axle steer...am i right?

[muddeprived]

My rear axle is steering. I'm thinking it's the upper rear links not being parallel? or the upper rear links being 1 1/4" shorter than the lower? My front flexes fine. What you guys think?

[Offroader5]

I think it may be because the uppers are triangulated backwards. They should converge on the axle end rather than the frame.

[BESRK]

Best link setup to avoid flex steer is a dual triangulated 4 link. You've got parallel lower links and reverse triangulated upper links (reverse to what you normally see). Look down at your rig from straight above. If you were to droop one side, that lower link (at the axle end) can only swing forward. Since you've got your upper links separated at the axle instead of the frame, even your upper links are swinging forward as they droop... and they're even shorter than the lower links. If I were going to triangulate the uppers, I'd separate at the frame and come together at the axle.

[muddeprived]

I see what you guys are saying. The problem with mine is a combination of the body shape and frame setup. There's clearance issues using the top clod axle mount in the back The interior's bottom is lower and right in front of the upper axle mount. I guess i'll try hacking the body for clearance and reverse the triangulated upper reas.

[Big Mike]

I think it may be because the uppers are triangulated backwards. They should converge on the axle end rather than the frame.

When I had my links mounted in basically the stock TLT positions in the chassis, I had bad flex steer. Making new servo plates and triangulating the upper links together right behind the servos on the axle really helped. (instead of triangulated in the chassis like a stock TLT)

Do you have a pic from the bottom?

[muddeprived]

Originally Posted by Big Mike

When I had my links mounted in basically the stock TLT positions in the chassis, I had bad flex steer. Making new servo plates and triangulating the upper links together right behind the servos on the axle really helped. (instead of triangulated in the chassis like a stock TLT)

Do you have a pic from the bottom?

[Big Mike]

Oh, yea - that's better.

You pretty much want to reverse the mounting points of your upper links - so they converge on the axle instead of in the chassis. That will help you a lot.
Like this:


Is that a Clod axle? You might also think about reversing it - so the motor is inboard out of the way instead of outboard where it will hang up on everything.

This thread will explain a lot more about suspension set up and how to "plot" where your CoG and IC are, and how to tweak it for better performance. It's a lot to absorb but it's worth it.

Anti Squat and Suspension Tech

[muddeprived]

Originally Posted by Big Mike

Oh, yea - that's better.

You pretty much want to reverse the mounting points of your upper links - so they converge on the axle instead of in the chassis. That will help you a lot.
Like this:


Is that a Clod axle? You might also think about reversing it - so the motor is inboard out of the way instead of outboard where it will hang up on everything.

This thread will explain a lot more about suspension set up and how to "plot" where your CoG and IC are, and how to tweak it for better performance. It's a lot to absorb but it's worth it.

Anti Squat and Suspension Tech

Thank you for your help. I did try mounting the axle with the motor facing the belly but it would hit on the bottom of the body so i had no choice but to flip it around, or cut the body which i do not want to do. The top of the motor would hit the upper triangulated links as well. My first setup had the upper links triangulated so they converged on the axle but then they would hit the bottom of the body just like the axle would so i tried it this way only to get hit with axle steer. I'm finding it hard to work around the body without cutting now...:(

The whole problem with the body is that it's a two piece body. The interior is bolted on and it hangs kinda low. If i cut the interior section of the body (which everything is hitting) then the interior.....well...disappears. So i'm trying to work around cutting but looks like that's not gonna happen.

[muddeprived]

OK i went ahead and cut the body. I managed to triangulate the rear uppers and still get the same amount of axle steer. No change at all from the old setup. It's gotta be my lower links causing it.

[mavicracer]

I had a similar problem, and this might sound stupid, but do you have your steer locked out with washers? I do, and I had this problem at first. I finally realized after remaking my links twice, that the washer had my wheels slightl out of line. that minor adjustment got it fixed and i was back out in a day. hpe tis helps and that I am understanding the problem correctly.
Steve

[muddeprived]

Originally Posted by mavicracer

I had a similar problem, and this might sound stupid, but do you have your steer locked out with washers? I do, and I had this problem at first. I finally realized after remaking my links twice, that the washer had my wheels slightl out of line. that minor adjustment got it fixed and i was back out in a day. hpe tis helps and that I am understanding the problem correctly.
Steve

Yeah that's what i thought it was too but it wasn't. I can visually see the axle tubes venture away from being parallel with the frame crossmember. I read that thread about axle link setups and tried to triangulate the lower links as well and whatdoyaknow, no more axle steer. Kinda strange cuz i got the front set up just like the rear was and the front has no axle steer. I think the problem was the lower links were angled too much and they would pull the axle forward.

[Offroader5]

Well, by just the nature of the triangulated 4 link, your going to get some axle steer.

I'm not really an expert on 4 link geometry, but with both of my chassis (WK axled and Clod axled), my links are almost parallel to each other when looking from the side...and I have close to zero flex steer..almost hard to even tell. I noticed that if I moved the chassis end mounts to the same pivot point (again looking from the side), the more steer I got when flexing. And it seems to make it even worse the further apart vertically your axle end mounts are when it's at the same pivot point on the chassis.

When I look at your pics again though...I think the biggest part of it may be that your uppers are sooo much shorter than the lowers. On my Clod, the links are all the exact same length...on the WK, the uppers are actually a bit longer than the lowers. Now this does entirely depend on where you put the mounts on the chassis to begin with. Mine mount up roughly in the same vertical plane on both the chassis and the axle.

I dunno, it's kinda a trial and error thing for me...I leave all the fancy math out of it and I know what works.

[muddeprived]

Originally Posted by Offroader5

Well, by just the nature of the triangulated 4 link, your going to get some axle steer.

I'm not really an expert on 4 link geometry, but with both of my chassis (WK axled and Clod axled), my links are almost parallel to each other when looking from the side...and I have close to zero flex steer..almost hard to even tell. I noticed that if I moved the chassis end mounts to the same pivot point (again looking from the side), the more steer I got when flexing. And it seems to make it even worse the further apart vertically your axle end mounts are when it's at the same pivot point on the chassis.

When I look at your pics again though...I think the biggest part of it may be that your uppers are sooo much shorter than the lowers. On my Clod, the links are all the exact same length...on the WK, the uppers are actually a bit longer than the lowers. Now this does entirely depend on where you put the mounts on the chassis to begin with. Mine mount up roughly in the same vertical plane on both the chassis and the axle.

I dunno, it's kinda a trial and error thing for me...I leave all the fancy math out of it and I know what works.

I'm all about trial and error too. I don't do none of the math when it comes to RC's. I just try different methods until it works

Here's what i came up with:



It flexes smoothly with no binding. From the side, the upper and lower arms are no where near parallel and i'm surprised it works. I set up a vertical bar to see if the axle drifts away from it while articulating and it stays on the same plane so all is good!

[Offroader5]

Here's some side shots of both of mine for comparison:


Click Me


Click Me

[muddeprived]

Originally Posted by Offroader5

Here's some side shots of both of mine for comparison:


Click Me


Click Me

Thanks for the pictures. I see you used the upper C mount. I used the lower C mount so it looks more like those long arm kits and also to use for sliding on rocks. If this wasn't a scale build, i would've used the upper mounts and saved a few headaches. There was no way to get my upper links on the same plane as the lowers cuz of the body being in the way so i had to parallel them with the ground.

What you guys think of the crossmembers i use to mount the links? Think it'll hold well? It's 3/16 x 3/8" rectangle brass. The rod end mounts are gonna be bolted with one bolt and jb welded a little cuz i dont trust one bolt.

[BESRK]

Muddeprived, I would be willing to bet that if you moved your lower link frame mounts in toward the center, it would drastically cut down on the flex steer. Now, whether space and frame layout will permit that is another question. It's the same when working on a factory framed 1:1 rig, sometimes, you just have to compromise, get as close as you can and call it good. That's why when I build a rig from scratch, I start at the tires and work my way in. Tires, axle shafts, housings, suspension layout, frame mounting points, frame layout....etc. Also, I try to make my weak point the friction between the tire and the terra firma.

[slugzracing]

Moving the links around on the axle is not going to fix his problem. The lower links are just too steep so as soon as the axle begins to articulate one side (the side that droops) will be pulled foreward under the vehicle and the other side (the side that compresses) is pushed out away from the vehicle. Double triangulated links will not prevent this from happening but a new lower link mount at the chassis will. The closer your lowers are to parallel to the ground the better

[muddeprived]

The way i have it now seems to work so i went ahead and finished it up. Here's how it articulates:



(front shocks are slanted cuz i didn't tighten the link mount)
Ride height:



Link view:



Axle steer is hardly noticeable so i'm satisified