This project is an overview of the build process for the Fusion E-Board that I designed and built whilst working at 3D Hubs. The project was commissioned to promote the new HP Multi-Jet Fusion technology offered by 3D Hubs, and to show off multiple 3D printing technologies and how they can be effectively combined.
3D Hubs were the first company to offer HP’s Multi Jet Fusion technology via an online platform. As part of the promotional campaign for this, I created an electric longboard using HP Multi Jet Fusion technology. I designed and built the board, using both existing components and 3D printed parts. All electronics were assembled and tested to ensure reliable operation, and the mechanical drivetrain was simulated to ensure it would function under the stresses.
This was a project I oversaw and completed on my own and it was great to have full control over the whole process, and very rewarding to see the final result when the board was complete.
I designed and built an electric motorised longboard, which can be used for short to moderate journeys or combined with public transport to offer a much wider traveling range. It has a high top speed, is very manoeuvrable and is easily carried when not in use.
I started by identifying the main components of the longboard; trucks, deck and wheels. These were off the shelf parts so I used these as the starting point of the design. The first stage was to design the drivetrain, this includes the motor mounts, gearing setup and included some modifications to the trucks. The size and position of the motor mounts would dictate the size and location of the enclosures so it was important that this was completed first. I calculated the desired top speed and torque requirements which then enabled me to select the motors and battery for the board. The gearing ratio was also calculated and the pulley sizes were selected, along with the drive belt length. This enabled me to work out the correct size of the motor mounts which ensured a well tensioned belt.
The next stage was to design the battery and speed controller (ESC) enclosures. The selected deck is predominantly comprised of bamboo so is quite flexible, bending substantially in the middle. This has advantages of being comfortable to ride, as it absorbs the bumps in the road, and doesn’t transfer them to the rider. However this also means that a split enclosure is needed to house the battery and electronics, as a full length enclosure wouldn’t be able to flex with the board and would make contact with the ground during operation. The electronic speed controllers (ESC) were placed closest to the motors due to electrical constraints. Because the motors are attached via the trucks the position changes during turns, so the enclosure had to be designed to allow for clearance of the motors.
The battery system was placed at the other end of the deck and housed the electronics related to power. This included the battery pack, comprised of 20 Lithium ion 18650 cells, the battery management system, on/off switch and charging socket.
The main body of the enclosures were 3D printed using an FDM machine, to reduce excessive costs and the ribs that secured the enclosure were printed using HP multi-jet fusion machines, for the high strength and flexibility that these parts achieved.
I used Autodesk Fusion360 for the entire design process, this software enabled me to quickly model components inside of the main assembly which speeded up the development time considerably. I also used the simulation features in Fusion360 to ensure the parts would be strong enough, especially the motor mounts. This enabled me to actually reduce the size of the mounts as I could verify the strength and deflection requirements and remove material whilst still maintaining an appropriate safety factor. After the design process was complete it was very easy to export the individual parts for 3D printing.
One of the main design decisions that were made was to separate the enclosures, which resulted in a clean look and enabling the flexible deck to function without any added stiffness from the enclosure. The power from the battery enclosure was transferred using flat braided cable which was ran just under the grip-tape on the top side of the deck. This allowed the cables to be ‘hidden’ and eliminated the need to run cables on the underside which would have looked ugly.
Another decision that had to be made was which side of the trucks to mount the motors, either under the deck, or out the back. The ideal location was under the deck as this made the design of the board look cleaner, however it meant that the size of the ESC enclosure had to be carefully designed to not get in the way of the motors. I decided to choose the more difficult option and in reflection the cleaner design was defiantly worth the slightly more complicated design process.
The main challenge I faced during the design stage was ensuring that the parts would be compatible and function correctly on the first try. I had a tight deadline and budget constraints which meant it wasn’t possible to reorder any printed parts if there were any mechanical conflicts with the design. I overcame this by modelling the curvature of the bamboo deck as accurately as possible. I created 6 different CAD models of the deck which allowed me to see the different levels of flex and could adjust the motor mounts and enclosures to account for the different positions during use. In the end everything fit together perfectly and the motors had plenty of clearance under the deck throughout the whole range of motion.