Anti Squat and Suspension Tech

[RCholic]

GREAT INFO... Thanks for the read!!!

[EeePee]

Originally Posted by Cole82

Ok EeePee is that the rear axle or the front axle you added the spacers to?
When I mount them farther apart on the chassis and under the front servo mount. The front then sinks down.

The spacers are on my front axle.

Our instant centers and center of gravity are different enough. That would be my guess as to why they are acting differently...

If I remove my spacers, the front doesn't compress when I lay into the gas on an uphill. I use a grassy uphill for checking these things out. It's too steep for traction, so the tires just spin, and I can see what happens. With my spacers, the front sinks down, slightly.

You might be going so extreme with your angles that the whole thing is acting goofy?

[Cole82]

Originally Posted by EeePee

The spacers are on my front axle.

Our instant centers and center of gravity are different enough. That would be my guess as to why they are acting differently...

If I remove my spacers, the front doesn't compress when I lay into the gas on an uphill. I use a grassy uphill for checking these things out. It's too steep for traction, so the tires just spin, and I can see what happens. With my spacers, the front sinks down, slightly.

You might be going so extreme with your angles that the whole thing is acting goofy?

Ya I use a sheet metal ramp it goes up spinning like mad.
I think your right on go to the extreme with my adjustment.
When I built my 1:1 link setup 1" of upper link movement changed the AS by 40% or something like that.

So to make things stupid simple. If you spread the front link mounts on the axle it will sink the front?


edit:
I told you it was goofy

[EeePee]

Originally Posted by Cole82

If you spread the front link mounts on the axle it will sink the front?

On my truck, with it's particular seperation at the chassis, yes.

So, I was looking for some other proof to supprt the garbage I was typing, and found that an early C-Type Jaguar used an asymmetric link system to change the squat characteristics to cancel it's driveshaft twist effect on the chassis. Cool.

But I didn't find anything else on front axle squat stuff... cause I gave up.

[Cole82]

That's something I'll try the asymetrical links
If I understand the picture half way through this thread. What I found should be correct.
http://www.pirate4x4.com/forum/showt...hreadid=114352

[EeePee]

I like to reference this picture.



And when doing so, and reversing everything because it's the front, with spacers under the front links, I should have dialed in more ANTI squat. I think. However, I witnessed with my own eyes the front end suck down.

So my only guess is it has to do with the point of convergence.

Like I said, trial and error.

I remember when I put my upper links below the upper link mount in the back, the rear end sucked down majorly. So when I went to try the front, I just did the opposite. Had I put the fronts underneath the link mount, it would theoretically lift up. Again, it's all about the point of convergence.

Brain hurts.

[Cole82]

I was told by a Mud truck chassis builder that you can't just flip it around for the front. In his words "The front is a whole other ball game." I fully understand the rear. The front on the other hand has to many conflicting opinions. It's hard to get concrete awnsers with the front end.

Oh well trial and error wins it for me.

ALL of these figures have been while the truck was on flat ground the CG changes with how steep an angle. Also idealy the cg should be calculated with just the chassis not including the axles. It makes a huge difference in the numbers.

This four link stuff kills me. I think I'll go back to a torsion truck. I still haven't seen any truck climb as well as a torsion rig.

[EeePee]

Originally Posted by Cole82

This four link stuff kills me.

I think that's why so few people respond to these type of threads.

I think this is part of the fun.

[Cole82]

Originally Posted by EeePee

I think that's why so few people respond to these type of threads.

We are in a class all to our self's

To much THEORY, not enough APPLIED theory

[EeePee]

Hey, those spacers are proof I'm working on that APPLIED crap!

[knok2222]

I think this is the best thread ive ever seen....


...thats all i got for sticks

[joesbruiser]

Here is something to throw in the mix.
A freind of mine is building a new 1.1 tube rock bugggy i will have to try to get some better pics in a day or two it is at the powder coater right now.On the front he switched the placement of the arms, the lower bars that you normally see on the out side are raised up high on the top of the axle housing and the bars that are normally the uppers that attach in the center of the axle housing are now hooked to the back of the housing way down low.How this is going to work i do not know but it is for sure different.
Here is a pick of his rig right before he took it apart to get it powder coated.

[rockmike]

very good conversasion guys alot of this was already covered in a thread i started a while back.Theres been a few more things youve tapped into,very interesting im just sitting back learning and injoing i feel like i giant sponge.im going to do some testing tonight with a new 3 link frnt end,ill post my finding.The grass hill,plate steel,i luv it ive been useing a big slab of concrete i've leaned up on the wall, glad to hear you guys are using a similar way to see the suspension work,this **** is to much fun.Of coarse my thread was about t.t. but eepee showed me it was more about squat ,anti squate.is what ineeded to adress.this suspension tuning and learning is what i enjoy most about rc crawlin.Its just togh for me to find the time to consistantly test,to big of gaps in between test.Ill have to start taking notes on every test from now on.

[Big Mike]

Very, very interesting thread guys.
I was hoping when I got into this that this was how it would be - super-techy. I love messing with stuff like this.
I looked at a few torsion style chassis at first, but I decided to go w/ a TLT for the "realism" aspect. (and TLTs are cheaper than Clods) Stick chassis just look too unrealistic. Real crawlers and monster trucks use link setups (and driveshafts, for that matter) that's really why I went the 4-linked TLT route.
I know this much - when I tried to move my link mount off of the bottom of the axles, the suspension travel got cut in half just about. I figured out it was because my links were no longer parrallel. Once I moved the upper link mounts to match, it freed everything up again, but the torque twist got a little worse. I've been playing with the shock preload to compensate.
My front and rear are also mirror-images of each other, unlike your rigs. Something else I may need to experiment with apparently.
I did'nt think to try to adjust the link angles, I just moved the top mounts back to parrallel again.
I know what you mean about trail and error. It looks like you guys are getting closer to real usable data though.
Keep this thread rolling...

[Big Mike]

joesbruiser - dude, that rock buggy is sick! Could you ask your friend how much $$ he has tied up in it?

[trailduster79]

There is so much trail and error involved with getting the perfect 4-link set up that it almost seems stupid to not build in more than one mounting location for the links on the chassis.

I recently redid the links on my clod and went from having waaayyy too much anti-squat to having a little squat, and it made a world of difference in how driveable my rig is.

I an now at a point where I just need to fine tune the suspension.

I want to add a little anti squat in the rear, and move towards a little squat in the front, although I don't want to go overboard.

If I move my rear lower link mount on my chassis up, that will increase my anti-squat in the rear correct?

And, if I moved my lower link mounts in the front down, that will bring in some squat? Or do I need to move them up as well since everything is backwards in the front?

The main part that confuses me is when I am doing the front, and makeing everything backwards.

I really enjoy learning and experimenting with the 4-links.

I love this thread, keep it coming.

[EeePee]

Originally Posted by joesbruiser

the lower bars that you normally see on the out side are raised up high on the top of the axle housing and the bars that are normally the uppers that attach in the center of the axle housing are now hooked to the back of the housing way down low.

It reads like there isn't very much vertical seperation between the links at the axle side? That usually results in an axle that will try to twist itself around the tires under power. It also puts a lot of stress on everything. Maybe close up pictures will clarify that. Or maybe he has a fifth link to control the axle wrap? It also reads like the links are double triangulated. Which is good for controlling axle steer. Do the upper links at the axle hang below the centerline of the axle tube?

Rockmike, I remember that thread, and I still make these type of adjustments to my trucks all the time. It's part of the reason I keep buying new chassis to try out. Different suspension geometries.

[EeePee]

Originally Posted by trailduster79

If I move my rear lower link mount on my chassis up, that will increase my anti-squat in the rear correct?

And, if I moved my lower link mounts in the front down, that will bring in some squat? Or do I need to move them up as well since everything is backwards in the front?

Allow me to take a sentence from Joebruiser's post:

The location of the IC relative to the CG and the Normal Line (or Neutral line) is what determines what the chassis is going to do.

Here's a picture: http://www.baselinesuspensions.com/info/4_LINK.pdf

[Cole82]

EeePee the only thing the steers me away from the picture is that is a race car setup.
Our links are completly different. Rise% CG everything isn't even close. Every book I have seen has had the lower links really far below the axle center line. and the top barly above the axle. Ours are opposite to gain clearance. I would think that would have a huge efect on the geometry.

[Cole82]

IMO a 4 straight for link with panhard bar would be best for us. You can adjust everything independent of each other. When we raise our links on the axle upward it also raises the roll center too which can cause a very floppy rig.