Months ago I saw a kickstarter project named Boosted Boards and was amazed by their product and thought that it would be quite fun to ride one of those things. But what would be even more fun and exciting would be to build one!

The reason

I don't even know how to ride a skateboard, why should I do it?
One of the things I love to do is to learn new stuff, so instead of learning Rails, or MongoDB, or the next big thing in web development, I decided to learn how to ride a skateboard, and alongside, building an electric one from scratch!

Existing projects

There are a lot of other electric skateboards out there, so the first thing I've done was to learn what have been done, the pros the cons, and set a path to build one using simple tools and ordinary materials, so everyone could build their own.

Here's a list of a few ones:

Parts

I'm going to list all the parts needed to convert a longboard to electric, and for each one, what made me decide for that specific part.

Deck

I think I should've made a better choice here, and buy a longer one (this is 1 meter long). But at the time I didn't knew better... Although, it's 100% bamboo.

Street Surfing

Wheels

I had to choose wheels that have spokes so that the pulley bolts can go through the wheel, otherwise I had to drill holes on them, and I didn't want to do that. From what I’ve read, these are the best characteristics for an electric longboard which main purpose is to cruise or to commute between transportation:

  • wide contact patch
  • squared edge
  • centerset core
  • soft wheel

There are a lot of brands you can choose from, but I've choose the ABEC11 Flywheels.

ABEC11 Flywheels

Motors

The motor is one of main parts of this project, and choosing the right one is critical because a lot of variables are taken into action:

  • speed
  • power
  • space available
  • gear ratio

Of course I could do all the right calculations to determine the right amount of power I would need to get me going, and make the right calculations to build the right motor (man, I have to get my college notes from the attic), but I prefer to make a quick prototype, see how it handles, and take my conclusions from there.

You can check wikipedia or this article to learn the basics of an electrical motor. Basically what we want is a motor with low KV and something between 400 and 600 Watts (I’m going to use 2, so the total will be the double of that).

I went to a lot of websites, picked several motors that I thought they could handle, made a list and then compared with each other eliminating them one by one. At the end I picked this one:

E-Power BL2820 Brushless Outrunner Motor

E-Power BL2820 Brushless Outrunner Motor

It has more power then needed, but that was the best I could find in near (europe) stores. I’ve made some calculations to determine the top speed:

KV = RPM/V
919 = RPM / 15
RPM = 13785

Since the motor isn’t 100% efficient, I’m going to assume (I don’t have the datasheet) a load factor of 70%. So:

RPMreal = RPM x 70 / 100
        = 9649

Since the diameter of the wheels is 76mm, and I’ll probably use a gear ratio of 3:1, so:

RPMwheels = 9649 / 3 = 3216
TopSpeed = 76 x pi x 3216 x 60 / 1000000
        ~= 46 km/h

These calculations are far from accurate, and another interresting thing to calculate would be the amount of torque of the motor, but I would have to know things like the number of poles, and other things that I don’t know.
But, since a lot of boards these days have between 600 and 1200W, with around 1746W I think that will be more than enough.

For the ESC, I just have to choose one that can withstand the maximum amount of current that the motor can get, that is 59A. So a 80A ESC will do just fine. Also, I wanted to buy a ESC that had heatsink so I could replace it for a bigger one if needed, or bolt it on to the aluminum box. I've choose a Hobbywing Platinum 80A.

E-Power BL2820 Brushless Outrunner Motor

Stay tuned for more!