[Unusualtravis] came up with this fairly slick electronic catapult. This easy to construct and moderately cheap rig has an arduino as the brains and controls for 3 servos. One is the release, another controls tension, and the third controls the angle. Both the circuit and the construction are very simple making this a perfect weekend project. He would have preferred it to be a bit smaller, so shoot him your design if you manage to shrink it.
We’ve always been rather fond of catapults of whatever complexity, so feel free to send in any variations you’ve worked on.
[youtube =http://www.youtube.com/watch?v=R8D8ZZJyCLA]
That is pretty awesome!
I want to see/build a torsion version.
Same… the tension spring approach means the arm is no stronger than the servo, and those are pretty cheap servos.
First hack the servo for 360 degree rotation, then line it up to large gear. Have the gear be connected to the torsion rope via removable lock, and a second servo connected to that lock AND the firing pin. Two servos, one strong catapult. Almost no damage to the servos too.
Can you describe the “removable lock” a bit more? I’m not sure I understand.
Basically just take a simple transmission (http://i169.photobucket.com/albums/u214/JRLloydIII/WebStuff/Tech/transmission-simple.gif – Not my gif) and replace one gear with a stationary one. Leaving it in neutral will fire through, so maybe adding a simple gear pin will prevent accidental firing.
Sometimes I surprise myself with how poorly worded I can comment.
Ouch!
I’m cringing every time the catapult arm hits the stopper. He is just hammering the arm right into the servo axis with no linkage or shock absorber taking up the hit.
won’t that arm servo (which I presume controls the distance and height of the throw) become horrible damaged?
Cool! I wonder how consistent it is. I built a beer pong cannon with a solenoid from a pinball machine. It works ok and uses PWM combined with transistors to vary the force, but I never thought of this approach.
That was my point.
Even with an all metal gear servo you will eventually damage a small gear tooth or at least the bearing housings since it is still plastic.
yeah, I agree, that poor servo is living a worst-case-scenario in terms of abuse.
Poor servo’s….
While this is just asking for spewing servo gears all over the place. (so what, just use the broken servo as ammo :P )
It is a nice idea for a fully automated desktop catapult.
I agree. I cringed the first time the arm hit the stop and the servo took the hit.
It also needs a loading magazine. When the arm comes back down, it triggers a release to drop a ball on the arm. Then it would be fully automatic.
I wonder if this can be used with a linear actuator instead. At least they can be used and reset without the abuse that those servos are taking. Plus the collapsing fields would help absorb the shock better by slowing it down.