Electric mountainboard – post #2 Plans

Today I’d like to write a short post about my plans concerning my board project.

Right now I have almost working board with very simple “control unit” with LCD to display motor’s temperatures (by “almost working” I mean being able to ride for about 5-10 minutes, then some mechanical part breaks). Batteries are mounted using transport strap, wires are attached to the board using adhesive tape, to make it ready to ride I have to connect 4 plugs. But it’s just a first prototype to check whether my idea is viable (i.e. building a reliable board with brushless motors using only 3D printer and generic tools – no milling machine and welding).

So here’s my plan for the next 1-2 months:

  • Mechanical part of the project:

Mainly power transmission problems – I have troubles attaching sprocket wheel to the motor’s shaft in a reliable way. But after today’s tests I hope that I need to make just minor improvements to my design and I will be done with that problem.

Second mechanical issue is bearing the motors and shafts. As I mentioned in my previous post, recently I added shaft’s support on second end to eliminate moment load). After quick tests I noticed that the bearing I added was getting a bit too warm (but I haven’t measured it exactly yet) – that’s probably due to the fact that there are 2 bearings inside the motor and adding third bearing makes one of the bearings overly loaded (due to inaccuracies in bearings position on the shaft).

If I manage to fix these two problems I will probably done with the mechanical part – at least I hope so, but probably a few other problems will show up.

  • Electronics part of the project:

Sensors

Right now I only have attached thermometers to the motors. I’m planning to add temperature measurement to the motor’s drivers, a GPS, current sensors (two, one for each motor), batterie’s voltage measurement.

Control unit

My initial plan is to use Arduino Mega as the “brain” of the whole board (but I’ll probably write code in C++, without using Arduino “framework”/libraries). I already have an LCD 192px x 128px. The display will be mounted in front part of the board in a 3D-printed case. I will also add “ignition switch” to eliminate tiresome connecting connectors.

Power management

Aforementioned ignition switch will connect power (from small Li-po) to the Arduino, which will make sure the main batteries are connected and it will turn on IGBTs, which will be located between batteries and motor’s drivers. I will describe this in more detail in one of future posts. I still haven’t figured out how I’ll charge the batteries (how to make it the least tiresome)

  • Designing cases/mounts

I’ll have to create cases for control unit (already started) , batteries and motor’s drivers. So far I have printed mounts for drivers, but I already see that I’ll have to redesign them (I didn’t consult additional space for board with IGBTs).

I also want to make proper lighting – both for safety and better style. To test my design idea I printed and assembled one back light, render and real photo:

back_light_30_06_201520150630_203159_resized

Obviously there’s a lot to be done yet, but I’ll never give up – I’ve already sacrificed too much time and money for this project to surrender.

Electric mountainboard – post #1 Motivation and what I’ve done so far

Hey,

I live in the capital of Poland – Warsaw. Since it’s a pretty big city, commuting takes quite a long time – especially from my new flat, which is located 5 kilometers from my faculty and 7 kilometers from my workplace. If I take a bus, one-way commute can take between 30 minutes to 1 hour. Right now I don’t want to buy a car (a bit too costly + traffic jams).

Commuting by bike takes 20-25 minutes, but the weather has to be good (temperature + no rainfall)  and being sweaty for next hour or so is pretty discouraging.

That’s why I came up with an idea of building an electric mountainboard. I can ride it even when it’s cold and if it starts raining I can grab the board and take a bus/tram.

In theory it’s simple: take a mountainboard, mount a motor or two on it, add remore control and motor drivers, batteries and Bob’s your uncle.

But in real life situation is not that simple:

Theory and practice

 

Nevertheless, I decided to try to build it.

I started thinking about building some kind of electric board in the end of 2014. Learing using Autodesk Inventor during 3rd term and buying 3D printer in February 2015 enabled me to turn vague thoughts into reality.

My initial approach was using a deck from a regular skateboard with mountainboard trucks and tyres, two BLDC motors with drivers, Li-po batteries, 3D printed motor mounts, power transmission via two sprockets and a chain.

I created a very simplified model in Autodesk Inventor:

render_20_05_2015

After printing the mounts and assembling the unit (without chain and sprockets):

eboard_motors_08_05_2015

Wheel sprocket was supposed to be mounted to the motor’s shaft using prop adapter.

My main problems with first version of the board were:

  • mounting sprocket wheel on motor’s shaft
  • radial and axial play of sprocket wheel mounted to a wheel’s rim
  • taking turns
  • board a bit too short
  • bearings inside motors were overly loaded with moment (long distance between motor and sprocket, shaft was unsupported on second end)

After first tests I bought a proper deck, redesigned motor mount (to minimise distance between motor and sprocket), added shaft support:

oprawa_lozyska_v1_2

 

For the last few days I worked mainly on electronics part of the board – I thermometers to monitor motor’s temperature and display in the front part of the board. I also worked on mechanical part – modified motor’s mounts a bit, prepared new sprockets with hubs.

Right now my 3D model looks like this:

board_11_07_2015

Most recent photos of the board:

20150604_102008 P1060848

I’m planning to make a test of my latest improvements tommorow. Fingers crossed!