Landracing Forum
Tech Information => Steering - Suspension - Rear End => Topic started by: 1977MGBV8 on December 25, 2007, 04:28:20 PM
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As a newbie, trying to get my hands around some of the concepts for this kind of racing I am wondering why don’t I see more Watts linkages instead of panhard bars (link attached to wikapedia: http://en.wikipedia.org/wiki/Watt's_linkage (http://en.wikipedia.org/wiki/Watt's_linkage))? I know that suspension travel is short ~1 inch on the salt and that a 24” panhard bar moving up/down 1 inch would move the axle about 0.03” laterally which is a very small amount but in a front end suspension application this might have an impact of bump steer conditions. For the rear end (assuming this is the driven axle) I could understand the added complexities due to changing out the gears though this too could be resolved. Any thoughts or comments would be appreciated.
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I think that you "hit the nail on the head" regarding the simplisity of the panhard rod for locating an axle. If you make it long enough and don't have much travel then it doesn't do much steering on either end. I have used watt links on several road racing cars that I helped build and race and they had 9 inch Ford rear axle assemblies and I think for that application the watt is the best way to go but for the salt a well designed panhard is simple and easy.
Rex
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half as much to buy half as much to build and half as much to wear out and half as much to replace go with the panhard bar -- make it long and strong willie buchta
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what about the wishbone locator
http://chassisengineering.com/shopDetails.asp?CatId=10&SubCatId=69&ProductId=1620
with the anti roll bar
http://chassisengineering.com/shopDetails.asp?CatId=10&SubCatId=5&ProductId=908
thanks for any comments
not trying to steal anyones thread here just wanted to know yall thought
thanks
robbie
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we tried them on the drag race cars --and they worked good --but then we were running with 2 flat tires willie buchta-
they seemed like they had to much slop--and the way they are set up they wouldnt last long in the salt or durt keep it simple you will have to many other things to worry about ---we always used the one from the chassisworks
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Don't overlook the wishbone option. Buddy and I are building a lakester, were going to go with Watts then space got tight, considered panhard but it was going to have to be short, currently working up a wishbone.
Ed Purinton
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i was thinking of going with the wishbone and 4 link in my studebaker because i think it will stay hooked better in high gear just my .02
robbie
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Stratman, you are asking for trouble. If the car was glued on a rail then the wishbone locator is fine, but if you are sliding sideways at 200 mph, you are asking the heim joints and their brackets to work in ways for which they are not designed. Leave the drag race shit on the drag race car and do it right. Ask the salesman at Chassis Engineering if they would put the track locator on a roundy round car. Your Studebaker is going to weigh a minimum of 3500#. Either a panhard or a watts linkage put the heims in the plane on which they were designed to work............Bob
p.s., I think the wishbone locator would work fine on a lighter vehicle (as in m/c streamliner ) or a vehicle to slow to spin....lol)
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thanks bob for bring that to my attention. the salesman at chassis engineering said nothing about it when we but it does make alot of sense. do you think the panard bar with four link will be ok.
robbie
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It seems like there has been no ill effects wittnessed by using only a panhard bar.
I also have concerns about having the spherical rod-ends/heim joints loaded in an axial manner (forces applied to the bearing axis). I don't pretend to know a lot about salt flat racing but my experience as an mechanical engineer tells me this could be a problem based on some info I have seen. There is a limit to the axial performance of these joints generally, the is a rule of thumb I have seen applied of a reduction factor of at least 10 in difference between radial and axial load capabilities, Ultimately, (in a slide as posted earlier) you are loading a joint that was not maximized for axial loads) that could be generated in a slide. But it could be calculated to see how much margin there is. But when doing so there is a combined load of twist and axial loads on the joint.
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Stratman59
We run a 4link with panhard bar ''Alston chassis'' no problems hooking up in any gear except low gear,still will not blow tires away except at slowest speeds.No problems in other gears,or high gear over 288 mph.
Good luck JL222
k
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I've used the wishbone type successfully in other applications. Don't use a rod end for the single joint. Use a spherical joint, which is the joint they use in a rod end, and mount it horizontally in a machined socket. Just be sure you have the mounts built to give it adequate travel. The only other thing to be aware of with this set-up is that it gives a very low roll center which helps to keep the rear end stuck, a good thing.
Pete
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I agree with Pete, turn the joint side ways to take the load and the other trick is to use a BIG rod end, 3/4 inch minumum and buy a premimum part, not the $10 ones that work for steering shaft supports. I use a "wish bone style locator on my streer roadster and the rod end is a 3/4 inch, aircraft quality piece that I paid about $75 for a number of years ago. (I never throw anything away!) Remember where ever the rod end is mounted to your rear housing that is the roll center. So you can do it high or low. My preference is like Pete's, low.
Rex
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The lower triangle is probably the best approach although a Watt's linkage could offer more roll-center adjustability- be sure to either have it in phase with the other links to avoid "hinge bind" or if it's built with a slip joint that thing needs to be Seriously STOUT and kept well-greased! 7/8 ball joints, NMB quality, would be my choice (take out a bank loan) The off road industry has manufactured housings for them that allow the part to be welded into your triangulated structure. G&J Aircraft Ontario, Ca should have them.
I'm not challenging the merits of the low roll center, but am interested in the it's why's and wherefore's as to its advantage on a basic straight line, low accelerating machine.
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When I built my car, I made a panhard bar using heim (sp) joints, it had too much slop, you could rock the car left and right. I replaced it with a panhard bar using tierod ends with grease zerks in them, works much better.
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Tie rod ends are a wonderfull idea... i think they would be way, way stronger than rod ends... altho not as trick looking but probably alot cheeper...
kent
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I like the tie rod idea. Do you have a trick for making the mating tapers. I am thinking how you could make this work other than making some tapers and bung weld thing into a chassis?
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With mild steel---an 18" breaker over bar and an old tie rod end.. lol
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Better not tell anybody, but there's at least two suspended roadsters going over 200 with TCI urethane bushed rod ends on their 4 links AND panhard bars- I know one has never spun (don't follow the other's runs).
Personally, tie rod ends went out in the day of Tom Beatty, Alex Xydias, et al.
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Straddle mounted good hiem joint assembly is stronger than tie rod end. It also has virtually no play. Can't fall out even if worn out.
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I am not a fan of tie rod ends but if you are going to use them then do the taper the right way and use a taper reamer to make the hole fit. You can get them at Coleman Racing, www.colmanracing.com. They have both the 7 degree and 10 degree reamers depending on the rod end you use. The one they have is for the GM or MOPAR ball joints but will probably work for tie rods also.
I agree with Hitz, a good rod end (Read NMB here) is far better than a tie rod end and in double shear it is probaby 3 times stronger.
Rex
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Rex, knowing your road racing experience from previous posts , maybe you could respond to my query a few posts up on this subject about roll center height regards relatively slow acelerating vehicles going in a straight line. ( Some roadsters excepted). Probably specifically regards live axles. ???
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Interested Bystander.
Regarding roll center and acceleration I am wondering if you really mean "anti squat" or "anti dive"? The roll center is important when discussing side loads, typically those you have when going around a corner and since B'ville cars really don't worry about cornering much I would think that roll center placement would not be a big concern. Having said that I would also not recommend having a high roll center on either end of a B'ville car as it "may" assist the car to roll over if it is in a spin, as a high roll center imposes high jacking forces that want to lift the car when it is subject to high side loads such as a spin.
As far as anti sqat or anti dive, these charteristics defined by the location of the axle location arms as seen from a side view of the suspension. My thinking is that at a place like Bonneville or El Mirage where traction is very limited you would not want much of either anti squat or anti dive. At a place like the Texas Mile or any of the concrete strips a little anti squat may help acceleration. Anti dive is more realted to braking forces being used to prevent the car from nosing down during braking and again not really applicable to land speed cars. To much of either of these can cause the suspension to bind.
I think that when going in a straight line the most important thing is that the location of the axles be kept in the very best optimum alignment possible which means no tricky suspension stuff that is used on road racing cars and long locating links to minimize any type of roll steer. I think it is really hard to beat a straight axle, front and rear, each located with long, parallel links. Having said that I am going completely against that recommendation in the design of the suspension for my lakester!
Rex
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I have a stock wheelbase 1933 Ford Vicky chassis. The front is a 5" dropped axel. Super Bell I beam , front suspension is 4 bar type complete from Pete and Jakes. I hope this will work ? The rear is a 9" Ford ( Nascar det/Loker Unit) using Pete and Jake Ladder bars with Panhard bar and coilovers.
Will I be ok,, I will Run this year at Maxton then hope in the fall to run the USFRA event.
Charles
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Just my own preference but I'd rather see a 3 or 4 bar set up than a ladder bar rear end. If the car does get sideways you'd stand a much better chance of recovery with the much softer set up. Ladder bars effectively form a seriously stiff anti-roll bar unless one side is built to rotate on the housing. The stiffer end of the car in roll will usually give up grip first, thus my preference for keeping roll stiffness at least somewhat similar front to rear.
Pete
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Pete, thanks for the info, it does make sense, heck I even understood it... My old drag racing days and search for that nostalgic look sent me to the ladder bar set up. We did mount the front to the inside of the frame rather than as Pete and Jakes had them angled towards the tranny mount. We also used front bushings rather than the hard style mount. Panhard bar is just over 22 inches, Should I back off the spring rate on the rear coilovers?
Also what are your thoughts on my front suspension set up ?
Will it work on paved as well as salt ( I see the same suspension on lots of cars in all the books I have on Bonneville, most 29 to 34 Roadsters I see have the Dropped axel set up???
Charles
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The longer you can make the panhard rod the better. A longer rod moves the axle side to side less than a shorter one in relation to the frame / body assembly. I might even look at a watts link because there is no sideways travel. Try the springs you were intending to use. Good luck!
Pete
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Thanks, I have two panhard lenghts, I will see if I can use the longer one.
Hope It all come together in time for Maxton's April Event...
Have a nice night.
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SIMPLISTIC advice regards suspension linkage.
AVOID HINGE BIND in all dimensions!
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If through the entire compression and rebound strokes of the suspension, if it does not bind then. One could assume that on the track it would not bind either ?
Is there another way to check before I get it on the road?
Thanks