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Simple Hot Rod Tech...Making a Rear Panhard Bar for a '32 Chassis

Discussion in 'The Hokey Ass Message Board' started by Bass, Nov 1, 2008.

  1. Brian how do you weld the brackets on the rear end with out warping it?
  2. Bassfire
    Joined: Nov 17, 2006
    Posts: 468

    from Mart, Tx.

    You make me proud to be known as Brian's dad. Keep up the good work.
  3. Some of the aftermarket frames have very short panhard bars.
    I have a leftover one hanging on the wall fwiw, not sure where it came from since I make my own, but it's shorter than I like.

    When you think about it, the panhard bars transverse motion is not really felt.
    Some of the short ones noted above have more transverse motion than you do and I haven't heard anyone complaining about it
    Granted, these are on coilover cars, but that really doesn't affect the panhard bar other than being part of the packaging problem.

    To toss another factor into the mix, most of us are running lower than the usual rear tire pressure in these lightweight cars and that will dampen out some of the transverse movement of the chassis.
    Especially when running big radials at 20# like I do. (285/70R-15, 30" diameter.)
    Along with coilovers on the 32.

    I realize you are running bias, but much the same thing will happen with your car.
    A little less pressure makes for a less stiff sidewall and kicking the rear out the .21" or so won't be felt at all.
    I don't think that small amount of transverse movement will be noticed even if you hit a bump on a "let it all hang out" corner.

    What seems to happen on some (especially high tar strip) bumps is the rear axle leaves the ground for a short ways and when it comes down the car is pointed in a slightly different direction.
    Easily handled if you let it happen or saw on the steering wheel a bit so the car travels straight over that area of the curve.

    So, here's an interesting personal experience and one of those little screw-ups we all get involved with now and then.

    I did pretty good on the final assembly of my 32.
    No bolts came loose, nothing leaked and no electrical probs after startup.
    I'm a patient guy and work alone most times.

    Where I did screw up was, the bolt on the rear axle housing panhard bar mount wasn't long enough to fully engage the nylon in the nylock bolt and eventually backed off.
    Said panhard bar mount on the axle housing is tall enough so that the bar is almost horizontal.

    The way the bolt goes in, there's not room for it to fall out when the suspension is loaded.

    Interesting part was, with the panhard bar effectively disconnected there was quite a bit of transverse travel, but the tires didn't rub on anything.
    Nor was there any weird handling attributable to the now excessive transverse travel of the chassis.
    Part of that due to the flexy sidewalls of the rear tires masked the chassis sway to an extent.

    Granted, not a recommended way to run a panhard, but interesting and perhaps useful to this discussion.

    A new bolt 1/2" longer did the trick, along with a new nylock nut.

    As noted, bias plies will probably reflect the transverse chassis movement a little better than a radial due to the stiffer sidewall.

    While this has been an interesting discussion as well as some interesting math being brought to the fore, I think that in the real world - especially since your panhard bar is a reasonably practical length, bend or not - it doesn't make any real difference in the real world....
  4. M_S
    Joined: Feb 20, 2008
    Posts: 542

    from SoCal

    Not trying to be a smart ass (ok, maybe just a little), but do the laws of physics realize it's a hot rod and not a race car?

    I know the point you were trying to make (i.e., going in straight lines, slowing down to make turns and not driving @ 10/10ths all the time), but the rules still apply and it sounded to me like that author was only trying to warn of a possible dangerous situation.

    When I was building my Mustang for road racing I was on a site that discussed chassis/suspension quite a bit (I've forgotten more than I remember) and they used to quote a certain book as the bible of suspension design. If memory serves it was "suspension engineering" or something like that. If anyone remember the title or has a copy, have them quote the section on panhards. I would trust the information in that book over a site geared toward circle track dirt racing (not saying that any of the info on that site is incorrect).
  5. GreggAz
    Joined: Apr 3, 2001
    Posts: 931


    looks good Bass, that bar should work great, and the chassis looks killer.

    here is a shot of one I did on a gasser, the bar had to either be high, and have a tall bracket on the rear end, or a long bracket off the frame... there was no nice way to do one down from the frame so I did this. there is less than 1/8 movement each side of center throughout the travel.

  6. super plus
    Joined: Dec 14, 2006
    Posts: 566

    super plus

    Hey man I don't know who built what & I don't give a rats ass , I just commented on what I read & looked at . If you can't take any corrective criticism you shouldn't have put this thing on here for everyone to see and thick we would all pat you on the back . I also read that every time someone has something to say that may differ from you you have to come out on top .One who thinks they know everything never learns anything :)
  7. Anderson
    Joined: Jan 27, 2003
    Posts: 6,450


    Super, you don't have a clue. Lets see what you've built.

    Brian has done this a time or two...
  8. Bass's point was not that he didn't like the criticism it was that everything you mentioned had already been discussed at length in this thread. Had you bothered to read through the whole thread you might have realized that. :rolleyes:
    Joined: Jun 6, 2005
    Posts: 1,887

    Member Emeritus

    HI,Brian, See why I PM'd you before. I edited the post to clarify the 2/3d's thing it, should be track width. Thanks for proof reading. ehdubya is using the tech out of an Afco racing catalog that is based upon Imca race car and while not incorrect it tends to complicate things for practical street application but does point out the effect of a panard rod position on the roll center of a vehicle. Good luck.....
  10. super plus
    Joined: Dec 14, 2006
    Posts: 566

    super plus

    Fidgiter , No coment , K13 I did read the whole thread & this is what I think , looks to me that the rear cross member will flex before the spring will compress , & the shocks are at the wrong angle & If the panhard bar needs to work to stop side motion of the frame it looks like it will flex at the bend , nuff said .
  11. E.C.
    Joined: Apr 7, 2007
    Posts: 521

    from Tx

    Dude- This is Simple Hot Rod Tech thats it....Its for a Model A coupe not a cadillac... you should post some of your hot rod tech with pictures so we have an idea how Superior you shit is.

  12. Well then maybe you should have responded by saying that even though I see that you have reponded to these issues I still have some concerns/doubts about them and this is what I think (see above). Makes you look less like an ass (joking) coming in at the end of a conversation and restating things that have already been discussed.:)
    Last edited: Nov 6, 2008
  13. super plus
    Joined: Dec 14, 2006
    Posts: 566

    super plus

    holy cow, maybe I should have said , great welds but I think it will ride like a old buck board
  14. SinisterCustom
    Joined: Feb 18, 2004
    Posts: 8,264


    Nope....the trianglation of the P&J ladderbars keep side-to-side movement to a minimum....for the most part. The spring, under the weight of the vehicle, will keep it in check.
    Panhard bars, generally, aren't needed.....

    My PU had the same setup. You could rock the truck side to side and get some movement when parked, but going down the road, it drove just fine and rode great.....
  15. mine on my roadster is built the sameway as Bass did. it's been on it over 10 years and its not bent or stressed. nice job Bass
  16. willie57
    Joined: Feb 21, 2007
    Posts: 378

    from wisconsin

    I'am building a 54 buick for my wife and this was good information.
  17. tfeverfred
    Joined: Nov 11, 2006
    Posts: 15,795


    I don't know how I came upon this thread, but I'm glad I did. First off, Mr. Bass does great work. A couple weeks ago, I installed my panhard bar set up on my T Bucket chassis. In my opinion, it seems like I could use a bar with a bend in it, like Bass did. BUT.... not only is my chassis not completely done, it also isn't set at ride height yet. So, I'm probably two steps ahead of myself and sweating nothing.

    Another thing Mr. Bass stated was that the weight of a hot rod is quite a bit less than the average car. Since welding in my panhard bar set up, I've been searching the net and even made a trip to a shop and asked about panhard bars in light weight cars. What I found was, "The results can differ, depending on application." In other words, it's a little trial and error, mixed in with good judgement?"

    My past T Bucket had a Watts Linkage. After installing it, everyone said the bars should be horizontal under load. Guess what? Mine NEVER ended up horizontal. Not even close. I never had any problems and I drove that car every where and almost every day. I think the factor in my favor was the lack of weight in the rear end.

    So, I've got a build thread on another website and this time the fuss is over my panhard bar. One person made a VERY insightful comment, " ...the panhard has more to do with the roll center so if you aint racing it I doubt it is that big of a deal. I think its more about aesthetics in these cars (keeping the rear centered/appearance from the rear view) or "fit over function". " For now, I tend to agree.
    hrm2k likes this.

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