Introduction: DIY INSANE Electric Longboard (note: Testing in Progress)

By
About: I am a college student at NC State University and I enjoy doing projects that interest me and teach me more about the field of engineering.

SPECS:

45+ mph top speed

35 mph cruising speed

7.5 HP ( 6400 watts)

18 mile range

Regenerative Braking

INTRODUCTION:

Forget what you thought about electric long boards. This isn't some 15 mph toy cruiser. This is a dual wheel drive monster, and its two motors combine to make 7.5 HP of raw brushless power. This is the supercar of small electric vehicles that brings a thrilling experience by replicating the feel of long-boarding and snowboarding with sport-car like propulsion. Who said you can't carve up hills? This extremely unique combination provides an incredible new way to travel that any thrill seeker would enjoy.


Step 1: Get All Parts Needed


LONGBOARD:

Wheels and trucks

Deck - longer is better

HARDWARE NEEDED:

Timing belts

Timing pulleys

Receiver and transmitter

Batteries - 10s high capacity/discharge

Power Analyzer - watt meter, power consumption

Motors, ESC, Power Switch

BATTERY CHARGING HARDWARE :

Battery Charger - get what you pay for

Power supply - buy higher wattage than battery charger is capable of

Parallel charge board

Bullet Connectors

XT60 connectors


ODDS AND ENDS:

10 gauge AWG stranded wire

Heat Shrink 10 gauge

6x 1/4" by 2.5" bolt

6x 1/4" - 20 nut

4x M4 by 12mm bolt

4x M4 washer 2.5" washer

2.25" washer

METAL NEEDED:

6mm strip of aluminum

ABS plastic

WHERE TO BUY:

The prices of these materials fluctuate quite fast, but doing your research and looking for the best option to fit your goal is the way to handle your project. I chose the best materials to build the fastest board I could make.

Step 2: Wiring / Putting Together Battery Charger

Building The Charger

Building this charging system is not easy; there are many things to consider in building an efficient battery charger. First, I started with sizing the power supply appropriately. The power supply powers the battery charger. This charger (like any other charger) can normally only charge one battery at a time, and I have four batteries (each of the two packs is composed of two 5S batteries in series). The Parallel charging board I constructed makes it possible to charge all four batteries at once. I sized all my materials appropriately and after soldering everything nicely together I used heat shrink to make the professional finish.

A little about LiPos

First you must understand that is is one of the most complicated LiPo battery types, and thus is one of the most complicated battery charging procedures. I designed this system to be able to charge both (which is in essence 4 batteries) for my longboard at the same time, making the charging process faster. Before moving onto this step, it is recommended to get on you-Tube and research what LiPo batteries are and how to charge them (trust me, it will save a whole lot of heartache).

Basically you want to understand :

S = nominal LiPo voltage 3.7 (So a 10S battery = 37 volts)

There are 3 stages to LiPo discharging. Full charge = 4.2v ( quickly discharges to nominal and stays steady), nominal LiPo voltage = 3.7v ( steady at this voltage until closer to end of capacity), Cut off Voltage 3.3v (it is not good to run these batteries completely dead, so 3.3 volts is the accepted safe cut-off point).

C = Capacity, and deals with Discharge rate. To break it down to its simplest terms, the C rating is the maximum safe continuous discharge rate of a pack. If you see 10C on your battery, it means it can be discharged at 10 times that pack's capacity. Capacity refers to the milliamp-hour rating of the battery, which will be listed as a number followed by mAh (2000mAh, for example.)

I have two of these bad boys and have them tied together in parallel to provide a 9 Ah system. This is far beyond the commercial electric skateboards in terms of storage/performance (10S vs usual 6S = faster motor RPM/more power). This translates to longer range, more torque for the motors, faster riding, and less strain on fast accelerations on the batteries.

Step 3: Designing / Cutting Motor Mount

DESIGN STAGE

By first getting the hubs and belts tightened by hand, I measured and designed a design on paper that could easily be machined out of a 6mm (quarter inch) strip of flat aluminum metal. I suggest doing this after you acquire the correct belts to make sure that you didn't design a mount that can not be tight with your materials. These lengths fluctuate with different sized cogs / gears. The design that i chose allows the motor to be mounted on a variety of different sized belts and cogs, and allows the to be tightened by simply sliding and re-tightening.

MACHINING STAGE

I custom designed my own motor mounts and programmed a CNC machine to cut them out.

WELDING ONTO TRUCKS

I then TIG welded the trucks and reinforced with custom brackets and chamfers. Welding these motor brackets to the truck was a little bit tricky, but inexperienced welder should have no issue with this.

Step 4: Fit Gear to Motor Shaft

So using a lathe I was able to properly bore out the inside of my aluminum gear closely to the motor shaft size, then using a very precise boring tool I precisely machined it out exactly.

Next I keyed the motor gear.

Step 5: Machine Gear for Wheel Attahment

For my gear that attaches to the wheel, I have decided to go with a simple bolt pattern that allows me to use either 3 or 6 bolts to hold the gear in place. I first used a CNC machine and lined my washers up with my gear in order to machine the gears and washers at the same time to have 6 holes that would fit through the rims of the wheels that I have. The bolts simply slide through and bolt down with nuts to have the gear securely in place. With as much power as this board has I decided to go with ALUMINIUM gears instead of the plastic polymers. After this was done all I had to do was boar out the middle of the gear so that it would not touch the truck axle of the long board. I had the washers and the gear bored out at the same time to save some steps.

Step 6: Lay Out Parts to Design Casing

Once I had everything in place mechanically I finally could get to the final stage of designing a custom case that would be the right size. After laying out all the parts I constructed a model casing out of cardboard. This cardboard held up very well and I was able to actually test the board with this casing before I make it out of ABS. I designed this case to be as small as possible as well as have enough room to take the batteries in and out for charging easily, and enough room to access the wiring and programming wires for the motor controller. This allows easy access to make modifications and repairs without having to take the case off, for example if and when I am to add lights to it and such.

Step 7: Wiring

Wiring this beast was no small task, the wiring harness itself has four parts that are wired in line before it even gets to the motor controller. The two positive wires from the two batteries and the two negative wires plug together in parallel so that there is one positive and one negative at the beginning of my wiring harness. I have my power switch wired in line, following I have a power analyzer, and A HVAC 5 volt system. it's a mess

Step 8: Attaching Gear to Wheel

This step may seem pretty straightforward, and if you look at the pictures it is very easy to understand how it works, however it was very challenging to tighten the bolts in such a manner that the gear stayed lined up perfectly centered. I eventually got it perfect, but it was no easy task and required many tries.

Step 9: Programming

The ESC can be programmed on my computer for different acceleration rates, braking rates, motor timing, cut-off voltage, and many other variables.

Step 10: Casing