Plunger w/o spring

[TJ_Jadem]

How do I make a plunger without a spring? Is it possible?

[patent_girl]

So - my son's team is competing tomorrow and we'll have to see how it works out, but they built a plunger out of binder clips, some elastics, and an unsharpened pencil.

Here is a link to a picture of it https://dl.dropboxusercontent.com/u/635 ... lunger.jpg

They pull back on the pencil gently and it springs forward to hit a marble that starts the action by rolling down a ramp, etc. They based the idea off of a pencil gun/shooter from the "mini weapons of mass destruction" series of books (I think volume 2), but added/changed elastics to limit the how much the pencil goes back. They also had to reinforce the rest of their design (it is all Legos) to compensate for the force of pulling the pencil back. There are smaller binder clips (3 I think) inside the larger ones, to form a channel just big enough to hold the pencil. And they removed the binder clips metal prong parts.

It is basically built like this, only they adapted it to just have a pencil pop out a little bit when the elastic is pulled back (like a plunger). Here are instructions that are basically like the book: http://www.officeguns.com/gunadv_super_maul.html

[NeilMehta]

The only alternative that comes to mind is to use a portion of a cut rubber band to pull back and release a dowel