Designing a Chassis/Drivetrain

[nathan_hui]

Well, how good are you with the stress analysis tools with SW?

FRC teams use a variety of chassis designs. There probably isn't one optimal design (no design is ever optimal in all aspects, only optimal for a particular application). 2473 has used a mix of custom welded chassis and the kit base chassis. I've heard of other teams using sheet metal chassis. The base function of the chassis is to support the drivetrain, control system, and manipulators. Now there are a bunch of ways to organize this, and that should be the decision of your team. Such ways include discrete modules that bolt onto the chassis, fully integrated systems, etc. Each has their own advantages and disadvantages, but in each scheme, the chassis is the backbone and support for everything.

In other words, the chassis must be strong and rigid enough to support the entire weight of the robot as it is moving and getting banged around. Note too that the robot must be stable as it corners (robots don't get up after tipping), so the center of gravity for the robot should be fairly low. Eliminating weight in the chassis may not be the best idea, but again that is dependent upon your chosen design criteria.

I would suggest coming up with a couple concepts at this point. Look at the different drivetrains that are possible, and evaluate the strengths of each of those. Since you guys are in your second year, I imagine you don't have many experienced student members, so I'd stick to a simple drivetrain (6wd or 4wd). Then, look at some ways of mounting such a drivetrain. The kit chassis is okay. It's not particularly rigid, but it's fairly modular and will take a fair beating. Welded aluminum chassis give some more room for customization, but they do require a design and an understanding of the manufacturing process. To my understanding, sheet metal chassis are completely custom, but require a full design prior to manufacture. When you do design these chassis, remember your factors of safety, and do as much analysis and prototyping as possible. Once you commit to a particular design, you may not have time to redesign it if it fails.