All wheel drive

Joe ee

1 µW
Joined
Mar 29, 2018
Messages
2
A question. If I add a second identical 1000 watt motor to my bike will I double my max speed, double the torque of the bike increasing hill climbing ability by a factor of 2?
 
Torque will double, top speed will be just a bit faster than with one motor.

On the flat:
Click on this link to see a simulation of a typical 9C '1000W' kit at 48V. It hits 30mph.
http://www.ebikes.ca/tools/simulator.html?bopen=false&motor=M2706&batt=B4823_AC&cont=C35&hp=0&axis=mph&cont_b=C35&motor_b=M2706&batt_b=B4823_AC&hp_b=0&add=true&blue=Lbs&grade=0

Click on this to see the 2WD version. It hits 34mph.
http://www.ebikes.ca/tools/simulator.html?bopen=true&motor=M2706&batt=B4823_AC&cont=C35&hp=0&axis=mph&cont_b=C35&motor_b=M2706&batt_b=B4823_AC&hp_b=0&add=true&blue=Lbs


On an 8% grade:

The 1WD hits 22 mph and will overheat in 11 minutes:
http://www.ebikes.ca/tools/simulator.html?bopen=false&motor=M2706&batt=B4823_AC&cont=C35&hp=0&axis=mph&cont_b=C35&motor_b=M2706&batt_b=B4823_AC&hp_b=0&add=true&blue=Lbs&grade=8

The 2WD hits 30mph and will never overheat
http://www.ebikes.ca/tools/simulator.html?bopen=true&motor=M2706&batt=B4823_AC&cont=C35&hp=0&axis=mph&cont_b=C35&motor_b=M2706&batt_b=B4823_AC&hp_b=0&add=true&blue=Lbs&grade=8

The assumption in the 2WD case is that the controllers are chosen/limited so the sum of the max currents do not exceed the max current of the battery. This is not really strange - the battery has to be able to essentially drive one big motor. The other assumption in the simulations (which you can change if you wish) is that the controllers, wheels, motors, tires are the same. This gives optimal efficiency using just a cheapie controller like you get with typical kits (non-torque throttle).

Anyhow - read the simulator page and play around - should answer your performance questions.
 
Hey, that’s great information and thank you. I will look at those links. I suppose I should have mentioned that I plan to power each motor independently using 48 Volt 10 AH LIFEPO4 batteries. I also plan to run both off of one throttle. I don’t know if that would change the gist of what your response was but thank you kindly for the reply.
 
How much more performance you get with two motors versus one depends somewhat on how underpowered one motor is, and how close the motor's free speed is to its cruising speed. But note that doubling your top speed takes four times as much power to the ground, not two.
 
Do not forget this...

www.ebikes.ca
Tools
Trip Simulator BETA
Left Column - Chart Options - Input Type - Google Maps
Right click your starting point
Right click your ending point
And move the route accordingly.
 
I would advise you to consider a geared hubmotor for the front wheel. As to the rear wheel, use a motor that is as powerful as you like.

Also, be aware that simply adding a motor doesn't add power. Your battery may be maxed-out on the existing motor, so adding a second one will mean that splitting the existing power will allow both motors to run cooler.

It can be done with one throttle input, and of course easily done with two throttles. I believe the best 2WD system will have 2/3rds of the power going to the rear hub. As long as the amount of power going to the rear hubmotor is less than 48V X 25A = 1200W, you might use a MAC/BMC on the rear, which would be more efficient and lighter than a DD hubmotor. A MAC/BMC has a roughly 22mm width stator, and the BPM has a 17mm wide stator, so a BPM on the front would be a good match for the MAC/BMC on the rear.

Once you want more power on the rear, so much so that the amps might overheat a geared hubmotor, a Direct Drive (DD) is called for. Using 1200W on the front geared hub will mate well with 2500W on the rear, so an Edge 1500W DD hub is a good size (which is well-known to handle frequent peaks of 2500W). A combination like this would have roughly the same power as a MXUS 3K Turbo on the rear (single-motor system at 3700W?), but...it would have the added benefit of 2WD traction. Of course, in this instance, you would need a battery capable of 48V X 80A peaks...
 
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