Testing coasterbot construction ideas

The definining feature of a coasterbot is that its chassis relies on CDs or DVDs. Most of the ideas uploaded to the MAKE flickr coasterbot pool have a robot with one CD, or two of them stacked vertically. There is a good reason for this. A small footprint allows for a more agile robot, and the construction is simpler.

But if there is one thing I’m sure of, it’s that I won’t do well in the contest by using a standard design. This is my first robot, so it’s unlikely that it will move better than others, or have a better object avoidance algorithm. I need an original chassis.

Some folks have figured out how to bend the CDs or melt them into a curved dome. But I haven’t seen anyone use multiple CDs horizontally. I think it might be interesting to chain the CDs together that way. It would allow for any number of additional sensors, one of the contest goals. So, with that in mind, I broke out the Tinkertoys and started putting things together. I started with this:

The drive axis orientation is independent of the discs, allowing for them to rotate relative to it. What I really want is for the discs to swing freely relative to each other for a more sinuous motion, but here I was limited by the toolset.

When the kids saw me playing with the Tinkertoys they wanted to help. They pulled out some additional pieces. I thought it might look better if the shaft joining the discs was covered, leading to this:

A few days later I thought that it might be fun to treat the second disc as a “tail”. Tails are usually smaller, and longer. Why not put a few mini-DVDs in line? I had to go out and buy the mini-DVDs (which felt slightly wasteful) and have yet another another possibility, shown below. Note that in this case the joining shafts are visible, because the Tinkertoy set did not have a sufficiently small piece.

I like where this is going, but the lack of “swish” in the tail — i.e. rotational freedom — is very clear in this version. I would like the bot to be a little more snake-like. To do that, however, I will need some different couplings. Tinkertoys won’t cut it.

There are risks in making a longer, looser robot. It will not maneuver as quickly, and going into reverse could be interesting. I will have to do some experiments.

Tags: coasterbot, robotics