questions about anti-squat in 4 link design (1 Viewer)

[workingdog]

Sorry to get very geeky, but I'm studying 4 link design and I'm confused. There's this great picture in a great article at Crawlpedia that shows the 100% anti-squat line as a line from the rear tire contact patch through the point where the center of gravity intersects a vertical line through the front axle. Makes sense to me.

But, the amazing 4 link calculator gives the following image that shows the light blue lines as the 100% anti-squat (and 100% anti-dive). Note the front and rear of the car are reversed from the above image. and the blue lines seem to be very different. My center of gravity is like 31".

Can anyone explain the anti-squat in the calculator? It seems oddly very steep - I'm never getting to 100% chasing that.

 

[workingdog]

Yes, my COG was too low, I raised it, but it didn't really change anything. I think your purple dotted is 100% and the green dotted is actual anti squat (because your upper link is actually pointed down - which is interesting. But still, your 100% anti-squat line makes sense, mine does not. There must be some number out of whack in my model. I should try it again in the old model and see if it makes more sense there.

 

[workingdog]

So I found the version you used, and entered the same data from my sheet into it, and get a totally different line for 100% anti squat (and therefore a very different value for anti-squat). So, there's something in the newer version I have (version 4 that does the front and back at the same time) that's different. So, I guess I'll work with version 3 and be happy with that.

Edit: So, I looked further into version 4 and it's using drive bias front and rear to adjust the 100% anti squat line. If you change the front drive bias from what was in the calculator I download from .5 to 0 (to force the rear wheels to calculate at 100% drive bias), then the 100% squat line matches the version 3 - so, hopefully some other geek will run across this in the future and benefit from it.

 

[Vandal FJ]

I saw an episode of 4 wheeler this weekend on this very subject. I THINK he said the COG would be the camshaft height on the motor...

Don't quote me... I run leafs

 

[workingdog]

Yes, you are right, they are saying for a modern V8 with aluminum heads and plastic intake, camshaft height is a good approximation. I wish there were a way to really figure it out.

 

[Thomo]

So I found the version you used, and entered the same data from my sheet into it, and get a totally different line for 100% anti squat (and therefore a very different value for anti-squat). So, there's something in the newer version I have (version 4 that does the front and back at the same time) that's different. So, I guess I'll work with version 3 and be happy with that.

Edit: So, I looked further into version 4 and it's using drive bias front and rear to adjust the 100% anti squat line. If you change the front drive bias from what was in the calculator I download from .5 to 0 (to force the rear wheels to calculate at 100% drive bias), then the 100% squat line matches the version 3 - so, hopefully some other geek will run across this in the future and benefit from it.

Seems like I've been having the same issue with AS numbers on V4 of the 4 link calculator. @workingdog I know you said setting the drive bias to zero made the 100% AS line look more normal, but did you ever ascertain whether or not drive bias affects AS? I've been googling for hours and still can't figure out whether or not it's just a kink in the calculator or if drive bias does affect AS numbers.

 

[workingdog]

No, I never did anymore on it.

 

[A10Driver]

Try version 3, version 4 uses front and rear anti dive/ anti squat