Previously I posted that I had picked up a Thunder Tumbler from CVS for $10. This past weekend I started working on making it into a robot. Here it is with the body off and the circuit board pulled out. The coiled spring is the antenna. I'm not going to use the existing circuit at all but I saved it because it might be useful for something else in the future. I removed the front wheels because I plan to use it vertically. The front wheels and/or the wheelie wheel are easily removed with just a few screws, which makes it very easy to customize to whatever configuration you want. I also soldered some extensions onto the existing wires to make them easier to work with.
I don't have a fancy laser cutter or 3d printer so I had to find a cheap and easy way to mount and arduino, sensors, etc. I bought a 10 pack of aluminum flashing shingles for a few dollars from Home Depot and used a pair of tin snips to cut one to size. It worked very well.
Here is the bracket I made attached to the base. I already had the standoffs, I've been hoarding the leftover hardware from computer cases for decades, but you can pick them up from amazon for pretty cheap.
And here it is with the arduino mounted. One of the mounting holes in the arduino is too close the surrounding components to fit a screw into. For now I just glued a cardboard washer to the standoff to keep it from shorting anything. I may remove the standoff completely, or look into some nylon standoffs so there is no risk of shorting anything.
So far I'm pretty happy with it. For $10 you get a base, wheels, two motors, and a battery holder. Not to mention the wireless transmitter and receiver which are also very hackable. The base can easily be set up for a three wheeled or four wheeled robot and there is plenty of room for mounting other stuff. I think I may even stop by CVS and buy a few more to have around for future projects.