How to build a panhard rod--my approach

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GoldHawg
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How to build a panhard rod--my approach

Post by GoldHawg »

I'm going to use this thread to describe my approach to detail one way to design a panhard rod for those that may want to do this as well. The first question is why would one want a panhard rod at all? I wasn't sure myself and asked about this on this thread earlier:
viewtopic.php?f=3&t=33010
If you watch RCMike's video, that showed how potentially it could be useful. I think that this solution is only for those that have 1) very wide tires and are close to inner fender contact, and 2) intend to go thru curves very hard. Clearly RCMike is driving his cars way harder than almost any of us. But I'm going to run 205 50 15 tires, and even with my narrower RX7 rear end, I'm a bit concerned that in hard driving I might have issues. Probably not, but maybe. And in my resto I want to do anything that requires frame mods to be done before powdercoating. So, now's the time to do it.

I am basing my design on a similar concept used by Maier Racing for Mustangs,
They have two components that I have to make something analogous, a bracket for the driver's side that replaces the lower leaf spring bracket, and a bracket for the passenger side that is welded to the frame. The also have the panhard rod itself, and another bar that connects to the opposite frame rail. Since our Datsun's already have that cross bar that the shocks mount to, I don't see any need for an additional bar. One thing I don't like about his design is how long that passenger frame bracket is. Seems like it might get in the way in the future when maintenence is underway. My design will be a simpler two part piece.
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GoldHawg
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Re: How to build a panhard rod--my approach

Post by GoldHawg »

Rather than go with the complex design they had for the lower spring mount, I made a design on Fusion 360 that is made out of 1/4" plate that will be plenty strong to deal with the loads it will see, so a bit less welding. I'm in the process of reading some entrepreneurship books (latest is Eric Reis The Startup Way) and key for new businesses is experiment and test w/a minimum viable product, and get customer feedback early on (another reason to post here--get your feedback and ideas). Well, I'm the first customer so have to build something. But the bracket went thru several mods, the first being I had incorrectly modeled the build based on the Ridetech R-joint endlinks (the bar I'm going to use), which I thought were 1.25" wide. But the total size was actually 1.75", so I paid a few hours time by not more carefully discussing with their tech. So this is my first design thought:
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GoldHawg
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Re: How to build a panhard rod--my approach

Post by GoldHawg »

But with the error, needed to change the design; fabbed a 1.75" steel spacer to go with the 5/8" bolt hole size. So here is the next attempt:
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GoldHawg
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Re: How to build a panhard rod--my approach

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I started to have some slight concern about the spring contacting in the rear part where there was a gap. But I decided to head to the passenger frame side. In my mind, I thought the easiest way to have a two part bracket was to use a piece of 3/16" thick square tubing welded to a bracket that would wrap around the frame. I was following the lead of Maier racing as they wrap their weld around the frame, and honestly I haven't been super impressed by the stock steel frame as it has layers of thinner metal. Spreading the load around seemed to make sense, and using the CNC plasma, I cut out a number of holes that can be plug welded once final in position done--should be quite strong. I used the Mig Welder for this; I really love my Millermatic 211 and highly recommend it. This is first prototype; I had to weld some add'l metal to get to the requisite 1.75" thickness. Idea is to have two grade 8 1/2" bolts that will secure the lower bracket to this bracket. The lower is removable if desired during other work.
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Last edited by GoldHawg on Tue May 05, 2020 6:24 am, edited 1 time in total.

GoldHawg
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Re: How to build a panhard rod--my approach

Post by GoldHawg »

Lots of ways to fabricate this, but I happen to be blessed with a small CNC plasma. I'm interested in learning more at machining to be as efficient as possible, and while I have a nice drill press, it would be a ton of time to get the holes in my square tubing perfect. And I wanted to have it just perfectly at .5"; so the bolts will have no slop. So I built a jig for the square tubing with a perfect 90 deg setting, and could set the part in the CNC machine and zero out at the first hole. Now its not perfectly accurate, because 1) I have to measure and scribe it, and 2) I'm eyeballing as best I can where the center of the arc will come out. So I cut the holes at .45, and then finish up in the drill press. With the jig in place I can just do one side, flip it over, and then repeat. Even it slightly off side to side, then going thru the drill press will get them exactly centered. I made enough that I could do for others if desired (another reason to use plasma as I did 7 units). These are 1.75 OD, which will do what I'm interested in doing as the design progresses. Went ahead and tacked this one in place.

Now for those trying to do this at home, if you can become somewhat proficient at some of the drawing programs to create a DXF file, you can send that out and someone can make it for you. When I need more accuracy, there is a local shop with a million dollar fiber laser machine that will do work for me. Now there is a $100 set up fee but after that its cheap...
Or you can do this with a drill press (although the lower spring mount would be a good bit harder to do) and an angle grinder w/flap disc. You can always trade labor time to eventually get to the same result.
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Last edited by GoldHawg on Sun May 03, 2020 9:28 am, edited 1 time in total.

GoldHawg
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Re: How to build a panhard rod--my approach

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Now back to the driver's mount. After being concerned about the possible spring contact with the bracket, I also realized with mocking up a bar across that the bar would sit lower than I'd like. I wanted to get it closer to the axle tube itself. So the new design eliminated the spring potential contact, and increased the height of the panhard mount. I'm still not super happy with the angle of the shock mount; you can see I bent it a bit too much, and I will straighten it some. Very difficult to get the right bend as it has to be twisted in addition to being bent down to match the stock angle. If I ultimately don't like I could weld on a tab for the shock mount instead, but that would be a more time consuming process.
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GoldHawg
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Re: How to build a panhard rod--my approach

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Turning back to the final mounts. Originally, I was going to take two pieces of 1/4" plate and cut several holes for adjustability like Maier did, and then weld a 2.25" piece on the lower part to keep from flexing. A wiser friend counseled against that--why bother welding with the force is lateral, and the bolts and the rod end itself will keep this thing right where it needs to be--no flexing. So I build my first pair based on how much sag I expected, but that ended up too short. Once I jacked up the rear to the point of picking the car off the lift, and my 250 lb friend did a pull up to try and load the frame, and we only compressed the springs maybe a bit over an inch. I decided to make a version about 1.5" longer, and that is about just right. Has three positions for adjustability. Now I have to wait for my Ridetech panhard bar to come in--since its powdercoated and custom, it will take a couple of weeks. I will be putting this setup on my friends running 69 that also has 205 55 15 tires. When the panhard rod comes in, he'll use mine for the test vehicle. The bar will be 27" long, and with the short compression, there will not be much of an arc. I think the rubber in the leaf spring mounts can handle that w/o binding but we'll see how it feels.
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RCMike
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Re: How to build a panhard rod--my approach

Post by RCMike »

My two cents?

Where it is possible to ad a rib, or box it, etc, do it. I know where the forces are SUPPOSED to go.. but they seem to find a way to go where they want.lol

But I really like the look of this set-up! good work!

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Alvin
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Re: How to build a panhard rod--my approach

Post by Alvin »

Try a before/after video test to confirm that the panhard is doing its job properly.
In the videos below, a GoPro is attached for a through-the-leaf spring eyelet POV.

You can see how much the leaf springs move laterally without the panhard



Video Without Panhard Bar Sharp Turn and Swerve Test 1


Video With Panhard Bar Sharp Turn and Swerve Test 2


For reference:
https://www.lightningrodder.com/threads ... ad.394436/
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Gregs672000
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Re: How to build a panhard rod--my approach

Post by Gregs672000 »

Wow, running the videos together really shows the difference even more.
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GoldHawg
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Re: How to build a panhard rod--my approach

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I need a go pro!

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notoptoy
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Re: How to build a panhard rod--my approach

Post by notoptoy »

Wow, that is one illustrative set of videos. Thanks for posting Alvin. Now it's also much easier to see how much work the bushings do and why they would wear out. Would be interesting to see this with standard and urethane bushing as well.
"When all else fails, force prevails!" Ummm, we're gonna need a bigger hammer here.

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GoldHawg
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Re: How to build a panhard rod--my approach

Post by GoldHawg »

Got a box this afternoon...WooHoo! When my 250 lb friend sat on the back, it was almost perfectly level. I really like this. Now to install it on an operational vehicle.
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RCMike
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Re: How to build a panhard rod--my approach

Post by RCMike »

Have you checked the clearance on the e brake hardware? Assuming that fits, this is REALLY nice.

GoldHawg
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Re: How to build a panhard rod--my approach

Post by GoldHawg »

No go...this may be just a mod for me. I was worried about the e-brake rod on pumpkin, but hadn't pictured it with the mount on the passenger side. Almost no room there. I put my friends on the lift yesterday and discovered the difficulty. I don't have a stock rearend, nor am I going to use rod activated e-brake linkage. Long story maybe for my build thread but since I didn't have the brackets that go with my GSL-SE calipers, I made a bracket that allows me to go to 11" rear disks (not that I need it) but it gives more room to hook up dual e-brake cables.

It might be possible to have the bar sit lower, and flip the mounts passenger/driver side. But I'll have to get creative to avoid the exhaust tubing on the driver's side.
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