As a boy, one of the best toys my brother and I owned was an electric race car set. Sure, everyone had one, but ours was special because it didn't come from a toy store (at least not directly) and it wasn't new when we received it. It came with track and a box full of motors, wheels, axles, brushes, car bodies, and chassis. If we were going to play with it, we would have to figure out how it all worked and build our own cars. We spent far more time figuring, reconfiguring and testing vehicles than we actually did racing them.
I was reminded of this yesterday when we played with these simple homemade "drawbots." I was first put on the track of this concept by a passing mention of "bristlebots" in a post by Kami over at Get Your Mess On! I followed her link, and then other links into the world of "vibrobots," simple robots that operate on the principle of a vibrating motor. I immediately ran out to Radio Shack to purchase some inexpensive motors and battery holders and we were in business. Ultimately, I copied the basic design presented by Steve over at Finkbuilt. (If you read through the comments to his post, you'll see that there is a raging controversy over who, in fact, invented the drawbot, with some folks saying they were making them in science class back in the 1950's. In other words, it seems to be an idea that's just out there in the world, so I'm going to thank Kami for getting us going and Steve for the design and hope there are no hurt feelings.)
This is the prototype I made at home on Sunday: a paper cup with markers duct taped to the side like a three-legged stool. I then taped a motor to the top . . .
. . . and a AAA battery pack to the back. I'm kind of wishing I'd purchased a battery pack with an on-off switch, but then again, there's something more "tinkery" about having to either remove a battery or disconnect a wire to turn it off and on. Before connecting the wires, however, I had to figure out how to attach some sort of small weight to shaft of the motor, unbalancing it enough so that it would vibrate. Without the vibration, it won't move. If you look carefully at the first picture you'll see that I finally settled on a paper clip wrapped up with a lot of duct tape.
The final step was to attach the wires -- red to the + (positive) terminal and black to the - (negative). If I'd wanted a more permanent robot I could have soldered the connection, but since I was harking back to my old race car set days, I just used a pair of needle nosed plyers to hook the wires through the tiny holes in the terminals.
This robot tended to move fairly slowly and really wanted to go in a circle, which probably had a lot to do with how evenly the markers were positioned and the relatively small amount of vibration created by the unbalanced motor.
I took over our building/tinkering station from Anjali's mom Reshma yesterday (sorry, Reshma) and set up half the work bench with paper, then turned the kids loose with the robot. To be honest, I thought there wasn't much for the kids to do but watch it draw and keep it from tumbling off the workbench, but they found at least a dozen different ways to knock it over, disconnect the wiring, cause the paperclip to fly off, and remove the batteries, which was perfectly fine because each time it happened I got to demonstrate how to make it operational again. I pointed out that this is why their electronic toys at home so often get broken -- they play with them a little too roughly and things get disconnected. "This toy is better," I declared, "because it's not all closed up in plastic and we can fix it ourselves." Some of them made a game of trying to steer it toward one another and most of them tried the experiment of using their fingers to stop the paper clip from spinning.
While one half of the workbench was occupied with that kind of experimentation, complete with a fair amount of bickering over who broke it this time, I got to work on the other half constructing a second drawbot. It took the better part of an hour to complete between repairing the original robot and allowing the children to handle the materials I was using. Naturally, they were particularly interested in the motor. I demonstrated how to connect the wires, showing them the + and - markings. Several of them wanted to try it themselves, completing and breaking the electrical circuit over and over.
The motors, especially working outside, where hard to hear whirring, but the kids knew they were working by letting the spinning drive shaft tickle their fingers. We spent a lot of time taking turns touching the spinning shaft before finally getting down to the business of actually making the next drawbot.
I let the kids lead a little here. They were eager to copy the original by taping the markers to the cup. Since we were using duct tape and I'd neglected to bring scissors with me, I had to tear the tape for them, but at least they could peel off the lengths we thought we'd need, then position the markers while I taped them on. We had several balancing failures when the "legs" were positioned too closely together, but we finally managed to figure out that they needed to be spaced evenly in order to stand upright. I lost a lot of kids to other outdoor activities during this process, but several kids like Thomas, Annabelle, Ariya and Charlie B. stuck it out for the most part. This kind of tinkering isn't for everyone, especially with other things going on.
We then mounted the motor and the battery pack, connected the wires and stood back. It didn't do anything but whir. Why? We hadn't added any uneven weight to the drive shaft to make it vibrate. Hmm, Ariya's idea was to try the first thing that came to hand: a wood chip. I got out our hand drill. Thomas suggested that we'd need our smallest drill bit. I put an off-center hole in the wood chip (I really should have had a kid do it) and we stuck it onto the drive shaft. When we re-installed the batteries, we got vibration, but the wood chip soon flew off. We put it back on several times before it finally broke, rendering it useless for our purposes.
Thomas then found a broken craft stick on the ground, probably left over from our glue gun construction project from a couple weeks ago. We again drilled a hole, discovered it was too small, switched to a slightly larger drill bit and did it again. Presto! It slid right onto the shaft. When we replaced the batteries this time, there was a little vibration, but not enough. We'd installed our propeller too evenly. We were running out of time, so I took matters into my own hands and taped a washer to one end of the blade.
We then once more re-installed the batteries . . .
. . . and it went crazy, bouncing in a vibratory staccato across the paper. The uneven installation of the markers and the extremely "eccentric" motor gave it far more life than the prototype. This had to be repaired several times as well once the kids started laying their hands on it.
My mind is reeling with new vibrobot projects to try.
(Note: we did this project outdoors, but I took the pictures inside after class.)