upper arms tuck neatly up inside the frame so you can't see them unless you lay on the ground. I filled the stock radius rod forged bracket and drilled then reamed the hole with a 7 degree tapper ream to properly mount the tie rod ends.

    As far as power is concerened: Once we go to an open drive line, under hard acceleration (well, any acceleration including braking) the axle tries to rotate the radius rod upwards (or downwards), and therefore try to bend it into an upsided down "U". This is not what Ford designed them for. But by going to a 4-bar set up, now the radius rods are only under compressive forces and the upper bars are only under tensile forces during acceleration. Any rod / bar can handle ALOT more compressive and tensile forces than it can handle bending forces.

    I'm running a flathead 6 (80 HP) so obviously I'm not concerned about power breaking things. If I where up around 400 HP and tires that could hook up I would run a 3/4" pipe down the center of the radius rod, weld the tie rod ends, pipe, and radius rods all together at each end. That would be stronger than four links on a drag car. The weak point then becomes the tie rod ends, one could upgrade to 1 ton truck tie rod ends, they are massive! More importantly though is to taper the holes where they mount to the frame and axle.

    roadster suspension.jpg
    roadster suspension 2.jpg
    roadster suspension 3.jpg
    roadster suspension 4.jpg
    roadster suspension 5.jpg
    roadster suspension 6.jpg

    Panhard rod: none, to control side to side motion I angled the upper rods. It's hard to see, but they are angled in about 30 degrees. Similar to rear suspension on '80s Monte Carlos style cars. 45 degrees would probably be better if you can fit it in.


    Kipp
     
  19. If you properly preload the spring a pan hard rod is not needed.
     
  20. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,201

    Ned Ludd
    Member

    Could you explain what you mean by "preload"?
     
  21. 55willys
    Joined: Dec 7, 2012
    Posts: 1,615

    55willys
    Member

    He means that the shackles will be hanging at a 45 degree angle with a transverse mounted spring meaning that the spring under tension therefore keeping the car centered. If the shackles were hanging straight down then they would let the axle shift sideways under the body.
     
  22. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,903

    gimpyshotrods
    ALLIANCE MEMBER

    In this case, a better term would be pre-tension.
     
  23. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,201

    Ned Ludd
    Member

    That's why I ask. Though it's about the shackle geometry rather than anything to do with residual load in a spring assembly at full droop, like motorbike springs against their extention stops. The hardware in this case doesn't allow for it.
     
  24. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,903

    gimpyshotrods
    ALLIANCE MEMBER

    Indeed.
     
  25. clem
    Joined: Dec 20, 2006
    Posts: 3,178

    clem
    Member

    As the axle moves up, would the pinion not rotate downwards, due to those extra adjustable things on top. Not that there is much travel anyway.
    Am I the only one that thinks that this won't work correctly?
     
  26. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,903

    gimpyshotrods
    ALLIANCE MEMBER

    You are.

    Yes, the pinion will tilt down when the axle moves up, but it is well within the acceptable range of u-joint operation.

    It is not because of the extra links on the top. All radius arms and ladder bars do this.
     
    RICH B likes this.
  27. clem
    Joined: Dec 20, 2006
    Posts: 3,178

    clem
    Member

    The links on the top are shorter, therefore accentuating the issue, in my opinion.
    I guess it is similar to a triangle 4 bar with shorter top bars?
     
  28. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,903

    gimpyshotrods
    ALLIANCE MEMBER

    Doesn't matter how long the upper links are, they are attached to the lower links. The whole assembly moves together, as one.
     

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