Electric Cars Faster 0-30?
01-29-2002, 05:07 PM
#32
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Actually torque is created by force cross producted with the radius vector from the axis of rotation. This torque, integrated over time, can be used to determine power as well.
The integral of the force over distance of the pistons (which is *NOT* a torque issue) is the power of the engine. So is the integral of the torque over angle for the crankshaft.
So does power "create" torque or vice versa? Both. The energy output (power) of the combusting gas forces the piston down (not torque yet), which in turn applies an offset force on the crankshaft, which in turn creates torque. However, that torque eventually finds its way to the wheels, which impart a linear force on the car over distance, which is again, power (via the integration of force over distance that others have mentioned).
Ultimately, both torque and power is driven by heat
So we are all wrong 
And no, I don't have the curves backwards orthonormal. I make (or made until the company ran out of money) a living on simulation that includes vehicle dynamics as well as motor dynamcs. If the physics I'm using for these arguments were wrong, I can both sue the teachers I've studied under for misleading information, and most likely my simulators wouldn't behave properly (they do according to every test I've thrown at them).
The integral of the force over distance of the pistons (which is *NOT* a torque issue) is the power of the engine. So is the integral of the torque over angle for the crankshaft.
So does power "create" torque or vice versa? Both. The energy output (power) of the combusting gas forces the piston down (not torque yet), which in turn applies an offset force on the crankshaft, which in turn creates torque. However, that torque eventually finds its way to the wheels, which impart a linear force on the car over distance, which is again, power (via the integration of force over distance that others have mentioned).
Ultimately, both torque and power is driven by heat
So we are all wrong And no, I don't have the curves backwards orthonormal. I make (or made until the company ran out of money) a living on simulation that includes vehicle dynamics as well as motor dynamcs. If the physics I'm using for these arguments were wrong, I can both sue the teachers I've studied under for misleading information, and most likely my simulators wouldn't behave properly (they do according to every test I've thrown at them).
01-29-2002, 05:11 PM
#33
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[QUOTE]Originally posted by Orthonormal
[B]Getting back to the point, electric motors are at maximum torque at zero RPM, while gasoline engines take a while to build to near their maximum torque. (typically 2000-3000RPM on the cars I've driven).
So if an electric and a gas car have identical 0-60 times, the electric car most likely does better 0-30 and the gas car does better 30-60.
One reason that the Porsche is quicker off the line is the rear weight bias.
[B]Getting back to the point, electric motors are at maximum torque at zero RPM, while gasoline engines take a while to build to near their maximum torque. (typically 2000-3000RPM on the cars I've driven).
So if an electric and a gas car have identical 0-60 times, the electric car most likely does better 0-30 and the gas car does better 30-60.
One reason that the Porsche is quicker off the line is the rear weight bias.
01-29-2002, 06:25 PM
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[QUOTE]
So does power "create" torque or vice versa? Both. The energy output (power) of the combusting gas forces the piston down (not torque yet), which in turn applies an offset force on the crankshaft, which in turn creates torque. However, that torque eventually finds its way to the wheels, which impart a linear force on the car over distance, which is again, power (via the integration of force over distance that others have mentioned).
So does power "create" torque or vice versa? Both. The energy output (power) of the combusting gas forces the piston down (not torque yet), which in turn applies an offset force on the crankshaft, which in turn creates torque. However, that torque eventually finds its way to the wheels, which impart a linear force on the car over distance, which is again, power (via the integration of force over distance that others have mentioned).
01-29-2002, 07:11 PM
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Originally posted by dsp
...side note to self: remember to retreat from math arguments when a guy whose handle is "orthonormal" pipes up. i got a (very generous) C in linear algebra.
...side note to self: remember to retreat from math arguments when a guy whose handle is "orthonormal" pipes up. i got a (very generous) C in linear algebra.
anyways dsp,
we need to use dot products with vectors such as W = Force[dot]Distance
multiplication of scalar quantities is for liberal arts physics
01-30-2002, 05:45 AM
#37
Originally posted by Tedster
Who's heard the story of a race won by using the starter motor to limp across the finish line?
Ted
Who's heard the story of a race won by using the starter motor to limp across the finish line?
Ted
Tim
P.S. That's the opening to Firesign Theater's "Ultimate Joke" skit. Near the end, the guy wants some alterations made to a suit, and the tailor says it'll cost an arm and a leg. The tailor takes the guy's arm, wraps it around his GF like a mink, which turns into, "A man walks into a bar with a beautiful arm on his girl..."
01-30-2002, 04:54 PM
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Originally posted by dsp
i think the EV1 also has a CVT, which is an advantage. the weight is about 3000 lbs, which isn't too bad. can't remember the horsepower.
i think the EV1 also has a CVT, which is an advantage. the weight is about 3000 lbs, which isn't too bad. can't remember the horsepower.
137 hp @ 7000-13500 rpm
110 lb-ft @ 0-7000 rpm (hey what, no torque?
)2870 lb curb weight (1175 lb of which was Pb-acid batteries)
0-30 2.8 sec
0-60 7.9 sec
top speed = 80mph (electronically limited)
No CVT. Single speed, like most EV's. The low top speed, wide rpm range, and torque characteristics allow it to get away with that.
BTW, I calc a max wheel torque of 1200 lb-ft for the EV1 vs 2280 for the S2000 vs 3185 for a C5 vette. The S2000's and C5's are, of course, in first gear at peak torque rpm.
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