Sk3 6374 149 or 168 kv for eMTB?

Hallo esk8èrs

I`m planning to build a Trampa eMTB board…

I have not decided yet, what drive chain to use (direct drive or belt/pulley)

But since Hobbyking has sale on both Sk3 6374 149 and 168kv motor at the moment, i want to buy the motors now. What would you guys choose ? Im going after torque since its a eMTB, but it would be nice to also have a top speed around 30 kph / 18.6 mph

Thanks

You kind of answered your question yourself, for torque you should go for 149kv since it’s also enough for 30km/h. I use 130kv motors with 1:5.5 gearing and a top speed of ~35km/h on 12S

Hi @Silverline, please don’t be tempted by these offers just yet. What ESCs are you running? If you’re like me and running FOCBOXs or another VESC type ESC then you’ll find that an unsensored eMTB is a total pain in the ass!! Even in FOC the cogging is quite limiting. I’m currently running SK3 168kv and the torque + top end is excellent, however I WISH i had spent a couple of extra $$ and bought sensored motors. I’m now currently looking into this. I’d consider your build not around good motor deals but what you’re going to use it for. If anything, I’d pick the motor last! Trust me I did it and I’m now trying to change it!

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Hey guys…

Sorry i forgot to mention that its going to be a 12s Lipo build with 2x EScape vescs… (same as Vesc6)

@Der6FingerJo Yeah thanks… 149kv was also my first thought

@DanSkates Yes, the sensor thing is also something i have been thinking of. I already have sk3 motors on my Trampa Urban carver build, and love them, the only downside is the “stutter” thing from 0 kmh, that is pain in the ass.

But the price is so good. But maybe i should look after something else.

Implementing hallsensor would be quite difficult without taking the motor apart. You can also implement external encoder setup.

Well, more kv = more speed, less kv = more torque. But it also depends on your pulley-system and if you want a dual- or single drive. If you want to know what the topspeed will be: speed in kph = ((voltage of batteries * kv)60) * gear transmission * ((diameter of your weels3.14)*1000000)

Get a motor with sensors, its not much more $ but its worth it if you want a more “premium” ride

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I have 8 6374 sensored 170kv coming 4 I could see myself parting with.

12S - focbox - 149kv - dual - 60kg - 15/60 I have litterally no cogging at all so i cannot follow the “you need Sensors to run without cogging” logic but thats only me.

@DeathCookies You running FOC mode ?

@bimmer You are in the US right ?? Thats why i bought the Escape, and not your B-box vesc… since im from EU.

Yes, FOC on rocking 12S.

*If you use a lower voltage than 12S i can understand the cogging Problem :smiley:

Makes sense

What I have experienced is that higher voltage produces more torque.

Rider weight can have something to do with it as well. Would you mind sharing your weight?

I think he is ‘only’ 60kg… I’m 92kg :-/

That’s a big difference.

I don’t run sensors on my motors but I always push off with my foot before hitting the throttle. I can see how that wouldn’t work on a EMTB with foot straps.

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Both is definitivly true.

My mtb does not have sensors too but i can work around the small coggs i get hardly.

I try to speed up. If it is cogging but not really moving i stop immediatly and give the whole board a little push forward by moving my legs forward. While i make this little push the motor will rotate slightly and get another position. When i know give some throttle it always goes along without cogging. It is just once in a time that it coggs.

Like i said before i dont get that “a mtb NEEDS sensors” but maybe it is just a good setup and i am a feather weight or i have hidden sensors :smiley:

Another trick that you could try is to transfer your weight to your front foot and lift your rear foot slightly to allow the wheels to slip and spin and then transfer your weight back gradually. Kind of like a clutch.

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Thanks for the help guys…

I think i just go with a sensored motor on my eMTB :slight_smile: At around 150 kv,

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Really intersting comment on here. Yeah I agree, a small movement forward (shimmy or a shove) or jumping into your runs (like a snowboard) you won’t notice cogging, but try riding a dirt track or forest trail etc and getting stuck at the bottom of a jump and then see how easy it is to get going again! :rofl:

I guess it all really depends on how you’re going to use it but from experience I’m telling you now i’d recommend not starting with a board that coggs if you can help it as it’s driving me nuts!

You won’t regret it man! Also agree with the lower KV, I’m rocking 168kv which gives me a 50+kph top speed and I can’t hit that off road and would much prefer a bit more torque. I guess if it were to be a road machine the top speed would be better than more grunt though…

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