Spring-loaded cannon Answered
My friend and I are considering building a spring loaded cannon. The idea right now is to have a pvc pipe for the cannon chamber, and pvc pipes flanking it to hold springs in parallel. A cross-bar will go through all 3 pipes through slits cut long ways in the pipe. The springs will be attached to some point forward in the flanking pipes and to the cross bar, which will be used to pull the springs back and, once released, will launch the dart/ball in the center tube.
My research so far - the spring rates of springs loaded in parallel are additive. With 5x 10-in*lb springs, we can produce 667 newtons of force when pulled back 3 inches (springs in question are 5.5 in long) . That will produce an acceleration of 303 m*s^2 on a 1 lb (2.2 kg) albeit for only a fraction of a second.
http://www.amazon.com/Extension-Spring-5-625-Long-080-count/dp/B001292S08/ref=sr_1_1?ie=UTF8&s=industrial&qid=1257718057&sr=1-1 These are the springs we're looking at. We'll need to use an even number of springs, so either 4 or 6 (or 8 or 10).
So, what do you guys think? Practical? Will we be able to get any distance? Any suggestions?
A ROUGH picture is shown below. === are spring tubes, | are handles, and left arrows indicate direction in which springs will be stretched, and the right arrow is a dart flying out of the center launch tube.