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My university senior project was extremely ambitious. Over the course of a year (2011), myself and three other mechanical engineering students designed and fabricated a complete solar race car chassis including the frame, suspension, hubs, spindles, brakes, & steering.

Its been almost 5 years now but vehicle design is just as fascinating to me today. In retrospect any one of the above systems would have been an adequate senior design project. My decision to attempt all of them together reveals the ignorance/arrogance/ambition of my younger self. In the end we were successful though and I learned a heck of a lot about chassis design. I'm sure there are a few more ambitious university students out there who could benefit from my experiences.

This instructable will discuss the engineering process of designing a custom 3 wheel vehicle chassis. The project consisted of research on vehicle dynamics theory and calculations, 3D modelling, structural stress analysis, designing around human factors, component sourcing, and lots of time spent fabricating.

Note: My senior project group's involvement in the car was limited to the mechanical chassis portion only. All the solar panels, battery design, bodywork, and system integration were later done by other students.

Step 1: DESIGN GOALS & CONSTRAINTS

At the start of any design project you have define your goal and all the constraints that will shape your project. You don't want to miss anything and later have to change your design because of it.

Timeline: We had to actually finish the new chassis by the time we graduated, otherwise it would be unlikely that someone else could jump in and finish our work. See Gantt chart above. The real timeline turned out to be everything shifted and squished to the right because we were all busy full time students.

Meet Regulations: We designed the car to meet the American Solar Challenge Race regulations.A 27 page document listing things like: Driver must be sitting in upright position at no less than 27 degrees. Driver must have no less than 10" of space between any part of his body and the frame. The overall dimensions of the car must not exceed X'. There must be adequate crush space, visibility, and so on.

Improvement vs Old Solar Car: Our goal was to make quantitative and qualitative improvements when compared against the schools existing old car. We ran the old vehicle through a few tests as specified by the regulation including a slalom, figure 8, braking distance, and turning radius test.


Practical Constraints: The car had to be able to fit through a standard double door, so we could get it in about of buildings. The wheels were heavily regulated by the race organizations and they were so expensive to buy new that we had no choice but to steal the existing wheels of the old solar car. The vehicle had to be powered by a single very special high efficiency electric motor that was designed to mount to one of those wheels.

Another issue was that some of the schools tools were shared by multiple engineering clubs. This was a problem because the clubs saw themselves as competitors for the same scarce resources and so they hoarded them. We ended up using a lot of our own personal tools and making the school buy us some new tooling. Without getting too deep into our financial setup it should suffice to say that money was also a significant practical constraint.

We purchased most of our parts online from Jegs.com, SummitRacing.com, Ebay, McmasterCarr, and Amazon. The fasteners and raw materials came from local stores.

<p>where did you get the wheel</p>
<p>The wheel rims are special parts designed for solar car racing. We reused ours from the old solar car because we could not find new ones. We did get new tires from Dunlop though.</p>
<p>Where do you get components such as steering system from to fit your design? </p>
<p>The steering rack came from <a href="http://www.desertkarts.com">www.desertkarts.com </a> &amp; steering wheel from <a href="https://www.dansperformanceparts.com">https://www.dansperformanceparts.com</a>. Lots of things came from <a href="http://www.jegs.com">http://www.jegs.com</a> &amp; <a href="https://www.summitracing.com">https://www.summitracing.com</a></p>
<p>Is there any info about the hub motor published any place? It looks really interesting.</p>
<p> We used an ancient motor and never had the budget for a new one so we never spent the time thinking about it. (Later on the team got a new one donated to it.) All I know is this caliber of motor is extremely energy efficient, heavy, very specialized, and also costs on the order of tens of thousands of dollars. </p>
Very nice article. I competed in Sunrayce '97 and '99 so I know the difficulties you faced. Well done!
<p>Very nice project and write up! I've long been fascinated by the construction of these solar racers. Another book I'd recommend is &quot;Race Car Aerodynamics: Designing for Speed.&quot; </p>
<p>Nice job on the write up and your work on the vehicle. Many people (me too) don't realize the amount of work needed to get just a car on the track, much less a winning car. </p><p>BTW, braking performance looked impressive. </p>
<p>As a non-engineer but a pretty skilled mechanic, I've been looking at tadpole designs for years with a basic understanding of why they are preferable over a delta. But I've never seen the principles laid out as well as you have! Thanks so very much! Steps 4 - 6 are a treasure for those of us with an idea of what's needed! And an Excel file to boot!</p><p>Thank you, a well earned vote.</p><p>Ron</p>
<p>Dang! Nice job on this!</p>
<p>What kind of solar panel did you use ? <br>And what is the total length of the panel.</p>
nice frame!use a gear box so that your motor can support both rare wheels !just an idea
<p>Good job man, love all of your instructables</p>
<p>Thought I recognized those wheels... My high school physics class built an aluminum framed 3 wheel solar car in 2001. We had a 48V hub motor.</p>
<p>Nice work! I actually worked on the SIUE solar car electronics way back in 2005 - 2008... but we never really did anything spectacular - no one in the club was that dedicated, and mostly just talked about what we should be doing instead of actually doing it.</p>

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Bio: Hi I'm Michael! I'm a dog owner, husband, writer, and mechanical engineer and I love getting my hands dirty building stuff. If you ... More »
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