Hoppers!

This is a guide to building simple hopping toy. I've seen mechanically-driven versions of this, and like those, this one entertains a 4-year old for a good period of time.

Hoppers are simple mechanical toys. The weight spins around and moves the bot about by balancing badly. These things skitter around delightfully when you flip the switch and they're fairly safe for pets and young children.

Parts needed
- a frame (1/32" sheet metal)
- legs (marking flag wire)
- battery pack (from Radio Shack)
- switch (also from Radio Shack)
- red and black wire (20-24 gauge, though in a pinch, CAT-5 cable will work, but double it up))
- motor
- 2 small wire ties (long enough to wrap around your motor)
- off-center weight (2" of thin-walled, 1" electrical conduit)

Tools you'll need:
- Permanent marker
- Hack saw/rotary cutter/tin snip (and a file, depending on your cutting skills)
- Pliers (fairly heavy, you'll need to bend the wire)
- wire cutters/stripper
- soldering iron
- hot-glue gun

I got interested in these when looking at BEAM mechanics. I've got another set of these that will use a simple photovore head to control two counter-rotating weights to follow a light source. However, this tutorial shows the basics of building the form.

You'll start with small L-shaped piece of sheet metal. I find that the guts of flat-bed scanners have all kinds of good stuff in them. The legs are made from a single piece of wire, and I use the 18" wire marking flags for can get from Lowes or Home Depot. Switches and motors came from Radio Shack .

The template below is the frame of the bot. The Sketchup files are included, as well.

Print out the template and mark it on your sheet-metal, or just mark it out. Cut along the solid lines, and make sure you end up with the same number of fingers as you started with.

Once you've got the frame cut out, drill the hole for the switch. Then, cut out (BUT DON'T BEND) the tabs that will hold the legs on.

Finally, bend the frame into the shape shown below.

err...steel. Take a marking flag, remove the flag from the wire and, bend it in half (see below). The "U" shape is made by using a needle nose pliers. This is an example of where a picture is worth a couple dozen words, so look below...

First, attach the legs. Gently bend the tabs over the wire with pliers. Crimp them down as tight as you can.

Then, wire-tie the motor to the top of the mast. Use two ties.
Attach the switch in the hole you drilled, or hot-glue/epoxy it on.

Then, hot-glue/epoxy the battery box to the bottom - making sure that you can change the batteries.

When all of the parts are attached, solder the circuit together (see the crudely drawn wiring digram).

Finally, drill a hole in the pipe. Start with about 7/8" in from one end. File the hole clean and glue/epoxy it onto the motor shaft.

Add some batteries and turn it on. Stand back and enjoy the fun.

Bend the legs or frame around to change the behaviors. Enjoy!