Panhard Bar

[Trevor Jessie]

I'm a complete novice when it comes to material science. For a panhard bar do I need a very strong tube. Will something like .065 wall 4130 3/4" diameter be appropriate? What would be the minimum you would use for an aggressively (street driven) 1/4 elliptical spring car.

 

[jlaird]

Wait wait. I'm not 100% sure but think a panhard bar on a 1/4 elliptical car is no good especially on the street or when you are turning both ways.

Which wheel do you want more pressure on? Which one is spinning when you turn? LOL

 

[aeronca65t]

I'm not sure.
The 4130 isn't much different from 1020 (carbon steel) in applications like this.
The thin wall you spec with the small OD may result in "tall column buckling"...since 0.065" is pretty thin (in my estimation) for a working member in a jolting tension/compression situation..

For reference I built a panhard rod using normal, cheap ERW carbon steel tube "just to see" if it would work. Mine is about 1.0" OD and 0.125" wall.
Mine was sort of an experiment copied from the pictures at Peter May Engineering. I did not even bother to put LH and RH threads on the bar (I just used two right hand rod ends).
I figured I'd do a better one "someday".
But you know how it is?....So far so good.
The "experiment" works fine, "someday" hasn't come and it's still on the car. :laugh:

Peter May sells a unit for 1/4 elliptical cars.
You can see it on this page:

https://www.petermayengineering.co.uk/specialistProducts.htm#2.23

Here's mine (semi-elliptical car).

 

[Trevor Jessie]

I asked specifically about the thin wall 4130 because it is sitting in my garage, left over from another project. They are not terribly complicated so I may do like you and make a cheap one and then decide how/when to improve.

I may have gone too large on tire size and I get a slight bit of rub when taking a fast turn, so I'm hoping to eliminate the lateral travel of the axle.

 

[aeronca65t]

Yeah, when my car had its original ('78) square rear fenders, I added the panhard rod to control rubbing more than to help handling. But it makes a useful improvement in handling too.

Later (after a crash at Watkins Glen messed up the back of the car anyway), I "radiused" the rear fenders so they looked like the RWA-style on my '72. Now I have lots of outside room, but the inner tire clearance (to the leaf spring) is still tight. Panhard rod makes no difference to leaf spring clearance.

As for using stuff "laying around" (like that tube), I do that all the time. You really don't have much to loose, so why not?.
The "tripod" part will probably be OK with the 0.065" tube. But the actual long, skinny panhard rod may bend. I'd say give it a shot.
Not sure if that tube will have enough "meat" to allow a thread to be tapped into it. You'll have to experiment to find that out.
G'luck!

 

[mccalebr]

My understanding is that the panhard bar will be effective on a quarter elliptic, whether race or street. The Bugeye I sold to folks in California had the bar from Winners circle:

That's the same one I'm installing in my stree version (the Spridget Project):

Ray

 

[jlaird]

How in the world can a 1/4 eliptic rear end go from side to side. Those flat springs can not move that way as short as they are.

Someone learn me please. I just don't see it except maybe at extream speeds on the track and even then would expect with good bushing for it not to be hardly measureable.

Now, if it is coolness, heck yes have a bar.

 

[Trevor Jessie]

How does it move? Dunno, but it does.

 

[GeeBee1]

Jack

It does move under cornering, realize that the only connections are in the front. The springs, trailing arms, and shocks (for whatever there worth). On a half eliptical there is alot less side to side flex.

When putting larger wider tires and a power upgrade it is more common then one would expect to get some rubbing. I have installed the setup from Speedwell and am very happy with it. It is the tripod design and does make a noticeable difference in the flexing of the springs.

If you are running a stock engine/slightly modified with standard rims/tires and a stock rear suspension, on the street then they are really not needed.

Since I have wider tires, softer springs, lowered the rear and a 90 something (flywheel) engine, I found it a necessity.

 

[jlaird]

"If you are running a stock engine/slightly modified with standard rims/tires and a stock rear suspension, on the street then they are really not needed."

That was my point, raceing or really modified cars every little bit helps.

 

[Trevor Jessie]

I dunno Jack I think it would help on a stock bugeye that some one put too wide of tires on. Regardless of the engine you can still take curves fast enough to induce tire rub if you have a little taller/wider tire (don't ask what size tire I'm attempting to run).

 

[GeeBee1]

Trevor,

We have a modified 948 with 155's (standard offset) on it and I never recall it ever rubbing.

For the few times that may come into play, I wouldn't think it worth the cost.

Unless you put a huge pair of gumballs on the back with some offset issues. Then again if you were to do that then maybe the logic of cost just flew out the window :wink:

 

[Trevor Jessie]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Unless you put a huge pair of gumballs on the back with some offset issues. Then again if you were to do that then maybe the logic of cost just flew out the window[/QUOTE]

...umm ... have you been peeking in my garage? :wink:


It is not that I do not have the money to spend on a pre-built panhard bar, I just want to save cash were I can.

 

[aeronca65t]

I'm running 185/60-13" ~Toyo R888s~ on stock, Rostyle Midget rims.

I'd prefer to run 175 width, but it's not available.

Normally I use a 3/16" wheel spacer to keep the tire clear of the leaf spring.

 

[Trevor Jessie]

Trying to run 185/60-14's on 6" wide rims with 12mm positive offset. Everything is good in the back except for rubbing on fast sweeping turns. The front tires however need about another 10mm of positive offset (or it is time for some custom flares). This combination of rims/tires really shows how much wider the front track is than the rear.

 

[JerryB]

""""" For a panhard bar do I need a very strong tube""""""
Yes. And bracketry at both ends that wont move.


Will something like .065 wall 4130 3/4" diameter be appropriate?
That will be ok. If you want to use dom then 3/4" x .083" or 1" .065"

Fab or get spuds for 3/8" rod ends and use good Teflon lined rod ends. If you use sewing machine rod ends then go to 7/16". You want the bar as long as possible. On a 1/4 housing you can come off the outboard side of the spring perch. On the chassis side you want a double shear bracket for that rod end or a really stout bracket picking up the floor sheet metal and the vertical inner wheel well. Easier locating the housing with LH/RH combination of ends but RH-RH is fine if you are not doing much adjusting. Establish the center line of the car and adjust the housing so its on the C/L of the chassis. You want to make sure that the spring bushings at the housing brackets are in good shape and use shims on each side so the springs wont walk laterally into the insides of the brackets.

"""""""""""""How in the world can a 1/4 eliptic rear end go from side to side."""
On a street car with the tiny stock tires there is not much movement as the tires dont have much grip. With tires that grip you have maybe 500 pounds laterally trying to push the housing one way then the other.

 

[Trevor Jessie]

Thanks for the info I followed all of it but this:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]use shims on each side so the springs wont walk laterally into the insides of the brackets.[/QUOTE]

Can you clarify? Do you mean where the springs mount in the axle brackets?

I have new bushings, so I good there.

 

[64rocksprite]

Jerry,
Any chance you have a picture of the set-up you are describing? I can see the value in making sure the chassis side is stout..I've read some accounts of sheet metal tearing (must be some serious cornering!)
When you say 'outboard', I'm taking this to mean the rear (facing the gas tank) of the spring perch? I've seen some set ups with a stud welded on there.
Sorry, but what is a double shear bracket? is this the "L" shaped bracket seen with the kits?

Thanks in advance!

 

[Trevor Jessie]

Double shear bracket sandwiches the rod end so that the mounting bolt is supported on both sides of the rod end.

 

[aeronca65t]

By the way, there is an alternative to the panhard rod and I've thought about it for my next live-axle race car.

Sorry, but I can't recall what it's called (old age I guess).

It involves a "giant" A-arm that is attached (by left and right side pivots) near the front mounts for the leaf springs. The A-arm "points" rearward and is mounted under the axle. At the "point" of the A-arm, it attaches (by a large rod end) to the bottom of the differential (right where the drain plug is).

This prevents left/right axle motion.

Obviously, ground clearance may be a problem with these.

They used to sell these in Summit Racing for big American cars (maybe drag racers used them too?).

I've seen pictures of them and I think Hap has mentioned them too.