 A bunch of notes on building my e-Skate and the iterations it went through
I’ve been skating for a long time with all sorts of skateboards. But now that I’ve moved to Spain and enjoy going to work almost every day on a board, I wanted to give a try to build my own electric board…Especially since going back home is uphill ! I’ve seen many Kickstarter initiatives or commercial products but either they are really too expensive or too heavy. And I have already many boards so better try to build one on one of my favorite, the Carver.
There are many blogs and websites about building your own e-skate but I ended up finding the endless-sphere forums to be the best source of inspiration/guidance. This article is just about the different iterations the e-Carver went through before reaching its current state |
Building an e-skate is not that hard actually, basically you need :
– Batteries : the LIPO batteries are lightweight batteries that can produce a lot of power for a small package size. Very efficient but to be handle with care : they must not be overcharged nor undercharged and must be protected as a punctured battery can catch fire. Of course you also want a charger.
– Motor : Brushless motors are motors that can produce higher speed/torque in a smaller frame size. A Brushless motor speed is expressed in kv : 1 kv = 1 turn/minute per volt
– ESC ( Electronic speed controller ) : Brushless motors require a controller to be able to control their rotation speed. ESC can also control braking.
– Remote Control : In order to control speed and braking you want a remote control in your hand. This is quite easy to setup as most ESC have plugs to put the receiver part.
– Support and transmission : That was actually the part that puzzled me the most : how to get the motor to make the wheels turn. Most solutions I had found requiring soldering a support to the truck to hold the motor then have a pulley belt between motor and the wheel.
– And of course a board , in my case I wanted to use my Carver swalloz 29.0″ :
After spending a lot of time reading forums, doing the maths, etc… I finally ordered what I thought would be enough to start building my first prototype :
Most of the parts were ordered from HobbyKing except for the support which came from AlienDrive
| Batteries | ZIPPY Flightmax 8000mAh 3S1P 30C x 2 | 78 € |
| Motor | Turnigy Aerodrive SK3 – 6364-190kv | 62 € |
| ESC | HobbyKing® T 150A High performance Brushless Car ESC | 68 € |
| Remote Control | Quanum 2.4Ghz 3ch Pistol Grip Tx & Rx System | 20 € |
| Charger | IMAX B6-AC Charger/Discharger 1-6 Cells | 32 € |
| Support | Kit from AlienDrive | 130 € |
| Misc Wire/Plugs | XT 90 connectors, 10 AWG wires, Box | 40 € |
| 430 € |
Notes on the choice of motor/battery/Esc :
Batteries will be in serial to produce a total of ~ 22.2 V
So the motor max speed will be 22 V x 190 kv = 4180 rpm
The ratio between motor and wheel is 12 T/ 36 T = 1/3 so wheels max speed is 1393 rpm
Given the wheels diameter is 75 mm, that makes a 0.23 m circumference
so actual linear max speed should be 1393 * 0.23 = 328 m / mn = 19.7 km/h
I went for the Alien drive kit because it was providing most of the part I needed from a single place that is :
| Truck support to hold the motor |  |
| Hub drive for my ABEC 11 flywheels ( the pulley that is connected to the wheels ) |  |
| Belt and motor gear |
With the experience I would now build something cheaper but that kit really helped me getting started and they give a lot of detail explanation on how things are supposed to be assembled
Now the problems I didn’t anticipate :
 The support is meant for some specific brand of trucks, in order for it to fit on my carver trucks I had to shape them with a dremel for the support not to rotate |
The support I took is perfect for small motors such as 50mm diameter. But the motor I have is larger and will not fit and the holes to fix it do not match. Need to build a small replacement part. For this I ordered a piece of aluminium , 5 mm thick and 50 mm wide to build a custom support. Luckily aluminium is easy enough to drill, the result is not really good looking but it did the trick
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The gear that goes on the motor needs to be tightly linked to the motor axis, that’s why there is a keyway but the motor I took didn’t have one: need to use Dremel to drill one…
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First prototype v1.0 :
november 2014
Learnings from this first test after ~2 months :
First of all this is awesome ! With a 190 KV motor the torque when going uphill is impressive and I was able to climb to hills while pushing another adult on a scooter ( total weight ~ 160 kgs )
Top speed on flat is around 18 km/h and 13 km/h while going uphill
In terms of weight the board went from 3.4 kg without anything to 7.1 kg with everything…
Autonomy : Around 15km flat ( around 1 hour ).
First test going uphill:
Lessons learned :
| There are a lot of vibrations : | |
 I’ve lost a bunch of screws very quickly => loctite thread locker is a must have.Even with loctite the weight of the motor can slowly make the attachement rotate around the axis of the truck. Eventually my motor felt on the ground and was badly damaged by the time it took me to notice it was grinding on the floor |
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| Electronics are exposed : | |
 A piece of rock actually touched the receiver part while riding and cut the power. Just a surprise that can catch you unprepared…I also ended up riding on a wet ground and some water went into the ESC which stopped working for a day until everything was dry |
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| Regenerative Braking : | |
| The first part of my daily trip to work is downhill, so I’m mostly braking from time to time. A nice side effect is that this is regenerative braking so it charges back the batteries. A problem though is that, if you start with a fully charged battery pack, the ESC will disable itself as LIPO batteries must not be overcharged so you have to restart it in order to accelerate once you reach a flat surface. So better have a non fully charged battery pack before going downhill 🙂 | |
| Cumbersome charging : | |
 So my batteries are protected inside the box under the skate but in order to recharge it I have to unscrew 4 screws then recharge each 3S battery separately |
Second Protoype v2.0 :
January 2014
I wanted something a bit thinner under the board so tried to create a battery pack with some protection. Also I wanted to have the electronics a bit more protected. Since I don’t have 3D printer to make something really nice, I went for my lego box to build a case ( + some glue between parts for them to hold tight … ) 
Battery pack : I bought some serial connectors for the power and balance plugs so my 2 3S battery can be used as a 6S pack. Added a plastic protection and put all of this in a protective pack which was glued to the board
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In the process I also changed the motor , the old one was a 190kv version but was seriously damaged after grinding on the ground, the new one is a 270 kv version bought on the AlienPower website. It is much lighter than the other one but faster and still able to ride me uphill.
which ended up looking like this : 
Lessons learned :
Hey, it’s way faster with a 270 kv motor, top speed is now closer to 25 km/h which is perfect but there is less torque so, in order to start when going uphill it is better to help a bit by pushing…
Faster but… less autonomy with a 8000 mA battery pack, I now have ~10-12 km autonomy
Ok, glue just does not work : after a small ride the battery pack was starting to slowly drop… Not feeling secure with this setup so let’s move to another setup …
Third Prototype v3.0 :
January 2014
Lego box is ok but want something more secure to hold and protect the battery pack while still being able to remove the it quickly for charging…
For this I will just use the top half of the box fixed with some hinge to the board
which opens quite easily to acces the battery pack
Fourth Prototype v4.0 :
February 2015
2 months the board is being used almost on a daily basis and first spare part to repair: the pulley belt broke while riding up hill :
Which made me think of a last problem to solve with this setup. The fact that the motor is behind the truck and if you are not careful ( or if you get a friend to try the board for the first time 🙂 ) On a wheely you may grind the motor on the floor…
So the idea was to move the motor in front of the rear truck. For this I needed some space in front of the truck so had to remove the lego box. I also got rid of the ESC fan as the ESC is never actually getting that hot and the dissipator is enough.
To move the rotor in front of the truck I just had to rotate the support but it really didn’t feel like it would hold in place with just the screws ( especially since it needs to be carefully positioned in order not to touch the truck ). So I decided to give a try welding it to the truck.
The ESC was moved a bit forward and without a case, just a plastic cover to avoid water projections
What’s next…
– a smaller remote control would be nice => looking into building one with an arduino
– 3D printing of an ESC+ cable cover so it looks better than the cheap transparent plastic part
– even smaller/lighter board : smaller battery pack ( 4000mA , smaller ESC, smaller board 1.8 kg )