Designing a Height and Distance Adjustable Spring-Loaded Projectile Launcher

[Penguin10]

Projectile Launcher Ideas?

I was originally going to make a trebuchet, but my teacher informed me that trebuchets are not very effective, though accurate if made right. I decided to make a spring loaded projectile launcher, yet I can't find any material lists or designs on the Internet. The launcher will need to be height and distance adjustable. It needs to be able to be launched within 2-6m, 2.5m height limit, and a 10cm-1m platform range

 

[spacester]

But trebuchets are so cool! I think there some kind of rule that if you're on the internet you have to love trebuchets! Does your teacher hate computers or something?
J/K

Seriously, what did s/he mean "not very effective"? In what respect?

The mathematics of trebuchets are very well developed and much more interesting than for springs.

My guess is that a spring-loaded device would be much less repeatable than a trebuchet, meaning more stochastic in actual practice (more subject to random statistical variations). That's just my engineering gut-feel.

With a stiff spring it will be hard to make sure you store the exact same amount of energy every time, and a weak spring will require more movement when releasing the energy, giving rise to variations in friction. Aiming will be a challenge unless the projectile travels thru a barrel, but then you will have friction that, again, will be rather stochastic.

What is the mass of the projectile?

 

[Penguin10]

I'm using a racquet ball. I don't know the mass of that. I might end up doing a trebuchet anyway since I have all the plans and materials drawn out. I don't really know what he meant by ineffective, though

 

[Dale]

A pneumatic device will be much more accurate and powerful than a spring-loaded device. Plus the sound makes it fun! All you need is some PVC pipe, a quick release valve, and a pump.

 

[Penguin10]

Could you explain what it looks like and how it works?

 

[Dale]

It is just a tank, a quick-release valve, and a barrel. Pump a bunch of air under pressure into the tank, drop your ball down the barrel, release the valve, and thump! You can find plans and details all over the internet:

http://www.duke.edu/~jwc13/tennisball.html

 

[Penguin10]

I need to be able to adjust the angle, however. The pneumatic device looks accurate, but I have to launch it from a distance. Also, I probably don't have enough time to pump air into it between launches.