Using spring to push against wall

[locksleyu]

I'm looking for a mechanism to allow compressing a spring with something like a servo or motor, and then release it so that it pushes with great force against a wall, propelling my robot.

I haven't been able to find any similar designs for this on the web, has anyone tried this before?

[rbtying]

You mean a solenoid?  Although, building a system like that isn't particularly hard: You can use half-toothed gear to ratchet the spring back, and it will release on the half of the gear that the teeth aren't on (this is how airsoft guns work). 

[locksleyu]

Thanks for the response!

The solenoid is an interesting idea. Unfortunately, most of the solenoids I could find required high voltage (12/24V) and didn't move fast enough to get significant motion from a wall push. Do they make any solenoids that move quick enough to make something fly and use only 4.8/6 volts?

The half-toothed gear is an interesting idea. Do you know of any companies that sell half-toothed gear for use with standard servos
(Hitec, Futaba, etc.)?

Thanks.

[Soeren]

Hi,

The solenoid is an interesting idea. Unfortunately, most of the solenoids I could find required high voltage (12/24V) and didn't move fast enough to get significant motion from a wall push.

How do you know how fast they move?
The magnitude of a push is a combination of speed AND strength.

Do they make any solenoids that move quick enough to make something fly and use only 4.8/6 volts?

Usually, they're a few ms, but if you want to push a few thousand grams, they'll be much slower and the longer the stroke, the weaker they are.
The types made for low voltage just have fewer turns of a thicker wire and will use a much higher current.

The half-toothed gear is an interesting idea. Do you know of any companies that sell half-toothed gear for use with standard servos

Find a suitable regular gear wheel than can be mounted to a (strong) servo horn and grind of half the teeth.

Why do you want to push out from a wall like this - don't you use a motor for normal motion?

[Conscripted]

Does the robot have to compress the string? Is it possible that you would compress the spring before placing the robot against the wall. After the spring fires the first time the bot will not be against the wall anymore.

I'm guessing it's some sort of race and you want a quick start. Am I right?

Conscripted