3-link front and rear set-up discussion Class 3 setup

[mjderstine]

hey guys, after talking DoubleJ at ECSC back in august and seeing Warpig's Izuzu trooper slither through the C3 courses i made the decision to transform the Deuce from a casual trail runner to a C3 4ws rig. Construction of this wasnt that hard as the twin/mad force axles from my man Rick at Supershafty are easy to work with.
I decided to go 3-link with a panhard setup on each axle to avoid bump steer as much as possible.

one question i have is there an advantage or disadvantage to having the panhard mounts on the same side of the chassis for the front and rear axles. i understand that through movement the axles actually move side to side with a panhard setup. so i figured mounting them on the same sides would allow the axles to move in the same direction (side to side).

have any of you guys tried a setup like this on your C3 scalers?

here are some pics and a video of the steering operating.

Bobbed Deuce steering GT3B Mixing scaler with winch - YouTube

[mjderstine]

Originally Posted by maslin

Panhard mounts need to be on the same side.

With a chassis mounted servo, the panhard bar needs to match the angle of the drag link. As the suspension cycles, the drag link will push the steering left and right. The panhard forces the entire axle to move with the steering, thus eliminating bump steer.

So the panhard should be mounted on the same side as the steering servo. If you have rear steer, this should be mounted on the same side as the front.

Let me know if that isn't clear

that's actually completely clear because i know all that already

i was just asking about the front and rear mounts being on the side, and the geometry of the whole thing. thanks for the response though. i have been making panhards for a couple years now, this was just the first time i have done it on the front AND back.

[mjderstine]

yup got that, the panhard in the rear might be 1/2" shorter then the front, but the steering and panhard links one their respective ends are exactly same the length and angle.

[doublej]

I want to say that with 1:1s there was a major fubar with them being on the same side front and rear....
I'm at wok but let me do some digging to see and I have a few people to poke....

Are you going CMS in the rear also? And why 3link rear vs axle mounted servo and a 4link?
Both can be built to act the same but as your already seeing - 3 link gets a lot more complicated to package. And then you run into all the things we were talking about the front counter acting the rear, but with a 3link I believe it's harder to tune out and when there is a problem the 3link really shows it.

[mjderstine]

Originally Posted by doublej

I want to say that with 1:1s there was a major fubar with them being on the same side front and rear....
I'm at wok but let me do some digging to see and I have a few people to poke....

Are you going CMS in the rear also? And why 3link rear vs axle mounted servo and a 4link?
Both can be built to act the same but as your already seeing - 3 link gets a lot more complicated to package. And then you run into all the things we were talking about the front counter acting the rear, but with a 3link I believe it's harder to tune out and when there is a problem the 3link really shows it.

thanks bud.

yup CMS in the rear. you can see the mounting holes in the pics, and probably see the servo in the video.

why 3 link? first was because the pumpkin isn't centered and making the center mount was turning into a puzzle. 4-link and AMS would def be the best for the rear. and maybe i will go there. would have to do some major rebuilding of the rear of the truck so i could have full travel of the suspension without the servo getting in the way and banging into the chassis on suspension travel.

there was one obstacle last weekend where it was a tight climb and if you get the front wheels over most guys were able to pull themselves up it. my truck kept wanting to lift the front wheels and roll back over the rear wheels. i had to take a 20pt hit on that obstacle where most other guys were able to get around it pretty easily. and the balance wasnt an issue, the Deuce is a beast on most hill climbs, this was a very technical little twisty spot.

[Grizzly4x4]

I always thought it would be better to mount the panhards on opposite sides of the chassis. But after looking at some Campbell builds, they seem to put both the front and rear frame mounts on the same side.
The buggy has them on the driver side and Walker's "jeep" has them on the passenger side. It appears that they always put the axle mount on the pumpkin side.

I don't think I could find a reason to doubt that the Campbell's know what they are doing, even if I wanted to try.

[doublej]

That obstacle is exactly what scx10 wackiness causes. It's where a lot of guys just start adding more weight in the wheels to counter act it. But is rather fix it at the source.
Saying your a builder - I would try or things at a time to see where it goes. Esp since you know how it acts now with this past comp...

[Grizzly4x4]

As evidence to doublej's point.

War Pig tried to make a rear CMS work on the 34D but couldn't get it to work the way he wanted.
Both the 34D and the Troober have 4 link setups and axle mounted servos in the rear.

[doublej]

Good find Grizz - that was where I was going to first look.
There is reasons behind the pumpkin side mounts - It counter acts the rotation of the axle shafts better if I remember the simple answer.

[Grizzly4x4]

Originally Posted by doublej

Good find Grizz - that was where I was going to first look.
There is reasons behind the pumpkin side mounts - It counter acts the rotation of the axle shafts better if I remember the simple answer.

I've never put much thought into it so I suppose that makes sense.

The factory setup on my 1:1 Bronc has the axle mount on the opposite side of the pumpkin so I definitely be interested to know more about what works better.

[mjderstine]

so one thing i am noticing is the angle of the panhard mount. its high on the axle and low on the chassis. that should limit the side to side travel since you are on both sides of the side to side movement through compressions.

well i'm not gonna give up on the panhard yet, but i think i might mess with the location of the mounts. i;ll see if i can make them taller on the axle and lower on the chassis. and the go from there.

if you mount on opposite sides would probably get a lot of chassis twist on the vertical axis. the nose and the tail would be moving in opposite directions. i could see that causing some issues with weight transfer and steering!

[Grizzly4x4]

Originally Posted by mjderstine

so one thing i am noticing is the angle of the panhard mount. its high on the axle and low on the chassis. that should limit the side to side travel since you are on both sides of the side to side movement through compressions.

well i'm not gonna give up on the panhard yet, but i think i might mess with the location of the mounts. i;ll see if i can make them taller on the axle and lower on the chassis. and the go from there.

if you mount on opposite sides would probably get a lot of chassis twist on the vertical axis. the nose and the tail would be moving in opposite directions. i could see that causing some issues with weight transfer and steering!

Yea, I think it's best to set up the panhard so that it is flat when your shocks are at mid-travel, if possible. Like you said, that limits the axle shift.

Give it a shot and see if you can get it to work good for you.

[bigstu]

This is the way it was explained to me, and I may be wrong, this is just what I have seen during my own tests.
I have definately had an issue with this on my two C3 scalers and both have 3-links front and rear.The only thing, I don't have 4ws on either of them.

The mounts for the panhards need to be at opposite ends to help eliminate torque twist.
I've noticed on both of my scalers, with 3-links front and rear, and the top mounts both on the drivers side of the chassis, they torque twist like a MO FO.
From a dead stop to full throttle, on a high traction surface, will initiate a one wheel lift in the front or you can see the whole chassis torque to one side.
In reverse, it doens't twist nearly as much.
Both trucks are using wraith axles and transmissions, with MIP drive shafts.
Just for grins I make up a VERY cheap mount and switched the rear to the other side of the chassis. It was literally zip-tied to the truggy frame, and it definately reduced the torque twist effect.
So much so that I have been trying to come up with a new mount that I can either bolt too the truggy chassis, or machine out and have welded to the bars.

Not trying to be a smarty pants, but you can't use the Campbell chassis for ANYTHING. The geometry on those things is set up specifically for those radical rigs. I mean, look at the diff/pumpkin placement. That passenger side axle shaft must be about 4" long on the rear axle..

I do understand what you guys are saying about the truck and the axles moving the same direction when going over bumps. Because they do move side to side when cycling up and down.
I would say that is only necessary in VERY high speed applications where upsetting the car may be detremental to the drivers life.
That's the reason most guys use a 4-link suspension. Little or no side to side movement.

The big thing, design a steering drag link that is straight, the same length, and angle as the panhard bar.. Those three being the same mean zero bump steer.

The comments about Grizz's bronco got me thinking.
My Jeep TJ has the mounts on oppsite sides of the frame, and the axle mount in the front is at the non-pumpkin side of the axle.
Just like this.
The only thing is, Jeeps have a 5-link in the back. It is a 4-link with a panhard bar. Kind of crazy, but it still flexes and works. Just no 4ws.