Author Topic: Diablo chassie, why that much anti squat?  (Read 970 times)

orbitzz

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Re: Diablo chassie, why that much anti squat?
« Reply #5 on: December 01, 2015, 02:24:02 AM »
Fast and good answer.  I will build it with neutral arms. Thank you 76mx

76mx

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Re: Diablo chassie, why that much anti squat?
« Reply #4 on: November 30, 2015, 10:04:24 PM »
Graeme,
   I do not know the exact numbers of either. I saw the plans and have been doing this and setting up racecars long enough to be able to just look at it and tell whether it is close. I also do not know why it was done that way on a Countach but there are a lot of things on one that I would like to understand the logic of. For instance, why go out of your way to put a much wider wheel in the front than the tire requires so that now an even smaller footbox is needed to accommodate the larger fenderwell?
   I can eyeball one pretty close but I use Robert Metcalfe at Metcalfe Racing Services to computer analyze a chassis. Orbitzz is on the right track when he wants to make the car neutral. Any engineering design process is about how you handle the compromises. A chassis performance is determined by its application and how the engineering handles the compromises for that application. But here is something Robert told me a long time ago that should be helpful. If a chassis is predictable and doesn't do anything crazy under conditions, it is a good chassis. As long as the driver knows and can predict what it is going to do, it is a good chassis. If the shocks do not bottom out (DANGEROUS) and the roll centers do not change, it is a good chassis. 

lambo

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Re: Diablo chassie, why that much anti squat?
« Reply #3 on: November 30, 2015, 07:29:33 PM »
Hi Charley , Did the NEARC have more built in than the factory drawings in the 6.00 manual to suit the gm arms, I am using the 6.00 manual geometry to lay out my Countach frame i'm building, I have also noticed that the 6.0  manual had more than 6deg caster on the front which I thought was high, I assumed it might be that high for the 4wd VT system but throught that 3 or 4 would be fine for a 2wd road car, do you have any thoughts, the 6.0 also had quite a bit of antisquat in the rear, but figured lambo know more about it them me, I did get lucky enough to measure a real Countach from end to end  back in 87 and noticed that the upper front arm was higher by about 20mm at the rear  than the front, sort of an anti dive in reverse, but cant find out why they did that, could it have been a form of anti lift , I have searched the web for years as to why they did that with no luck, all standard production cars seem to have the rear of the top arm lower for anti dive, from a packaging perspective raising the rear of my top arm would be much better as it moves that point away from my pedals, do you know or can explain why they did it.
Graeme

76mx

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Re: Diablo chassie, why that much anti squat?
« Reply #2 on: November 30, 2015, 09:45:43 AM »
Orbitzz,
   The NAERC as well as the Chassisworks chassis were based on Corvette geometry and the weight distribution of a front engine car. Not only is there too much anti-squat in the rear, there is also too much anti-dive in the front. Fortunately both of these are easy fixes if you catch it now.

orbitzz

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Diablo chassie, why that much anti squat?
« Reply #1 on: November 30, 2015, 02:24:50 AM »
Hi! I'm building a diablo with cusotm chassie (Naerc). I have bought my chassie half builded with suspenision, spindles and uprights.
All of that has to be rebuild again, crappy work.  In the front i've used corvette c5 spindles and rack/pinion. In the rear i'll be using Ferarri mondeal uprights.
I have talked to famous chassie builders in sweden if i should use that much of antisquat in the rear suspension. The answer is no, it's better to get the a-arms at zero and make the spring constant at 2.5Hz. That makes the car more neutral end more easy to balance.
Well this is a little bit over my suspension knowledge, but i'm getting there.
My question with all this is: What do you think about that big anti squat built in to the rear? is it necessary?