Randall Young wrote:
>
> All that work, and the thing only develops 190 lbf of thrust ? It was a
> whole lot faster before he modified it !
>
> Unless my envelope slipped a digit somewhere, his 0-60 mph time should
> be something like 40 seconds ... the thing only makes around 1/2 as much
> power as my TR3A, and doesn't have any torque multiplication !
Pretty close. Sort of fun to try to remind myself of some basic
acceleration stuff and some international units I've long forgotten from
disuse. But, it goes something like this:
Ignore rolling resistance and aerodynamic drag. Assume 2100 lb. curb
weight + driver = 2250 lb, or 1020 kg.
1 Newton(f) = 0.225 lbf
One Newton is the force required to accelerate 1 kg of mass at one
meter/second/second, or:
1 Newton(f) = 1 kg(m) x 1 m/s/s (F=mA)
190 lbf = 844 Newtons
Using the standard Newtonian force equation:
F=mA
844 Newtons = 1020 kg x 0.827 m/s/s
To sort of bring this into perspective, let's take 1/4-mile performance
as an example:
To determine final velocity starting from rest for the quarter mile,
divide 1320 ft by 3.275 to get meters = 403. Not yet knowing the elapsed
time, the acceleration equation from rest for final velocity over
distance would be:
Vsubf = square root of (2a x delta d), where Vsubf is final velocity in
m/s, a is rate of acceleration in m/s/s and d is distance, or
403 x 2 x 0.827 = 667
Sq rt of 667 = 25.81 m/s, or 84.6 ft/s. Taking the shortcut to calculate
mph, 88 ft/s = 60 mph, so this guy's trap speed in the quarter is 57.65
mph, less a bit for total drag.
Working backwards from the final velocity to distance result, the
equation for elapsed time is:
Vsubf = a x t, or t = Vsubf / a
therefore, this guy's elapsed time in the 1/4 mile is:
t = 25.81 / 0.827 = 31.21 seconds (neck and neck with a stock Renault
Dauphine, I would guess...).
Let's hope this guy's specific thrust estimates are way low--otherwise,
he's probably invented the world's slowest jet-powered car.... <smile>
Cheers.
--
Michael D. Porter
Roswell, NM (yes, _that_ Roswell)
[mailto:mporter@zianet.com]
`70 GT6+ (being refurbished, slowly)
`71 GT6 Mk. III (organ donor)
`72 GT6 Mk. III (daily driver)
`64 TR4 (awaiting intensive care)
`80 TR7 (3.8 liter Buick-powered)
`86 Nissan 300ZX (the minimal-maintenance road car)
`68 VW Type II Camper (Lancia twin-cam powered, but feeling its age....)
Remember: Math and alcohol do not mix... do not drink and derive.
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