40 More Handy Tricks

Step 2 Instant Electric Go-Cart Conversion

James Burgett of computer recycling fame showed me this nifty electric go-cart at ACCRC.

The chassis and clutch came from a dead gas-powered go-cart.
The motor is a big DC motor from an old computer tape drive.
The batteries are discarded 12 volt gel-cells from an emergency lighting system or UPS.
The wiring is "Monster Cable" from a dead stereo system.
The batteries are series/parallel wired to provide 36 volts to the motor.
There's no speed control, so when it goes, it just GOES.

Comments

[chriskendall1]

How about a dimmer switch(like step 14) for the speed control?

[ImageMaker]

Nice idea, but dimmer switches (the kind used for house lighting) only work with AC current at a minimum of about 100 V (though they don't care if its 50 Hz or 60 Hz). They're based on an electronic device called a Silicon Controlled Rectifier (SCR), which turns on when the voltage on the control gate reaches some designed-in minimum, and turn off when the voltage on the switched terminals hits zero. Wire up a couple in opposite polarity with a resistor/capacitor circuit to control how much of each half cycle actually gets passed, and you have a light dimmer -- I built one in a college electricity lab in about fifteen minutes, thirty years or so ago.

Unfortunately, it's much harder to build an electronic speed control for DC -- the simplest way is to use a whale of a variable resistor in circuit, but then you have to throw away the waste heat somewhere. The next simplest is to use a DC motor and AC generator (alternator, for instance), with a variac to control the voltage that then gets fed to a rectifier that powers you drive motor. The problem with this is that the motor and generator in the converter have to be about as big as the drive motor, or they burn up. What's actually used in most modern electric vehicles is a "chopper" control -- it's got a huge, well cooled transistor of one sort or another that's turned on and off very rapidly, and the ratio of "on" to "off" is varied to control the motor speed. Small ones are cheap and come on a single chip; big ones are expensive and can be complicated to wire up -- and a go cart like this one is getting into the "large" category.

[skids927]

Better idea: Have a series of momentary push button switches, so when you press one in, it goes slow, two and it goes medium speed, and three it would go fast. You could wire your batteries in parallel and as you want more amps push the switch between each cable.

[HillBilly Homer]

Maybe the pedal off a sewing machine will work?

[ForgetMyProfile]

Remember how Fred Flinstone stopped his car? Same here.

[stasterisk]

And when it stops, it stops? Or can this coast?

[TimAnderson]

It can coast, but it doesn't coast all that well due to drag from the chain over the small sprocket etc. There's a wacky old gas lawnmower in mars' garage that has all kinds of parts like this on it. Go nuts!

[bedbugg2]

the friction in the electric motor can work as a brake too ;)

[Logicisking]

It is completely unnecessary to use a clutch for a DC electric motor. They develop torque then instant power is applied to them. Only gas powered engines need them since that cannot make torque at zero and thus must be continuously running at idle; the clutch is there to isolate the engine when its idling, but engages when the engine is revved up.

[Vulcanator]

Monster cable is expensive!!