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View Full Version : Anti-squat discussion - what's a good target?



JeepinHank
09-14-2004, 10:28 AM
I'm doing the whole long arm design thing again. (yeah, yeah, its about time I build the damn things)

Anyway, I've been playing with my measurements and plugging them into the 4-link calculator, but I just wanted to see what the general consensus was for a target anti squat value? I know more anti-squat could lead to wheel hop in climbing situations, and the rear of the vehicle rising under acceleration, but beyond that I'm not too clear on the concept.

I'm getting a value of ~115% right now. Is that way too much, not enough, or just fine? I just want to get this kind of stuff ironed out before I start building my subframe and all. I'm 4-linking the rear and going with a radius arm front if that makes much of a difference....

robselina
09-14-2004, 11:47 AM
don't know much about this Hank, but I've been looking into one-link setups for my waggy since they're substantially easier to design/fabricate. Anyway, seems successful one link setups run around 130% anti-squat and work fine. I've seen others up to 160% working without wheelhop. 130% is considered on the higher side by most 4 link guys, but I'm betting you'll be fine where you're at.

The other thing you're going to run into on a ZJ is that there's just no good place to put the upper links to keep them closer to parallel. You're automatically going to have a relatively high anti-squat value just because you're so limited in the number of places you can mount links w/o really compromising clearance....

Anyway, got any drawings of what you're considering?

JeepinHank
09-14-2004, 01:47 PM
Anyway, got any drawings of what you're considering?

No good drawings to speak of right now. Just a bunch of graph paper with a lot of scribbling on it. I've got my basic measurements, but I'm building for an 8.8 that I don't have yet, so, there's still a lot of guessing going on.

Basically, I'll be using a sub-frame similar to what Alaska did. I'll tuck my UCA mounts up and inside the frame rail, while the LCAs are going to be on the bottom. I'm looking at going with Claytons crossmember for my front mounting points.

If I get around to doing a better drawing, I'll post it up. That's a big if though - I'm not much of an artist.

Kraqa
09-14-2004, 02:51 PM
try mounting your uppers very close to the pumpkin and rasing your lowers up paralelle to the axle tubes.
http://img.photobucket.com/albums/v280/Kraqa/Suspension/DSC01085.jpg

i have around 100%

JeepinHank
09-14-2004, 03:11 PM
Thanks for the pic Kraqa, that points to one of my basic questions....

Everything I'm reading says the lowers should be a lot longer (Around 25-35%) than the uppers, but most of the ZJ suspensions I see built have the links about the same length. Is this just a constraint of working with a ZJ, or is this by design? Right now the frame placement is what I'm looking at the most, cause I want to build my subframe while I'm getting the axles ready to go.

I guess I should also point out that (in my situation at least) I'm building this for an all-around Trail Rig. My ZJ pulls daily driver duty, but still needs to be capable of hitting up some pretty tough trails at the same time.

robselina
09-14-2004, 03:51 PM
Thanks for the pic Kraqa, that points to one of my basic questions....

Everything I'm reading says the lowers should be a lot longer (Around 25-35%) than the uppers, but most of the ZJ suspensions I see built have the links about the same length.

k, I could have sworn it was the other way around, with the uppers being longer or equal length to lowers...... :? don't really remember.

Either way, what kraqa suggests is good for anti-squat and for clearance, since obviously you can keep your lowers tucked up and use them as skids and the uppers are as close to parallel to the lowers as they're going to get when viewed from the side....

Raacerx
09-14-2004, 06:36 PM
Here are my arms with Claytons flush brackets and his 8.8 truss. Not a very good picture but you can see the angle between the uppers and lowers.

http://www.fototime.com/{FA362927-F0E7-4209-92EE-08BD56C91F1C}/picture.JPG

Here are my arms now. Good bit more parrallel because the uppers mount right above the pumpkin.

http://www.fototime.com/{373B1ACD-6B9D-487A-88B0-FDB711629D11}/picture.JPG

Can someone do the 4 link calculation for me? I dont have excel and the other page is down. 29 3/4" lowers and 33 1/2" uppers? Ill have to measure again, those are what I remember

JeepinHank
09-15-2004, 09:36 AM
Can someone do the 4 link calculation for me? I dont have excel and the other page is down. 29 3/4" lowers and 33 1/2" uppers? Ill have to measure again, those are what I remember

Thanks for the pics. If you give me the info, I'll run the calc for you...
Here's a pic of the input screen so you can get your measurements together (pretty big so I'm just linking it):
Click Here (http://lewis-lewis-cpas.com/Jeepin/Writeups/SuspensionCalcpic.JPG)

Get me the numbers and I'll post up a shot of what's returned...

nmzj
09-15-2004, 05:00 PM
THere is a link to the suspension calculator at the top of this forum. Last time I checked it was a working link thanks to Alaska.

Raacerx
09-15-2004, 06:49 PM
THere is a link to the suspension calculator at the top of this forum. Last time I checked it was a working link thanks to Alaska.

doesnt work for me. says the page does not exist.

Alaska ZJ
09-15-2004, 09:09 PM
Me too.

Damn I knew I should have grabbed all that code and hosted it myself....

If anyone comes across it again, let us know. We can host it on this site or I will host it on my business site.

It was a cool little sucker.

Raacerx
09-16-2004, 02:35 AM
Me too.

Damn I knew I should have grabbed all that code and hosted it myself....

If anyone comes across it again, let us know. We can host it on this site or I will host it on my business site.

It was a cool little sucker.

well what is the deal with having longer uppers then lowers? Im still vague on this whole area.

Alaska ZJ
09-16-2004, 09:34 AM
pinion rotation through the suspension cycle.

You want it to rotate UP as you "droop" If not you will bind the joint and/or dig the pinion into the surface below.

nmzj
09-16-2004, 09:43 AM
Wouldn't uneven bars create a bind? when one side goes up the pinion tries to go up and when the opposite side goes down the pinion tries to go down. That puts a twisting force on the housing.

luvthejeep
09-17-2004, 09:14 PM
yes it will rotate the housing either way, ones a good rotation, one is bad- thats the idea- with a shorter lower arm as opposed to the upper the pinion will increase in angle as it droops- (i.e. point more and more up twards the t/c) thats a good thing b/c as alaska explained this decreases the chance of extreeme angles on the rear axle pinion u-joint (i.e. it wont get all bound up and broken)-

with a shorter upper arm it will rotate the pinion down, away from the tc- (i.e. not good)

depending on geometry and articulation though it may change angle more or less, depending on design- my setup, (kevins) has a short upper and a long lower, not ideal- but in actuallity, with the 3 link the upper arm barely moves up and down so my pinoin angle barely changes- ill explain more later, gtg

Kraqa
09-17-2004, 10:29 PM
the rotation on the pinion can be not only changed by the length of each arm but your vercical seperation at the frame side aswell.

Alaska ZJ
09-18-2004, 09:17 AM
Wouldn't uneven bars create a bind? when one side goes up the pinion tries to go up and when the opposite side goes down the pinion tries to go down. That puts a twisting force on the housing.

Yes it does infact create "bind" in a way and the thing that gives is the rotation of the tube.

use some straws and a papertowel roll to simulate a axle and control arms. You can draw a "pinion" on the papertowel roll and as you cycle the "suspension" you will see.

Tommy
09-27-2004, 04:14 PM
Here are some good calculators. The second link will draw a picture for you. Found these on POR.


http://home.earthlink.net/~triaged/Files/4LinkCalculatorV1.5.xls


http://home.earthlink.net/~triaged/...ulatorV2.0a.zip

TrojanMan
11-13-2005, 08:35 AM
Sorry to bump this from hell.. but I just did about 6 hours straight reading about LA's on PBB and such.. and now i'm starting to think seriously about my build. I'm also really curious about what other people are running for anti squat numbers. Over on PBB they were saying shoot for 85 or lower, why is everybody seeming to have 100+? I haven't started playing with calculators yet (jeep is back at home 3 hours away so I can't take measurments). Are there constraints with the ZJ that cause the arms to be in a certain configuration? What AS numbers do clayton, kevin, and ty have?

Again sorry to bump, but I say it needs more discussion:smt003

*edit* Along with the number, is anybody getting any wheel hop issues?

deadman
11-13-2005, 02:00 PM
Just if you missed these... I think they are a good read:


Link Suspension for Dummies:
http://www.pirate4x4.com/forum/showthread.php?t=168577&page=1&pp=50

The God of Suspension:
http://www.pirate4x4.com/forum/showthread.php?t=7503

TrojanMan
11-13-2005, 02:27 PM
Just if you missed these... I think they are a good read:


Link Suspension for Dummies:
http://www.pirate4x4.com/forum/showthread.php?t=168577&page=1&pp=50

The God of Suspension:
http://www.pirate4x4.com/forum/showthread.php?t=7503

I read link suspension for dummies.. missed the god of suspension haha.. thanks man.