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Fast electric longboard – Dual hub motor

PostPosted: Sun Mar 29, 2015 8:46 pm
by Stielz
I figured it’s about time I shared my electric longboard project here. I finished this 2 years ago lol.

First of all, this thing is incredibly fast with massive acceleration. I have to really lean forward during acceleration to stop it throwing me off the back. I have been using a data logging device which has recorded power levels of over 4kW during acceleration and been up to 60km/hr on flat road – still haven’t maxed out the speed, that’s as fast as I am game enough to go with my limited protective gear.

Quick specs
Speed: >60 km/h
Power: >4000W
Range: 30km easily
Battery: 6S, 20Ah
Controller: dual Hobbyking 150A Sensored car ESC
Motor: dual Turnigy SK 6374 145kv modified as rear wheel hub motors with Hall & temp sensors
Longboard: Loaded Dervish bamboo deck, Paris trucks, Abec11 92mm Flywheels
Cost to build: $1,200 NZD
Time to build: 4 months

Here’s some photos I took during the build. Unfortunately I don’t have any photos on file of the finished board with the hub motors in place, I really need to take more at some stage.

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Hall sensors for the motor. Had to use SMD package to fit in the stator slots.
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Extra bus caps for the ESCs, Low ESR, High ripple current.
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The fibreglass electronics enclosure was designed to flex with the board. The Loaded Dervish bamboo deck I really like the way it rides and so didn’t want to interfere with that so I built the enclosure to bend with the deck.

Inside the enclosure I have 8 x 3S,5000mAh lipos, configured in 6S 4P so 22.2V nominal, 20Ah. Heaps of battery for a skateboard, I ride it for about an hour on a single charge.

Also the ESCs. Ive been using Hobbyking 150A sensored car ESC (I added halls to the motors so it gets really good startup torque from a dead stop). These ESCs have worked pretty well, until they don’t which leads me to the issue.

I’ve gone through 5 of these ESCs. Most of the time they just die for no apparent reason – brain board dies but power board still ok. I had the longboard working all good for the last year until recently one of the ESCs started pouring out huge amounts of smoke – after I had stopped! Very strange because I hadn’t been pushing them hard. In fact it was just after a downhill run. It happened moments after I stopped recording this video.



So now I’m assessing my options for some better ESCs. Recommendations please!
Already spent $1,200 on this so hopefully not too much more..

Re: Fast electric longboard – Dual hub motor

PostPosted: Sun Mar 29, 2015 9:02 pm
by torqueboards
Nice custom setup.

VESC for that board :)

Re: Fast electric longboard – Dual hub motor

PostPosted: Sun Mar 29, 2015 9:17 pm
by Stielz
VESC does look good for sure. My only hesitation is I need 2 of them at $150 USD each - which is a fair price, I know how expensive it is to make ESCs at low volume. Just a bit more than what I was hoping for..

Re: Fast electric longboard – Dual hub motor

PostPosted: Sun Mar 29, 2015 9:23 pm
by torqueboards
Worth it :) You'll practically have sensorless motors acting like sensored.

Re: Fast electric longboard – Dual hub motor

PostPosted: Mon Mar 30, 2015 12:55 am
by LEVer
Hobbywing Xerun 150A. Very dependable and still runs strong after 3 years.

I've also recently been testing the SkyRC toro 150A. Bluetooth connection is sweet, if you get past the bugs.
Adjustable throttle and braking curves is a must for me.

Re: Fast electric longboard – Dual hub motor

PostPosted: Mon Mar 30, 2015 1:30 am
by bugboy1641
Nice!
Carving up the mean streets of Palmy!

Any interest from the cops?

I'm aiming to use mine as a commute option.....

Re: Fast electric longboard – Dual hub motor

PostPosted: Mon Mar 30, 2015 5:39 am
by Jan Christian
Your escs is probably blowing up because you dont have any reduction on the motor. Then the esc have to compensate by using more amps to get the torque. These small rc escs is not made for longer periods with high amp draw. I also smoke them with reduction but thats in longer periods with acceleration/brake/acceleration/brake.
With your hub motors you are maybe limited to 6S unless you want to gear it for world guinnes record.
Speed fully charged 6S: (145KV*4,2V*6S)RPM *(1/60) *pi*0,092 *3,6=63,4 km/h
Speed fully charged 10S: (145KV*4,2V*10S)RPM *(1/60) *pi*0,092 *3,6=105,6 km/h
My impression on the vesc is that you need to run 10S or 12S to get maximum out of the esc without the thermal protection kicking in. Then you would need lower kv motors.

Re: Fast electric longboard – Dual hub motor

PostPosted: Mon Mar 30, 2015 6:59 am
by onloop
Sweet build....

Not many folks on here have done a DIY eboard with hub motors...so your one of few congrats.... but we need pics for it to be legit...

I think you need to go near 100kv. And also higher voltage Would be better.

60kms is crazy... did you ever ride this fast? Or mostly ride at half throttle.... ? Vedder was saying about riding at half throttle can increase motor current. Vs riding full throttle...

you need a solid ESC.

I can get you a vesc delivered to your door for about $133usd. Or approx $178NZD... so slightly cheaper than you think.. Its about $120USD ea.

PM me.

Re: Fast electric longboard – Dual hub motor

PostPosted: Mon Mar 30, 2015 11:55 am
by Vanarian
This is a sweet build !

Re: Fast electric longboard – Dual hub motor

PostPosted: Mon Mar 30, 2015 4:06 pm
by Stielz
bugboy1641 wrote:Nice!
Carving up the mean streets of Palmy!

Any interest from the cops?

I'm aiming to use mine as a commute option.....


No interest from cops yet. But in saying that I only use it on cycle ways and quiet back streets.

Pediglide wrote:Hobbywing Xerun 150A. Very dependable and still runs strong after 3 years.

I've also recently been testing the SkyRC toro 150A. Bluetooth connection is sweet, if you get past the bugs.
Adjustable throttle and braking curves is a must for me.


Thanks for the tip, I'll look into this

Jan Christian wrote:Your escs is probably blowing up because you dont have any reduction on the motor. Then the esc have to compensate by using more amps to get the torque. These small rc escs is not made for longer periods with high amp draw. I also smoke them with reduction but thats in longer periods with acceleration/brake/acceleration/brake.
With your hub motors you are maybe limited to 6S unless you want to gear it for world guinnes record.
Speed fully charged 6S: (145KV*4,2V*6S)RPM *(1/60) *pi*0,092 *3,6=63,4 km/h
Speed fully charged 10S: (145KV*4,2V*10S)RPM *(1/60) *pi*0,092 *3,6=105,6 km/h
My impression on the vesc is that you need to run 10S or 12S to get maximum out of the esc without the thermal protection kicking in. Then you would need lower kv motors.


All good points, thanks. I know that having it 'geared' to go 60km/hr on a 6S battery is quite demanding on the ESC. What sort of speeds are others aiming for when selecting gear ratios for a 6S system?

You're definitely right about the VESC, with the 60V FETS, 1.5mOhm Ron it is better suited for higher voltages to get full power.. Could always swap the FETS for AUIRFS8409-7P which are 40V, 0.55mOhm Ron. That adds more cost though.

Just a note: the wheels are ‘stretched’ slightly around the motors to get a tight fit. I think they ended up being 96mm diameter.

onloop wrote:Sweet build....

Not many folks on here have done a DIY eboard with hub motors...so your one of few congrats.... but we need pics for it to be legit...

I think you need to go near 100kv. And also higher voltage Would be better.

60kms is crazy... did you ever ride this fast? Or mostly ride at half throttle.... ? Vedder was saying about riding at half throttle can increase motor current. Vs riding full throttle...

you need a solid ESC.

I can get you a vesc delivered to your door for about $133usd. Or approx $178NZD... so slightly cheaper than you think.. Its about $120USD ea.

PM me.


Fail, I completely forgot to take photos last night. Too busy working on my e-bike project. Try again tonight. Seem I've got lots of video backed up on my work computer. If you pause at the right time you might see the hub motors lol.

Higher voltage, lower current would be ideal. Doing a motor re-wind for lower kv and running higher voltage is another option.

60km/h is only on nice quiet, flat road. most of the time I'll just be cruising at 30-40 km/h.

Thanks for the offer, that sweetens the deal a bit :D
I don't suppose you would consider making a version of this ESC using AUIRFS8409-7P FETs?
I think they would work really well for lower voltage, It should run a lot cooler and so higher current limit. Cheaper too.

Re: Fast electric longboard – Dual hub motor

PostPosted: Mon Mar 30, 2015 5:35 pm
by Jan Christian
What sort of speeds are others aiming for when selecting gear ratios for a 6S system?


Maybe around 35 km/h, but that is boring:) I like the look on people faces when I go faster than their car on the sidewalk. Specially buses is fun.

Re: Fast electric longboard – Dual hub motor

PostPosted: Mon Mar 30, 2015 6:40 pm
by Stielz
A video of some general hooning on a river track


Re: Fast electric longboard – Dual hub motor

PostPosted: Mon Mar 30, 2015 7:17 pm
by LEVer
Damn, you don't need an ESC...you need a cockpit. :D

Are you selling these sensored hub motors?

Re: Fast electric longboard – Dual hub motor

PostPosted: Mon Mar 30, 2015 9:03 pm
by Stielz
Haha yeah really need some motorcycle protection gear. Ive been lucky in that I haven't fallen off yet. Think I can thank the Loaded longboard for that, its nice and stable at high speed.

Haven't really considered selling the hub motor .. All it is is a wheel glued to the outside of an outrunner motor and ther's your hub motor. The trick is fitting it to skateboard trucks. I selected the Paris trucks specifically for it. They just need a small amount of machining with a lathe then with a milling machine. I don't have either of these tools lol

Re: Fast electric longboard – Dual hub motor

PostPosted: Mon Mar 30, 2015 11:36 pm
by LEVer
Stielz wrote:Haha yeah really need some motorcycle protection gear. Ive been lucky in that I haven't fallen off yet. Think I can thank the Loaded longboard for that, its nice and stable at high speed.


I think it's also the sensored setup. I've been testing out some big sensored, industrial inrunners and they are as smooth, predictable and quiet as brushed motors.

Outrunners are still the best because of their power-to=weight ratio, but I really dislike riding unsensored ones.

Re: Fast electric longboard – Dual hub motor

PostPosted: Tue Mar 31, 2015 7:39 pm
by Stielz
So I got around to taking the photos of the finished e-longboard, with the hub motors installed this time.

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That last photo also shows my e-bike mid-drive project which in only waiting on a motor controller to finish it. Reoccurring theme here.

Re: Fast electric longboard – Dual hub motor

PostPosted: Tue Mar 31, 2015 7:42 pm
by Silenthunter
Awesome job man!!!

Re: Fast electric longboard – Dual hub motor

PostPosted: Tue Mar 31, 2015 10:08 pm
by LEVer
What?!...you are just using the motors can, even the plastic fan on the skirt bearing? How is it holding you up?

Re: Fast electric longboard – Dual hub motor

PostPosted: Tue Mar 31, 2015 10:35 pm
by Stielz
Silenthunter wrote:Awesome job man!!!


Thank mate

Pediglide wrote:What?!...you are just using the motors can, even the plastic fan on the skirt bearing? How is it holding you up?


Its solid I can assure you that. The fan you see that is supporting the motor can against the skirt bearing is actually aluminium, as comes on the stock SK 6374 motor. Th part I was concerned about is the small bearing at the other end, but even this has proven to be fine. I reckon I've put around 300 km on it and still going strong - except for the ESCs of corse :(

Re: Fast electric longboard – Dual hub motor

PostPosted: Tue Mar 31, 2015 10:46 pm
by johnrobholmes
Do the ESCs always pop after going downhill or soon after you let off the throttle? The way you install the caps isn't the best, but I would hazard a guess that you are getting an inductive spike or regen that is surpassing the voltage rating of your ESC.

Re: Fast electric longboard – Dual hub motor

PostPosted: Tue Mar 31, 2015 10:49 pm
by LEVer
Ok. I gotta try this. I actually started trying to disassemble my Sk3 before but got stumped by those small screws that are holding the fan.

How did you remove it without stripping the head? Also, how did you keep the stator from rotating, did you put a keyway?

I think I also remembered you built an e-mtboard, how is it? I saw your E-bike videos, your builds are amazing.

Re: Fast electric longboard – Dual hub motor

PostPosted: Tue Mar 31, 2015 11:19 pm
by Stielz
johnrobholmes wrote:Do the ESCs always pop after going downhill or soon after you let off the throttle? The way you install the caps isn't the best, but I would hazard a guess that you are getting an inductive spike or regen that is surpassing the voltage rating of your ESC.


It just seems random to me. Sometimes when I go out for a ride one of them just wont go. Sometimes its when accelerating. Sometimes its after i've stopped. But most of the time it seems to be the brain board that dies, not the FETs.

Whats the best way to install extra caps? on the battery wires?

Pediglide wrote:Ok. I gotta try this. I actually started trying to disassemble my Sk3 before but got stumped by those small screws that are holding the fan.

How did you remove it without stripping the head? Also, how did you keep the stator from rotating, did you put a keyway?

I think I also remembered you built an e-mtboard, how is it? I saw your E-bike videos, your builds are amazing.


For the small screws holding the fan, getting the right size screwdriver head is important. And putting lost of force down on them to avoid stripping the head.

Stator is held in place by a machined flat on the trucks. You'll see how to do it when you get the motor apart.

Motorised mountainboard has been retired since building this longboard which is much better :D

Re: Fast electric longboard – Dual hub motor

PostPosted: Wed Apr 01, 2015 6:03 pm
by Stielz
I'm thinking if I were to go with the VESC I would need to make some modifications. I think that the 60V MOSFETs that come with the board will run hot with my high geared, low voltage setup (high current demand).

So the options would be:

- Get lower kv speed constant motors and compensate with higher battery voltage.
- Swap out the MOSFETs for lower voltage, lower Ron MOSFETS so it can handle higher current for longer.

Does anyone know how easy/difficult it is to re-terminate these Turnigy SK3 motors to wye?
From memory I think there is epoxy glue holding the windings in place at the base of the stator so could be impossible to separate the wire ends..

Re: Fast electric longboard – Dual hub motor

PostPosted: Wed Apr 01, 2015 6:33 pm
by 777arc
I thought this was an april fools joke when I read the original post, between the crazy performance and no pic showing the hub motor. Looks like you have a very special board, I hope you share as much as possible so others can duplicate the method.

People have been saying the VESC runs very cool even without a heatsink and fan, so at low voltage high current you could probably just slap a huge heatsink to the FETs, and make sure the heatsinks get nice air flow. No need to modify the VESC.

Re: Fast electric longboard – Dual hub motor

PostPosted: Wed Apr 01, 2015 7:53 pm
by Hummina Shadeeba
wow. none of your pics or video is showing up for me though. you say you glued it. I'd really like to see!