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Hot Rods Cross steer drag link not parallel to axle - looking down

Discussion in 'The Hokey Ass Message Board' started by Hot Rod Dan, Jun 11, 2017.

  1. Hot Rod Dan
    Joined: Jan 22, 2006
    Posts: 204

    Hot Rod Dan
    Member
    from Texas

    I'm mocking up a 51 Chevy car with an early 50s Chevy 1/2 ton I beam axle. The tie rod is behind the axle and a cross steer steering box is in front of the axle (no room behind the axle). I mocked up the steering box as far forward as possible with the pitman arm pointing back & a tri five steering arm on top of the passenger side pointing forward.

    Looking toward the back of the car, I can make the drag link parallel to the tie rod in horizontal plane. However, looking from above, the drag link is not parallel to the I beam axle and at a slight angle. Is this going to cause bump steer?
    IMG_1478.jpg IMG_1477.jpg IMG_1476.jpg
    IMG_1478.jpg IMG_1477.jpg IMG_1476.jpg
     
  2. oj
    Joined: Jul 27, 2008
    Posts: 6,231

    oj
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    You can't move the box back down the rail and run under the oil pan? Front steer (as shown) can get a little wonky on several points. For bump steer we'd have to see straight on not top down.
     
  3. squirrel
    Joined: Sep 23, 2004
    Posts: 44,682

    squirrel
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    bumps move the axle up and down, not forward or back, so it's not going to cause noticeable bump steer. Just watch the angles, you want that drag link connection to the steering arm to be perpendicular (relative to the kinpin location), so you get the same angle of travel, each direction.
     
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  4. roundvalley
    Joined: Apr 10, 2005
    Posts: 1,772

    roundvalley
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    Is that a Vega box??
     
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  5. Hot Rod Dan
    Joined: Jan 22, 2006
    Posts: 204

    Hot Rod Dan
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    from Texas

    I can't move the box back and make it a rear steer car because the clutch pedal Z bar & linkage and other stuff is in the way. I can take a picture straight on of the drag link, once I put it together more (brakes, wheels & tires, etc.) and have weight on wheels.

    However I'm sure I can achieve a horizontally level drag link with a little tweaking of the box mount height, pitman arm bend, steering arm bend, tie rods above or below the arms, etc. The last 2 cars I built were a 32 (avatar) and a 29 and it was easier to make the cross steer drag link horizontally and vertically parallel because the axle was further forward and I had room for a rear steer box.

    What I really need to know is "if the drag link is horizontally parallel to the tie rod, but NOT vertically parallel to it and the axle, is it likely to cause bump steer?"
     
  6. Hot Rod Dan
    Joined: Jan 22, 2006
    Posts: 204

    Hot Rod Dan
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    from Texas

    Yes, but I'm just using it to illustrate. I've got a 525 box I'll probably use.
     
  7. Hot Rod Dan
    Joined: Jan 22, 2006
    Posts: 204

    Hot Rod Dan
    Member
    from Texas

    Squirrel - based on what you've said do you think the angle in the picture is acceptable or it'll impact travel?

    BTW - Thanks for the feedback, I'll see if I can move it.
     
    Last edited: Jun 11, 2017
  8. Looks like the steering arm on the spindle needs to be moved outward quite a bit, ideally it should be 90 degrees to the drag link with the wheels straight forward for proper travel and equal steering response in each direction.
     
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  9. Hot Rod Dan
    Joined: Jan 22, 2006
    Posts: 204

    Hot Rod Dan
    Member
    from Texas

    Thanks for pointing that out. I need to research the proper way to heat & bend the arm straight.
     
  10. squirrel
    Joined: Sep 23, 2004
    Posts: 44,682

    squirrel
    Member

    that's what I meant.... and also, at the steering box end, the same thing applies. You are using a steering arm that is designed to put a tie rod end where it belongs for correct Ackerman geometry behind an axle. it's not where it wants to be for what you're doing.

    Moving the steering box forward, would also help get the drag link parallel.
     
  11. Hot Rod Dan
    Joined: Jan 22, 2006
    Posts: 204

    Hot Rod Dan
    Member
    from Texas

    Now that ya'll have mentioned it, it makes sense. Similar but opposite arcs should give you the same movement on right or left turn. (The straight axle kits often use a straight flat plate arm for the drag link arm.) I think I can get the passenger side drag link arm close to straight.

    Don't know if I can move the steering box any further forward. I've already replaced the front crossmember with a smaller one which gives me more space. A unisteer would probably fit, but that's a more expensive solution than I planned. Need to ponder on this a bit.

    IMG_1455.jpg
     
  12. I can see what you're trying to do.
    As an example on cross steer, '46 Ford cars had the drag link parallel to the tie rod end. And then a possibility of why hit my mind.
    With the pitman arm centered, and the drag link in parallel with the axle....Does the steering ratio change with the increase of turning, slowing the turn ratio of the spindle? Or is the worm gear cut to overcome the angle/ratio change?
    The drag link does need to be parallel of the axle centerline in a cross steer application when the steering box is at center of motion. Bump steer will be influenced by comparing the altitude of the pitman arm to the drag link arm on the spindle, i.e. increasing difference in height will increase bump steer.
     
  13. Hot Rod Dan
    Joined: Jan 22, 2006
    Posts: 204

    Hot Rod Dan
    Member
    from Texas

    Now that I've slept on it, isn't there a 525 reverse rotation box I could use? I could mount the box over the axle with the pitman arm pointing forward, straighten the spindle arm and run the drag link 90 degrees to both?
     
  14. mount the pitman arm 180 degrees on the box?
     
  15. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 7,792

    mgtstumpy
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    As others have stated, I likewise prefer to have the drag link parallel to the axle and pitman arm parallel to car centreline. Everything works better as a parallelogram and aesthetically, it looks tidier.

    Have you a side shot of how the box is mounted to frame? Given its location, the mounting would need to be robust for a cross steering application. Once you sort out that steering arm it will reduce the bump steer by placing the arc further out.
    Ackerman3.jpg
    upload_2017-6-13_12-57-29.png
    A longer bar equals a shallower arc and less lateral movement and bump steer.

    A Vega box is OK with a light weight vehicle however in a heavier car like yours I'd definitely use something a little more substantial or heavy duty for cross steer application. You'd be pushing the boundaries with a Vega IMHO limited to 2500lbs. I agree that the 525 box is more robust and better suited to heavier vehicles over 2,500lbs.
    http://classicperform.com/Dealer_Online/Html/CatalogPart3.pdf
     
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  16. southcross2631
    Joined: Jan 20, 2013
    Posts: 3,361

    southcross2631
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    I had a Falcon that used a stock box and an Econoline axle . The cross steering rod was not parallel to the axle or the tie rod. I made many trips of over 100 miles with no problems or bump steer.
    I did not build the car ,just traded for it . 1020131317.jpg
     
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  17. ,,,used a Chevy 525 box on my 37 coupe with cross-steer, here's a couple pics, works just fine, no bump steer. The box was a front steer off a Malibu, just rotated the pitman arm 180 degrees, now the box is behind the axle centerline.
    37 coupe build 217.jpg 37 coupe build 190.jpg
     
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  18. Hot Rod Dan
    Joined: Jan 22, 2006
    Posts: 204

    Hot Rod Dan
    Member
    from Texas

    southcross2631 - Thanks for your help, I'm going to try to get as close to "ideal" and see how it drives.

    rusty1 - Your pictures are VERY helpful. Were you able to connect the steering column to the box with just the double u-joint? I'll look again & see if I can fit the steering box back there with the clutch pedal linkage. I have a modified tri-five clutch bellcrank connected to the stock pedals. I may have to move it some, but if I can fit it all in that would be cool.
     
  19. Yes,..one double u-joint worked fine and I think my 37 is a narrower body than your 51,...
    so it should work for you....here's a shot of my homemade box bracket, which bolts to the bottom flanges of the frame...
    37 coupe build 147.jpg 37 coupe build 219.jpg
     
  20. This I worry about more than OP's drag link not being parallel with the tie rod. The stress at the coupler is something to take notice of because there is no radial support of any kind because of the double U-joint. Two single U-joint's, one at steering box and the other at the end of the column would be better. [​IMG]
     
  21. Hot Rod Dan
    Joined: Jan 22, 2006
    Posts: 204

    Hot Rod Dan
    Member
    from Texas

    rusty1 - I like your steering box bracket, I may borrow the idea. What is the bolt circled in red for? Does it tie to the bracket that appears to clamp over the frame (arrow) for strength? 37 coupe build 219b.JPG 37 coupe build 147b.JPG
     
  22. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,561

    sunbeam
    Member

    With the pitman over the axle make sure to limit suspension travel try flipping the steering arms so the point out . The
     
  23. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,561

    sunbeam
    Member

    If you move the pitman 180 degrees you will have a fun ride. Turn the steering wheel left and the wheels will turn right.
     
  24. Ned Ludd
    Joined: May 15, 2009
    Posts: 3,897

    Ned Ludd
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    Generally a cross-steer set-up with longitudinal semi-elliptics will exhibit some bump steer. It's a case not so much of eliminating as minimizing bump steer, e.g. by making the drag link as long as is practical and making sure it's horizontal when viewed from the front of the car - though it can sweep forward or back without affecting much.

    However: the one way to get rid of bump steer pretty much completely is to place the steering box the length of the steering arm on the spindle ahead or behind of the effective centre of rotation in bump of the axle in side elevation, depending on whether the arm is forward or behind the spindle. Because the springs elongate a bit with compression, and assuming the shackles are at the rear ends of the springs, that centre of rotation will be a bit ahead of the front spring perches. So you'd want the pitman near to the very front of the car, with the drag link running at an angle (in plan view) back to the opposite spindle.
     
  25. ...not if the steering box is moved from in front of the axle centerline to the rear , or visa-versa.
     
  26. Yes,..that was just an extra bracket that I mounted to strengthen up the mount, overkill maybe, but it works fine and had no problems with it,..and it all bolts on so could be removed or modified later without major hassles.
    ...here's another pic of it.
    37 coupe build 220.jpg
     
  27. That is not a rag joint, it's 2 flanges bolted together with grade 8 bolts..(.you are right a rag joint there would definitely not work) Those bolts do have lock washers, these pics were during mock-up.

    37 coupe build 146.jpg
     
  28. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,561

    sunbeam
    Member

     
  29. I did notice the rag wasn't there. Let me word it this way. Would you run a 6 lug wheel with only 2 lug nut's 180 apart and expect the rim not to flex and eventually crack or worse yet break apart.
     
  30. ...I see your point of view ,...and thanks for pointing that out,...I may do some improvising on that joint.
    ...on the plus side I've got 1000's of miles on this car in the last 10 .years with no problems, if it were a major deal I think it'd shown up by now?,...it's not a heavy car and I'm running a fairly narrow tire...which probly helps.
    37 cpe 11-1-11 005.jpg
     
    Last edited: Jun 15, 2017
    Johnny Gee likes this.

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