Opinions on my panhard bar setup, please.

I posted this on another forum and was told by one member that 'it's the worst case of bad engineering he's ever seen!' Here's his quote.........................

I've seen other setups at about the same angle and length so I thought it was alright. Did I totally screw up?! What say yee?

 

It would be a little better if it were longer, but the fact that you have the axle moving through the center of the arc that the end of the panhard rod travels is good. It could be better, but it is not all bad. This from a guy that has been doing this for 50 years.

 

yes, it would be nice if it was longer....but i wouldn't call it the worst engineering i've seen. i think you will be fine

 

This will work, but it will work better with stiff suspension. Believe it or not, if the car were to hit a decent bump, and you have designed in decent suspension travel, it will kick the car sideways.

Stock '51 Olds kick sideways over a decent bump, and their panhard bars run from left side fully to right side.

So, what to do??

Watts link. Or, modified Watts link (see late model Nissan Sentra rear suspension).

But, realistically, most modified cars don't have the suspension travel to worry overmuch.

Cosmo

 

As long as it does'nt bind rear end movement or try to pull or push axle sideways as it moves up and down should be good. That are some of the problems with a short bar.

 

it will work----built well--looks sturdy---stay off that other site

 

It looks like you are still just tacked to the housing. You might consider grabbing the D-side tube with a clamp (see Speedway's) to get longer arc. Also avoid heat distortion to flange area and tube

 

If the picture shows the set up at ride height, then it isn't the best way for it to be set up. It would be best if the bar was parallel at ride height. The reason being is the same as a drag link on your steering...bump steer. With the bar angled like it is, when you hit a bump, this bar will cause a little bit harsher reaction to the compression then it would if it were flat/parallel and it will cause the rear axle to shift sideways, towards the drivers side.


Now this will be minimal, but it will be. If you start with the bar parallel, then it would be neutral in state and as suspension compresses or rebounds it will react easier with the arc of the panhard bar and it will still cause a shift sideways it will not be as noticeable. If you disconnect the springs and shocks, you can easily move the axle up and down to simulate compression and rebound and you will be able to see how the axle will travel sideways due to the arc of the panhard bar. This will also allow you to check suspension bind if there is any. The longer the bar, the slower the effect that is why a longer bar is best, but a short will work. My suggestion would be to make sure the panhard bar is level/flat/parallel at ride height to start with.

 

Here's how I set mine up..following the advice of having the bar as long as possible...also, tried to have the bar parallel to the axle axis when at finished & loaded ride height.. On the last pic ,the bar is slightly angled . After I installed the body,fuel, and my fatass its parallel

 

x2

 

The shocks appear to be fully extended indicating the rearend is hanging even though supported by jack stands. That being the case, the housing tube when at ride height once experiencing a bump may come in contact with the panhard mount on the frame. Id move the frame side mount on the frame instead of in the notch and a longer bar to a raised mount on the other side housing end. Not that this setup wont work, jus could be done better.
What kind of control arms are those? I assume it loops under the tube to the rear mount to control the roll of the housing, otherwise you would have some form of upper control arm.

 

Blah, Blah, Blah, lots of repeated internet info here. If you were road racing or circle track racing, as long a panhard bar as possible would be nice, but in your case, it will be fine.

 

I like the panhard bar to be slightly downhill at ride height, as it moves through the arc it will level itself, and then be slightly uphill at full travel. If you started with level, then all panhard travel will pull the rear in one direction more.
I'd like it loger also, but I've ridden in friend's cars with a similar length and they didn't handle badly on hard bumps.
Some of the guys on that othe forum have a lot of knowledge, but seem to think their opinion is the only answer to any question. I wouldn't worry about his reply.

 

Getting away from Trad Hot Rods to my other money sucking hobby which is vintage sprint cars. My advice would be to follow standard practice with them. Make the frame mount point adjustable verticaly . Either by a sliding mount or say three holes about 1 in apart in the bracket determined at normal ride height with the bar parrallel to the axle centerline. The bar is also adjustable like a tie rod which lets the car ride really free when it is setup.as there is no bind at all on the at your nuetral position. THe bar can be dropped and reinforced to clear the pinion to stay long and on the axle c/l if you wanted.

 

While I can't see the pictures of the bar, simple fact is that while MANY do it incorrectly and live with it, it IS better to do it correctly...geometrically speaking..!

1. The bar "should" be about parallel with the ground at ride height.

2. The frame to axle mounting points "should" be as far apart as possible.
That is, the bar "should be mounted to the frame on one side as close to the frame (side to side) as possible and to the axle housing as close to the opposit side as possible.

Pretty simple really.
These little 18"/24" bars..provide not so stable handling. yea..I know..all the experts say the short bars work fine..
WHY do they say this...because they have no "better" referance to draw from...!

Just do it right, you'll be MUCH happier, down the proverbial road.

Mike

P.s. - if the car's a show queen...then short is fine..

 

The shorter the bar, the shorter the radius/arc the axle travels through when the axle moves up and down. Having a super short bar will cause the axle to move noticeably side to side as the axle moves up and down defeating the purpose of a Panhard bar. When the bar is closer to the length of the axle, the radius of travel is greatly increased and it causes almost no side to side movement. It is very similar thing with a front axle that has split wish bones. If you have super short split wish bones, then the axle rotates sharply backwards as it travels upwards causing the caster to change severely and adding more bump steer.

 

You know how it "should" be done. Building it that way is not a whole lot harder than building the way you have it mocked up(?) right now.

Ask yourself "Why should I be happy with something less than the best design when it is almost as easy and cheap to build it that way?" Looks like you are putting alot of work into that build, is this the place to take shortcuts?

 

It looks to me by how the frame is built that the rear end area is not going to me exposed so a long panhard bar will not be noticed. It also appears that the frame mount is on the wrong side. If it was me I would like to see it long and parallel to the axle housings even it you have to built a rearward tower off the axlehousing to clear the gear housing . This would accomplish less measurable arc and a lower roll center. Just my two cents for whatever it's worth.

 

I dpn't have an opinion on that particular panhard bar. I like mine to be parrallel to the axle at rest or ride height. I also like mine to be as long as possible. Longer smoother arcs are good.

 

As others have said the longer the bar the better it will work, Can't tell from your pic but the chassis mount for the panhard bar should be on same side as the steering box.

 

Actually I was playing with cars long before the internet. Don't judge me by your knowlege please. I didn't give him an opinion on his setup nor did I parrot someone else. I just told him how I liked to do mine.

 

You can't cheat physics i'm afraid.

 

1) Horizontal at normal ride height minimizes axle lateral movement with suspension travel. Sometimes compromised a bit (slight downhill from frame to axle with light load so that it'll be closer to level with a heavy load.)

2) the longer the bar the less lateral movement of the axle with suspension travel.

3) Roll center is where the bar crosses the center of the axle, if you're running other suspension members (e.g. parallel leafs) that try to locate the axle in roll you need to be sure they're mounted softly enough not to fight the Panhard.

The pictured bar will have a pretty high roll center and tend to move the axle sideways a lot.

Are those characteristics desirable/undesirable/tolerable in this specific application? I'll leave that up to the builder to decide.

 

Yah, what JEM said . He explained it much better then this old farm boy.

 

Echo

 

Pretty much do what everyone has said above^ make it longer and level with the ground at ride height. By the looks of that notch the panhard bar is the least of your worries

 

You probably already have it covered - and you haven't said what your steering setup is but I see in the pic above your panhard bar is anchored to the RH chassis rail.

Which is all good if you are using cowl steering or a push pull steering setup but as I understand it if you have a cross steering setup (ie like vega box in its original configuration then the panhard bar hould be achored on the same side as the steering box.

That way the steering and the panhard don't work against each other on opposite sides of the vehicle.

Appreciate that was not the question you asked - but might be helpfull to others reading

Cheers

 

Longer would be better but range of travel plays into that. Only real concern I'd have is the placement of the pivot high and center on the axle. Just theory but could possibly torque steer with a healthy motor?

 

Well, alrighty then.................. First off let me say that all opinions are read, evaluated and GREATLY appreciated! As suggested, I removed the coilovers and ran the suspension through it's arc of travel from the point where the coilovers bottom out to the point where the panhard bar housing bracket actually hit the bottom of the crossmember. I measured the lateral movement of the housing and at midpoint it moved 3/16" and then returned to normal at the highest point. There was no suspension binding whatsoever through the entire arc. Next I reinstalled the coilover and wheels and had my 6'3" 275lbs grandson sit on the rear crossmember to somewhat simulate the weight of me, my wife and 10 gallons of gas. The panhard bar was still at an angle, although not as severe as the pic shows. Next up is to get my 325lbs brother-in-law and grandson to sit on the x-member. That outta flatten out that panhard bar!

The only other concern I have is the point that acme30 brought up. I am
running a cross steer setup so ideally the bar should be mounted to the drivers side. Anymore thoughts on that?

 

My .02.. 3/16" is a bunch of steering correction especially if it's short wheelbase car..you'll be "chasing" straight ahead everytime you hit a bump OR accelerate or decelerate.. please , listen & make it longer & pivot from the same side as your steering pivots..
dave