Proto Labs Helps Equip New Lightweight Electric Vehicle

“Creating an entirely new mode of transportation has been a complex, iterative process, progressing from sketches to CAD models to paper mockups to prototypes.”

It’s a choice commuters make every day: convenient public transit—bus, train, streetcar—or to-the-door private transport by car or perhaps bicycle. Now they can have the best of both. Boosted Boards, a San Francisco startup created by three Stanford-trained engineers, is beta testing a unique electric vehicle that can be carried by a passenger onto public transit, then carry the passenger for the last mile (or miles) and be stashed under a desk or in a locker until needed.

The company’s motorized longboard has serious transportation boasting features like regenerative braking and stats would be hard to believe if they weren’t being confirmed by early users. At less than 15 pounds it is the lightest electric vehicle ever made. Twin electric motors generate 2.6 horsepower, achieves a top speed of 20 MPH, and can climb a 15 percent grade (a useful capability in the Bay Area). The board has a range of about six miles on a full charge, and the lithium ion batteries take two hours or less to reach full capacity. And perhaps most astounding of all, operation costs about $2.50 per 1000 miles or about ¼ of a cent per mile.

The engineering know-how behind the project is impressive to say the least. Co-founders Sanjay Dastoor, Matt Tran, and John Ulmen met as students at Stanford and have degrees in mechanical, aerospace, and electrical engineering. One of the group’s mentors is a former director of engineering at Tesla Motors, and their staff has grown to include additional engineering and industrial design talent. The market is obviously impressed; the Kickstarter campaign that helped fund development reached over 400 percent of goal, and beta testers are raving about the product.

This kind of success doesn’t come easily. Creating an entirely new mode of transportation has been a complex, iterative process, progressing from sketches to CAD models to paper mockups to prototypes. “We’re packing a lot of functionality into a very light vehicle, so everything has to be just right,” says Ulmen. “Covers for the electronics and batteries were particularly challenging. They have to fit perfectly and be tough, abrasion resistant, and fireproof.”

Boosted Boards used Proto Labs to prototype the housing on the underside of their longboard to protect the electronic components.

For early beta models, covers were made of laser-cut, heat-formed sheets of ABS. As designs progressed, prototypes were 3D printed and eventually injection molded. “3D printing is good for evaluating form, but it has its limitations,” says Ulmen. “For example, we found out that 3D-printed prototypes of the hand-held wireless controller would melt if they were left in a warm car. The plastic covers for the electronics and battery were going to be some of the most exposed parts of the finished board, subject to bumps, scrapes, and heat. We needed to know exactly how the finished parts would perform, and that meant injection molded prototypes.

“We’re a small startup with limited funds,” he continues. “The challenge was to keep development moving and bridge the gap between prototypes and production. That meant molded prototypes, but traditional injection molders were slow and expensive. Friends who had used Proto Labs told us about their injection molding service and that they’d had great results. We looked into it and were amazed that their standard lead time was 15 days instead of two months from other molders, and that for an upcharge we could get parts in as few as three days if necessary. At our low to medium volumes the costs were significantly lower as well. When we saw the numbers they seemed too good to be true.

We started designing parts and getting feedback from Protoquote®, Protomold's online interactive quoting and design analysis tool. Because it’s highly automated we got quotes and analyses overnight and were able to identify and fix problems quickly. The changes were mostly small things like wall thickness and pin placement. We also got a lot of help from engineering support staff at Proto Labs. That helped us move quickly through the design process and eliminate potential mistakes before we started spending money on prototypes. When we finally did upload a final 3D CAD model and order parts they came back exactly as specified with no surprises. We were still a bit shocked at how quick the turnaround was and that the quality was so good.

“We ended up having three molds made, one for the electronics cover and two for the halves of the battery cover. Because the role of the covers is so demanding, one of the biggest challenges was choosing the right resin. The ability to run multiple resins in the same molds helped us find the right one. We started out with clear polycarbonate that let us see through the cover to the operating parts inside and do interference checks. Then we went to non-fire-retardant nylon. We knew we’d eventually need a fire-retardant resin, but we wanted to see how regular nylon worked before we spent money on the more expensive version. We had parts made using a 20 percent glass filled nylon supplied by Proto Labs. They looked good and were super strong, but the glass fill gave the plastic a slight grey color that wasn’t exactly what we wanted.

The longboard is capable of reaching 20 MPH and climb a 15 percent grade hill, a useful feature for the Bay Area of San Francisco.

“Proto Labs directed us to an outside vendor, RTP, for a darker 15 percent glass-filled fireproof nylon. The darker color hides the glass fill, and the finished parts were just what we were looking for. RTP shipped the resin directly to Proto Labs, and Proto Labs is storing the leftover resin for us at no charge.

The whole process went very smoothly. We started out with no experience with injection molding, but the folks at Proto Labs and the great web resources they provide coached us through the whole process. We’ll be going into full production in a couple of months and ordering covers from Proto Labs for at least the first thousand or so; after that we might go to hard tooling for ongoing production, but we’ll do it knowing that our design has been fully tested both by us and in the market.”

The wand is based on a hybrid ultrasonic-inertial positioning technology. Ultrasonic emitters mounted on the ceiling act as position beacons that the wand detects using tiny microphones. The wand reports its position data via 900 MHz or 2.4 GHz radios, providing input data to Mezzanine’s “Perception” subsystem.