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Technical Frame clearance at rearend

Discussion in 'Traditional Hot Rods' started by four5four, Apr 15, 2019.

  1. four5four
    Joined: Mar 23, 2014
    Posts: 37

    four5four
    Member
    from omaha

    I tried searching but havent found what im looking for. So.....I have a little over 2.5" of clearance at the frame where it comes over the rearend. How much clearance is needed? And what could I do, I would like to keep it at this ride height.
    Thanks
     

    Attached Files:

  2. walter
    Joined: Nov 4, 2007
    Posts: 635

    walter
    Member

    Marginal clearance! It will work but you will need a heavy spring rate to control the travel. Probably end up with a rougher ride
    Walter


    Sent from my iPhone using The H.A.M.B. mobile app
     
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  3. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,355

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    What could you do to improve the situation? Either raise the ride height to allow for reasonable axle travel....or...modify the frame shape/contours (aka 'C' notch for example) to accommodate axle travel at the current ride height. Not much else come to mind if you want to gain/retain a decent ride quality.
     
  4. four5four
    Joined: Mar 23, 2014
    Posts: 37

    four5four
    Member
    from omaha

    I will have to get a better picture but my frame tapers to nothing after the crossmember. So a notch would have to be 1"-1.5 At the most. How much clearance do I need?
     

  5. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,355

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    I see your dilemma. The easiest solution would be to raise the frame in relation to the axle....different spring? Short of that, altering (raising) the frame rail at some point ahead of the axle/spring is about the only alternative that comes to my mind. Which is not to say, the only options, only all that I see. Other may have different suggestions.
     
  6. sdroadster
    Joined: Jul 27, 2006
    Posts: 420

    sdroadster
    Member

    Once the frame is loaded, you may have to install taller or stiffer coil overs to maintain 2.5 inches of ride. Then put snubbers at the axle and frame contact point and you'll be fine. There's a lot of red polyurethane snubbers available in a variety of designs, that have give built into them. I wouldn't worry at all about 2 inches of ride.
     
  7. This is a subject that doesn't seem to get much press. If starting with a clean sheet of paper, what is a good amount of suspension travel. I know that in most cases, one must live with what he can get, but what is plenty? What will get you by?
    The last one I did, I shot for 4" from ride height to full bump. Rubber snubber at 3.5"
     
  8. Desmodromic
    Joined: Sep 25, 2010
    Posts: 571

    Desmodromic
    Member

    Or you could lower the rear axle (use smaller diameter wheels)!

    More seriously, if there are any significant loads on the frame behind the axle (body support, rear shackles if parallel leaf springs, spring crossmember if transverse spring), there is a significant loss of bending strength associated with "cee"ing. For example, assume the frame cross-section is a 1/8" thick channel, 4" high, with 2" wide flanges. If the "cee" is 2", reducing the frame height to 2", the bending stress will increase by 2.5 times. This can be compensated by a disproportionate increase to the thickness of the flanges to about 1/2"! If you have space above the frame locally, it would be much better to raise the top of the rails, to keep the depth at its original value.
     
    zzford likes this.
  9. Happydaze
    Joined: Aug 21, 2009
    Posts: 1,903

    Happydaze
    ALLIANCE MEMBER

    The ladder bars look perilously close to the crossmember - but that might be the camera angle? Have you sat it down without the coilovers fitted to see what the true travel is?

    Chris
     
  10. mcmopar
    Joined: Nov 12, 2012
    Posts: 1,734

    mcmopar
    Member
    from Strum, wi

    Im at this spot right now also. I have about 3 and 1/4 inches and have a little worry about travel. When I look at the travel of the shocks, my QA1 they have 2.5 up and down, so I don't think that I have any issues. If shocks only have so much travel I think that is what you are stuck with.
    Tony
     
  11. linechaser32
    Joined: Apr 8, 2006
    Posts: 1,469

    linechaser32
    Member
    from Iowa

    I make a snubber that cushions the rear before it hits the frame. Works well.
     
    four5four likes this.
  12. sdroadster
    Joined: Jul 27, 2006
    Posts: 420

    sdroadster
    Member

    My 48 Ford has about 1.5 inches of ride before it hits the snubber. I drive it all the time, but I do watch for pot holes... 002.JPG
     
  13. Mr T body
    Joined: Nov 2, 2005
    Posts: 2,228

    Mr T body
    Alliance Vendor
    from BHC AZ

    I have 3" to the snubber
     
  14. nugget32
    Joined: Aug 21, 2011
    Posts: 260

    nugget32

    Move the lower cailover mount point up on the rear end housing

    Sent from my VS500 using The H.A.M.B. mobile app
     
  15. Here ya go.
    Make your setup like the pic and it will all work just fine.
    The front part of your frame is ‘32 but the rear is something else and not like a 32 so it won’t work like a 32 either.
    If I were in your spot, I’d re do the ass end of that frame and make sure the ladder bar doesn’t hit that tube crossmember at full suspension travel. It would be pretty easy to fab up some 32ish tails. It’s more like a model A back there and needs a tardel traditional Z

    30BEC49D-1C12-440B-A418-B04DDAD75360.jpeg
    1580996C-988E-44B7-B200-90FB6D27C1EB.png
     
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  16. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 5,256

    sloppy jalopies
    Member

    find a car like yours with coilovers…
    most c/o have a small rubber ring on the shaft... it gets pushed up to the most travel... measure it... should give you an idea of how much travel you will need...
    install bump stops if not sure... '32 ford bump stops were about 3/8" thick...
    … thanks...
     
    Last edited: Apr 16, 2019
    four5four likes this.
  17. Bump stops
     
  18. missysdad1
    Joined: Dec 9, 2008
    Posts: 3,305

    missysdad1
    Member

    Just don't date any fat chicks and you should be fine. :rolleyes:

    Seriously...I'm with 31Vicky on this one: Cut it off and do it right if you have that as an option at this stage of construction. If not, I think you'll be okay as long as your coil-over springs are well chosen for the actual sprung weight of the rear of the car, which really isn't very much. If you used the "total weight divided by two" method your rear springs are probably already too stiff - which may be a good thing in your case.

    Good luck! Carry on.
     
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  19. four5four
    Joined: Mar 23, 2014
    Posts: 37

    four5four
    Member
    from omaha

    Those P&J instruction are what I used except I moved them in on the rear to miss the frame rail, I think its 29" on mine. The first thing to hit is the axle tube everything else has clearance. I should have done a full 32 rail but I like A's at A wheelbase and with this rear crossmember I dont have to do subrail work. It's my first hot rod so I learn as go and with help from you smart MFer's on the HAMB!!!


    Just camera angle, the ladder bars are just inside the frame rail.
     

    Attached Files:

    Last edited: Apr 16, 2019
  20. four5four
    Joined: Mar 23, 2014
    Posts: 37

    four5four
    Member
    from omaha


    I do have 3 hole shock mount on the rear but would like to keep this ride height. If I gusset or box the 2x3 crossmember to tie in at the upper frame rail and notch the bottom of the frame rail would it be strong enough?
     

    Attached Files:

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  21. Happydaze
    Joined: Aug 21, 2009
    Posts: 1,903

    Happydaze
    ALLIANCE MEMBER

    I think we're at cross purposes. The crossmember I was referring to is the one with the driveline hoop on. There doesn't look to be much ladder bar clearance below that - it's about half way along the ladder bar so would need about half the travel that the axle has. If it's not going to hit then fine, but I bet it's close, and any increased travel made available to the axle (by c notching the rails or whatever) will bring the ladder bars even nearer to said crossmember.

    Chris
     
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  22. Happydaze
    Joined: Aug 21, 2009
    Posts: 1,903

    Happydaze
    ALLIANCE MEMBER

    Car sits nice so I can see why you wouldn't wish to raise the ride height! You just have to make everything else work within those confines. I see subrail modifications in your future!

    Chris
     
  23. bantam
    Joined: Oct 16, 2006
    Posts: 374

    bantam
    Member

    I run 2” of clearance with coil overs, 1932 frame, triangulated 4 bar, 9” ford, radial tires. I bottom out if I go over an area where, for example, a drain line runs under the road and the road has sunk a couple of inches over about a 12” patch of road. If I hit this spot at 35 plus mph I bottom out. Slow down below 35 mph and generally ok. I have this exact spot 1 mile from my house and have learned to manage my speed over it.

    Otherwise 2000 miles and no other episodes of bottoming out and honestly that little bit of axle travel provides a very comfortable ride.

    That said, I wish I had 3” of travel to avoid bottoming out altogether.

    Bantam
     
  24. nugget32
    Joined: Aug 21, 2011
    Posts: 260

    nugget32

    The picture looks like the frame rail tapers to from maybe 4 inch to ?? at the area where the crossmember is attached. Looks like the top Coil over mount is very close to the frame rail, this is good. the weak point will be the cross section of the rail tubing at a location on the c notch vertical centerline. Fish plating what is left of the tube after c notching will strengthen the cross section at the c notch area.

    Sent from my Chromebook 11 Model 3180 using The H.A.M.B. mobile app
     
  25. nugget32
    Joined: Aug 21, 2011
    Posts: 260

    nugget32

    It does not look like there is a place on the rail to put a c notch because the rail tapers from a large cross section to very little cross section above the axel tube.

    Sent from my Chromebook 11 Model 3180 using The H.A.M.B. mobile app
     
  26. Joe H
    Joined: Feb 10, 2008
    Posts: 1,525

    Joe H
    Member

    What about the crossmember? Will the ladder bars hit before the axle tube hits the frame?
     
  27. lostone
    Joined: Oct 13, 2013
    Posts: 2,820

    lostone
    Member
    from kansas

    Show us a picture straight down on top of housing and cross member so I can get an idea how much room we have to play with in the cross member to housing clearances.
     
    four5four likes this.
  28. Or learn to live with the occasional bottoming out. HRP
     
  29. What body is going on this frame?

    Can you eliminate the frame horns and have the frame end just ahead of the rear axle tubes? No frame, no bump!!

    You would have to mount the coilovers in front of the axle, but that just takes a little noggin' time to figure out...
     
    nugget32 likes this.
  30. guitarguy
    Joined: May 26, 2008
    Posts: 650

    guitarguy
    Member

    Can you add a piece of box tubing to each side and C-notch it if you need more clearance...like I drew on your pic?

    upload_2019-4-16_16-48-3.png
     
    Montana1 likes this.

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