esk8 calc donate now

keyless locking bushings. anyone use them?

how to figure the torque output of the motor? i dont think its hard math but dont know it and hoping someone will post it. not much surface area to hold with an interference fit but maybe good enough.

i hate keyways and grub screws!!!


Sounds good to me.

for a MTB would be nice, it’s already heavy and expensive


You enter RPM and Watt and you obtain Torque with this tool. For more accurate result you want to consider effective Watt output with heat losses.

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Im confused on such a calculator but maybe since an electric vehicle I can input the maximum speed and the the torque will be the same torque output at all speed? I think so. Big assumption though


Yea that’s what I assume too :sweat_smile: when I put max watts and max rpm together I get more realistic values even with 1:1 ratio (hub or DD rpm).

IIRC apart from increasing losses the torque output theoretically remains the same from 0 to max RPM in electrical brushless motor

You can also convert in Nm if you prefer

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looking at a graph of torque and speed w an electric motor the lines image

show highest torque at starting and not consistent.


im thinking i should know this and if the esc is putting out a consistent current youd think would be consistent torque across all speeds. i know theres a lot of false leads on the web related to the power source being from the wall

ok last one
image and this i believe is us with an assumed continuous current applied. which makes me not rely on the calculator.

there you are

Just calculate your Kt from Kv and multiply by the phase current you use

Kt = Kv/9.55

T = Kt*I

Results are in Nm

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so consistent torque through all rpm or drop with speed? if given consistent current

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Yeah, constant torque if you have enough voltage to push the needed current through the motor windings, the higher the speed the greater the back EMF, so more voltage is needed

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Typical 6374 sized motors typically don’t produce over 8Nm, even that’s a lot. More like 4-6Nm. I used it for my gear calculations

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but if the kv is low enough could produce up till the iron saturation and imagine be much higher possibly with enough current

The formula @Pedrodemio used is right, it’s what I used. Just need your kv and your amperes. That’s all that matters when determining the maximum torque at a given moment.

I guess if the kv is super low, you will saturate the iron and more amps will stop producing additional flux. It’s been a while since I’ve studied this stuff.

Just use the formula lol


your first and third graphs here assume no current limiting, its as if you connected a dc motor directly to a battery. The same is not true for our bldc motors unless you have a controller that can output a huge amount of amps at low speeds.
By comparison the second graph assume max current is available across the entire operating voltage range of the motor.


so difference being between a brushed motor and brushless @deltazeta ? as im understanding what you all are saying its as simple as current and kt and forget about the speed and doesnt effect the torque

The speed doesn’t matter necessarily. The speed may affect the amount of amps drawn which may indirectly affect the torque. (I’m guessing).

If we want to be precise, the higher the rpm the more core losses you have, so a bit of the torque goes to that, but it’s low on ours motors, so the torque is almost a flat line

Kt = 1355/Kv i see. but i’ll run with your formula.

What do you want to know? The coupler you linked is more than enough, rated at 41Nm. None of our motors can push that

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actually plan for a bike but thanks for your info and i su

ck at math . does 17nm

and then i’ll be adding a 9.5:1 gear ratio!! so multiply by 9.5 im guessing. will use a jackshaft so the second belt will hit this torque to the wheel

sorry the 12mm shaft. thats what it will go on. it does 17nm

and on an 8mm shaft will stay put up to 14nm. you guys should get one

the difference is current.
torque comes from the magnetic force between the coils and the magnets, the magnetic field in the coils come from the current in wires. the stronger the current in the wire the stronger the magnetic field and the more torque you’ll get.
theoretically you are limited in both speed and torque by your input voltage, since you usually can’t generate more current than just V=IR, and then as you get up to speed the back emf will lower the voltage difference and reduce current. that’s where you get the first and third graphs.
realistically your esc and motor can’t handle high enough currents at low speeds so you just set it at something reasonably low that won’t catch your motor on fire. and this is where you get the second graph.
the dc motor example was just something easy to visualize since doing the same with a bldc motor just generates a bunch of waste heat.