Electric Skateboard questions

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Fewski

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Dec 17, 2012
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I'm interested in building an electric skateboard using a brushless RC motor. Read every thread here about mountain boards and skateboards, so already got a lot of useful information, but still have a few questions..

I'm seeing anywhere from 190-280KV motors, I know the lower has more torque, but how low is to low?

Where can I find a gearing calculator or what is the equation when I decide on all the variables?

Apparently the motor of choice is a Turnigy from HobbyKing. The shipping they charge is ridicules - is there any other place that sells outrunners at a reasonable price?

Lastly, HobbyKing recommending an 85-100A HV ESC to use with a motor I was thinking on. Can I use a 100A ESC even if it doesn't say HV, or is a HV ESC special?

Thanks!! :)
 
How low is too low depends on the power of a motor. A 2kW motor at 280kv is still going to have an insane amount of torque, more than enough for an electric skateboard.

Gearing is based on ratios, there aren't really any special formulas for it. For example with a 5:1 reduction, if you have a motor going 2000RPM, 2000/5 = 400RPM. So if you want 5:1 "gearing", you could use a 11 tooth sprocket on the motor, and a 55 tooth sprocket on the wheel, or you could use a 5 tooth sprocket on the motor and 25 on the wheel, etc

I don't think you'll find outrunners any cheaper than from Hobbyking - Turnigy and Hobbyking are the same company, so you'd expect their prices on Turnigy motors to probably be the lowest.

The HV stands for high voltage, which depends on how many series LiPo packs you're using. Just check the input voltage range of the ESC first.
 
Thanks for the quick reply!

Here's what I'm thinking....

Motor:
http://www.hobbyking.com/hobbyking/store/__18128__Turnigy_Aerodrive_SK3_6364_245kv_Brushless_Outrunner_Motor.html
Stats:
Kv (rpm/v) - 245
Max Current (A) - 70
Max Voltage (V) - 37
Power(W) - 2700
--OR--
http://www.hobbyking.com/hobbyking/store/__18176__Turnigy_Aerodrive_SK3_5065_275kv_Brushless_Outrunner_Motor.html
Kv (rpm/v) - 275
Max Current (A) - 65
Max Voltage (V) - 37
Power(W) - 2050

ESC/Controller:
Most Likely: http://www.hobbyking.com/hobbyking/store/__9328__TURNIGY_K_Force_100A_Brushless_ESC.html
or
http://www.hobbyking.com/hobbyking/store/__16367__Turnigy_dlux_100A_SBEC_Brushless_Speed_Controller_w_Data_Logging.html

Battery:
5000mAh 6S1P 40C
http://www.hobbyking.com/hobbyking/store/__9965__ZIPPY_Flightmax_5000mAh_6S1P_40C.html

Does this look like a good setup?

245 I would imagine would be a large amount of torque, but if my dad wants to ride it, I want to know it could move the extra weight. Is there a way to limit the torque with through the ESC? Or would the second choice (275KV) work just as well even though the power(w) is about 700 less?

The ESC is showing the max input voltage to be 2-6 cells lithium. I'll be using a 5000mAh lithium... is that pushing the ESC to the max?

Thanks for all the help, I'm learning as I go and bet I've read well over 100 pages on this forum alone... good stuff.
 
That first motor is the exact same one I'm using on my scooter mod.

Your motor choice should really rely on your gearing and target speed. Keep in mind though, that things like skateboards and scooters aren't designed to go at such speeds, so thinks like speed wobble may be an issue, just don't get too overenthusiastic with the speed, or it'll be near impossible to ride & dangerous.

With hobby ESC's like that, it's not possible to limit current. Limiting current will reduce torque, but not speed (Unless the motor stalls). I'm not sure how people limit the torque on hobby ESCs, to be honest.

Seeing as you'll need to come up with a throttle system anyway, you could limit your throttle max range. Hobby ESC's like that require a PWM based throttle input, so you'd have to use a microcontroller (Or a servo tester is also common). You could put a resistor in series with the potentiometer to limit the high range of the throttle. You'll still have full torque though, which you need to take into account when choosing a motor without a current limiting controller, as I have a feeling with either one of those 2 motors you selected, it'd throw you off the board instantly.
 
think about wheel size...
gear ratios, basically if your max rpm is 6 000 rpm on the motor if you use a 1:1 ratio on a small skateboard wheel the motor should give a nice speed at about 70kph or something so if you want a wheel thats 2 times bigger and half the speed then 4:1 ratio is required.
i personally would go with lower torque cos then you dont need to gear down as much and lower chain speed . if the big gear is as big as the wheel then all you can do to increase ratio is make motot gear smaller, and the smallest for this aplication may be 8 tooth on small gauge chain.

ok look at this 150KV at 44 v = 6600rpm, lets say practical max rpm is 6k rpm
if you use 10inch wheels and want to go 35 kph (about as fast as most can ride a normal bike on flat) then how many rpm is the wheel going..
circumference of wheel = 80cm = .8m = .0008 Km
35kph /60 = 0.58 km per min 0.58/0.0008= 729rpm
therefor your ratio would be 8.2:1
8 tooth on motor and 65tooth on wheel.

heres an idea of sproket sizes that are available http://www.transaus.com.au/files/TA_PTCatGen_Sprockets.pdf
 
sorry totally muffed a calc above and edited... anyway check the small chain gague gears, 65 tooth is 202mm dia. so that leaves you with a cm or 2 clearance. i had a scooter with a chain ring about this much smaller than the wheel and it was ok, just couldnt lean to one side too much :)
 
I started a thread in the Stand up e-scooter forum, but realize this forum might be more suited for it.

Here's what I'm thinking....

Motor:
http://www.hobbyking.com/hobbyking/stor ... Motor.html
Stats:
Kv (rpm/v) - 245
Max Current (A) - 70
Max Voltage (V) - 37
Power(W) - 2700
--OR--
http://www.hobbyking.com/hobbyking/stor ... Motor.html
Kv (rpm/v) - 275
Max Current (A) - 65
Max Voltage (V) - 37
Power(W) - 2050

ESC/Controller:
Most Likely: http://www.hobbyking.com/hobbyking/stor ... s_ESC.html
or
http://www.hobbyking.com/hobbyking/stor ... gging.html

Battery:
5000mAh 6S1P 40C
http://www.hobbyking.com/hobbyking/stor ... P_40C.html

Does this look like a good setup?

245 I would imagine would be a large amount of torque, but if my dad wants to ride it, I want to know it could move the extra weight. Or would the second choice (275KV) work just as well even though the power(w) is about 700 less? How important is the power (watts) here... I know the traditional electric skateboards use a brush motor with acid batteries and range from 350W-800W - I'm at 2050W for the lower wattage motor option. What does the watts effect, speed or distance?

The ESC is showing the max input voltage to be 2-6 cells lithium. I'll be using a 5000mAh lithium... is that pushing the ESC to the max?

Thanks for all the help, I'm learning as I go and bet I've read well over 100 pages on this forum alone... good stuff.
 
Awesome, thank you both for the great replies.

For the controller, I plan on using an RC transmitter and receiver - it will work good as the ESC is already for an RC receiver and it will be wireless.

Interesting about the gear ratio also, definitely will have to do some math on that.
 
Things said:
Keep in mind though, that things like skateboards and scooters aren't designed to go at such speeds, so thinks like speed wobble may be an issue, just don't get too overenthusiastic with the speed, or it'll be near impossible to ride & dangerous. .
Click to expand...

going fast on a skateboard is dependent on your skill level, and how u set it up.

skaters have gone over 80mph on a longboard.
and not uncommon for good skaters to rountinely hit over 40+
 
Hi guys,

I'm trying to build a 2rwd(boosted boards) style e-board on Landyachtz Tomahawk platform..

Now i've already ordered the board, and i'm trying to figure out the electronics..

I'm thinking about using 2 x Turnigy Aerodrive SK3 - 5045-500kv Brushless Outrunner Motor... I figure i can fit 2 of them on 10'(184mm) Caliber trucks.

The problem is i can't figure out what ESC to use.
I was thinking 2 x Turnigy TrackStar 80A 1/8th Scale Brushless Car ESC. but it states that it supports 2-4cell LiPo but the motor above supports 5-7cells... wouldn't this be a problem?

Then i came across TURNIGY K-Force 70A-HV OPTO V2 Brushless ESC but i don't know if this is suitable for e-board as it might not have braking..

I'm confused as to what ESC to use. any recommendations? Is there and ESC with true regen braking?
 
hmin7186 said:
You think this ESC can be used?

Turnigy Super Brain 60A Brushless ESC

it supports up to 6cells and also has braking.. don't know if it is suitable for the motor i mentioned above
Click to expand...
I asked Kepler about these cheaper 6s controllers as he had had allot of experiance with rc and rc ebike esc. he said they dont sync(ronize) well (with the big slow motors under load i guess) . he sugested the k force i beleive https://www.hobbyking.com/hobbyking/store/__9328__TURNIGY_K_Force_100A_Brushless_ESC.html
 
pendragon8000 said:
hmin7186 said:
You think this ESC can be used?

Turnigy Super Brain 60A Brushless ESC

it supports up to 6cells and also has braking.. don't know if it is suitable for the motor i mentioned above
Click to expand...
I asked Kepler about these cheaper 6s controllers as he had had allot of experiance with rc and rc ebike esc. he said they dont sync(ronize) well (with the big slow motors under load i guess) . he sugested the k force i beleive https://www.hobbyking.com/hobbyking/store/__9328__TURNIGY_K_Force_100A_Brushless_ESC.html
Click to expand...

I've seen this ESC being mentioned before.. however i wasn't sure if this was suitable for electric board (drag braking, stop and go etc)...
have you used this ESC? does it support enough braking to use on electric board?
 
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