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AND... just because their links intersect (the IC) at the crossmember behind the COG, doesn't necessarily mean that they have a ton of AS (I think that is what TN Toy is getting at?).

Look again at that black and white picture of the car and the AS/COG. The AS is determined by whether or not the IC is above or below the sloped line from the tire contact patch to the COG (or the height of the COG over the front axle), not just the location of the IC front to back.

As the picture shows, your IC could be behind the COG and still squat.

The links in those pics are relatively flat, so I don't see them giving a ton of AS...
 

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Also, I think in terms of S/AS you primarily need too look at the lower links. As was mentioned earlier, those links (when located at or near the axle compared to the uppers) see the most force and therefore have the most affect on handling.

I would think that if one of these engineer types took all the different vector forces and summed them up into one force, the resulting force would look like a link going through the axle center line and the IC... which would be where your lower links are if they're located at the axle tube.

Would that be correct?


If so, all that matters is your axle location and IC location in relation to the COG.
In other words, putting your lower links on top of the axle to make them "flatter" really has no effect unless it changes the location of the IC. The advantage is solely ground clearance.
I'll attempt a picture...
 

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Here what I'm saying...

The links get progressively steeper as you go down in the pic, but the S/AS stay the same. The common denominator is the axle and IC location.
 

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ErikB said:
The links get progressively steeper as you go down in the pic, but the S/AS stay the same. The common denominator is the axle and IC location.
Thank you Erik, that illustrates my point very well. This is *exactly* why I posted "IGNORE THIS" in huge letters when "make the links parallel from the side view" was posted earlier. All that matters as far a squat/anti-squat is the relation of the instant center to the COG... and having an infinite instant center (i.e. having the uppers and lowers parallel, not intersecting somewhere up in the chassis) makes this a bit more difficult. You can have the links nearly parallel or steep as hell... your drawing illustrates this very well. THAT is the point I was trying to make. :)

Originally posted by Air Ride
It works because they have shock-absorbers
:laughing: ROFLMAO!

I was just trying to call Strange Rover on what he was saying was getting a little over simplified. Not trying to be a jackass - just stirring the pot to squeeze a little more outta this thread.
 

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TNToy said:
All that matters as far a squat/anti-squat is the relation of the instant center to the COG...
I don't think that is entirely true though.

You need the third point-- the location of the axle (or maybe the tire contact patch, which is related to the location of the axle by the size of the tire), so you can have a line with a slope that intersects something to actually figure out the S/AS.
(the "something" should be that line from the tire contact patch to height of the COG over the front axle).


I think the difference between parallel and non-parallel links (when viewed from the side)is this:

With non-parallel links that converge "at the same crossmember," as TN Toy put it, the IC is always right there at the crossmember and cannot move in relation to the COG. The only thing that changes as the suspension cycles is the slope of the line from the axle to the IC, and therefore where that line intersects.

With parallel links, the IC is an infinite distance away in front of the vehicle, and changes height depending on the slope of the links. IOW, the IC location changes position as the suspension cycles, as well as the slope of the line.

With non-parallel links that don't converge at the same crossmember, the IC location and slope changes position as the suspension cycles, just like the parallel links, but not as much depending on how close to parallel or actually converging they are.


So... I'm thinking the changing IC location is the reason others have said that parallel links "aren't the best way..."

They may or may not have said that before, but I don't think I really understood that until now.
 

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Shupes rig looks like it does have a lot of anti squat and it does have a tight limiting strap. IMO it does rely on the limiting strap to stop it hopping. As soon as that rig points up hill I would think that the limiting strap would become tight even with no power on. Just the weight of the rig comming off the springs and onto the links would extend the rear downwards and tighten the strap. Shupes rig does climb well and it doesent hop.



Now for the harder ones - DSI, Toyman and SnortClown,s rigs. They do run alot of anti squat (and I mean shiat loads). I have never seen any video of any of these rigs climbing but I would find it very hard to believe that they dont hop on the steep climbs. Now this doesent mean that the rigs dont work. Its just that they work differently - id imagine that on the climbs that they have to drive carefully to keep the rig from hopping (meaning that they would have to back off the throttle if the rig started to hop). I really carnt comment much more cause I havent seen them work.

The only video that I got is last years super crawl and there are lots and lots of examples of differing levels of anti squat and how they perform on the steep climbs. The two most stable climbing rigs there IMO was the jeep that won the production class (Amy Bullock ?? - white jeep with yellow cage and links IIRC) and the Walker Evans rig (now red rocket). Both these rigs didnt hop at all no matter what they did and from looking at the link angles they both ran the lowerst anti squat of anybody there. Every other rig that hopped on the climbs (and im talking very small hops - like Jonny G in the zero G chassis and even Shaffer's rig) run more anti squat. Now Im not saying that the rigs that have a bit of anti squat and hop a bit arnt less capable that the really low anti squat rigs. Im just saying that for me the correlation between the amount of anti squat a rig has and the way the rear hooks up on the climbs (or the rear hops on climbs) is very strong.

Sam
 

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Strange Rover said:
Shupes rig looks like it does have a lot of anti squat and it does have a tight limiting strap. IMO it does rely on the limiting strap to stop it hopping. As soon as that rig points up hill I would think that the limiting strap would become tight even with no power on. Just the weight of the rig comming off the springs and onto the links would extend the rear downwards and tighten the strap. Shupes rig does climb well and it doesent hop.



Now for the harder ones - DSI, Toyman and SnortClown,s rigs. They do run alot of anti squat (and I mean shiat loads). I have never seen any video of any of these rigs climbing but I would find it very hard to believe that they dont hop on the steep climbs. Now this doesent mean that the rigs dont work. Its just that they work differently - id imagine that on the climbs that they have to drive carefully to keep the rig from hopping (meaning that they would have to back off the throttle if the rig started to hop). I really carnt comment much more cause I havent seen them work.

The only video that I got is last years super crawl and there are lots and lots of examples of differing levels of anti squat and how they perform on the steep climbs. The two most stable climbing rigs there IMO was the jeep that won the production class (Amy Bullock ?? - white jeep with yellow cage and links IIRC) and the Walker Evans rig (now red rocket). Both these rigs didnt hop at all no matter what they did and from looking at the link angles they both ran the lowerst anti squat of anybody there. Every other rig that hopped on the climbs (and im talking very small hops - like Jonny G in the zero G chassis and even Shaffer's rig) run more anti squat. Now Im not saying that the rigs that have a bit of anti squat and hop a bit arnt less capable that the really low anti squat rigs. Im just saying that for me the correlation between the amount of anti squat a rig has and the way the rear hooks up on the climbs (or the rear hops on climbs) is very strong.

Sam
A good example of this to me is the amount of antisquat chris durham runs (dont get me wrong its fun to watch and hes a top guy) but his rig climbs about as well as mine. Check your supercrawl video..... i dont think he cleans one obstacle in it! :eek:
 

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Thanks everyone for the great info

planning on building my own Krawler then start competing so all this info will come very handy. Thnx again.
 

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Here is a couple pics of a Campbell rig 4-link setup. Notice the difference in link length between the uppers and lowers and the pinion angle in relation to the TFC output. His upper links appear to be near the 70% in length range and as his suspension cycles the pinion stays pointed at the TFC output.

Now when the axle droops straight down (equal droop on both sides) is the pinion still going to be pointed at the TFC output or would that be why he has a limit strap?
My guess is the length of the limit strap will allow exactly enough droop to keep the drive shaft u-joints from binding?

I see from reading this entire thread that some think that more droop would be better for certain circumstances?
Thus changing your lcp to keep proper pinion angle in full drrop is necessary.
What would those circumstances be?
Cycled


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jeeplvr said:
Now when the axle droops straight down (equal droop on both sides) is the pinion still going to be pointed at the TFC output or would that be why he has a limit strap?
My guess is the length of the limit strap will allow exactly enough droop to keep the drive shaft u-joints from binding?

I see from reading this entire thread that some think that more droop would be better for certain circumstances?
Thus changing your lcp to keep proper pinion angle in full drrop is necessary.
What would those circumstances be?



You're part way there. Most people these days are agreeing that they need to look at drag racing to learn something on these rigs. All the sudden people are willing to sacrifice travel AND articulation for traction. The pinion angle is not going to stay constant unless you use a parallel /equal length 4 link. These don't climb well, so people don't run them. The limit strap will protect the U joint, but you'll probably find that it limits the droop even more than that just to make the rig perform better, especially on steep decents.

If you get ahold of a college statics manual and do some reading on 4 bar linkages you'll get to understand a little more about your pinion angle movement under wheel travel. Unfortunately you can't optimize pinion angle without sacrificing something else, and on a competition rig you can bet that U joint life / maintenance is NOT priority 1.
 

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One other way to keep the pinion angle stable as the whole axle droops or compresses with a CV driveshaft is to have the links all converge at the same point (crossmember) near the CV.

Like the ones Booger was asking about in this thread:
http://www.pirate4x4.com/forum/showthread.php?s=&threadid=182951

And TN Toy posted above.

Another way is to make your upper links longer than your lowers, but that isn't usually physically practical.
 

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I was just flipping through this thread, and I found Land Croozer's explanation of AS. For those of you that see it this way, ie. 200%AS being the opposite of 0%, what is the difference between 200% and 300%. What if I build a suspension with 400%AS, how will that act different than 200%? If 200% is really the max (as in opposite of zero interms of downward force) I dont see how this can change once over 200%. But really, it must change.

Ryan
 

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Read whole thread, learning a lot. This is good stuff, guys!

There seemed not to be one single mention of two link and panhard rod setups. Is there something inherently wrong with this approach? This is the way stock wranglers are designed, right? This setup would allow me to use the anti-squat link setup without forcing me to relocate my gas tank (4Runner). No, Im not going to compete, I just want a rear suspension that wont collapse on every hillclimb.
 

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2-link w/ panhard is better known as a radius arm setup like what Ford used in the front of its older trucks and Broncos for years.

Wranglers (TJ's) use a 4-link w/ panhard front and rear (same as the rear of later model 4runners) which is different.

Yes a radius arm rear will work, especially if you aren't looking for extreme flex because one of the disadvantages of radius arms are that the design inherently binds (the axle itself trys to act as a giant sway bar) unless you run one of arms "wristed." And wristed arms have some handling quirks that you may or may not want to put up with.

Try a search on radius arms and wristed radius arms and you will find a ton of info.

I'm not sure what you mean about the suspension collapsing on hill climbs. If you're talking about squat or anti-squat, then that basically depends on the angle and length of the links, no matter which design you use.
 

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ErikB said:
Yes a radius arm rear will work, especially if you aren't looking for extreme flex because one of the disadvantages of radius arms are that the design inherently binds (the axle itself trys to act as a giant sway bar) unless you run one of arms "wristed." And wristed arms have some handling quirks that you may or may not want to put up with.
I assume that's because the radius arm essentially pushes the axle outward as it rotates upward.

ErikB said:
Try a search on radius arms and wristed radius arms and you will find a ton of info.
Will do. Thanks!

ErikB said:
I'm not sure what you mean about the suspension collapsing on hill climbs. If you're talking about squat or anti-squat,
I am - with the existing chevy rear spring setup, my rear end collapses badly on acceleration or hillclimbs. If a 4cyl can cause serious squat on acceleration, then somethings wrong!!
 

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4_link Variables:

O.K. first off let me say, great thread, I've learned a lot. I wanted to sum up all of the variables and equations that are shown in several of the illustrations above. (these were all pulled from this thread):


-Anti-Squat % (COG Height * IC Position)/(Wheelbase*IC Height)

-Instant Center (The instant center is the intersection of lines drawn through the top and bottom links as viewed from the side.)
-Instant Center Height (measured from ground to I.C.)
-Instant Center Position (measured from center of rear axle forward to I.C.)

-Roll Center (The roll centre is the point that the body wants to rotate about on the axle or the point that the axle supports the body laterally)

-Roll Axis (The line drawn through the two Link Convergence Points [L.C.P’s] is the roll axis.)

-Center of Gravity (top bolt of your bell housing is a general rule of thumb)

-Wheelbase (center of rear tire to center of front tire)
 

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With radius arms in the rear the IC is where the arms mount to the chassis. This normally means they create lots of anti squat (same as triangulated links that converge to a single point on the frame).

If you wanted low anti squat with radius arms (say 50% to 80%) then I would guess that the arms would have to mount to the chassis somewhere near the back of the motor which is very long.

So IMO if you want low anti squat then radius arms arnt the way to do it.

Sam
 

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How would squat/antisquat be affected on a leaf spring suspension when you add a traction bar?
And how would you caclulate the geometry to achieve the desired amount of squat/antisquat?
 

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I posted but it didnt go to the top so T.T.T.
 

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Tossing leaves into the mix screws up trying to figure it out alot! Best I could tell you is ASS U ME that the front half of the leaf is a "link". Then figure it out like you normally would.

If you want to look into it further than take a look at this
http://community.webshots.com/album/13190727rhRhHDXluW

That is MJ's webshots. He has lots of cool shit in there and everyone should have it bookmarked (or just do like I did and download every picture)
 
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