Easy "Panard Bar"

[Robert J]

Although this is not officially a Panhard bar by design as it does not match Panhards original eclecticism.
http://bringatrailer.com/2012/02/10/backward-and-forward-1964-panhard-bt17/

This is an interesting and fairly easy way to reduce spring twist on an MGB.  Pictures from my new car's underside:

[chimes]

Not near a panhard rod, it's a tramp bar! Won't stop lateral movement one jot!

[MGBV8]

David's right. We call 'em traction bars (or slapper bars).

[BlownMGB-V8]

A reasonable mistake for someone not familiar with this technology. The slapper bar is a traction device designed to prevent spring wind up and uses the counter torque of the axle housing to plant the tires on acceleration by applying a jacking force to the body. Useful in straight line acceleration but not helpful coming out of a turn. It helps to think in terms of the forces one is trying to counteract.

Jim

[Robert J]

Thank you for the input.  So, what is the best available true panhard bar for the MGB project I am presently building?

[MGBV8]

Are you looking for one that will just bolt in?  Or, are you looking for DIY suggestions?

[Robert J]

I would prefer to fabricate it myself.  I'm a competent welder and have a small shop full of useful tools.  Is there a tech posted here somewhere?

[ex-tyke]

You might get some good pointers from this archived thread...
http://forum.britishv8.org/read.php?7,1069

[MGBV8]

Robert,

Way back in the early days of the "MG V8 Newsletter" there was a very good how-to article. I don't think it was ever digitized here. A lot of us fabbed our own using ideas from it. The general consensus is to make the bar as long as possible, level with the ground, & even (or below) with the axle centerline.  Lots of pics here to gather design ideas.

[ex-tyke]

A couple more from the archives:
http://www.britishv8.org/Articles/MGBRearSuspension.htm
http://www.britishv8.org/Articles/Suspension-Design.htm

[roverman]

If your running real close tire to fender side clearance, consider the "arc" lateral movement of the rear end, as it travels up/down. Watts links, Jacobs ladders and Pickle forks, all used for controlling lateral location, do Not have "ark" traverse. Good Luck, roverman.

[Moderator]

These two articles show particularly good installations, although quite elaborate:
http://www.britishv8.org/MG/ChrisJones.htm
http://www.britishracecar.com/LesGonda-MG-MGBGTV8.htm

[Bill Young]

There are other options that you may want to look into such as the "Jacobs Ladder" or a Watts Linkage to control side to side movement of the rear axle. http://www.spitzracing.com/index_files/Page724.htm  or  http://en.wikipedia.org/wiki/Watt%27s_linkage

[Robert J]

OK, thank you all for the links.  

This is going to keep me busy cogitating and measuring for a while.

[roverman]

Thanks for the "links" Bill. As we can see, either of these systems should provide a smoother ride and ehanced handling, with leaf springs, vs a panhard bar. It's easy to change rear roll center height with Watts linkage by having multile threaded holes (vertically), to mount central pivot point. This is also available feature for "pickle forks".  Just say NO to lateral arc.  roverman.

[Moderator]

Just say NO to lateral arc.

Art, the arc you're talking about is a function of Panhard bar length. The formula for calculating its size is given in the second article Graham linked to (above). With a 36" long Panhard rod, the arc effect results in a maximum lateral movement of only 1/8". (It would be a bigger lateral movement on an off-road vehicle, but MGBs just don't have that much wheel travel!) If an eighth inch is too much to suit you, you can make the Panhard rod even longer.  So long as you don't make it shorter, the Panhard rod's effect on ride quality will be trivial. Watts links or great... but a Panhard rod will be cheaper to make and easier to install than any Watts link. If you want to play with roll center height, a Panhard rod makes that quicker and easier too.

[Bill Young]

I agree about the cost to build a panhard bar versus a watts linkage as I don't know of any pre made watts linkages on the market, but you can buy a Jacobs Ladder very inexpensively from such places as Speedway Motors. Still have fabrication work to do for the mounts, but you have almost the same with a panhard bar. I see  it as a good option. The only downside for any of these is to get the best roll center and such the lowest mounting point needs to be pretty low and that might restrict ground clearance on a street car.

[roverman]

What I got from the ,"Jacobs Ladder vs Panhard Bar", is an 87" long panhard bar would generate approximately .100" of arc in 4" of vertical travel ? Is this more travel than a street use British sports car would use ? roverman.

[MGB-FV8]

I have a Watts linkage system; it's a little different but it came with my pinion mounted parking brake.  I was trying to reduce the rotating mass mostly to increase MPG (and HP) but my main concern was the composite spring that I had purchased from Doug Jackson.  There were some reports of spring shredding under high-torque.  Doug Jackson which is now retired defended his product saying that the ones complaining refused to use tramp bars.  Jim Stuart has this system with tramp bars for the past 8-10 years in his GT with the Buick 300 and has had no problems.  I'm running a 331 FSB stroker, which, will test the springs to its limits.

I originally went with his system as no link bar system were available at the time.  However, after I've called a couple of composite spring manufacturers, I understood the advantages of the composite springs mostly being the lightness and the fact that they react 8 times faster than steel springs.

I'm struggling every year to finish the project and I was thinking about replacing my DJ tramp bars with the "Slide-A-Link" tramp bars; the problem is that I would have to fabricate new front spring eyes with an extended area for the rollers to ride on (if you know what I mean).  Again, the reason for switching to this type of bars is to free up spring extension for a better ride; as it stands now, only the back half of the spring extends with the swing of the shackles.

I'll attach a previous post that I had started depicting my concerns, it has nice photos.  Take a look at the "Watts" linkage, the manufacturer assured me that they work great with narrow frame rails.  The other photo with a top link is not mine; I was just questioning its usefulness.

http://forum.britishv8.org/read.php?7,21259,21413

Please, let me know your thoughts; some of you have great engineering minds and I could use the help.

Cheers,

[Bill Young]

Art, the point is that the panhard rod would have to be 87" long to equal the movement of the jacobs ladder, now I don't know of any sports car that's 87" wide so you wind up with most panhard rods being in the range of around 40" or so to fit between the springs in the rear. Not optimum length to minimize side to side movement. Would it be too much, not really, way too many of us running short panhard rods without problems. Just wanted Robert to know that there were alternatives that actually worked better and had less influence on the roll center.

[roverman]

Seems I recall "Stock Car Products/used" to sell a watts link that mounted on 9" Ford front pinion bearing flange, maybe 8" ?  What if someone were to have a clever design of putting the panhard bar in "torsion", for double use as a anti roll bar ? Internal threads,(acme) on each end, would be zirk lubed and 2 axis load bearing. Properly done as the bar torsions,the arc could be reduced in vertical movement. What if ?  roverman.

[Preform Resources]

Yes a panhard bar is a compromise to the watts or jacobs ladder, but for most apllication they are easier to fab  and locate and work well  for street apps.
Dave Craddock

[ex-tyke]

That's one thing I liked about the 4-link purchased from CCE - a great light coilover suspension that precludes additional axle location devices.

[BlownMGB-V8]

Yes, he's done a good job on that and it seems to work well. Just going to the coil-overs to get rid of the ox-cart springs was a big plus. Apparently having the axle 1/3 of the way down the arch isn't particularly good design which surprises me a little considering the quality of engineering on most of the car. Was it an afterthought once use of the Jag IRS fell through? We may never know. But I've heard rumors that this was their plan when the body was designed. I think I've come fairly close to the suspension that was originally intended for the car given that it is a first attempt, but if I do another one I think I can get a lot closer, maybe eliminate the need for flares for instance. Probably have to do a set of front hubs to match offsets. But this has little to do with panhards aside from them not being needed.

I thought Art's idea was interesting, though I'm not sure where he is going with the acme threads and I haven't been able to visualize how it could work.

Jim

[roverman]

Jim B. and clan, If bar is mounted with "high angle" heims, and they have enough rotational,(torsional) potential, then heim could be locked inside panhard/anti-roll bar. This bar will need approx. 90 deg. ends/levers attached at ea. end to facilitate anti-roll input/resultants. This would be simplest approach. If using single axis pivots on ea. end,(bushings), then bar would need to rotate on "Acme" style threads(dia. acts as bushing). Pure race cars try to design so that one part/assembly serves more that one function. This saves weight and facilitates better space utilization. Share my vision, till I learn to ^$$^*(*  post pictures.   Thanks, roverman.