What would be interesting, if there was a way to determine the lateral movement without the PanRod. I bet things would move around a bit more, and the springs might bind and cause some odd handling.
What would be interesting, if there was a way to determine the lateral movement without the PanRod. I bet things would move around a bit more, and the springs might bind and cause some odd handling.
Sky_Render wrote: Did you even watch the video?
Nope because you didn't make the video and I know how to do the calculations....
JGRAHAM wrote: I'll add some of my own setup dimensions. The Ranger's panhard bar is 24" long I have 4.5" inches of travel That means I have .1057" of side movement induced by the 24" panhard bar. My work is shown below:For curiosity sake I increased the bar too 36" (which I'd never be able to fit one that long) The side movement decreased to .071" In all honesty, driving the ranger blindfolded I highly doubt I'd be able to tell if it had a 24" or 36" long bar installed.
^^^^THIS is how you refute known information and show your statement is good enough.
My argument wasn't with your statement Sky_Render but your argument. Unlike a majority of the forums, this board isn't full of berkeleying blathering idiots (given your Super Dork status I assume you know this). A Watts link is better. We all know it, but your argument was combative and wasn't to the previous posters point. Which is a panhard bar, in this application, is good enough. 
Also you still haven't shown tire deflection. So your argument still isn't proven. 
Plus as a Mechanical Engineer I take every opportunity to give Electrical Engineers E36 M3.
This EE is wondering why we're talking about tire deflection when the issue is proper "action" of the suspension in regards to things like bind, articulation, and possibly if these sorts of things are affecting the axle wind-up that seems to be going on with this truck currently. Seems doubtful... could try a couple launches without it.
I guess we could try debating if a about .025" of lateral throw saved by a longer panhard rod would be worth building for. Maybe with a rod behind the axle which would have to stand away from the housing many inches to actually connect properly? If I'm honest, and suspension design isn't my bag, I'm wondering why the axle is wrapping with traction arms like what seems to be currently installed. There's one on each side, right?
Actually, I would argue that a panhard rod is better than a Watts Link, because it's lighter, cheaper, and has fewer moving parts and thus fewer failure points and less required maintenance.
And I did show my calculations, dang it! Also, that video showed a measurement of tire deflection during a lap around a road course. It approaches 2 inches.
In reply to Sky_Render:
so that is YOUR video????
Why does it matter who made the video? It shows lateral deformation/flexing of a tire carcass around a road course and clearly shows that it is over an inch.
In reply to Sky_Render:
Because you are supposed to show your maths for this application, that's why it matters...damn electrical engineers
I can just imagine you at work.
Coworker: "The manual says to--"
FlightService: "DID YOU WRITE THAT MANUAL?"
Coworker: "Well, no, but--"
FlightService: "THEN HOLD MY COFFEE AND WATCH THIS."
Plugs 120-V tool into 208-V outlet
LOLOLOL
Sky_Render wrote:APEowner wrote: but a Watts link is better still.Prove it. A properly-designed panhard bar has less lateral deflection than the tires under cornering.
Umm. I'm going to assume that this is coming across as more combative than it was intended.
While it is true that a properly designed Panhard bar is going to induce less lateral movement than there is tire deflection the lateral movement wasn't my point and even if it was I don't think that the amount of tire deflection is really the best criteria to use for determining what's an acceptable amount of lateral movement. The sample in the video you posted would imply that 1.75" inches of lateral movement is acceptable. That seems excessive to me.
Pretty much everything in engineering is a compromise. If it weren't then there would really be only one rear suspension setup used under everything.
Watts links are more complicated and heavier than a Panhard bar. They also have more joints and will therefore have more side play (play, not geometry induced motion) than a Panhard bar with the same type of link ends.
The reason that I prefer them in cars that turn in both directions is that you get a frame jacking motion in corners that turn towards the frame mount and an axle lifting motion when you turn the other way. A Watts linkage will be consistent in both directions.
The point I was trying to make in my earlier post is that despite its asymmetrical behavior, a Panhard bar is probably better than all of the lateral deflection that you get with a conventional leaf spring setup and that because it behaves the same in both directions a Watts link might be an even better choice.
I think you missed the point of the video. 1.75" of deflection is caused by the tires. You can't get away from that. So why would 0.05" of deflection matter in that case? It's 2 orders of magnitude less. You cannot tell the difference between 1.75" and 1.80" of deflection.
Sky_Render wrote: I think you missed the point of the video. 1.75" of deflection is caused by the tires. You can't get away from that. So why would 0.05" of deflection matter in that case? It's 2 orders of magnitude less. You cannot tell the difference between 1.75" and 1.80" of deflection.
No, I got it. It's saying that the amount of lateral movement from the Panhard bar is acceptable because it's so small relative the the tire deflection. I'm saying that it's acceptable because it's a small amount irrespective of the tire deflection amount.
What happens with the leaf spring setup if a guy takes out bushings and replaces them with bearings and slider blocks; will the panhard setup start to have problems with bind in the case we're supposed to be evaluating here?
How is he supposed to make this leaf setup hook up and turn, did a direction forward ever get found?
In MY particular case with MY own opinion is that:
The amount of lateral movement induced by the current (24") pan hard bar is not enough to justify a redesign incorporating a watts link. Even redesigning for a longer (36") pan hard bar isn't worth it. The rear end is now constrained sub- 1/8" in lateral movement and that's good enough (for me and this ranger build).
Is even less than an 1/8" acceptable for others with maybe much more refined race setup? Maybe/more than likely not. If I were building and/or designing a high dollar race car I would strive for near 0 tolerance wherever possible. Tolerances can accumulate quickly and nearly exponentially in large designs and builds. As an engineer I would be incorporating those 0 tolerance opportunities whenever/wherever possible.
Now onto the work...
I've now got the 8.8 out from under the chassis. I pressed out all the old spring pack bushings and re-stacked the leaf pack with a 3rd leaf and overload spring. Before it had 2 leafs and no overload.
With the extra leaf, overload spring, urethane bushings all around, and a pinion angle adjustment I hope to be good.
Sky_Render wrote: I can just imagine you at work. Coworker: "The manual says to--" FlightService: "DID YOU WRITE THAT MANUAL?" Coworker: "Well, no, but--" FlightService: "THEN HOLD MY COFFEE AND WATCH THIS." *Plugs 120-V tool into 208-V outlet* LOLOLOL
That's why I went to the patent office. I get to do that now! 
I bet the truck will already feel mush more solid getting those old tired bushings out of there.
Were you able to keep the ride height you wanted after repacking the spring?
You've probably already thought of this.....You could probably go to a coil set up using explorer bits. I'm just thinking out loud, but that would allow a coil over for height adjustments.
I'm really finding this whole "make a vehicle with leaf springs handle" thing fascinating.
What's an "overload" spring?
As a guy working with explorer parts and leaf springs, im watching this closely.
The discussion about Panhard vs watts is interesting. I never realized how little difference there is between the lengths of bar in regards to lateral motion.
Can we discuss the roll center/mounting height? The way it is set up in this ranger is really the only way we could do it in the challenge car.
Essentially this rear setup is what im running, only with sliders instead of shackles. So im learning from this thread.
I hope that ride height will not change much with the extra leaf. If you look closely the third, added leaf is flatter than the others. This is a leaf out of an Explorer leaf pack. the leaf pack should should settle down to existing right height just before the 3rd leaf touches.
The overload spring is the flat thick bar added on the bottom of the pack. When the spring pack becomes completely flat this "bar" will make full contact preventing the the leafs from bending backwards.
It's definitely been a good exercise in trying to make the leaf spring setup better. Now I'm ready to get out and learn the new characteristics of the truck.
The pan hard bar location:
Like mentioned by others, ideally it shouldn't be mounted as high as I've got it. Since you're also working with an explorer 8.8 you know as well that this is the easiest way to get a bar on it. I'll look at flipping the mount on the housing and try to snake the bar under the driveshaft. I did pull a few rough lines and measurements and in it's current location it's really not that far off of my roll center height.
Again thanks for all the advice!
Sky_Render wrote: What's an "overload" spring?
It's the spring that seems to have separated from the spring pack. In reality, as the leaf spring compresses the extra "loose" leaf comes in contact with that stopper. This changes the effective spring rate of the pack.
So soft ride during the first bit of travel for unloaded situations and heavy springs when working. If you want a stiffer spring rate you just engage the overload spring with the pack. You can either shackle it on the ends of the leaf pack or make the stopper engage sooner/at rest.
And you wondered why I asked for you to do the math instead of showing some video.
For reference, my front roll center is 3.5" and rear roll center is between 12" and 13". It's typical with solid axle race cars to have a high rear RC.
pres589 wrote: What happens with the leaf spring setup if a guy takes out bushings and replaces them with bearings and slider blocks; will the panhard setup start to have problems with bind in the case we're supposed to be evaluating here? How is he supposed to make this leaf setup hook up and turn, did a direction forward ever get found?
As long as the bearings still allow lateral movement (90 deg from intended movement), it should not bind.
Still- with the brackets at the rear of the spring, I'm sure that will have some movement built into the structure.
I may see this wrong, or too simplified- but as long as the length of the front portion of the spring doesn't change much (which it shouldn't, if it's shallow enough), the upper control arm(s) should keep it nice and straight.
If it were me, I'd favor more of a 3 trailing link set up, which is a little simpler, and can have some torque moment compensation built into the design. So between it, and the height of the panhard rod, you can make sure both tires are pushed to the ground.
I put the panhard-bar/rear-roll-center at 4" on my Locost. Front roll center is at ground level. It ~did~ have a tendency to understeer initially, but I've since dialed that out with sway bars.
I think that wheelbase in the last picture will be a bit much going around cones but sure would make drifting a snap!
In reply to alfadriver:
I kind of think the bearings he has don't allow for lateral movement. I could be very wrong.
A 3 link sounds nice but I don't think there are many examples of them working with leaf springs. I'm kind of excited to see another leaf spring setup that is heavily influenced by the original vehicle design and can also act nicely.
In reply to pres589:
Even if they are not supposed to move laterally, there's usually enough slop to take the panahard rod arc. Especially when you take into account the rear, moving, bracket for a leaf.
And didn't Shelby use a 3 link on the Shelby Mustangs?
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