Back in 2011 an 8-year-old neighbor kid showed me a book with about a dozen small Lego projects. The book had a kind of “blister pack” attached at the bottom, containing the Lego parts needed to make all of the projects. He proudly flipped through the book, showing me the projects he had made so far (just about ALL of them).
One page showed a sophisticated plastic version of something I recognized from my childhood … a simple toy made from a wooden spool, a couple matchsticks, a piece of candle wax or soap, and a rubber band. Here is the version from the old World Book / Childcraft Make and Do book that we had growing up:
Here’s a modified version that I whipped up with my niece a couple weeks ago. We were going for speed rather than the slow-motion, hill-climbing “tractor” action that is usually mentioned in “How To” articles. Note the thin sheet of clear plastic between the bead and the spool…
While I wasn’t watching, someone (my Dad, maybe?) put a knot in the rubber band, which actually helped it run better. I’m thinking that it kept the twisted part of the band away from the edge of the hole, which reduced friction:
Here is another variation (among MANY) that I found online – from page 181 of the November 1959 issue of Popular Mechanics:
All of this got me thinking. An idea for a “multi-mode” version of the toy popped into my head, and I planned to work one up for the neighbor kid. Before that happened, I signed up for the 2011 Toy Swap on the forum at Family Woodworking … so an FWW member got the first version instead. After approximately 20 shop hours (including major mistakes and at least one total restart) I came up with what I call a “Multi-Mode, Rubber Band-Powered Roller”. (It’s not really a “tank” or “tractor” … although with some redesign it probably could be.) There are currently two different ways to configure it:
“Single Mode” …
… and “Dual Mode”.
Note the wide blue rubber bands for providing traction. They were salvaged from broccoli stalks, as purchased at the grocery store. They can/should be used in “Single Mode” too … not sure why I took them off.
The key to the two modes is the method of anchoring the “propulsion” rubber band(s):
To set up either mode, you have to pop off the end caps. They’re in there pretty tight, and they’re pretty smooth, so I chiseled out a couple of “screwdriver insert points”:
“Single Mode” uses a metal screw on one end instead of a thumb tack or matchstick:
I mounted the screw on the lathe and used a file to turn away the threads in the center, so it wouldn’t cut the rubber band:
“Dual Mode” uses a center pin to provide driving torque from both ends (at the expense of a shorter run time). You could use a single, long rubber band if you have one. I used two overlapping bands instead. Either way, the pin has to go through the “hole” in the rubber band(s).
The center pin arrangement was one of the trickier subsystems to figure out. Why didn’t I just use another screw? Well, I reasoned that the “user” would need a better (more open) view when trying to situate the rubber band(s) around the center pin. Maybe the removable end caps make that unnecessary; I don’t know. Anyway, I:
- Drilled and tapped the large block while it was still square-sided
- Turned a “bolt blank” on the lathe (basically a two-diameter dowel)
- Used a threading die box from Beall to put threads on the smaller diameter
- Turned away some of the bulk in the middle of the “bolt”
- Mounted the “bolt” tightly in the block and turned the ends flush as I rounded out the block
- Used a Dremel tool with a cutoff wheel to make a slot on one end of the “bolt”, so it can be tightened/loosened with a flathead screwdriver
When I turned away too much of the “bolt” threading to work with the first block I made, I opted to start over with a second block rather than make another center pin.
I made a “band puller” from a piece of 12-gauge ground wire, but just about anything will work:
The body and the long “rolling pin” of this prototype are made of purpleheart, and the center pin is made of hickory. For the end caps and “legs” I used a new-to-me wood:
I ran out of time before I could put a finish on the toy, so you get to imagine the finish of your choice!
That neighbor kid is now 14, and I still haven’t made him one of these toys. I wonder if that original block could be salvaged?