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FoamJumper

Page history last edited by PBworks 13 years, 2 months ago

Jumper video - http://video.google.com/videoplay?docid=-8522394199718784997&hl=en

pictures - http://www.flickr.com/photos/connors934/sets/72057594066578732/

 

The jumper car is a project that lets people experiment with the fun of electric motor control and the making of a functioning vehicle. Since the vehicle doesn't rely on wheels to move, you don't have to get into the fussiness of mating gears and axles. Basically, if the motor can turn, the vehicle can move. It moves by having a weight off center on the motor shaft. The quickest thing to use is a glue stick jammed onto the motor. The vehicle needs to keep itself off the table or floor, so some screws stuck into the body work fine. For the body, light weight helps. Pink insulation foam works well, foam core board works good too.

 

Originally, the main jumper car idea came from seeing a sample of a similar vehicle at http://robotvillage.com/ in New York City. They used it as an intro project for kids workshops. The core of the switch idea came from the book Build your Own Underwater Robot.

 

To control the motors, the best thing to use is a two or three position switch with 6 connectors on the bottom. Power from the batteries goes to the center. The outside connections are jumped in a cross pattern. The motor positive and negative come off one end. You can use screw type connections if that's what you have. Long term, you probably want to solder the connections. The wires connecting the motors can be wire nutted to telephone cable (four strands) or cat 5 cable (eight strands) 2 conductor lamp cord will work, but you will need a big snake of wire. You will need two strands per motor.

 

It makes a certain amount of sense to make one of the switches first and connect it to a motor. This way, you can see that you are doing something for a reason, turning the motor forward and backward. To feel what the motor is doing when you throw the switch, just hold it in your hand and try the switch. Add an off center weight with the glue stick to make it wobble like a pager motor. Then making a basic lightweight vehicle is a good next step. A second motor can be added in parallel to the first. If they are matched and opposite each other on the vehicle, it will bounce forward or backward depending on the switch position. Then, to make the second motor separately controllable, wire up another switch.

 

At some point, holding switches and battery pack in your hand gets to be a pain, so you want to make a remote. Hopefully you have been using switches that have panel mount threads and a nut. If you do, you can just drill a hole in a piece of metal or wood or plastic or... then stuff the switch through the hole. Put the nut on it and it won't flop around. Find a way to attach the battery pack to the clicker, tape, a screw, zip ties, whatever works and is on hand. Tape and adhesives work as a temporary solution, screws and mechanical fasteners are better long term solutions.

 

For the remote clicker, you might find that a project box works, but so will a cookie tin, video cassette box altoids tin, whatever is available and will fit your parts. Figure out how many switches you will need, then measure the width of the switch panel. Add one to the number of switches and you will get the number of spaces between the switches. Divide the width of the panel by the number of spaces and you will get the width of the spaces for even spacing. Use metric if you don't want to deal with fractions.

 

To wire up your power supply, you might want to make a power snake. You will need some wire nuts to connect it to the wires leaving the center connectors on the switch, some lamp cord or other wire and some alligator clips. Cut the lamp cord at least a few feet long. If you will be standing and the battery will be on the ground, maybe make it a bit longer. If the battery and vehicle are on the table, make it shorter. Cut one side about 4 to 6 inches shorter than the other. This will keep the battery connections from touching each other. Label one + and one - with tape or some other means. Put the rubber boots onto the wire. Strip a half inch of insulation from the wire. Crimp the gator clips. Slide the boot over the clip. Wire nut it onto the power connector for the remote. Now you can attach your clicker to a power supply. Lantern batteries run at 6 volts. Car batteries run at 12 volts. More volts will make the motors turn faster, but you may smoke the motor if the voltage is too high.

 

This project is intended to introduce students to working with electricity and motors. It also provides an authentic opportunity to work with the design process. There are plenty of practical applications to the skills gained doing this project. Have fun and use it as a starting point to figure out some neat stuff.

 

Extensions for this project include remote control design, vehicle design, underwater vehicle, hovercraft and working with a variety of tools to create the above designs. You could turn the vehicle into a car by designing and building a gear train. Tolerances are a little fussy with gear trains. There are lots of possibilities. Go where your interest leads you.

 

 

Jumper video - http://video.google.com/videoplay?docid=-8522394199718784997&hl=en

http://www.flickr.com/photos/connors934/sets/72057594066578732/

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