2017 has gotten off to a rocking start! In early 2017, Javelin partnered with coaches and advisers from Wheelchair Basketball Canada to design and print sensor housings for a kinetics project.
Scope: To design and print housings for an accelerometer that mounts directly to the rear axle of a wheelchair to measure and improve the acceleration of a wheelchair basketball athlete.
Objectives: Retain and process data on the acceleration of an athlete and relay that information to the coaching staff. Once the data has been rendered, the coaches will then instruct each athlete on better techniques to achieve faster acceleration to beat their competitors to the ball each time.
I have been working with their team lead, Jelmer Haringsma, on this project. Jelmer is from The Netherlands but is in Canada working with the Canadian team while completing a masters program in Kinesiology. Jelmer piloted this new technique in Canada to measure the initial acceleration of a player. He believes there are large gains to be made with the initial acceleration of an athlete.
Designing and 3D Printing
Jelmer used SOLIDWORKS and 3D Printing in his schooling back in Holland. While his English is almost fluent, our universal language is the design within SOLIDWORKS. We first discussed the initial design. Without having seen the housing mounted to an axle, it was hard to picture exactly how it would fit. We printed version 1.0 using a Stratasys Fortus 250 3D Printer. This was a trial to get quick, direct feedback. Rapidly made prototypes are a huge benefit of 3D Printing, as we could have designed and redesigned the mount for another week without any success. Having a printed version gives immediate feedback and highlights changes that need to be made.
Improving the Design
We decided to meet in person to discuss V1.0 and take the design of V2.0 to the printers. We quickly noticed a few things. Version 1.0 was Jelmer’s first time seeing the quality of Stratasys production series of machines. He was blown away by the quality, accuracy, and consistency of the build. The sensor fit into the housing we printed with a 1-2mm clearance all around. We didn’t have formal drawings of the sensor so V1.0 did a good job at approximating the dimensions.
Secondly, the parts were heavier than Jelmer expected. I built the mounts in a solid infill to maximize strength as these parts need to be cycle tested. Knowing that the load and stress on these parts is low, I will reduce the infill by 40% and honeycomb them using our Insight software. This will make a big impact on the overall weight of the parts.
Now knowing how the sensor fits to the axle, I will redesign the sensor so we can reduce weight, increase the mounting surface area which will yield with a better fit, as well as reduce the rotational inertia. This is one of the many benefits of 3D printing! We can add complexity while reducing material consumption. Therefore, parts are less expensive and take fewer hours to create.
There are two more blogs in this Wheelchair Basketball Canada blog series. Stay tuned for when we show the final design in action!