"Live" from Jegs Northern Sportsnationals 2012

[Mickey Whaley]

Originally Posted by Ed Wright

Heck of a MPH for a 10.25.

yep i wonder if we should blame the timing system Pro stock does not get any funky MPH they are real low just wondering?

[Michael Beard]

Originally Posted by Mickey Whaley

yep i wonder if we should blame the timing system Pro stock does not get any funky MPH they are real low just wondering?

Pro Stockers trip with the nose on both the mph marker and the finish line, so the speed calculation is correct. You only get the errant high numbers by hitting the mph mark with the tire, and then "shortening the traps" by hitting the finish with the nose.

I've been to one track where my mph was way different from lane to lane with my Turismo. One of the mph beams was higher than the other, so the nose would catch in one lane and not in the other. That car will trip with the nose just by lifting!

[dynomo]

Many topsportsman cars at columbus had goofy numbers at the 1/8 as well as the 1/4 mile marks.My geuss was the height of there equipment was the problem as some racers raised there ride height and problem went away.There also was a difference lane to lane possible track crown

[Stewart Way]

Being a numbers guy I thought I'd run some numbers on trap speed and time. Not trying to stir anything, just add some logic and engineering to this discussion.
Common number for speed is 60 mph = 88 feet per second (fps). With that we know 120 mph = 176 fps. The speed trap is 66 ft long so it takes .375 seconds to go thru the traps at 120mph. 66/176 = .375. The speed given on the timeslip is not a top speed but is the average over the last 66 feet of the 1320.
Now if we look at 125 mph or 183.3 fps the time required to go 66 feet goes down to .360 seconds. 130 mph is .346. So a 10 mph change from 120 to 130 mph only takes .029 sec.
So the opposite is true. If you dump .029 sec in the last 66 feet starting at 130 mph you will read 120 mph.
If we say the car has a 3 foot nose or the distance from the nose to the cross section on the tire where the beam would hit with the nose up all that has to be done to see the difference is redue the calcs using 63 instead of 66 feet. That gives a trap time of .357 at 120 mph. That will trick the computer into printing a 126 mph.
I guess the timing computer has a formula or small data base the the trap time is input into and out pops a speed. Doesn't matter if its a car, rail, bike if snowmobile.
Just a little info fo thought. Sorry for further hijacking the thread.