Getting it Working pt. 1 – Rolling Car

Design, Featured, General / Saturday, February 23rd, 2019

Since our last post we’ve been hard at work and a lot has happened. We’ve gone from CAD models to the testing track in the span of a couple weeks, and we are excited to keep moving forward towards competition.

As July draws ever closer, the pressure and pace of work has increased dramatically. With the new year, we implemented an aggressive schedule of drop-dead dates to ensure that our rate of progress stays high. We are proud to say that we have met, or beaten all deadlines we’ve set for ourselves thus far.

1 February Deadline: Rolling Car

Early this year, the parts to build our suspension and brake systems were manufactured and we redesigned our chassis. This meant it was finally time to take the momentous step of getting the car rolling on it’s own wheels for the first time.

The process began with the assembly of the major mechanical subsystems: the newly redesigned chassis frame and the suspension. We had the complex aluminum components of the suspension that we designed (see more about the design process here) machined by an outside expert before bringing them into our shop for final assembly

Suspension Components Being Assembled
Suspension Components Mid Assembly
Front and free rear-wheel suspension fully assembled

In parallel with the suspension design and construction, we designed and manufactured our first prototype chassis. Building off the lessons we learned from our original mockup (chassis mockup construction | chassis 2.0 design process). Among the updates taken from our experience with the chassis mockup that we incorporated into the new chassis were a more aerodynamic design with the inclusion of the main support bar at the back which dramatically reduces frontal area, support for a lighter round tube crush zone, and many precision manufacturing improvements.

Chassis halves in vertical construction jig
Chassis being welded

With both major sub-systems completed, the last step was to mate the two, integrate steering, and add a prototype plywood floor.

Wheels being mated to up-ended chassis
Final wheel attachment

Excited by the attachment of the wheels and eager to get rolling, we hastily added a pre-prototype plywood floor (an ill-fitting plywood sheet) and the steering column was attached with wood and baling wire. We then let our creation taste fresh air for the first time.

It (technically) rolls!

Ok, so obviously this wasn’t enough to meet our criteria for 1 February, it may roll, but its a long way from being a car. With several days left we set about solidifying the chassis, putting a more permanent floor in the car, and properly mounting the steering column.

Starting with the chassis: the large quantities of empty space and the prevalence of squares made the chassis unacceptably susceptible to bending. Our solution to this was brutally simple: steel trusses, lots and lots of steel trusses.

Triangular steel trusses to support the chassis

Despite the lack of nuance, this simple solution was incredibly effective. For the addition of under 10 lbs we now had a chassis able to carry the weight of many people without bowing. This also made the chassis more stable during early rolling tests, as it eliminated the tendency for the steel of the chassis to bend as the car turned.

The next step was to replace our baling wire and wood mounting solution for the steering system with a more permanent, sturdy, and overall less sketchy solution. This ended up being an easier change than anticipated.

Steel mount for steering column
Steel mount for rack and pinion system

Finally we replaced the improvised plywood floor with a slightly better fitting one which would serve as a template and test-fit for an aluminum floor which would be added later.

The world’s most expensive push cart ready for action

With that, we felt we had satisfied our 1 February obligations well enough to press ahead and continue work towards our 15 February goal: to get the car running under its own battery power. We had our work cut out for us, but after coming in early by several days on our 1 February deadline, we were confident we could make it.

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