Panhard Bar Mounting

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Crew Chief
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Panhard Bar Mounting

Post by Crew Chief » Sun Nov 25, 2018 10:29 pm

Greetings,
For the Stock car/Open Wheel IMCA Style Modified guys.

I am thinking about relocating the panhard bar on my modified to the front of the quick change. I see a lot of Super Late Models and Outlaw cars with the bar mounted from the left hand axle tube across on a diagonal angle to the frame on the right side.
My question is, does anybody know if there is a maximum or minimum diagonal angle to mount the bar on or does it matter?
Any ideas?

Thanks

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Re: Panhard Bar Mounting

Post by j-c-c » Mon Nov 26, 2018 9:51 am

Nothing to add, but I hope it comes up in this discussion, how large are the forces a panhard bar actually has to deal with. Ideally its only the mass of the rear of the car supported by the two tires, acting against that axles combined grip, based only on the amount of cornering g's at that moment, correct? I am discounting any potential collision forces for the discussion. I think this somewhat relates to the OP's question, if not, sorry.

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Re: Panhard Bar Mounting

Post by RCJ » Mon Nov 26, 2018 8:09 pm

This is a dirt car.? You will get a lot of different views on panhard bars.When moving it from behind the reared to in front you are putting it in a more rigid part of the chassis.I have seen signs of the tail section bending on mods.We ran a j bar mounted on the left frame going to a plate mounted on the right side of the pinion on the late model.Never found any magic in it,just raise it up or down to get the handling right.As far as the diagonal angle I tried to keep it to minimum just because I felt there would be less chance of binding

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Re: Panhard Bar Mounting

Post by Crew Chief » Tue Nov 27, 2018 5:24 pm

Not a dirt car, it is on asphalt tracks only....

tresi
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Re: Panhard Bar Mounting

Post by tresi » Tue Nov 27, 2018 7:58 pm

It's best to keep the panhard bar as level as possible

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Re: Panhard Bar Mounting

Post by PackardV8 » Sun Dec 02, 2018 12:05 pm

Conventional geometry suggests the Panhard bar will be less stressed and function best if it is as long as possible and parallel to the rear axle during most of its travel.

However, forty years ago, when Bobby Allison was building his own and customer cars, he settled on a half-width Panhard bar. He said, "Yes, in theory, a Watt's link is best and a long Panhard is second best, but I've driven as many different cars as anyone and I like the feel of this little guy best of all."

I thought about it a lot and decided the advantage of his short bar is it doesn't have to dodge around the rear of the quick change or the driveshaft in front. It ran horizontally from the right frame bracket to a bracket bolted around the pinion flange of the QC housing. close to and exactly parallel to the right axle tube.

Anyone else seen anything like this being used?
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Re: Panhard Bar Mounting

Post by Brian P » Sun Dec 02, 2018 12:36 pm

A short panhard rod will pull the axle side to side more with suspension travel away from nominal. It can lead to some wonky bump steer and ride motions.

You can make any bad suspension design work if you don't let it move. (Really stiff springing and damping)

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Re: Panhard Bar Mounting

Post by PackardV8 » Sun Dec 02, 2018 4:51 pm

Brian P wrote:
Sun Dec 02, 2018 12:36 pm
A short panhard rod will pull the axle side to side more with suspension travel away from nominal. It can lead to some wonky bump steer and ride motions.

You can make any bad suspension design work if you don't let it move. (Really stiff springing and damping)
I had exactly that discussion with him back in the day. He said, "Yeah, I know what the book says, but hey, it wins for me and I don't use stiff springs."
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Re: Panhard Bar Mounting

Post by Brian P » Sun Dec 02, 2018 5:48 pm

Careful placement of the panhard rod attachment points - not necessarily straight across the car in plan view - can deal with what would otherwise be the side effects of a short panhard rod. For example, if the panhard rod is diagonal and the chassis end of the panhard rod coincides with the trailing link attachment point (not necessarily perfect, but pretty close), the other end of the panhard rod will be swinging in a side-view arc as opposed to a front-view arc. Then it doesn't pull the axle sideways with suspension travel any more. It just requires careful analysis and understanding of the geometry in 3-D space.

If it's a circle-track vehicle that only has to turn one way in anger, you can probably make use of the asymmetrical rear-wheel-steering effects and turn it into a benefit, because it won't matter that it's messed up in the other direction.

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Re: Panhard Bar Mounting

Post by j-c-c » Sun Dec 02, 2018 6:27 pm

Brian P wrote:
Sun Dec 02, 2018 5:48 pm
Careful placement of the panhard rod attachment points - not necessarily straight across the car in plan view - can deal with what would otherwise be the side effects of a short panhard rod. For example, if the panhard rod is diagonal and the chassis end of the panhard rod coincides with the trailing link attachment point (not necessarily perfect, but pretty close), the other end of the panhard rod will be swinging in a side-view arc as opposed to a front-view arc. Then it doesn't pull the axle sideways with suspension travel any more. It just requires careful analysis and understanding of the geometry in 3-D space.

If it's a circle-track vehicle that only has to turn one way in anger, you can probably make use of the asymmetrical rear-wheel-steering effects and turn it into a benefit, because it won't matter that it's messed up in the other direction.
That all makes sense, but does not the possibility exist of rather strange handling arise, when the need comes to suddenly dodge a slowed on track car in the groove?

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Re: Panhard Bar Mounting

Post by Brian P » Sun Dec 02, 2018 7:52 pm

Absolutely. But it seems to be rather normal for circle-track cars to be set up to turn the normal direction much better than they turn the other direction, so what's an extra bit of Panhard rod bump/roll steer?

NASCAR at Watkins Glen or Sonoma (Sears Point) is a hoot because they have to turn both directions on those tracks.

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