WPI students are abundantly familiar with hills. We noticed that we where getting down them much too slowly and much too safely and with 4-7in of snow on the forecast We've innovated a solution we think solves both.
What it does
Our low emison commuter vehicle slides really well on ice and snow. The simple, durable, and reasonably effective steering column won't do much for hairpins but works great at following gently winding roads and paths. The shocks built into the chassis supporting the padded seat are great for ride comfort if you're bar is extremely low. The speeds reached on the vehicle are in excess of 25 miles per hour (+/- 7)!
How we built it
We started 6:30pm Friday Night with a set of discarded skies donated by Mitch, who found them by the side of the road earlier. We realized that we'd need a seat, suspension coils, a method of mounting them, and a ton of spare aluminum framing materials. Mitch began outlining the chassis by building a set of three bar linkages with a psudo-imaginary fourth bar made from the springs we cut to length. Nicco kept busy with assisting Mitch in the machining process of the Skis. James built some simple brackets to thread into the holes made for the original bindings. Everyone made it work and fit everything together. James hand cut steering column. Mmmmmm bed time Friday night (pretty late Saturday morning). Day 1 Progress: suspension and chassis mounted to skis but no, seat, steering, or chassis cross members.
Wake up brisk and early at almost 6:00pm on Saturday. Get to work immediately building all aluminum cross members (two short ones and one long). Nicco slotted the aluminum cross frame on a manual mill. We ran to an undisclosed home improvement store in the snow and bought the components for the rigid steering linkages. We thought we where entering final assembly early Saturday night but when we finished and tried steering we bent the long aluminum frame member and couldn't steer. Nicco threw together a replica made out of steel and it seemed to work fine. We decided to take a quick break and go sledding. with our sled we got in eight runs. Day 2 Progress: we finished the sled but broke it pretty badly in our excitement
One of the bindings broke immediately but nothing else broke for the run. The steering had too much slack and was failing to turn the sled. In the early morning Sunday we went about the grave task of repairs and fixed for our rushed v2. The epoxy settled and the steering column with tighter tolerances worked well as James ran into the room at 7:30am. Day 2.5 Progress: Fixed more than we broke.
Challenges we ran into
Aluminum is way weaker in this application than we thought and we had to hastily replace some of chassis with steel of the same thickness. Our steering system needed a second revision because we couldn't get the play out of our first. Our second used a different connection point to the ski beefy enough for a large bolt to hold down the ties.
Accomplishments that we're proud of
The sled works! And it's really fast! Just in time to play in the snow before we all crash.
What we learned
-Spec out materials for human scale applications ahead of time. -Make the team help clean up the lab before going to bed. -Genneral ski bindings aren't strong enough for the side loads of this operation and need to be supported with epoxy.
What's next for Zero Emission Commuter Vehicle Prototype
I think a comprehensive v3 should be drafted with the goal of maintaining functionality but optimizing for weight and comfort. While our suspension system does have some ability to be calibrated for different people and applications it would be tricky at best to do such a task away from a workbench.