Tools: Dexter Industries GoPiGo3 Robot Base Kit, https://amzn.to/2FHLpaL YIKESHU 4WD Robot Smart Car Kit, https://amzn.to/2DXNEF3 Actobotics Whippersnapper Runt Rover, https://amzn.to/2PTqOox Dagu Rover 5 Tracked Chassis, https://amzn.to/2SeVYDk Pirate-4WD Mobile Platform, https://amzn.to/2DVnp1W Here’s the first robot I started with. It’s the GoPiGo3 by Dexter Industries, and it’s the most expensive one on this list at around $100. The reason it’s so pricey is because it’s more than just a chassis, it’s a system that comes with it’s own motor and sensor board that plugs right in to a Raspberry Pi computer board that you need to supply and will also set you back another $35.It’s really meant as an educational robot platform that you can build off by adding more sensors and program using a web interface and built-in lessons. As a platform for your own robot, there are some cool things going for it. The chassis is made from a thick and sturdy acrylic and the motors have these encoder wheels and sensors on the back to more accurately read their position compared to a standard toy DC motor. But these nifty motors are also a liability. I damaged the ones I had and a new set cost me around $20 directly from the company.The other downside of this particular kit is that it’s a 2-wheel design with a metal caster in the back. It’s fine for short indoor carpet, but a real pain for outdoor use.Overall, though, it’s a solid little robot system for the price, but more than I needed since so much of the value is wrapped up in the polished educational software that supports it. So I swung to the other extreme after this and looked for the cheapest possible robot chassis, and here it is.The YIKESHU 4WD Robot Smart Car Kit is a $16 kit. It comes with four DC motors. The structure is a sandwich of thin, somewhat fragile clear acrylic. I painted mine up to give it some personality.I run into these all the time at Maker Faires, running some student robotics project. They get the job done, but they are light duty. They definitely couldn’t hold up to getting stepped on or a drop off a table. But at $16, you can treat it more like a t-shirt than a robot.Now aside from the motors, you have to bring all your own electronics to this. For me, that was a Raspberry Pi, an Adafruit motor board, a camera, battery, and a speaker. It still all added up to around $100. But unlike the GoPiGo, the components were easy to replace and recycle into other robots after I outgrew this one.The real achilles heel of this design are the flimsy plastic brackets used to mount the motors to the chassis. If you pick one of these up, I recommend adding some hot glue or E6000 into this equation so that you’re not just relying on the brackets. Alright, so after that, I liked the idea of bringing my own components but I wanted a design that wasn’t so flimsy. I was really happy to find the Runt Rover line from Actobotics.There are a few of these to choose from. I got the Whippersnapper model for around $30. Again, it’s just 4 geared DC motors, some wheels, and a plastic frame—but every element has a little something extra. The motors have more torque, the wheels came in grey instead of the yellow you see on every other robot, and the frame is awesome. What makes the frame so great is that it uses a textured ABS plastic. It’s less brittle than the acrylic and easier to drill through. And the best part is that it all snaps together. Aside from the motors, which mount on little machine screws, the rest all snaps into place. It feels really solid, and there are less parts to jiggle loose. My only disappointment with this one was that I was really trying to get a robot working that could handle going over the grass in my backyard. I even purchased this extra set of fancy wheels thinking it would help, but in the end it just doesn’t have the traction. And so that brought me to the Dagu Rover 5 Tracked Chassis. And it’s at this point that I start to wonder if maybe I have an addiction to robots. This comes already assembled, with two geared motors built-in, a AA battery holder that fits in the middle, and a price tag of around $45. You still have to bring your own controller board and motor driver and whatever else you’re looking to do. And if you want one of these fancy covers, I bought this one for around $7 from Pololu, but really I could have 3D printed something just as useful, or even used some scrap wood. What’s cool about this one is that the extra torque and the tracked treads really do allow it to crawl over grass and wood chips pretty reliably. It’s also cool that you can adjust the height of all four wheels to give it more clearance or just a different look.