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Discussion Starter #1
I am in the final stages of my design, can you belive it! I have been using AS numbers that people have been throwing at me and finally decided to add adjusment to my design. What I would like to know is this how will these adjustments help me in the real world when I get out there and can't figure out what to move to control undesired vehicle behavior.

Squat = Rear of vehicle going down under acceleration right?
Anti-Squat = Rear of vehicle going up under acceeration right?

So is 75% AS going to result in Squat or AS? What percentage does it change at from Squat to AS?

Now to the front end.

Lift= Front of vehicle pulling up under accel right?
Anti-Lift = Front of vehicle pulling down under accel right?

What percentage does this change from lift to anti-lift?

Now to braking

Dive = front end sucking down under braking right?
Anti-Dive = Front end lifting under braking right?

How is this calculated? Is it based of the Lift/Anti-lift formula?

I would think the ideal would be to have a rig that would have some AS and Some Lift to help plant the tires and Anti-Dive to help maintain control when fast braking and to help lift the front rig when making a steep decent down a hill and applying brakes.

Lets keep this one a tech thread, I am sure this will help answer just about all the mysteries of the squat calcuations rather then just going by number that they really don't understand.

Thanks for your help I know I will appreciate it and several others will benefit from it to! :cool:
 

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to make things simple.
if the instant center is ahead of the gc then it'll squat, if its behind it, it'll lift. nutral would be expresed as 100%
keep in mind that if you are going up or down hill the #'s change even if the suspension doesnt move. ie: if it was 100% when it was leval, it would squat going up hill, and lift going down hill.

its all a mater of some sort of comprimise.
 

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Discussion Starter #3
OVERLOAD..... WTF ????? Here is my link setup running at 73% anti-squat and another running at 140% Anti-Squat the Instant center is still ahead of the COG on both. You mean to tell me that both these configurations will SQUAT?





Can someone clear this up?
 

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AFAIK, (which I'll admit isn't a ton), over 100% is anti-squat.. i.e. 140% will lift. 73% will squat. it changes at 100. If you have 100%, when you hit the gas, the suspension shouldn't go up or down.

As for the front, one would think the lift/anti-lift is exactly the opposite of dive/anti-dive?
 

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I don't know for sure but after thinking about for a while it seems to me at around 50% you will start to see squating characteristics. A buddy of mine gets a squating characteristic on his 4 link when it is load up with gear. I noticed that at that point his antisuat #ers were at around 50%. Also, you have a package with some shocks going out today.
 

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Discussion Starter #7
PIG,

Thanks for replying, is T1H5_TA3's comment wrong?

Cool I will set up camp in the front yard and and wait for the UPS man!
 

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TPIJeep said:
PIG,

Thanks for replying, is T1H5_TA3's comment wrong?

Cool I will set up camp in the front yard and and wait for the UPS man!
Sort of...

T1H5_TA3 said:
to make things simple.
if the instant center is ahead of the gc then it'll squat, if its behind it, it'll lift. nutral would be expresed as 100%
keep in mind that if you are going up or down hill the #'s change even if the suspension doesnt move. ie: if it was 100% when it was leval, it would squat going up hill, and lift going down hill.

its all a mater of some sort of comprimise.
I don't have any reading material to back this up but have seen actual instances that dispute this suggestion. Also, is "gc" supposed to be cg? :confused: I am a little perplexed as to what else is trying to be said in that post. However, he is right about one thing for sure, it's all a matter of compromise.

I must say TPI that I am very impressed with your efforts up to this point and can't wait to see your finished product!
 

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ok, yes, mayby it was over simplified. and yes gc was suposed to be cg... :rolleyes: lol.. my bad. thats what i get for trying to type while talking to a customer on the phone.

i was trying to keep things real simple to help get some people up to speed.

basicly the Instant Center is the point where the links would converge. if you were to atempt to rotate the axle, this is the point where the force of lift/dive would be at.

the Center of Gravity is the balance point of the vehical. it never changes regardles of if the rig is upside down etc.

so to over simplify things, if the IC was ahead of the CG then it would be trying to lift the front half of the rig causing weight to tranfer backwards, GENERALY causing the back end to squat. if the IC was behind the CG then the point of lift would cause the back end to lift and transfer weight to the front.

keep in mind this is not in reference to a vehical in motion, just how the forces act. if you ad motion then yo ad the fact that the CG doesnt push strait down, it pushes at an angle, how much of an angle is dependent on how fast the vehical is accelerated etc. but the point here is that a IC that is behind the CG would normaly lift the back, but in some instances it may intersect the path of the CG causing the entire rig to lift eavenly planting the entire weight, basicly balancing the rig on the IC.

hopefully id helped some one with this explination. its easyer to draw it out and show it than it is to try to say it.
and keep in mind, i tryed to condense it and simplify it as much as posable. (while talking to a customer on the phone )
 

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I'm at work, so I can't take the time for more detail, but a few comments on the comments in this thread so far...

The drawing is using the CG of the vehicle for anti-squat calculations. That's wrong. You need to use the unsprung CG. In the drawing, that is at least another foot higher. Probably more, so both drawings are in excess of 100% anti-squat.

100% anti-squat means that there is enough lift acting on the rear during acceleration to counteract the amount of rearward chassis pitch at the CG. Therefore, 100% anti-squat results on Zero lift or squat at the rear. This applies to anti-lift at the front as well.

AFAIK, the lift isn't applied at the instance center, it's only used for purposes of figuring the amount of anti-squat. So, wether the IC is ahead or behind the CG isn't the issue.

Anti-dive is different that both of the above, because it is related to force applied by the brakes rather than torque from the axle. To figure anti-dive, you have to determine the unsprung CG as well as the front/rear brake percentage. Front brake percentage is applied at the anti-force against dive (pitching at the unsprung CG) The line of force for depicting anti-dive is typically steeper than the anti-squat/lift line of force.

HTH

MaX
 

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Hmmmm??? unsprung CG:idea: thats interesting, kinda makes sense. so I guess all my calc. and designs are way offf:confused:
 

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Discussion Starter #12
You know VooDoo, I am going to say fawk it and build it, with the adjustability I built into mine Hopefully I can change enough stuff to be happy with it.. Funny that this is the first time that unsprung COG has ever been meantioned!

Hopefully I have put enough thought into this and it will work fine if not I have a whole bunch of cool CAD pictures! :D
 

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I already built the rear and it seems fine. I think I'm just going to "common sense" engineer the front and go with it. I'm starting to think all this IC,COG,RC,AS,AD,AL,BS is more mental/tech sheet masterbation than any thing else. I've seen different rigs with radically different suspensions work equally good (or bad) in the same situation. Bottom line is It's still 80% driver and 20% vehicle. Thanks for all your input TPI. Let me know how your rig works with the different settings, or if you can even tell a difference:confused: I'm sure you'll be able to dial it in.
 

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How do I find COG? Is it just matter of jacking up the vehicle at different points untill you find the point where it balances?

I was under the impression that COG was in relation to how tall the vehicle is and its roll over point? (Dont flame me to bad, I still think leaf springs are cool:D )
 
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