i think something is not right, if the motor have the same Watt the maximum output power is the same so if i use a 1.8 time gear at the 90kv motor i should obtain the 170kv. is there anything special about brushless motor that make them more efficien at high speed as @grecoman say?
It takes more amps to get up to speed (way more) than to stay at speed. Once you hit max efficiency (about 95% duty cycle) the board will draw waaaaaaay less amps than if you were constantly stopping and starting.
i will adapt the gear to the motor, let’s say i use a 3.7:1 gear for the 170kv and a 2:1 for the 90kv motor, the final wheel kv will be about 45 kv for both configuration and 2200W, is there any advantage in one of the 2 configuration or the are equivalent?
Definitely 90kv. Problem with ebikes is that since the wheels are so big, they require a massive reduction. Our standard 83mm longboard wheels are significantly smaller than the, what is it, 24 inch bike wheel? E bikes are a lot more torque low rpm than that of our outrunner motors which are more low torque high rpm by comparison.
You are going to find you will need a crazy low gear ratio.
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Maybe this could help?
Welcome to the esk8 forum.
See below a quote from one of the major esk8 companies on the forum. He explains why running a motor close to 60k erpm provides the best efficiency by balancing low rpm copper losses with high Rpm iron losses.
Considering the above, I would suggest calculating your ideal KV as follows.
60,000erm/(Voltage x motor pole pairs) = Ideal KV
Example: 48V battery with a 14pole motor(7 pole pairs)
60,000/(48x7) = 178KV
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Your gearing is usually limited, so 1:2.5 is realistic. You can easily calculate the motor rpm for the desired top speed and you know your voltage, which should be as high as possible (12s). This in combination will tell you the ideal KV.
The vesc-project has a nice calculator: www.vesc-project.com/calculators
120-170kv is the range you should look at. Lower KV motors draw less amps and are better for the esc and battery.
Frank
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I think of e bike as assisted bike. we all have very efficient drive at low speed (aka legs). so my theory is e bike should focus on top speed and assisting for hills.
Just did the maths for you
12S battery , 14/37 transmissinon ( e.g. HTD 5M belt drive), 90mm wheel 40 km/h top speed (very fast) desired.
motor KV =145
Frank
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Thanks! that was exactly what i was looking for,. Now i just need to choose a good sensored motor, i was looking at ollin but the 170kv is out of stock, alien power system has some good motor, any suggestoin on the brand? same for the vesc, i need som suggestion, i think i will stay between 120kv and 180kv with a 8/10s battery to leave some sapce for improvement in the future
I just had 4 motors custom built by Alien power and I cant say anything but good things about the customer service I received. Excellent communication, very experienced and knowledgeable staff, and fair prices.
what vesc did you use? that seems to be the part more likely to fail
Ive had excellent experiences with the Enertion FOC box. Ive also been using the VESC 6’s from Trampa since they were released in Beta without any problems. Both companies have provided great customer support as well.
that looks really good but the price is way higher than the competition, i think i will go for a alien power system 3300W 130kv for around 80/90 pound, i don’t see why this motor is twice the price
i believe thise are handwind motor.
is there any real advantage?
presision and reliability i guess. I dont think it’s usful for personal ev per the price
Nice high end magnets, high temp. copper, Jap precision bearings, hardened axle shaft, hand would to max copper fill, dual keyway, filter disc, A4 stainless all the way through. Quality drives the price up, but these ones are very powerful and long lasting motors.
Frank
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i will start with cheaper component, if i will manage to brake them i will go for vesc 6 and tramp motor, right now i need to find a vesc to be delivered in UK without waiting for months and with good quality to support foc + sensored at 8/10s