Toy Car that Stops at Edge of Table?

Question

I need to upgrade a toy car (any kind) so that when it runs across a table, it will stop exactly at the edge. The design needs to be purely mechanical, and I can't do anything to the table. It's for a project, and I imagine similar questions have been asked here by my batchmates. Any ideas?

Answer 1

my brother has one of those toy cars. im not sure exactly how it works but theres a little wheel in the centre of the car that makes it turn around every time it hits the edge

Answer 2

use laser beam which can find what is ahead

Answer 3

Buy an electrically powered car and wire the switch onto a pressure (spring) switch mounted a few inches in front of the car.  When the spring switch is not depressed by the table top...power off.  Radio shack should have what you need.

-Fred

EDIT: The guy above me has it...I type too slowly...

Answer 4

well, you could put in a capacitator that stores up and releases just enough energy to propel the car the edge of the table.  or, you could set it up so that after it goes a certain distance something drops onto the tires to cause enough friction to stop it.... well, those are my ideas! i've got no clue how to exectue them, but good luck

Answer 5

Use the simplest toy toy car with no motor whatsoever.  Attach a string about 2 feet to the front of it and tie a washer or 2 to the other end.  Put the car as far back from the edge of the table as you can and still have the washer dangle a few inches below the edge.  If the car doesn't move by itself give it a slight touch.  You may have to add some weight to the string.  If the car does not stop at the edge- if it goes off the table add some weight to the back of the car.  You may have to fiddle around for a while to get the weights right but it is easy to do and complies with you requirements- purely mechanical.

Answer 6

Easiest is a spring loaded (or gravity loaded) microswitch that rests on the table top normally, but when the front goes over the edge the microswitch drops down, closing a contact which switches a relay that reverses the motor. If the tabletop is smooth, a simple bent piece of plastic or metal will work.

A more complicated way it a light beam that reflects off the surface to a photocell that will throw the relay. Like you see in computer mice.