Introduction: Build a Motorized Uniwheel Toy Thing (Mutt)

About: I am an American teaching English at Shangluo University, Shaanxi. I like making machines that do interesting but fairly useless things - I call them Quixotic Machines.
Warning: cd rotors can be dangerous, one of mine exploded because it was cracked. I now don't recommend this project for children.
Building a Mutt ( is great fun, doesn't take but a few dollars in parts, doesn't require any special tools. The following steps show how to build one. If you don't have exactly the same components, then improvise, thats what I did.

Required tools:
Needle nose pliers, screw driver, drill.
Required materials:
jump rope (the one that has metal bearings)
an old dvd/cd player (computer or otherwise) from which you will scavage:
        - motor, motor pulley, motor drive belt, rubber grommets
Erector set type metal strips 
plastic coated hanger
two small wheels, beads, metal washers
9 volt battery and battery connector
one electric slide switch

Construction time: about 3 to 4 hours

Step 1: Jump Rope Wheel Bearing

Remove the soft covering from both jump rope handles.
Remove the end caps, push the rope out the open ends and cut them off.
You will be using both end caps and one of the handle tubes to make the wheel bearing.

Step 2: Cut the Bearing Parts

Take one of the handle end caps and cut off the smaller diameter part leaving about 3/16 inch. 
Do the same with the second end cap.
Cut about 1/2 inch from one of the remaining handles to use as the bearing center section.

Step 3: Making Bearing and Bearing Retainers

The bearing is going to hold the dvd on the axle. But we need to put a retainer or holder on each side of the bearing to hold it in place on the axle or else it will just slide back and forth and bind on the bent parts of the axle.

Cut a piece of coat hanger to help build the bearing and retainer parts. 
Use one of the 5 hole Erector set metal strips and bend in the approximate shape as the left retainer.
Use one of the prebent (or bend a 5 hole Erector set strip) for the right retainer.
Drill a small hole in the center of each end end cap so that they will just slide onto the piece of coat hanger.

Now you have all the components for the wheel bearing and retainers.

Step 4: Epoxy the Bearing Parts Together

Use epoxy and glue one of the end caps to the dvd center hole. The smaller diameter should just slide through the dvd hole and extend out the other side.
Then epoxy the center bearing section to the other side of the dvd. It should just fit over the protruding smaller diameter section of the end cap.
Now epoxy the other end cap into the open end of the bearing center section. 
It should look like the picture. Hopefully yours will be straighter than mine.
Let dry.

Step 5: Make an Axle

Photo 1:
Cut the long straight bottom section out of a plastic coated coat hanger.
Bend it a couple of inches from the center into the shape shown.
Push the left Erector set metal strip retainer onto the wire as shown.

Photo 2:
Slide the dvd/bearing onto the coat hanger as shown.
Slide the right bearing retainer onto the axle as shown. You may have to bend things a bit to get everything into position. They don't have to be perfectly straight.
Use two pair of needle nose pliers to make the right bend in the coat hanger axle so that it looks like the picture.

Photo 3 and 4:
Close ups of the right and left sides.

Photo 5:
Make bends on left and right sides to approximate this photo.

Hardest parts are done. 

Step 6: Epoxy Bearing Retainers

Put a couple of small wheels on the axles.
Your Mutt should balance nicely on the dvd wheel and the other wheels should just touch the ground.
Once your Mutt looks about like the picture then add some epoxy to the retainers so they will bond to the coat hanger.
Don't get any epoxy on the wheel bearing. It must rotate smoothly on the axle.

Second photo shows expoxied right retainer. 

Step 7: Add Wheels and Wheel Retainers

The first photo shows the wheels and retainers.
The second photo shows closeup of wheels - on the inside of each axle,  I used a bead like beads that girls like to use to make bracelets. You can use washers or anything the will allow the wheel to rotate without binding on the bend in the coat hanger axle.
Then I added a metal washer, a wheel, another metal washer and finally something to keep the wheel from sliding off the end of the axle. In this case I used the rubber gromets from a dvd/cd player that is used to mount the internal board. I punched a small hole in the side of the grommet and then forced it onto the axle. You need to be able to remove the wheels now and then to add or take off counterweights and these grommets work just fine.

Step 8: Make Motor Bracket

You are going to have to get creative to make a motor mount, and it might not look like mine.
I used a motor similar to the motor from the dvd drive but it came from one of those cheap solar powered hat fans.
I think the dvd motor will work fine.
Use either some prebent Erector set strips and join them with one bolt to look like the picture. Otherwise, bend your own configuration so that you can suspend a motor below the wheel bearing.

Step 9: Wire the Motor

Wire a 9 volt battery lead to a small switch of any kind and to the motor leads.

Step 10: Put It All Together

Now the only thing left is to mount the motor.

In the dvd drive you have been hacking for parts will be a drive belt and a motor pulley.
Put the motor pulley on the motor shaft.
Slip the drive belt onto the bearing.
Bolt the motor bracket to the the right bearing retainer.
Slip the drive belt over the motor pulley.
Use a zip tie to hold the battery to the left bearing retainer.
Use another one to hold the wires to the right bearing retainer - so they dont get pulled off the motor.

And you are ready to motor away.
Flip the switch and enjoy the ride.