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Hot Rods Wishbone 3-link information please

Discussion in 'The Hokey Ass Message Board' started by grumpy65, Jan 27, 2018.

  1. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Hi Gary,
    I am definately happy that I put the call out for this information. We should all be extremely grateful to Kerry for taking what I am sure is precious time to walk us through this. Not too many guys out there that have this high a level of knowledge, AND are willing to pass it on so freely. Kerry is doing a great service to the hot rod masses, and has done so on this forum for a long time. I have read a lot of his stuff and it is always excellent info and always delivered in an appropriate manner. I would suggest that all go to his profile page and do a content search on him. Lets hope he doesn't think we are stalking him.;)
     
    gimpyshotrods likes this.
  2. Ned Ludd
    Joined: May 15, 2009
    Posts: 5,025

    Ned Ludd
    Member

    Apologies for not chiming in sooner. I think my brain is still on holiday; and besides, it looks like Kerry's got it pretty much under control.

    Here's some further background about roll centres: https://www.jalopyjournal.com/forum/threads/this-brouhaha-about-roll-centres.629334/ I hope it helps to clarify things. I'm told people sometimes come away from stuff I write understanding less than they did going in. I hope that isn't the case here.
     
  3. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Hi there Dawie. Thanks for the link. More info is always good. I am a strong proponent of the three L's. Look, listen and learn. I have read a lot of your stuff and I am sure you are wrong about people's understanding of it. If they are open to information, it gets in. Sometimes it just takes a little time for it to engage properly. Some of you guy's stuff is a pretty big mountain to climb for us beginners, but one step at a time, and if we really want to get up there, we can.
    Learn every day. Never stop. Hey, it can't hurt, right?

    Steve
     
    gimpyshotrods and Ned Ludd like this.
  4. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Last edited: Jan 29, 2018
    gimpyshotrods likes this.
  5. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,905

    Kerrynzl
    Member

    While still using Lotus for an example :

    For a T Roadster [or Bucket] with their flimsy ladder frame.
    If you're going to have a low seat position, fold up a reasonably high driveshaft tunnel out of sheetmetal[ >-< shaped looking from above]
    Use this as a "backbone" frame [stiffener] similar to Lotus Elan frames [pic attached]

    This would do wonders in the chassis handling dept.

    If you're going to use a rear cross-member or "X" shaped cross-member for the rear trans mount , you might as well get it to contribute to the overall torsional stiffness of the whole frame
    bodytochassis2.jpg
     
  6. GEGE
    Joined: May 18, 2002
    Posts: 215

    GEGE
    Member

    FYI 3 point link is not new for sure.
    I had a 32 pickup that was an every day driver in the early 70s that I also towed my 32 to bonniville and a boat to the river, it had a 3 link but 1 was at top center of rear end and the other 2 ends attached at the frame. It was built by j and j chassis famous for frames etc. at that time.
    Will look for photos.
     
  7. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Firstly, with regard to your post #29, are you saying that the suspension should be setup/tuned to match the conditions the car will see most? If lower speed cornering is all that is required, a little bit more of a soft ride can be incorporated. If high speed cornering is needed, it should be stiffer, thus sacrificing ride quality. Seems to make sense that the faster you want to corner, the stiffer it all needs to be.

    Re the Lotus Elan frame idea, if a "traditional" look was needed for the frame, could the folded tunnel be used between the rails, attached by some sort of mini K member/X member each side that is rotated 90 degrees? Also, the tunnel attached at the rear crossmember.

    In your picture, is the tunnel structure the dark piece in the middle, or is it part of the lower backbone frame?
     
  8. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Thanks gege. Pics would be great. Always easier to analyse stuff when visual. Unfortunately, my build plan is all in my head at this stage. Trying to nail it down as to what I want (and what will work well) before I start to put pen to paper. Still a ways off actually making sparks, but I think this process of design is necessary if I am to get the best result.
     
  9. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,905

    Kerrynzl
    Member

    This is the dilemma with car designers. On the race track we ,tune the suspension to the Average speed for the lap times [this is the speed that occurs most often] sometimes more gains can be made in slower sections, and sometimes the opposite.
    Is your car intended for open road, or is it going to be a "Boulevard Bandit" ?
    Just remember there is 2 types of "faster you want to corner" [one is increasing terminal speed, and the other is increasing G's]
    Increasing terminal speed is usually a result of a larger radius corner yet the G forces remain the same, so the roll stiffness doesn't need to change.

    In the picture I posted, I am referring to the backbone frame at the bottom. If you could use this section between the traditional frame rails it would increase torsional stiffness [and be hidden]
     
  10. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Must compliment you on your thread "this brouhaha about roll centres". Excellent stuff. A recommended read for anyone that is serious about making their rod the best it can be.
     
    Ned Ludd likes this.
  11. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Ok, so it is a case of tune to intended use. Makes sense. I will want mine for open road use. It will be definately a "driver" for long trips (winding roads included), not just a Saturday night special.

    Could the tunnel assembly be fabricated as shown at the bottom of the picture but with the ends trimmed off so as to make an X member, and then fitted as a unit between the frame rails (hidden)?
     
  12. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,905

    Kerrynzl
    Member

    That is exactly what I'm suggesting. You're going to need a rear cross-member and driveshaft tunnel anyway, so why not use it for structural integrity.[roll couple doesn't work correctly with the chassis twisting]
    Years ago when I was a kid, I remember seeing a speedway midget that had a ladder frame [probably model T rails] and a Holden Grey engine in it.
    I remember it having a deep cross-member in the centre of the car [it had high side rails of that era]
    From that cross-member it had 4 x diagonal braces going close to the corners of the frame creating an upside-down pyramid.[this frame would've had good torsional strength for it's simplicity]

    You want to do similar on the top of the frame [being low] , by triangulating down towards the corners at the ends of the tunnel.
    Fold up a cardboard tunnel etc to go around the bellhousing and over the gearbox etc and replicate it in sheet metal.
    Sheetmetal is stronger [and lighter] than space frames, which is why race cars have been using monocoque "Tubs" since the 60's.
     
  13. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,905

    Kerrynzl
    Member

    That is why I consider the XR6 a highly worthy and respectable goal. All Manufacturers actually have reached tremendous achievement levels.
     
  14. A Boner
    Joined: Dec 25, 2004
    Posts: 7,419

    A Boner
    Member

    You can skip the tubular type transmission crossmember, and instead make the transmission tunnel, transmission mount, seat pans and floor boards structural. Just use a heavier gauge sheetmetal. Sort of a uni-frame.
     
  15. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    So, torsional rigidity of the chassis would increase the outer tyre load by removing/reducing parasitic losses through chassis twist. It would also help to keep the loads more predictable and controlable.

    Now, I may be totally off the mark here. With the increased effect of the roll couple gained by a torsionally rigid chassis, would this allow a softer spring rate with progressive rate springs to be used and then tune it in with the antiroll bar? If this is possible, it would mean a more butt-friendly ride in general driving, and you would get a progressive antiroll effect and a rising load rate on the outer tyres as the corner got tighter or your speed increased. For anyone reading along with this, THIS MAY NOT BE CORRECT !!! I would strongly suggest putting your faith in Kerry's info, not mine. I am only the student here.
     
    King ford likes this.
  16. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Thanks a boner.

    Any thoughts on this Kerry?
     
  17. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,905

    Kerrynzl
    Member

    That's sort of what I have suggested.
    Build a high folded sheet-metal tunnel , and go out and down diagonally on the 4 corners to the frame rails.
    The height of the tunnel gives it the torsional strength, you don't need to use heavy steel.
    If you filled in the floor between the tunnel and the rails with swaged sheet metal floor you would increase the lateral strength also.

    Most modern topless cars use a High tunnel or High sills for beaming strength, but splaying out the tunnel at each end gives torsional strength [attached an example] 111 frame.jpg

    Torsional stiffness is needed to make the roll-couple work correctly. The last thing you need is for the front of the car to body-roll 5 degrees and the rear of the car 4 degrees. It would be difficult to balance/tune
     
  18. King ford
    Joined: Mar 18, 2013
    Posts: 1,477

    King ford
    Member
    from 08302

    Grumpy 65 , I have not been ducking you, I haven't been on the H.A.M.B. For a few days...however my input is no longer necessary as I am now a student of Kerryenzl as well!...Kerry, I have been the chief mechanic on a northeast US DIRT modified for 31 years now and have a pretty good working knowledge of chassis geometry and theory and you are adding to my education and I thank you greatly for sharing!
     
    grumpy65 and doyoulikesleds like this.
  19. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Oh dear, what hope have I got.:( You have 31 years experience in this stuff and I am setting of with just a reasonable grasp of general physics and a tenious understanding of the subject at best. No wonder I am struggling at times to get my head around this. Kerry has been an enormous help, but I worry that he might be wasting his time on me. I am, like you, grateful for his input. The learning curve has certainly been steep for the last week, but well worth it I think. I hope I am making some progress.
     
  20. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Time to start trying to piece it all together as a build plan. Unfortunately I do not have bottomless pockets, so the aim is to incorporate as much as reasonably possible into the chassis/suspension as I can. I have been thinking it over all day and, while it is not a full on race setup I am after, I am definately up for trying to acheive the best result I can (with somewhat of a balance between ride and handling).

    Do you have any advice on running a longitudinal torsion bar 4 bar front end (or can a 3 bar be done). I have the design for this mostly sorted already, so pros and cons in your opinion would be appreciated. I have searched high and low and can't find how to calculate roll centre for this setup. Can you advise.

    Will take you up on the offer to PM you when I have some stuff in ink. I am in Southern Queensland, Australia by the way, so anything I do will have to conform to our strict regulations. Hopefully this will not limit it TOO much. Thanks.

    Steve
     
  21. gnichols
    Joined: Mar 6, 2008
    Posts: 11,344

    gnichols
    Member
    from Tampa, FL

    We need a contest thread! Pick an OEM spec A or 32 Ford chassis and go from there. PLEASE. As much as I love hearing about this and that, doing this and that, I most need to see a chassis that will work and fit right under my Model A body. Any takers? Gary
     
  22. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Hi Gary,

    I am happy for you to take this thread off in that direction. I am at the stage now where I need to start slotting everything together as a chassis/suspension plan. Just like a good house needs a good foundation, as I see it, a good car build needs a good chassis/suspension as it's base. A little thought and time spent at this early stage can make a considerable difference to the final product. Well worth it.

    Kerry and others have helped an enormous amount in getting me to the point of having a BASIC understanding of what is required and desirable, but honestly, we have only scratched the surface. The knowledge some of these guys have on the subject is mind-boggling, and when they are prepared to help the rest of us out, we should be extremely thankful. I still have most of the mountain to climb, but a start has been made. Lots of reading to come. It's reassuring to know that help is only "the hamb" away.

    I will be interested to see what your "contest" turns up.

    Regards,
    Steve.
     
  23. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,905

    Kerrynzl
    Member

    I'd love to join in........But I'm sort of done with building another car [for a year or two]. I'd like to kick back and help a few, do a bit of club racing and cruise around a bit. [I built more cars in 2016 than most people would build in a lifetime]

    If anybody wants some inspiration, look at this T Roadster that "Frames" built in this thread [post # 4 ]
    https://www.jalopyjournal.com/forum/threads/fiberglass-body.1094236/#post-12407572

    This would make a great "Club Racer" along the lines of a "Lotus 7" [Caterham 7] or "Mallock U2" but disguised as a T Roadster.
    Add an Aero Screen, a Roll Hoop, and Road Racing Wheels & Tyres and it will be cooler than liquid nitrogen.
     
  24. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,905

    Kerrynzl
    Member

    If you use torsion bars, you must use a panhard bar or some sort of lateral locating device. This will dictate the Roll Centre



    If you use longitudinal torsion bars,
    Make some custom 4 Bar Batwings [laser cut] and only use the upper 4 bar links in the normal manner.
    In the centre of the axle make another bracket to mount a triangulated "A" frame.

    Where the lower brackets normally attach, modify it to use shackles or roller "sliders" for the Torsion bar arms.
    [ you could use 2 x heim joints at 90 degrees as a shackle from the batwing to the torsion arm]


    Use sprint car or midget torsion bars, to get the correct stiffness [they have a lot of choices]
    also use their torsion bar stops and torsion arms
     
  25. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Thanks Kerry. That is how I had worked out to do torsion bars at the front (apart from the 3 link option, which I will consider). Check this out. It is where my inspiration for front t-bars came from.
    www.jalopyjournal.com/forum/threads/spalding-bros-repro-for-too-tall-ganahl.983332/page-27
    A long and winding thread, but I have linked to it at page 27. There are some good pics around here (page 29, post#885). Only difference is I would be looking at running a dropped axle. See what you think. Also, thoughts on light weight diff. Toyota Hilux 2wd???
     
    Last edited: Jan 31, 2018
  26. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Sorry all. Page 29, post#855 on the thread linked above.
     
  27. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,905

    Kerrynzl
    Member

    A dropped axle would make it easier to "A" frame it underneath.
    Please don't take too much inspiration from the build you're linked above.[even if it is historical] They have used a straight tube axle with hairpins. [the whole front end is basically a swing arm similar to ATV's]

    The Hilux [Toyota G series] diff is basically a "Japanese 9 inch" [even though it has an 8'' Crownwheel]
    They're tough as nails, and have 30 spline hardened axles.
    Try and find one out of a Hiace van, it will have 5 x 4-1/2" PCD [Ford stud pattern]. Late 70's Hiace vans are narrower than the rest.
    If you can get an early 90's Toyota LiteAce diff it is already set up for triangulated 4 link [but 4 stud]
    There are a few ratios available, that can be decoded from the ID Plate.

    http://rsmotorsport.com.au/files/Identifying_Toyota_Hilux.pdf
     
    Drewfus likes this.
  28. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Model translation for US viewers:
    In the US, the Hilux is just known as the Toyota Pickup, followed by the Tacoma, and the T100. The axle varies by width, and later disc brakes. 2WD ones have the Ford/Mopar pattern,
    The Hiace was not formally sold in the US, but a handful made it in.
    The Liteace was also not formally sold in the US.
     
  29. grumpy65
    Joined: Dec 19, 2017
    Posts: 920

    grumpy65

    Only looking at the torsion bar setup off linked thread. Would use dropped axle, 4 link (or 3 link) and proper shocks.

    Have access to a Toyota Stout. What are your thoughts on using the front axle and diff? Am a bit concerned about weight of front axle as I am trying to keep unsprung weight down. Am leaning towards dropped tube, but unsure if that will meet the regulations here in Australia.
     

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