Simple Hot Rod Tech...Making a Rear Panhard Bar for a '32 Chassis

How about some simple rear suspension fabrication/ tech?

I just finished up the bulk of the remaining work needed to complete Bubba Luv's Dirty31-built '32 frame for his '31 Model A Coupe, to make it a rolling chassis ready for the body to go on.

As I was running brake lines, etc...I noticed that the rear spring shackle angle was less than optimal. Grabbing one of the frame rails at the rear crossmember and giving it a push/pull, it was apparent that a panhard bar would be needed. Without a panhard bar, the shackles were going to allow the back of the car to sway back and forth, resulting in a not so great ride among other things.

Re-arching the spring, changing the spring, or moving the spring hangers wasn't an option, so we need a panhard. Here's we're we begin:




First off we need a piece of tube. I ordered a 36" piece of .156 wall, 7/8" O.D. DOM tube... aka 5/8" tap tube. This is a common size that is pretty readily available...but if your area is like mine, it's easier to order it online. I typically use lefthanderchassis.com.

Now that I have the tube, it needs to be tapped 5/8-18 on one end. I take my tubing to my local machinist to have this step done...which just so happens to be Bob Wilson of Wilson Welding. (Buy Bob's brakes!)

Here's what I have after Bob runs a tap into the tube on his lathe:



Next I need to make a threaded rod end to go into the end of the tube Bob just tapped. Here's the required parts for the next step...bird dog is optional.



The bushings are TCI, which take a 5/8" bolt through the center eye. I bought the TCI weld-on sleeves that are essentially just a piece of properly sized DOM tube, at the same time...mainly to save a little fab time.

To make the threaded rod end, I used a 5/8-18 bolt with about 2" of thread...and one of the TCI weld sleeves.



I cut the non-threaded portion of the bolt just above where the thread stops and weld it to the tube. Take extra care to get everything perfectly centered before welding together!



And here we have a freshly made adjustable rod end, ready to screw into our freshly threaded piece of DOM tube. Don't forget the jam nut!



Now that we have the adjustment for the panhard bar out of the way, we need to figure out how to mount it to the frame rail. I chose to mount it directly above the center of the rearend housing to keep it close to the rear crossmember...mainly for packaging reasons..I.E. simplification of trunk floor.

With location decided upon, I need tabs to mount the frame-side end. I made a posterboard pattern for the tabs.



With pattern in hand, I use the trusty plasma cutter to whip out a couple of tabs out of 1/4" plate. After clean-up and one 5/8" hole in each tab, they're ready to weld.

I tack the tabs to the boxing plate, making sure that I get the through-bolt parallel to the spring hanger eye. This will prevent binding in the movement of the rear suspension.



With one side now tacked to the frame, I need to decide where the other end is going to attach to the rearend housing. It's widely agreed upon that you want to make the panhard bar as long as you reasonably can, which is going to be the case here.

In order to do this, the panhard is going to have to go directly across the top of the 9 inch housing and clear the pumpkin in the process. This means that if I want the panhard to be parallel with the rear crossmember (level) at ride height...then I'm either going to have to have a really tall mounting point, or I'm going to have to put a bend in the panhard.

I chose the latter...and got out the rosebud to heat the point of contact between the panhard and the rearend housing. I did this with the tube in a vise.

Here's the result:



Clearance bend out of the way, I now needed to simulate ride height to get the panhard bar level with the rear crossmember in the center of its range of adjustment.

I backed the adjuster off until it was centered, and had two friends come over and stand on each side of the frame. I figured there would be roughly another 1000 lbs on the car, so two guys totalling about 400-500 lbs should be about right for weight distribution. I then blocked up the axle-end of the panhard until it was level, and took measurements for mounting tabs, as well as marked the tube for cutting.

After cutting to the appropriate length, I quickly "fishmouthed" the end of the tube with a grinder, like so....



Now I can weld the sleeve directly to the tube, being extra careful that the two pieces are centered and aligned perfectly. I only wanted to have adjustment on one side, but if you wanted adjustment at both ends, you would simply tap this end of the tube and make another threaded rod end.

Tacking the sleeve to the tube:



After fully welding the joint and installing the bushing ,the panhard bar itself is complete. Now we need mounting tabs for the rearend housing.

I made these the same way as the frame tabs...pattern, plasma, grind, drill.



To get everything in proper alignment, I use a degree finder on each end and adjust the tabs on the rearend housing until the degrees match.



Here we have the tabs tacked to the housing...you'll notice that the panhard is pointing slightly down.



Before fully welding the tabs, I leave everything tacked together and articulate the suspension to make sure everything is going to work as it should.

It is very important to take your time when welding the tabs to the housing! I go slowly and move around so as not to get the housing too hot, while being sure to get good penetration.

I use a clamp and a piece of tube cut slightly longer than the rod ends to create a temporary fixture while welding...



After the frame tabs and housing tabs were fully welded, I made a simple gusset for one side of the housing tabs. Probably not absolutely necessary, but it can't hurt.



So that's it! Here's the finished product...simple, strong, and functional.



Total expense for parts was about $50, not including tapping one side of the tube. It could possibly be done even cheaper if you're really resourceful.

This isn't what I'd call a univeral application, but it seems to fit and work well in the '32 chassis with the 9 inch rear. Thanks for looking!

-Brian

 

Said it before, and I'll say it again; Bass, you're doing reaaalllly nice work!
Been watchin' earlier those pics of frame(s) you've made, really nice details there!
And unbelieveable welds!

 

Nice

 

Brian thsta EXACTLY how I did my panhard rod in my Deuce frame dude, bend and all - to the letter !!

Freaky !!

Nice work as we've come to expect from you !!

Rat

 

Nice work.

I hope some young builders will see this kind of work and know that is what they should be striving for.

 

Beautiful and functional. Great tech, very timely for me.

Thanks.

 

Is this always needed in a setup like this with transverse spring, and Pete and jakes style ladder bars? Ive seen it run with or with out, and Im trying to figure out if I'm gonna need it on my 32 chassis.

 

Several years back we had a conversation here on the HAMB about panhard bar required with a transverse spring in back.

Several very knowledgeable guys joined the discussion and there was a consensus that it was required.
Fwiw one of them is an engineer for a major auto manufacturer and a helluva smart guy.


A comment was made that it'll work without it, but be considerably better with it.
Especially so since the car it was going on was headed for the dry lakes.

It's a street roadster now, but the panhard remains.

I recommend a sway bar as well.


Nice work Mr. Bass.

I'm curious why you didn't come a little further forward with the panhard and avoid the bend?

It'll work fine where it's at, just got to wondering.

And I do realize there can be a lot of packaging problems to overcome when you start packing in a lot of stuff around the rear axle.

Funny thing is my 32 has the panhard in front of the diff and the 31 has it behind the rear axle pumpkin area.
Just misses the pumpkin when it bottoms out, but it does miss.

 

I'd say no....if you're shackles are close to 45 degrees or so at ride height, then a panhard bar isn't absolutely essential. At the proper angle, one shackle sort of counteracts the sideways movement of the other.

However, a long panhard bar doesn't really hurt anything other than taking up a little space, so it's not necessarily a bad idea to include one in the build plan.

As stated, mainly just a packaging solution. With the rear crossmember, upper shock mounts, and panhard all in about a 10" span, it simplifies fabricating the new trunk floor.

 

Is the panhard going to clear the housing at full droop? The clearance between the housing and the bar looks tighter than the housing and the C-notch (hard to tell without all the weight on the rear).

 

Its the little, simple things, often overlooked, that make good things great. Nice, simple, execution...

 

Yes, clearance is more than adequate...there isn't enough travel for the panhard to contact the housing. Simply put, the spring won't flex enough for that to happen on this car, even under the most severe load. After all this is a buggy sprung hot rod, not a trophy truck.

That may be true, but the C-notch is much taller than it needs to be. These '32 rails apparently come with the C-notch made into them, so it's not exactly tailored to this particular application.

I didn't do the fab. work on the spring hangers, but they would actually make contact with the frame before anything else. Again, the likelihood of even that happening is pretty much nil because of a lack of spring travel.

 

Beautiful, simple, well thought out. Very nice Brian

 

I'm striving man I really am. Sadly no tig welder for now. Tig welds make clean bracketry look so good.

 

Looks good

Now showbody me how to do one for the front of a '46

 

Great tech!! Thanks for posting.

 

The work looks very nice.

I see you made a point to make the bar level before the bend, I guess this is for aesthetics? They way I have always understood making a panhard bar "level" was the invisible line between the two pivots. Every one I have installed I have strived to make the pivots as close to level with the suspension is loaded, even if that meant bends int he bar making it look un level.

What you have will absolutely work, but its not technically "level" in my opinion (which isn't worth much).

 

One again Bass nice work and welds are off the scale. Hope to be able to have my welds look like that.

 

It would make me feel so much more satisfied with my own shit if people simply didn't publish photos of welding like this:

 

great simple tec!!! oh how ya doing brian ?

 

AMEN !!

 

bass,
nice work as always. cant wait to see it hit the road.
Al.

 

Brian, that's nice fab, I hate to be a wet blanket but it's my understanding that a panhard should be as long, straight and close to horizontal at normal ride height as possible, longer makes for a flatter arc and less side to side travel and bends simply bend.
Also I can't see how welding the bracket on the axle tube hasn't bent it unless you did an equal amount of welding opposite and ground it off
-Andy

 

I've always thought that too, a Panhard Bar should be straight, and when the car sits at ride height, the bar should be as parallel as possible with the ground. Maybe not? I've never seen a Panhard bar with a bend in it before. I don't see why it can't work though.

 

Ford managed to avoid using Panhard bars earlier than 1942 by mounting the springs in tension. Ever heard of a Ford spring-spreader? When the springs are mounted in tension they act as a Panhard bar.

The secret to reducing the need for Panhard bars on Ford-based suspensions is quite simple. Simply duplicate the width between the spring perches based on the spring you are using, front or rear, i.e., if using a 28-34 Front spring the perches should be (X)inches apart duplicating the Ford factory dimensions whether the spring is mounted over the axle or in front or behind the axle. This will require spreading the spring to install it with standard shackles. Unloaded the shackles will be parallel to the ground in most cases, then drop to the 35-45 degree angle generally accepted as "right" when loaded. With the spring in tension a Panhard bar will generally not be a necessity unless you're building a serious road circuit racer.

The factory Panhard bars (or track bars as called by Ford) for 42-48 Ford Passenger cars (the first use of them by Ford) were non-adjustable, rubber-bushed, and have stock bends in them.

In 42 Ford started mounting the springs untensioned like later models and lengthened the shackle bars. This allowed the chassis to sway on the shackles and necessitated installing a Panhard bar (or track bar) to eliminate the sway. SO Ford gained the public-demanded smoother ride without having to completely redesign their suspensions.

 

All the bends I've seen in OEM applications are a compromise, a straight horizantal bar pulls the axle towards it's pivot up or down, Brian's pushes up and pulls down, probably not such a big deal but such a big bend near doubles the amount of side to side travel.

-Andy

 

Heres what I did to get ours to clear without a bend, same thing only different. Nice job!

 

Yep, bent = pre-buckled....if the bar must be bent, it has to be stronger than would otherwise be necessary if it was straight.

I also hate to be a critic, but that frame tube holding the rear spring doesn't LOOK strong enuff to me....

 

I drew a straight bar about the length of Tinman's, it moved 5/16" horizontal over 5" vertical travel up and down pulling on the bar both directions. Then a bent bar the same horizontal length but with a drop like Brian's, It moved slightly more horizontally 5" up but pushing on the bar instead of pulling, 5" down however it's trying to pull almost 1" horizontally.
If Tinman's bar were 8" longer it would only move about 1/4" horizontally over the same vertical travel.
-Andy

 

Fantastic workmanship, Bass But I have to agree with ehdubya on this one,The bar should be mounted horizontal at ride hight and be as long as practical.Allthough the bar looks horizontal its not as your two mounting points are at different hights,Therefore the bar is infact mounted diagonally.Just my 2 cents worth.