So I am using a 12s battery(2 6s, 6200mAh 40C in series), a 18/32 gear ratio, and a VESC from diyelectricskateboards. What my question is what motor should I choose.
hobbyking.com1
Turnigy Aerodrive SK3 - 6364-213KV Brushless Outrunner Motor
Turnigy Aerodrive SK3 - 6364-213kv Brushless Outrunner Motor
OR
hobbyking.com2
Turnigy Aerodrive SK3 - 6374-192KV Brushless Outrunner Motor
Turnigy Aerodrive SK3 - 6374-192kv Brushless Outrunner Motor
I am aware of the 60,000 ERPM limit recommendation and I used calc.esk8.it and both choices are very close to that limit.
My goal with this board Im building is to go as fast as possible, so I am not sure which motor to choose, because one says it takes 10s and one says 12s and im not sure what the W or T or A mean for each motor and what that will do to speed, acceleration, range and so on.
To add to what @BigBoyToys said. There is also an erpm limit setting. You can simply set it to 60k erpm snd you won’t exceed it, even with a 300kv and 12s.
As long as you have the correct settings, you should be fine.
Yes I know that. But you might as well choose a lower kv motor that is running at its max speed when it’s near 60k. That way it will produce more torque
If you want to break 70mph, you’re going to need 2 things.
A LOT of power. Air resistance starts to be a factor at 40+ mph, so at 70 mph, you’ll need some serious power to overcome it. I’d recommend 4 wheel drive with 2500 watts per motor At Minimum. To be safe, I’d say run 2 motors per wheel, that are about 2500 to 3500 watts each, which should put you in the neighborhood of 25 to 35 horsepower, depending on exactly which motor you go with. The other reason you need a lot of power is…
a Tall gear ratio. As in get 8 inch pneumatic wheels and instead of running 60 teeth gears on them like most people do, run normal 36 Tooth gears on them, and then on the motor run somewhere around 15 or 16 tooth gears. The tall wheels will greatly reduce your torque in exchange for top speed, which is why you need all the power from your motors.
All in all, it’d cost roughly 5-10k USD to create a build that would reliably break 70 mph. Not worth it in my opinion unless it’s your life dream, or you just have extra money sitting around.
If both configurations are limited to 60k erpm:
Lets say the battery voltage sags 3.6v under load, which isn’t crazy, scenario 1 can only reach 60k erpm if the battery is fully charged. Once the battery is at 90%, it can no longer do 60k erpm. Scenario 2 can reach 60k erpm even if the battery is under 50% charged. Therefore it can maintain that top speed for way longer than scenario 1.
Now on to torque:
For any power condition:
A set voltage and current, scenario 1 will be slower but have more torque while scenario 2 will be faster and have less torque.
If the rider is looking for a board that accelerates hard and is powerful at low speeds, I agree that a low kv would be better but for a setup that is meant to go up to 50mph, he’ll need the higher kv.
Hmm yes ok I see your point on the higher kv motor. For me personally though I would choose the lower one so that I have more torque. Also I’m not sure a 240kv motor would be powerful enough to get him moving with the sort of gearing he is going to need. Dual would be a must for this build. I just calculated it and he is going to need a 1.7:1 gear ratio and 97mm wheels to achieve nearly 50mph
YOU ARE A GOD ! Thank you for your incredible explanation, I’m going to go with the 245 KV SK3 motor from hobby king And that 12s and the VESC!! I’ll be buying those parts soon, thanks again :)))
I would certainly go with an upgraded vesc like the ollin vesc or vesc6. I wouldn’t use a standard vesc4, especially from a vendor with an unknown track record with vescs.
I would not want to experience the "speed boost’ at 30-50mph
speaking of speed boosts my buddy had a vesc then switched to a focbox and said it went away. But if I recall I thought this was a hardware issue of noise on the current sensor. Both escs share the more of less the same hardware. Can anyone back this up?
I’m suprised people are endorsing this idea, 70mph is much too fast for someone who doesn’t understand the electronics taking them that fast not to mention a minor. Speeds like this should only be attempted in the safest of environments. This is a good way to get boards banned
absolutely agree. Furthermore even if he goes trough with it he is literally pushing alot of boundaries, meaning alot COULD go wrong. I think between me starting taking freeriding and downhill seriously until I hit 60mph were years. Years in which I went riding 2-3 times a week, with proper instructers and teachers who were world champions nontheless.
They were all about balls to the wall fast but with safety and brain. Got burned into me that whenever I want to push my limits you need to be able to do everything on that speed you want to beat. Coleman, toeside, drift, speedcheck, full stop etc. So you are even able to react when shit goes south. Speed is fun, pushing boundaries is thrilling but I already lost a beatiful human being this year to his willigness to take risks where caution would have been advised. Going over you own limit is super dangerous. (You dont need 70mp/h to kill yourself, 40 is plenty when you loose your laine and go outline into a car…
Other thing is, going speed even close to 60/70mp/h needs so much set up. Pefect conditions, super familiar with the road and its conditions. Then porper hardware, from the wheels, trucks and board. So if you would ask me, would you want to go 60mp/h+ on 97mm or even 107mm wheels ? Hell no. On stock caliber 50 ? Jesus no. On a set up that wheigs close to 10-14KG ? nononono.
Then come things like having race leathers with all the protection, a full face, gloves, closed of road, safety nets, medics on point, you in your best shape.
Considering just for fun or as a free time vehicle ? ludacris. That would be worthy of a Darwin Award if anything would happen and where to be discussed between Worldcup riders…