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Old 08-21-2017, 07:56 PM   #33 (permalink)
The Toecutter
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Join Date: May 2010
Location: Ghettoville, USA
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Rebellion - '16 KMX Framekit Custom electric velomobile
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Quote:
Originally Posted by Bicycle Bob View Post
With my body weight added, I'd have about 40 lbs/hp, so I wouldn't out-accelerate many cars, unless your motor is just rated at constant duty and the controller can heat it up.
It's not just power to weight ratio that matters, but torque. The Leafbike hub motor that I plan to use can make car-like torque without destroying itself, in a vehicle whose laden weight is 1/10th that of a car. In order to get this thing to take on cars at lower speeds, the traction of my rear tire will be the limiting factor, and I do not yet know precisely how much traction it has. It's a Schwalbe Marathon Plus, and if I pedal with full strength at a stop in 1st gear in either the 28T or 38T rings, I can make the back tire break traction without a motor. So its traction isn't all that great if it can't even handle human power, let alone human power coupled with an electric motor.

I ran a simulation of this hypothetical vehicle fitted with a 1500W continuous Leafmotor with the 5T wind at 72Vmax, 6 kW, 83A, 120A phase current, 30/40/60T front chainring, 42-11T in the rear, and the rider pedaling with 500W going through the rear gears up to top speed. At a 0.25 Cd, 6 sq ft frontal area, 300 lbs laden weight, 0.008 Crr, 26” wheel, controller voltage/current limiting factors(assume for this calculation a battery powerful enough to run this with minimal sag and that traction won't be an issue), and the rider starting out in a 60T front and 28T rear gear, no traction limit accounted for, I get the following performance:

0-10 mph: 0.8 seconds

0-20 mph: 2.3 seconds

0-30 mph: 4.1 seconds

0-40 mph: 6.6 seconds

0-50 mph: 12.3 seconds

Top Speed: 53 mph

1/8 mile: 11.8 seconds @ 49.6 mph

That's very car-like. I don't know how close reality will bring me to the above figures, but my acceleration will certainly be adequate for merging into traffic and accelerating like a low end car.

With modifications, the Leafbike motor could be allowed to peak at 10 kW. This will require drilling holes in the casing and installing fans. I plan to start with 4 kW, because among those on endless sphere who have used this motor, unmodified, the general consensus is that you won't hurt it at 4 kW. At 10 kW, acceleration would start matching some $30,000+ modern sports cars, *if* I can get enough traction(highly doubtful).

Quote:
Have you compared estimates between fairing the wheels separately vs installing a 40" door? Some houses are much improved by double doors, too.
Installing a door is not an option. I don't own the place I live in, and the landlord is not keen on the idea.

Last edited by The Toecutter; 08-21-2017 at 08:01 PM..
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