Introduction: DIY Electric Skateboard
This is intended to be a quick guide on what you need to create a homemade electric skateboard on a relatively small budget that can rival a new consumer brand that costs in excess of £1200. The board I built can reach speeds of about 26mph and with regenerative breaking can run for about 10KM. Above is a video and a few pictures of my build and the next pages will be about the parts and the changes I would make to mine if I were to make another. Please support my work by subscribing to my YouTube channel https://www.youtube.com/user/PracticalProjects
Please don't try and replicate this design as it is not guaranteed to work and there are several changes I would make to it. It is effectively just a prototype. Like any form of transport like this remember to wear a helmet. These are dangerous so I am not responsible for any injury's suffered.
Step 1: The Deck
Firstly I would recommend a longboard deck rather than a skateboard as this gives you more stability, a smoother ride and more space for your components. It needs to be solid with little flex and topmounted rather than drop through trucks to give more room underneath for the electronics enclosure and motor. The diagram from randall.com explains the different choices. It is the top one that is ideal. .
As for the wheels you need a relatively large diameter and about medium softness to give a smother ride. Some wheels come with plastic hubs such as the orangatang kegel, which is ideal for mounting the pulley wheel onto. In my case I just drilled directly into my solid wheel. This works for the moment but will not necessarily last a long time.
Trucks: now this is where you should consider the shape and design so that a motor mount can be made for it (more on this later)
So as long as you follow this you can choose any deck you like. In my case I made my own to save money as in the video.
Step 2: The Electronics
A power kit including appropiate motor/s and matching esc can be puchaced from bruno at http://alienpowersystem.com/shop/kits/alien-power-... This saves you a bit of time matching components and is almost guaranteed to work.
Single vs dual motor set-up. Usually one larger lower kv motor is enough, it was in my case and climes hills very well and is the cheaper option. More than enough for average commuting. Dual set-ups will give more power and will climb hills effortlessly but the cost can increase significantly. So for this guide I'll just stick to the single set-up.
Motor: suitable motors for electric skateboards obviously need to have high power and torque. Brushless out-runners for rc planes are commonly used. You need one with a low kv such as the turnigy sk3 213kv that I used or the smaller ntm prop drive 270kv are both good choices.
Esc: You need a speed controller that can support very high amps. These are usually identified by HV in the name of the esc. Get a good quality car one as cheaper ones can sometimes just burn out. The easiest was to choose is to get one that your choosen motor and batteries can plug straight into. Bruno at alienpowersyetem sells very good escs (i used one of his) but it requires some soldering and adaptor cables to make my hobbyking motor and batteries fit. If you buy the kit from him however this shouldn't be a problem.
Battery: Most people use Lithium Polymer (LiPo) in there builds. This is because they provide a huge amount of power for there size and weight. However the main disadvantage of these is they are volotile and have to be looked after very carefully in order to avoid a fire or destroying the battery. That being said if you charge them properly with a good quality balance charger and don't over charge or leave under charged for a long period of time they are ok. The best alternative is LiFePo4 which hold less but still a good amount of power and are sometimes easier to manage.
What you need to know:
mAh is how long it will provide the power for and C is the discharge rate (how quickly it can provide the power) The pack configuration is also stated, e.g 4S1P. This means that there are 4 cells all in series forming one pack. 8S2P would mean that there are 8 cells, 2 packs of 4 in series are connected together in parallel to give a higher capacity.
I used 2x 4S1P 25C 5000mah turnigy lipo batteries wired in parell for my build. An easier option is to buy one of brunos new ready made flat packs that can be found here. http://alienpowersystem.com/product-category/batte... often 6S is more that enough and cheaper.
Transmitter/reciever: any hobby one will do here, car ones are best as you have a trigger for the throttle. Only problem with these is that they are very bulky and require a lot of aa batteries. Some people have used an arduino mini and wii wireless nunchuck. I might do an instructable on that at some point.
Step 3: Drive System
For this part I thought I would first attatch a link to my website where it is more of a step by step thing with pictures http://practicalprojects.weebly.com/connecting-it-...
The pulleys can be obtained from belting online. I used a 36T to 14t T5 pulley reduction connected by a matching synconflec timing belt. The ratio is relatively important here, this works very well for my 213kv motor. For the smaller motor you might want to go for 36T to 12T.
I got the bore of the smaller pulley modified to match the shaft with two m4 grub scews. I ground corresponding flats on the motor shaft so that the pulley would lock onto it.
Motor mount: By mounting the motor directly onto the truck there is virtually no chance of the belt slipping off when turning. A mount can be made easily from aluminium and welded onto the truck. However this makes it more difficult to make fine adjustments and get correct tension on the belt.
To get around this the motor mount can be made in two parts with extended bolt holes to make these adjustments. I tried a few designs (that I may upload a cnc file up for so you can get it machined) but after some internet searching I found Richard from aliendrivesystems that had done just that! He offers this excellent solution for mounting these motors onto two different trucks that is actually cheaper than commissioning a cnc milling company to make your own. So I used his...
Step 4: The Enclosure
To protect your batteries and other expensive parts you are going to need a solid enclosure. Key features of this should be good airflow, sturdy construction and a suitable way to hold the electronics securely.
Firstly, I laid out my components onto a piece of paper and drew a rough sketch around it. This was to help organise the components in the most compact way. Then I came up with a few designs until reaching my final part as shown above. Mesh at either end allows excellent airflow to cool the electronics and is held simply my the pressure of the bottom plate. The tapered ends hold each lipo battery securely in place and allows adequate routing of cables in the spare space. Then the esc, receiver and receiver pack are secured using double sided foam.
Unfortunately the main body of the case had to be screwed directly to the deck. For aesthetics I used brushed aluminium for the bottom plate and carbon fibre vinyl around the main body.
Alternatively you could use a simple project enclosure to save time.
Step 5: Improvements I Would Make
Firstly if I were to build another I would reduce the size of the board or manufacture with carbon fiber. The board is actually pretty heavy and bulky which makes it less ideal for jumping on and off public transport and storing it at work or school.
I would not use lipos again. Although there power to weight is excellent, I am always worrying about them and the whole board has to be taken apart to charge. I would go for a custom lifepo4 pack with plug in charger.
I'd spend more time developing a more compact remote control system for it. Ideally one that could fit into a pocket with a battery level indicator.
Larger wheels with plastic hubs would be a better option. I would also considerer pneumatic tyres and uk roads make the journeys a little less comfortable than the could be...
So yes, that is all for now. Thanks for reading and there is a video on my youtube if you would like to see the board working. If I get time in the future I will probably make one of these again as this was a very enjoyable project...