“The diameter divides into the circumference, you know. It ought to be three
times. You'd think so, wouldn't you? But does it? No. Three point one four one
and lots of other figures. There's no end to the buggers. Do you know how
pissed off that makes me?"
"I expect it makes you extremely pissed off," said Teppic politely.
"Right. It tells me that the Creator used the wrong kind of circles. It's not
even a proper number! I mean, three point five, you could respect. Or three
point three. That'd look *right*." He stared morosely at the pie.”
On Tuesday, November 26, 2019, 07:41:20 PM EST, forrest.whitmore via EV
<[email protected]> wrote:
Hi David,
Thank you for the reply and the welcome! I can't believe I've been missing
out on EVDL for this long - it's a great resource! This helps understand the
relationship a bit better.
----------------
Hi Alan,
Thank you for the response - I appreciate the detail. My next step, as you
mentioned, is to find the best setup for acceleration and speed. I most
likely will use the motor with a 30% safety-margin from its max of 10000 RPM
= 7000 RPM.
If I understand correctly, gearing the diff and/or transmission to a higher
RPM (within set safety-margin) allows for less required amps along with less
heat? Initially, I was under the impression that a lower motor RPM
corresponded to a "cooler" motor.
Electric Vehicle Discussion List mailing list wrote
> Forrest,
>
> A 28.7" tall tire has a circumference of PI * 28.7 or 3.17*28.7 or 90.98"
> or 7.58 feet.
> 3,000 motor rpm *1 drive shaft revolution / 3.27 rear axle revolutions =
> 917.43 rpm
> 917.43 rpm * 7.58 feet circumference of tire = 6,954 feet / minute * 1
> mile
> / 5,280 feet = 1.317 miles / minute
> * 60 minutes / hour = 79.02 miles per hour.
>
> At 3,000 rpm, with no transmission, or the transmission in high gear (1:1
> ratio) the 3.27 rear end will spin at 917.43 rpm making a 28.7" tall tire
> run 79.02 miles per hour.
>
> To get the most acceleration and usable speed from the setup, you should
> find the maximum safe rpm of the motor, and gear the vehicle just under
> that rpm by a safe margin, at a maximum speed that you will not exceed.
> Some conversions use second or third gear to get the motor rpm's up. You
> could use a shorter tire. One drag racer went to a smaller diameter DC
> motor that could spin faster, and then used two motors.
>
> I hope this helps,
>
> Alan
--
Sent from: http://electric-vehicle-discussion-list.413529.n4.nabble.com/
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