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Technical Unsprung Weight Issues In Hot Rods: School Me

Discussion in 'The Hokey Ass Message Board' started by missysdad1, Jun 23, 2018.

  1. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284

    Kerrynzl
    Member

    Are you prepared to do some "Applied research and development"? [translated to: "Lets try it and see"]
    Two things:
    1: can you get another pitman arm for that steering box? If so, re-drill another tapered hole further down to attach the drag link .[half way down would be good]
    Try and "clock" the pitman arm straight up and down, but for research this isn't important.[it could have a "keyed" spline]
    2: With the steering arm from the spindle![pictured below] Can you rotated it 180deg so the ball joint is bolted in from above.
    This should reduce bump steer considerably and reduce the steering effort so the effects of what bump there should now be less noticeable.

    s-l500.jpg

    If this works out OK, Use the spline from the pitman arm and make up a new custom made one [plenty have done this here]

    DSCN6467.jpg
     
    Last edited: Jun 27, 2018
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  2. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,961

    Blues4U
    Member
    from So Cal

    Don't think that's going to help. If you think having a draglink parallel to the hairpin, or to the ground, will eliminate bump steer, it won't. 31vicky already posted some vid's a page or 2 back that illustrate the problem, check them out.
     
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  3. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,633

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    I am having a little trouble with interpreting you pitman arm suggestions. If you are suggesting the pitman arm be lengthened from the sector shaft to drag link attach point, that would lessen the effects of 'bump steer' at the steering wheel inso far as the motion induced in the drag link would rotate the sector shaft fewer degrees for a given amount of drag link motion. On the other hand, that would increase steering effort because of the longer length of the pitman arm.

    Conversely, you mention relocating the drag link 'halfway down would be good'. If that means the pitman has a shorter effective length then it would have the opposite effect by increasing the rotation of the sector shaft for a given amount of drag link motion, increasing steering wheel rotation, but would decrease the steering effort because the pitman is shorter.

    I do understand the recommendation of rotating the steering arm to place the drag link joint on top, increasing the angle of the drag link and theoretically reducing bump steer input.

    Where have I misinterpreted your comments?

    Ray
     
    Last edited: Jun 27, 2018
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  4. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,961

    Blues4U
    Member
    from So Cal

    It looks to me like he wants the drag link parallel to the hairpin, by locating the pitman arm end of the link down a few inches and the steering arm end of the link up a few inches.

    There are those who have the idea that if the drag link is parallel to the radius arm you won't have bump steer, which of course is not correct.
     
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  5. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,633

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    One thing I had forgotten when writing my post above is the the current steering configuration has the pitman arm facing UP, not Down, as I thought I recalled. Just revisited the photo (included herein) and that does change some things from what I conceptualized. I had pictured the suggestions resulting in the drag link being higher at front and angling downward at the rear, as shown in the video 31Vickie posted.

    Back to my mental 'drawing board' and more chalk dust from the eraser! :confused:

    Ray
     
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  6. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,954

    missysdad1
    ALLIANCE MEMBER

    Spoke with Jason at Pete & Jake's this morning and discussed the bump steer issue with him. Probably about the millionth time or so for him apparently because he was intimately familiar with setups like mine, the problems they cause and how the situation can be remedied. Very knowledgeable and very personable - a rarity in today's world.

    To make a long discussion very short, he recommended the same Model A 4-bar setup that Kerrynzl mentioned earlier in this thread. He was also very willing to make custom bars to accommodate the 2" wheelbase stretch my car has - if necessary - so that I won't have to change the steering box location on the frame.

    Coupester make-over 60.png
    So, with the bump steer issue handled - I think! - it's on to getting the scrub radius issue resolved and, hopefully, the unsprung weight under control as well. Hopefully it will end up stopping better, too. Lots of issues with this car, but it's my "bag of garbage" now so I guess it's up to me to deal with it...

    .
     
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  7. What about switching to a vega or 525 box. Then anything that meets the criteria of both not working and ugly gets cut off and redone.

    You want the tube axle? Get 4 bar.
    You want the radius rods? Get beam axle.
     
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  8. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284

    Kerrynzl
    Member

    No ! I was suggesting shortening the pitman arm. Because the pitman arm goes upwards from the steering box , I suggested re-drilling it further down [shortening it].
    Combine this with flipping over the steering arm, and the drag link would be at an angle to reduce bumpsteer

    I would suggest doing this, before parting with $$$ to see how it goes

    If this works out OK, then fabricate a new custom pitman as shown in the photo
    to the correct length​
     
    Last edited: Jun 27, 2018
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  9. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,954

    missysdad1
    ALLIANCE MEMBER

    I've decided to bite the bullet and order a P&J 4-bar setup and keep the Mustang steering pretty much as it is. The car runs a little over 7 degrees of caster, the steering ratio is very good as it is and without the bump steer the road feel / handling is excellent. After talking with Jason at P&J today I feel confident that this is the right way to go. I have another car that I'm building and need to spend my time and energy on that build, not experimenting with this one. After all, I'm not getting any younger and don't have a lot of time to spare. Thanks for all your input, especially the suggestion that the 4-bar might be the best way to go.

    I'm also looking at some aftermarket disc brakes to replace the GM parts that are on the car now. These should bring the scrub radius back into line, be quite a bit lighter and hopefully stop the car better. I don't want to turn this car into a street rod but I do drive it a lot - more than most people drive their hot rods I think - and want it to be fun to drive, not one problem after another. As I mentioned before I bought this car knowing it had problems, but I totally underestimated how much it would take to fix it.

    .
     
    Last edited: Jun 27, 2018
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  11. AngleDrive
    Joined: Mar 9, 2006
    Posts: 846

    AngleDrive
    ALLIANCE MEMBER
    from Florida

    I would ditch the disc brakes and put good drum brakes back on it.
     
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  12. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,954

    missysdad1
    ALLIANCE MEMBER



    Interesting thread, thanks for the info. The brakes I've selected use a separate aluminum hub / steel vented rotor combo that is purpose-built for early Ford applications and has no offset from stock as nearly all the other kits do. Calipers are light weight and have a logo you might recognize from other places in the automotive world. I ordered a matching setup for the 12-bolt. I'm no gold-chainer by a long shot but I think this is money well spent in terms of quality, engineering and safety. Besides...I sold a car yesterday and the money was burning a hole in my pocket. What better way to spend it?

    .
     
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  13. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,954

    missysdad1
    ALLIANCE MEMBER



    Interestingly, my new car has '40-style juice brakes all the way around, but it's more of a '50s vintage rod and won't be a beater hot rod like this black coupester. Drums and discs both have their place, but on this semi-daily driver that regularly sees 80-plus in freeway traffic I think the discs will be more appropriate.

    .
     
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  14. The worst brakes or the best Brakes need traction at the tires and firm attachment points at the chassis. Never will you get better stopping power than the tires can hold.

    Keeping the wheel mounting flange in the same dimensions helps a lot, now keeping the same wheel offset the same would be the next hoop.
     
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  15. F&J
    Joined: Apr 5, 2007
    Posts: 13,217

    F&J
    Member

    yes.

    I have original 40 front brakes with 6;70-15 front bias, linings that fit the drum perfectly, and not the hard composition linings... I can hear the front tires start to squeak a bit if I jump a little harder on the pedal on purpose.

    Discs cause scrub issues, Never saw an early rod that had correct scrub with discs in my local area.

    Worse yet, on hamb...the contant babble of newbies also looking to put disc brakes on the rear of a rod that has so little weight back there with skinny tread bias...pure ignorance of physics...oh, then they start another thread saying they have brake problems...lol ...and yes, I know they will say the discs won't fade as much, but are we running the Watkins Glen road course where we need discs?...but on skinny bias? yea, right.. :)

    .
     
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  16. Lots of truth there F&J
    There's some tit for tat stuff that can't be argued about discs brakes being better than drums but drums do work quite well. However retro fitting brakes from a donor capable of stopping 4000 lbs curb weight and 5200lbs GVW running 6" wide front wheels are not necessary on a 2400 -3000 hot rod. I was getting at this in an earlier post as well.
    Hot rods that go like hell should stop better than they go, obviously.
     
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  17. Texas Drifter
    Joined: Oct 8, 2016
    Posts: 60

    Texas Drifter

    I built a T-Bucket many years ago on a budget. Lots of junk-yard parts. But, it was a long wheelbase. Like 110 inches, which is Looong for a T-bucket. Ran GM disc brakes on the front with drums on the back. Lots of off-the-wall things. But, looking at the photo of " Missy dad"s front end, can't help but looking at your front tires. Those look like implement tries, at least they look like they are of really hard rubber and heavy.
    One of the things I do now, run front springs with teflon buttons, if not, put the teflon sliders between each leaf. I also run inserts on the rear transverse leaf spring. Had to do bunches of research to get the proper spring rate on the rear. It ended up being a Posies spring for a 1940 ford. (Note: its not a high arch spring but needed the correct spring length and rate) Dropped a top leaf and put teflon leaf inserts from Speedway Motors between each leaf. Has the correct angle on the shackles and actually rides great, for a completely transverse car.
    Like one of the guys said, it won't ride alike a new car, its a trade-off. Style verse functability. On yeah, I run 26 psi in the front tires and 24 in those wide hummers in the back . This is like off-road tires, chalk across the top of the tread and let the air out until the tire wipes off the chalk. Another way is to put a business card under the property (OEM) aired tire and let the air out until the card can barely be pulled out. Either one will allow you to run tires inflated to your cars weight. I use the card method. So- - - -enough said - -good luck. There are lots of guys who've run into the same issues so just read everything and make a educated guess that fits for you.
     
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  18. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,954

    missysdad1
    ALLIANCE MEMBER

    I should have listened to the guy who said it would all go away if I just switched to radials...

    Coupester make-over 62.jpg
     
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  19. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,954

    missysdad1
    ALLIANCE MEMBER


    Remember, I did not build this car. It has multiple problems, some of which I was aware of when I bought it and some which are just now coming to light. It had full fenders and running boards when I bought it which hid a multitude of sins. But in a life prior to that it had been a fenderless highboy...with a 2" stretched frame to get the Chevy to fit without cutting the firewall which had already been cut! There is simply no rhyme nor reason to this car. None.

    The latest revelation is that the Mustang steering box was put 'way too far back on the frame, necessitating a tilt steering column and a very long drag link which ran inside the splash apron when I bought the car.. The new location will be where the green tape is in the photo, as dictated by the location of the steering box mount on the new Pete & Jake's 4-bar system. I plan to mount the P&J 4-bar setup according to instructions even though the frame is 2" longer than stock. I was going to fudge the steering box location and use longer bars for appearance's sake, but that won't work due to engine clearance limitations.

    Oh, well. I'll just take it one step at a time.

    Coupester make-over 63.jpg
    Lots of bondo, very little solid weldment. I am REALLY GLAD this became an issue at this point in time. I had no idea how bad this was until I started cutting the mount off.

    Coupester make-over 64.jpg
    And so we start again. The green tape is where the new Mustang box will be positioned. Compare with the previous photo to see how far back it was before. I can only speculate that it was placed there in order to get the radius rod end and the drag link end in the same general area.
     
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  20. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284

    Kerrynzl
    Member

    Cool , progress at last ^^^^^^

    please don't do the "Death Dismantle" and don't lose sight of ball.
    I've seen many cars where the owner stripped it down to nothing and it never sees the road again.

    You won't regret having a nice handling car [for more important than Horsepower]
     
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  21. Stogy
    Joined: Feb 10, 2007
    Posts: 17,564

    Stogy
    ALLIANCE MEMBER

    That wasn't me...:D
     
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  22. Yeah yeah yeah, I've got a mind like a steel trap.
    Do you Remember my analogy between you getting this car and where I gave you a bag of garbage out of my kitchen ? There was a reason and moral to it. As you go thru this you'll have revelations on the revolutions and eventually get to the bottom of why you have what you have.
     
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  23. RichardL
    Joined: Mar 6, 2010
    Posts: 288

    RichardL
    Member

    I've seen one of the suspension companies weight cars on wheel scales at several different shows. They're gathering information. I believe it's Ride Tech that does this.
     
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  24. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,954

    missysdad1
    ALLIANCE MEMBER


    Making as much progress as work schedule and bank account will allow. The most important first step is the Pete & Jake's 4-Bar front suspension setup with new Mustang quick-ratio steering box and SoCal VW-style steering damper. I got this much mocked up already, now waiting for other parts to continue which will include a Speedway steering column, Speedway drag link and a Borgeson lower steering joint.

    Coupester make-over 65.jpg
    The Pete & Jake's 4-bar setup uses a Mustang side-steer box which I happen to like. The old box was an early '60s Fairlane and had been joined to a GM tilt column. Took it all out and threw it away. The new setup uses a later model large-spline Mustang box, in this case a quick-ratio so I can use a shorter length Pitman arm. The new box also uses a rag joint, unlike the earlier box which had a one-piece steering column.

    Coupester make-over 66.jpg
    The front suspension got some components changed out just to freshen it up and ended up with about -4 degrees caster all on its own without influence by the adjustable bars on the P&J suspension. I can change the caster using the bars if this number does not work well, but from what I've read it should be just about right.

    Coupester make-over 67.jpg
    Yes, that's the end of the SoCal VW-style steering damper clamped to the lower bar of the P&J suspension. The tech guys at P&J were clear that this damper absolutely should be used with their setup and that it should be attached in just this way. It's the same damper from the previous setup, I just moved it from one to the other.

    I'm still in mock-up at this point so I can still make changes if I have to, but I don't expect that to be necessary. We'll see how it goes...
     
    Last edited: Jul 6, 2018
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  25. Paul
    Joined: Aug 29, 2002
    Posts: 15,060

    Paul
    Editor

    That should work much better
     
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  26. Wow! I drove 26 COOP for the first time yesterday.......That's why I'm reading about Death Wobble, etc. on this thread.
    First some pics of the front suspension: DSC02064.JPG
    DSC02063.JPG
    DSC02070.JPG
    DSC02075.JPG
    I bought the rolling chassis with the body kinda mounted thru the HAMB, out of Albuquerque, NM. I has a '40 front axle with '56 F100 brakes. The wishbownes are split and the Model A front spring is mounted to plates welded to the wishbones. I added the MGB rear shocks and modified the tie rod to sit behind the axle for good Ackerman. Caster is about 5-degrees. Tires are Coker Firestone bias ply - 5.60-15 on the front and 8.20-15 on the rear. The rear suspension is a triangulated 4-bar and coil-overs on a 9-inch rear.

    It felt good running around the cul-de-sac at low speed. Then I went out on the smooth secondary road up to about 55 mph. I absolutely thought the car was going to shake itself apart. The frame was twisting so that I saw the engine moving side-to-side and the tires jumping up and down.

    CRAP! I'm supposed to drive this beast out to Bonneville on August 7.

    Thursday I am having the alignment of the chassis checked (front and back axles square with the centerline and toe-in adjusted. I talked with the guy who balanced the tires and he thought that the problem is with balance, and would check it the same day.

    So last night, worrying about the death wobble, I found this thread at 4 AM. After reading all the problems and potential fixes, I decided that if I didn't get it fixed this week, I was calling off the trip.

    Then I found where someone had suggested adjusting tire pressure. I decided to reduce the pressure as a first test. Well, low and behold the tires were under 10 psi!!!!! :((I assume that I had checked them months ago.....Assume makes an ass of u and me). I upped the pressure to 22 psi and the problem seems to have gone away!:)

    Now I feel good about finishing the details and driving out to the Salt with my trailer in tow:

    20180714_122037.jpg

    Thanks to all who participated on this thread. It helped me from the sidelines.

    P.S. I have experienced no bump steer with the '66 Mopar steering box extended thru the side of the cowl and the drag link parallel to the wishbone. It doesn't mean there is none, only that the travel is so slight that the bump steer is miniscule.
     
    Last edited: Jul 16, 2018
  27. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,954

    missysdad1
    ALLIANCE MEMBER

    Just a quick update on my quest to eliminate the bumpsteer in my butchered up coupester. The P&J 4-bar system is in, the SoCal damper is installed and the custom-length drag link from Speedway is in place so the next step was to yank out the old GM tilt column which had been necessary due to the far-to-the-rear placement of the previous Mustang steering box and replace it with something better.

    I settled on a plain steel Speedway Motors "Nostalgia" column which is 30 inches long, has GM-style turn signal switch and will accept the reproduction '40 Ford steering wheel which I already had. I used a Borgeson lower steering joint and ended up extending the steering column splined end by 3" to get the steering wheel where I wanted it. I used a splined section of steering column material and a short splined collar to get this done, all from Borgeson.

    The installation isn't quite finished yet, but here's where it stands today. Once this is buttoned up I'll move on to finishing the brakes...

    Coupester make-over 69.jpg

    Coupester make-over 70.jpg
     
    Last edited: Jul 17, 2018
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  28. Boryca
    Joined: Jul 18, 2011
    Posts: 687

    Boryca
    ALLIANCE MEMBER
    from Detroit

    Could you take a close-up of that pitman arm to 4-link area? It looks like the pitman arm would hit when you turn left. Could be the angle, I'm just curious. Glad you're getting this thing fixed up right!
     
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  29. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,954

    missysdad1
    ALLIANCE MEMBER

    Photo was taken during rough mock-up. Final assembly/adjustment will find the pitman arm at true vertical when the wheels are straight ahead, at which point there is no interference...tight, but no touchee. :D:D:D
     
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  30. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,954

    missysdad1
    ALLIANCE MEMBER

    I just got the car buttoned up and have put about a hundred miles on it so far. Totally different car to drive! The bump-steer is totally gone, the pesky vibration is totally gone and the car is actually civilized and pleasant to drive! Thanks very much to all who made suggestions and helped me see what I couldn't see.

    The stretched wheelbase proved to be no problem. I just moved the P&J 4-Bar assembly and Mustang steering box two inches further forward on the frame. Things got a little tight around the steering box but changing to a small oil filter cured most of the problems. Still tight but it all clears.
    Coupester make-over 78.jpg

    The changes also included a switch to adjustable spring perches to eliminate the spring bind this car used to have. The front end now sits about an inch lower than it did before but nothing hits and nothing binds. The exhaust clearance below the Mustang steering box is close but still clears okay with no changes. Miracle!
    Coupester make-over 79.jpg

    The Pete & Jake's 4-Bar system installed easily and didn't require pulling the engine/transmission. Because of the frame stretch I did have to lengthen the Speedway Nostalgia steering column about 3 inches to get the steering wheel where it belongs. Borgeson supplied all the pieces to get this done while also adapting the column to the Mustang steering box. I used a custom-length Speedway Motors drag link to hook it all together.
    Coupester make-over 75.jpg

    For brakes I finally decided on Speedway's GM "Metric" conversion system which was pretty much a bolt-on deal though I did upgrade the brake pads that they supply which are pretty bad. This did not bring the wheels in as I expected, so at some point in the future I'll invest in some different wheels to improve the scrub situation.
    Coupester make-over 76.jpg

    All in all I'm very pleased with the appearance of this change over as well as with the way the car drives and stops. I'd have done this a long time ago if I had known that bump-steer was the problem all along. Thanks to those HAMB members who helped!
    Coupester make-over 77.jpg
     

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