Trap speed is the average MPH over that last measured bit of track.
I guess you can use an interpolation of the 1000' to the 1/4 mile to see
what your average acceleration is at the top, and apply it to the last bit.
Get a hold of John Force or one of those guys, I'm sure they have a formula
worked out ;-)
Rading the speedo is useless. Because of several things: 1) it hasn't
caught up yet, and 2) differing tire sizes.
TonyC
-----Original Message-----
From: jon@dakota-truck.net <jon@dakota-truck.net>
To: dakota-truck-moderator@bent.twistedbits.net
<dakota-truck-moderator@bent.twistedbits.net>
Date: Thursday, October 17, 2002 12:24 PM
Subject: DML: Trap speed vs actual speed (was: A few 4.56 gears Qs.)
>
>"Tony Cellana" <acellan1@tampabay.rr.com> wrote:
>: My 99 R/T has a set of 4.10s and I use the 26 ET Streets on the track.
MPH
>: through the traps is right at 100, and my rpms are around 5400.
>
>
> Speaking of which, does anyone know if there are any accepted
>methods to calculate actual speed from trap speed, or vice/versa?
>Drag strips use a 66' (I think) trap at the end of the run to
>calculate your speed, based on the amount of time it takes you to
>cover that known distance. However, you are actually acellerating
>all the way through that distance, so your actual speed at the end
>of the 1/4mi is higher than what is listed on your time slip. (This
>is why the G-tech reads a higher 1/4mi speed than the track.)
>
> However when working out gear changes and tire sizes as we are doing
>here, actual speed is what we want, but we only have trap speed
>(except for the cases where we might be able to glance at the speedo
>at the *exact* moment we cross the line, and even that calls into
>question speedometer accuracy, etc.) It would be nice to be able
>to convert trap speed to actual. Granted, different vehicles will
>be accellerating at different rates, so its probably not like you can
>do something like actual speed = trap speed - 5%. But maybe some
>assumptions can be drawn based on the trap speed itself, maybe throw
>HP or some other things into the mix, and a table of percentages for
>different trap speed ranges could be made? That's certainly not 100%
>accurate either, but it might at least get it a few MPH closer...
>
> I did a web search but came up with nothing.
>
>
>--
>
> -Jon-
>
> .---- Jon Steiger ------ jon@dakota-truck.net or jon@jonsteiger.com -----.
> | I'm the: AOPA, DoD, EAA, NMA, NRA, SPA, USUA. Rec & UL Pilot - SEL |
> | '70 Barracuda, '92 Ram 4x4, '96 Dakota, '96 Intruder 1400, '96 FireFly |
> `----------------------------------------- http://www.jonsteiger.com ----'
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