DIY skidpad testing

[nlzmo400r]

well guysive been reading up on how to do skidpad testing. As far as the math goes, here's what i found:

G= 1.225XR (radius of the circle) DIVIDED BY 2T (the time in seconds it takes to get around the circle)

Well when you just simply plug in numbers, saying it took you 16 seconds to get around the skidpad, you end up with... (on a 200ft diameter skidpad) 3.8Gs!?? WTF? why is it coming out so wierd. Someone help me here. I divided by 32 (16x2) and thats what i got. I know this isn't right. Someone wanna help me.

[1101]

that seems to be a bastarization of the physics formula for centripital acceleration.
a = (v^2)/r to find that in g's we do
a/g = (v^2)/(rg) remember g= 9.81 m/s^2

anyways

v = 2(pi)r/t

so we get
= ((2(pi)r/t)^2)/rg
= (4(pi)^2 * r) / (t^2 * g)

~= 4.02 (r/t^2)

now the r of stated circle is 30.48 m

pluging in we get
= 4.02 (30.48/(16^2))
~= .48 g's

Now I dont know if this is right, but it makes sense from my limited experence with physics.


Did some quick google searching
http://www.2quicknovas.com/formulas.html : I believe this is the site you found
http://www.westernracing.com/reference/formulas.htm : Has the same formula i just dirived but it's in feet units, the previous site just said 2t != t^2

hope this helps.

[nlzmo400r]

^^ wow,way over my head. I found the formula i got in SCC, and other places online, so im almost sure its right, im also sure that im plugging in the numbers wrong. If you care to try again,and put that into words, that would be awesome, but i dont even think i can comprehend what you wrote in taht thing^

[1101]

http://murray.faithweb.com/formulas.htm
Another site that says it should be t^2 not 2t

[nlzmo400r]

^Thats much more correct sounding. Because then if it took you 16 seconds to get around, itd be more along the lines of .47G's,which still sounds insanely pathetic. Something still isn't adding up. SCC's project Silvia with 225/45/azenis sports went around HALF the 200ft skidpad in 7.13seconds. Soo, figuring it would take about 14 seconds to get around completely.......that would equal .6g's (when their actual number was just over 1g). W.....T......F?

[lilredstiffy]

are you starting from a stop and timing?
that might not work too well

[1101]

that 7 s figure was stated as before they tuned th suspension more after their diff change.

going around 1/2 a of a 200ft skid pad in 7 seconds is SLOW

(pi)r = 1/2 the distance around the circle
finding the rate of travel we divide by time

so (pi)r/ t gives us feet / sec multiply by .681 to get miles / hour

so going around half that circle in our case would be :

[ (pi)(100)/7.13 ] * .681 ~= 30 mph quite slow.

They said in the article that there ass end was out for most of it also. I never saw them give any more skid pad figures later to back up their 1+ g reading.

[nlzmo400r]

they ran 7.33 around half the skidpad with everything but their quaife differential. When they put the diff on, they pulled a 7.13. So is this method correct?