Parts for Project: Finding What You Need for Success

[FSTg16]

First, hello all! Sorry if this is in the wrong forum (or wrong site, even), but I'm not sure where else to go, and I stumbled upon here doing some research (for project ideas). Feel free to delete this if it's off-topic.

I am building a simple research project, and need some help choosing the right hardware to get things going. Essentially, I have two marbles held together by a spring. The spring is held compressed by something, and that's tied to the base by a taut string (or similar). When the marbles are hit with something and moved, the string will "pull" the mechanism holding the spring compressed and the two marbles will shoot out.

There's a link at the bottom of this post to a horrible drawing of what I need. Blue = thing that holds the spring compressed. What would you guys recommend that I use to hold the spring compressed that could easily be pulled out? Also, where could I find small springs and whatever I use to hold it compressed? Do general hardware stores carry things like that?

Again, sorry for the horrible explanations (and the off-topic-ness). Feel free to delete if it's cluttering up these forums. I just wanted to see if anyone here has had similar experiences in the past and has advice to give.

http://img355.imageshack.us/img355/9622/sketchde1.jpg

 

[robb_]

Maybe you could mount the setup to a wooden base. Drill a hole in the base and have a dowel rod stick out attached to a metal u-shaped bracket as in your drawing. The base could be propped up onto two other pieces of wood allowing access to the underside of the base where you could pull down on the dowel rod releasing the tension in the springs. Ghetto, but just a starting point.
edit- springs can be found at a hardware store, or you can make some on a lathe.

 

[andrevdh]

Tie the spring up with some string. Burn the string to release the spring. Reverse engineering (taking things apart) can provide one with some springs.

 

[sas3]

Here are some sites that you can get springs from.


http://www.centuryspring.com/

http://www.sciplus.com/

 

[FSTg16]

I like the dowel rod idea (and especially the burning string...that's pretty awesome), but I actually won't be controlling when the spring is released. I need the marbles to split whenever something hits it (from any angle). That's why I was thinking about tying the "compressor" to the board so it would pull it out when moved, but I haven't found anything allowing me to do that yet.

I would also need to have the spring "stick" to the marbles somehow (to hold them together), but would need them to be able to split apart when the spring is expanded.

I'm thinking this project may not work after all. :(

 

[andrevdh]

Have a look at the mechanism on ball point pens with the little protrusion at the side that one pushes on to make the point exit from the tube. See if you can adapt it to your project. Maybe insert a stronger spring?