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Mad7
02-14-2012, 06:17 AM
I have built a Logrunner and covered it with fiberglass. It is heavy and looks like a ups truck. It is about 4 ft high and 3 ft wide and about 10 ft long. I have 4 12 volt batteries for 48 volts. My controller is a 48v 3 amp. I am using a tread mill motor I got for free. I installed it on the trike with the wheels off the ground It worked great. Wow the tire spun really fast. As soon as I took it for a ride It was not strong enough to move the trike. Do I have a problem with the controler or the motor. Can anyone help me with this.
Thanks Wolfgang.

charlie_r
02-14-2012, 06:34 AM
A bit more info would be needed here. You say the wheel spun really fast. How much faster did it spin than you would have been able to spin it by hand through the cranks?

I would expect that you exceeded the torque output available from the motor. Do you know how fast the motor turn without any load on it? You may need to put in a gear reduction set. Trade some of the motor shaft speed for the torque you need to drive the vehicle.

Mad7
02-14-2012, 06:48 AM
Thanks Charley_r
I don't know how fast it spins.bbut it took about 90 seconds to stop spinning after I cut the power to the motor. That is many times faster than I could spin it with my hand.
No load rpm idk. It's a 2.5 hp bldc motor
10 tooth on motor
Just a single free hub about 24 teeth on wheel

charlie_r
02-14-2012, 07:19 AM
You definitely need to add another reduction set in there. My gueestimate is that the BLDC motor is turning somewhere between 500 and 1000 rpm. Needs to be geared down to 60 to 100 rpm.

Remember, when you reduce speed through gearing, you increase torque, so build accordingly.

Prime example -- It snowed here yesterday. When I tried to start from a standing start in my lowest gear, I spun my drive wheel every turn of the crank. When I changed to closer to midrange gearing, no wheelspin, but the effort required to turn the cranks increased substantially, as expected. to put this in bike terms, lowest gear is 15 gear inches, or 3.9 feet of movement for each turn of the crank (development). Torque multiplication gave me enough power to spin the wheel. Midrange gear I selected, gave me 33 GI or 8.6 feet development at a much lower torque. So no wheel spin.

In your case, guesstimating the motor shaft speed at 500 - 1000 rpm, with 10-24 gears and a 26" MTB wheel, would give you 107 GI, and 27.9 feet development. Road speed between 16 and 32 mph (26 - 51 kph).

Search the forums here and/or google mid drive.

KoolKat
02-14-2012, 09:58 AM
Do you have a picture? Would be great to have it in our gallery. Send to gallery@atomiczombie.com .