BriancWS6

iTrader: (18)

So I know that the "trap speed" is determined by the average mph over X amount of feet, but how many feet is that over? Thanks.

94z28L

iTrader: (4)

believe different track have different lengths and systems, but like you said its as simple as velocity=(time)/(distance)

BriancWS6

iTrader: (18)

There shouldn't be any differences between different tracks. If there was there would be huge contraversary about trap speeds, etc on this board when people post up their results.

What I am asking is this: How many feet at the end of the 1320 is used to determine the trap speed?

Tom the roofer

iTrader: (9)

Trap Speed is measured during the last 60 feet of the 1/4-mile.

More info can be found here: http://www.staginglight.com/guide/defns.html

BriancWS6

iTrader: (18)

Bingo, that's what I was looking for. Thanks for the info

DOTracer

For some reason, I remember mph being calculated based upon 66' before the finish line. Not too many years ago, mph was calculated from two points, one 66' before the finish line and another 66' after the finish line. problem was many racers would hold the thottle through to the last mph photocell to get more mph on their time slip. On tracks with marginal length finish lines, that could be considered a safety issue. Due to this, NHRA eliminated the second mph photocell.

I think there really can be measurable differences in time slips between tracks. Only thing I can figure is minute differences in photo cell placement, be it distance (length) from each other, or even possibly the height at which they are mounted, or even the amount of crown the track surface has which affects the height and rollout. I'm refering to all photocells, not just staging beams. We have two tracks I run at and on is at 525' elevation, the other 325' elevation. The first is a good tenth to .15 in ET slower as well as 2 mph slower than the second. Just 200' in elevation will not creat such a great difference in ET & mph. Really makes you scratch your head to the exact cause to the ET & mph difference.

kp

iTrader: (34)

Well unfortunately thats not the case, there is a variation between equipment manufactures, a few feet here or there, beam height, temp affects the timers (crystal time based) and you are talking about thousanths of a second with miles of wires, lights that get ran over many times etc etc. Trust me the timeslip racers know the places to go (and even which lanes are better at some tracks) but drag 'racing' is a sport, whoever cuts the better light and crosses the finsh line first wins - not who has the best timeslip

mrdragster1970

You are correct on both issues. There are always little things about every track, and people were bitching about burning up their cars the last 66' just for a better MPH, the race was already over.

The little crappy track near me has always had short 60' lights. If you get a good launch, the 60' will be a tiny bit better than other places, but the ET is the exact same per weather. We know for a fact the track is not hooking better than other tracks, because we have to soften the launch 75% of the time. So obviously it's in the equipment, if dozens of people get the same results.

I also read an article, where a guy secretly measured a bunch of tracks, and found a bunch of old tracks were short, 10, 30, 50 feet. He said most new track were good. He also claimed on one track, the elect system was so old, that when the food trailer was cooking something, the ET would be slower from the power drain. Slowing the clocks down????

Be safe everyone.

Maggie

Exactly!
When we first started using data management, logging engine RPM vs drive line RPM and plotting events at various track locations, that sort of stuff drove us nuts!...especially when some of the tracks started looking to be 20 to 100 foot short!!

BriancWS6

iTrader: (18)

Oh I definately understand that aspect. I meant that there wouldn't be X track using 60ft for the traps and Y track using 75ft for traps.

Thanks for all the replies guys, good info in here.

kp

iTrader: (34)

Well that I dont know if they all use the exact same distance, lot of 1/8 mile tracks give the 594' time so I assume the trap is 66' since an 1/8 mile 660 feet.

For some reason the 66' thing sticks in my head but different timing systems may use a slightly different length traps for mph.