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Panhard bar basics??

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Chewy72ss

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Discussion starter · #1 ·
Tried the search...on several websites.

I would like to do a custom panhard bar setup on the Chevelle, but I am pretty new to hardcore suspension designs. Does anybody out there have any tips they could share to get my project started??

Here's what I know:
- The longer the bar, the better.
- Bar should sit about level at static ride height, with half tank of gas.
- One frame mount, one rear end. (Both double shear.)

...and, thats about it.

Can anybody help point me in the right direction. ...Dennis??? ha.

Thanks.
 
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#2 ·
From what I have gathered you know how it works. Dennis did a setup on his car so he might have some pics to show you. Just keep it long and level like you said. I am thinking about setting one up myself. The only problem you should have is choosing the links on the end, which is easy, and figuring out where to attatch it to the rear/car.
 
Discussion starter · #3 ·
When would I fab it up though?? The car is completely disassembled down to the bare frame right now, with new suspension on the way. After the body is back on, and the car is sitting at ride height, would I just weld the panhard brackets so that the bar is level??
-or...
Is there a certain height in relation to the rear end at which the bar should be mounted, and then adjust it so it's level???
 
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#4 ·
You should definately wait until its at ride height like you said, with a half tank of gas. You want it level so that the force is transmitted in pure tension or compression during normal right height. When the car rises or lowers the bar will move +- a few degrees. By having it be level most of the time, the degree difference is minor, so the rear will not move side to side too much. By making it longer, the smaller the degree, which means the less it moves side to side.

So just wait till correct ride height, then fab it up so it is perfectly level and long as possible.

If you are familiar with trig, then you can setup a triangle reliationship and see how much side to side movement there is for how much up and down movement there is with the rear. sin=opp/hyp and so on...
 
#7 ·
Personally I would do the fab work while the body is off because the access is MUCH easier. You can estimate what you want for ride height, remove the rear springs, and cut wooden 2x4 blocks to hold things at the right height.

The one thing I *would* have installed is the exhaust system to insure clearance.

Many PHB installations incorporate multiple mounting points for the bar to provide some adjustment. The height of the bar will determine your rear roll center after all, so you might want to be able to expirement with tuning it once the car is back on the road.

If you make the bar long enough, then you will not suffer too much if it is not perfectly level. The main driver for level is to minimize lateral movement of the axle as the suspension articulates. The long bar will do much more here than the horizontal position and is thus the critical parameter. I might consider starting with the bar out of a late Camaro/Firebird (F body?) and make mounts to fit. This could also be interesting as a starting point (but they only go up to 37"): http://www.speedwaymotors.com/xq/aspx/paging.yes/dept_id.108/display_id.2091/qx/Product.htm

These could be fun as ends: http://www.speedwaymotors.com/xq/aspx/paging.yes/dept_id.107/display_id.1534/qx/Product.htm

The frame mount that Dennis used was pretty crude. I would suggest you check into the kits for Mustangs that are out there to get a better idea of what a frame mount should look like. The Chevy rails are really very flexible back there, so I think it is important to brace and triangulate the mount to the frame rails on both sides.

And of course if you are going to the fun of putting in a PHB then you might also want to go just a bit further and convert to a 3-link setup with a single upper control arm.
 
Discussion starter · #11 ·
I have thought about a 3-link in the past. The idea still crosses my mind every now and then. I don't think I have enough knowledge of all the suspension geometry and how it works to fab my own 3-link from scratch, just yet.

Does anybody know of any books they would recommend about suspension engineering that would help me with doing my own suspension???

If I can gather enough knowledge about suspension (i.e. 3-links) to the point where I am comfortable with doin' my own setup, I'd definately give the 3-link/panhard bar system a shot.

I've heard that SC&C is developing a bolt-in 3-link for A-bodies. Anybody know anything about this?? I'd still probly rather do my own, just for the whole pride/bragging rights thing.
 
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#12 ·
It really isnt that complicated once you see some pics. Have you tried a search? I know there was a picture just a few weeks back I saw.

And sorry about that last post where I assumed you wanted a three link. I have since changed it, but I agree that could involve a little more fab work. Anyway I found a pic. I dont really think the panhard bar is neccesary though. I dont get that much side to side movement back there with the new bushings in, except for tire wall.

That pic is worth 1000 words. See how it is level and inline with the rear.

BINGO!
Image

For copyright purposes(not my car) I believe it is Denny's and he is fairly comfortable with suspension design, to say the least...
 
#13 ·
Yep, that picture is of Denny's El Camino and is not what I would call an outstanding example. Functional yes but not outstanding ;-)

On the stock A-body rear suspension the upper control arms serve both to control axle torque forces AND lateral axle movement. This why they are angled into the center forming a triangle. The point where they meet determines the rear roll center, which is quite high.

The angled layout also means that they must be allowed to move and flex a bit to accomodate the multiple planes of movement. And is why hard bushings, like poly, are not recommended for the upper control arms. But because the design requires flex it is not able to do a very good job of locating the axle. On a similiar design lateral movement of up to 1.5" has been measured during operation. Compare that to a PHB, I believe Denny claimed to be able to run 1/4" tire to fender clearance without rubbing?

The PHB being a lateral axle location device removes the requirement for the upper control arms to provide that function. Which is why many OEM designs with PHBs use a single upper control arm in the 3-link configuration. One concern with running the stock converging 4-link setup with a PHB is that there could be competition for lateral location of the axle between the two different roll centers. The result could at the least result in some binding and at the worst force overloads and part breakage. Denny did not note any issues but he kept the roll center fairly high (reduces the distance between the two roll centers) and had not run the setup very long. Last I heard his El Camino was up for sale.

SC&C is reportedly developing a 3-link setup for A-body cars. As a basic start to some of the concepts involved in a 3-link design you might check out the Fred Puhn "How to make your car handle" book. There are others... some might even be better... but that is what I have on my bookshelf :)
 
#14 ·
Vroooom has excellent points. The upper control arms could slightly interfere with the PHB in certain suspension scenarios. Denny also had a very low and stiff suspension setup, so I doubt there was much movement in there.

Looking back, unless you go 3 link, I say just stay with what you have. Install a swaybar and new bushings, good shocks, get it lower, and your car will handle very well. The stock 4 link can be put through its paces pretty well.
 
#15 ·
Herb Adams "Chassis Engineering" is a pretty good beginners book... Lots of good diagrams and formulas, just don't take some of his theories as gospel. ;)
 
#18 ·
Keep in mind that Denny's El Camino was very (VERY!) low to the ground and that made his mounting much easier. Take a look at mine for a basically stock height example. It's not as easy as it sounds, expecially if you want to run full exhaust. Dennis could also run close tire gaps because he had very stiff springs as well.

Ryan
 
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#19 ·
Thats a cool senior design project! I will be doing mine next year. I think we might have different requirements though. I will look into it, would love to do something with my car.
 
#20 ·
I was unfamiliar with the term "double shear" so I found this little tidbit for those of us who were wondering what it meant. It appears to me that the picture in Brettd85's pic shows "double shear" with his phb. :)


As it happens I used double shear when installing my rear sway bar. I put tubes and hardened washers on the inside of my LCA's so that the through bolts wouldn't crush the control arms since they are not boxed.


http://www.roymech.co.uk/Useful_Tables/Screws/Bolted_Joint.html
 
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