UCI Solar Car

Suspension Engineer · January – May 2025

I joined UCI's solar car team (ZotSun) as a second-year student and spent two quarters on the suspension subteam, working on UCI's first ever solar car. Over that time I took the suspension from analysis and reverse-engineering through fabrication and assembly to a competition-ready rolling chassis for the Formula Sun Grand Prix.

The UCI solar car team on campus steps behind the car's aerobody, a low white shell numbered 95 and lettered SOLEATER — The team, with the aerobody.

Vehicle dynamics and load cases

Before any of the suspension hardware could be sized, I needed the car's mass properties. Working from the master CAD assembly, I measured the height of the center of gravity, the wheelbase, the distance from the front axle to the center of gravity, and the front track width. From those I calculated the car's static tipping angle and got 35.42 degrees against a required 45 degrees, which showed that the geometry itself, not just the parts, had to change for the car to pass. That analysis also set the load cases the rest of my work was built around: a 1G cornering load, a 2G vertical bump, and a 1G braking load.

CAD view of the whole car with dimension callouts for center-of-gravity height, wheelbase and track — Pulling center-of-gravity and geometry measurements off the master CAD assembly.

Closer CAD view with measured distances and a cross-section area of a suspension member — Pulling center-of-gravity and geometry measurements off the master CAD assembly.

Reverse-engineering the steering upright

The master CAD carried only a rough placeholder for the front steering upright, the part that holds the wheel bearing, the steering arm, and the brake caliper. A rough model cannot be analyzed or manufactured, so I rebuilt it from the real part. I collected coordinate data on a CMM to generate a point cloud and a map of every hole, and had the physical upright 3D laser scanned. From the scan I built a high-fidelity, manufacturable CAD model, added the reference axes the suspension geometry is defined against (the spindle axis, the ball joint, and the lower control-arm and caliper axes), and re-integrated it into the front suspension master assembly using sketch geometry so the rest of the assembly updated around it. The accurate model made meaningful FEA and simulation possible for the first time.

The real machined aluminum steering upright resting on a workbench — The real upright, the CMM point cloud, the laser-scanned model with the old placeholder superimposed in blue, the rebuilt part, and the upright in the front suspension assembly.

Sparse 3D point cloud of the upright from CMM coordinate data — The real upright, the CMM point cloud, the laser-scanned model with the old placeholder superimposed in blue, the rebuilt part, and the upright in the front suspension assembly.

Fabricating the rear trailing arm

The rear trailing arm was carried over from the first-generation car. I ground the old mounting tabs off it and welded up the new members to finish the arm. As one of the few people on the subteam with welding experience, I then welded the front suspension tabs and the trailing arm onto the chassis while other members set the welding jigs. With the tabs and the arm on the chassis, both the front and rear suspension were ready to assemble.

CAD showing the position of the rear trailing arm in the suspension assembly — The trailing arm in CAD, freshly welded, and going onto the chassis.

The freshly welded bare-metal trailing arm — The trailing arm in CAD, freshly welded, and going onto the chassis.

Steering column supports

The steering column had to be rigidly supported and its travel positively limited for the car to pass technical inspection. I built the early iterations of the column supports: I cut the bearing collars at the machine shop, fitted the bearings, and welded them to tubes that were then welded to the chassis. When that arrangement did not fully take the play out of the column, I worked with the EV team on the fix that did, mounting flange bearings above the suspension box and behind the dashboard. That brought the column into compliance, made the car steerable, and completed the front suspension.

An early flange-bearing support for the steering column, mounted on the chassis near the brake reservoir — Early iterations of the steering column supports on the chassis.

Close-up of a flange bearing bolted to a plate on the chassis with the steering shaft through it — Early iterations of the steering column supports on the chassis.

Building the rolling chassis

With the suspension welded up, I assembled the front and rear suspension, less the wheels, setting the front rod ends centered between their tabs. The whole subteam then set the front and rear ride height, mounted the major components, fitted the tires to the wheels, and lowered the car onto the ground as a rolling chassis, and then a powered chassis once the drivetrain was in. That was the milestone that let the other subteams start running dynamics tests.

The chassis with the front and rear suspension assembled, still up on a stand — The suspension on the chassis, and the finished rolling chassis on its wheels.

Close-up of the assembled rear suspension pushrod and rockers — The suspension on the chassis, and the finished rolling chassis on its wheels.

Optimization: flange bushings

With the car assembled, I started tightening it up. Several suspension mounting holes were larger than the bolts running through them, which allowed slop at points where the geometry needs to be precise. I designed flange bushings to take up that clearance and printed them in carbon-fiber-reinforced nylon, bringing those joints in line with the regulations.

CAD render of the flange bushing — The flange bushing, and an example shock-mount location.

CAD showing an example shock-mount location where the bushings fit — The flange bushing, and an example shock-mount location.

The finished solar car, numbered 95 and lettered SOLEATER, running at speed on a track with a motion-blurred treeline behind it — The finished car on track.

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