About this project
This Kickstarter project is for the final design and production of a laser-cut desktop Magnetic Catapult kit. The Magnetapult is capable of accelerating a projectile at over 16 g's * to a distance of over 40 times the length of the firing arm.
(* See FAQ to find how we came up with these values.)
The aluminum Magnetapult. Photos updated when the prototype is complete:
The Mini Magnetapult: Fits in the palm of your hand, but packs a big punch! (See video in update 6.)
The etching on the Mini Magnetapult. (Hard to find room!):
The Standard Magnetapult, locked and loaded with a ping pong ball:
The standard kit will come with everything needed to build and use the Magnetapult, including laser cut parts, supermagnets, chicago screws to hold it together, flux concentrators, an instruction manual, and two projectiles. You supply the (hopefully moving) targets! I'll update this page when I've finalized the projectiles.
Unique Kickstarter Version Only Etching!
Show how cool you are by showing that you backed the Magnetapult on Kickstarter, instead of getting it retail.
Now with N52 Neodymium Magnets
I wasn't satisfied with the original N42 Neodymium Magnets so I bumped it up to the strongest currently available N52 Neodymium Magnets to maximize the acceleration and launch distance. Please see the Strong Magnet warning in the FAQ!
Metallic Flip Stabilizer and Flux Concentrator
This helps prevent the super magnets from somehow pulling out of their cages and flipping around. As a nice side effect, they act as a magnetic flux concentrator, making the pushing side a bit stronger. A small extra cost for a big improvement in safety, and slight improvement in acceleration.
Not only is the Magnetapult precision laser cut, I've decided to use Chicago Screws to give it a nice streamlined look. As an added bonus, the screws are the same silvery shade as the supermagnets.
Varying launch angles
I've played around with launch angles and trajectories, and added a few arm stops so you can vary the launch angle and distance.
Release the arm without holding down the Magnetapult and the enourmous magnetic forces will flip the Magnetapult around. Not only does this result in a shorter launch distance, but it can also damage the Magnetapult. To stabalize the Magnetapult I've added a pair of legs on each side, and a hole underneath the arm to make it easier to hold down the Magnetapult with one hand.
I'm currently waiting for samples from different companies for the projectiles.
What will the money be used for?
BULK! The more money I get, the better bulk prices I can get. I plan to spend all the money from this kickstarter project on buying enough material for as many kits as I can. The first ones will go to my great backers, of course!
Once the Magnetapult Project is fully Launched (pun intended), I will be creating an instructables with plans on creating your own Magnetapult from scratch under a Creative Commons Share Alike Non-Commercial Attribution license.
This project uses two very powerful magnets to accelerate the launching arm and projectile. You should avoid this project if you wear a pacemaker or are in any way negatively affected by powerful magnets. Be super careful assembling this kit because if your fingers are caught between the two magnets, they will pinch, and it does hurt if they do! Do NOT hold each magnet with just your fingers and see how close you can get them, as they WILL fly out of your grip and collide, possibly sending off shards of magnet at high speed! By backing this project and assembling the kit you are acknowledging responsibility for any personal or property damage that may occur! Not suitable for unsupervised children!
I calculated this from a picture and verified with distance. Numbers are approximate, and are measures with the original N42 magnets. The new N52 magnets will give even more acceleration and launch distance!
The shutter is 1/25th of a second, and the streak that is the ball is a foot long. Interpolating shows the ball to be traveling at 25 feet/second, which is 7.62 m/s. The distance from the ball at rest until the launch point is about 7 inches, or .18 m. As we all know, velocity squared = 2*acceleration*distance, and solving for acceleration, we get acceleration=161.3 m/second squared. Gravity is 9.8 m/second squared, so we're accelerating at an average of over 16 g's!
Measuring the angle of the ball's initial trajectory, you can see that I've nailed it at 45 degrees, the optimal angle for distance. (There's also stops for higher angles.) The vertical velocity is calculated as sin(45) * velocity, or about 5.4 m/s. Since t=2v/a, we substitute to get t=2*5.4/9.8=1.1 seconds in the air.
We can calculate the total distance from the horizontal velocity as cos(45) * velocity, or again, about 5.4 m/s, or 17.7 feet/second. Since d=v*t, we substitute to get d=17.7*1.1, or 19.47 feet. We've been getting about 20 feet in our tests so we can see our calculations are correct.
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