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Ask Jörg Sprave About Building Dangerous Projectiles
Jörg Sprave's day job is as a manager in the world of consumer electronics. But he has been for many years making manifest the sort of things that once filled my school notebook margins with doodles: slingshots and other devices for launching bolts, steel balls, and other stuff at high speed at targets or just into the air. (Some of his "slingshots" are hard to recognize as such; he eschews the classic American wrist-rocket braced design as well as the old Tom Sawyer forked branch in favor of things a bit more elaborate.) Thanks to the Internet, hobbies that were once obscure are now easy to follow, and Sprave's homemade slingshots are no exception; you can follow his exploits through an ongoing series of YouTube videos and a forum site that builds on these videos. He's doing it in Germany, too, where firearms may be harder to come by than in the U.S., but giant honkin' firecrackers are available (at least for part of the year), and acts accordingly. Amazingly, he has yet to lose an eye; his goggles are a wise precaution. Sprave has agreed to answer your questions about his own take on physics as a hobby. As usual for Slashdot interviews, you're invited to ask as many questions as you'd like, but please divide them, one question per post.
Dangerous gear
Need not cause one fear
First make the grade
On straight razor blade
Burma Shave
Get thee glass eyes, and, like a scurvy politician, seem to see things thou dost not.--King Lear
From watching a few of your videos, I see a lot of end results which are fun to watch. Take, for example, the firecracker slingshot mentioned in the summary. But one thing I can't seem to find is any testing videos or explanation of testing (maybe you have it in German and I can't find it). So how much testing do you do on these? When I saw your firecracker launcher design I immediately thought that the worst case scenario is that the firecracker detonates before leaving the chamber or possibly barrel. Now, a firecracker that goes off in the palm of your open hand versus one that goes off with your fist wrapped around it produces two very different results. A short or dry fuse in your device could be problematic. Did you detonate firecrackers inside the chamber from a distance to see if there was enough room in the chamber to allow the explosion to vent without splintering your device? How much testing did you do on it before you were confident enough to pick it up and use the butane lighter on it? Is this discussed somewhere?
My work here is dung.
What are your thoughts on the current gun debate in the U.S.A.
Some people die at 25 and aren't buried until 75. -Benjamin Franklin
We still don't have terribly reliable/safe/cheap ways to deliver payloads into space. How about giant slingshots as a space launch platform?
Do you know #6 !!
I see the majority of your projects depend on Thera Band Gold and then the throwers (like your circular saw blade launcher) use a spring. Have you investigated other methods of using elastic energy (which I guess is technically potential energy?) to propel a an object forward by transferring to kinetic energy? Are you engaged in any areas of materials science study in order to find more efficient and reliable materials? Or do you just use Thera Band Gold as your gold standard and leave it at that?
My work here is dung.
Have you looked into the feasibility of creating a slingshot that could fire smaller slingshots that, in turn, could perhaps fire something smaller themselves?
Try not. Do or do not, there is no try.
-- Dr. Spock, stardate 2822-3.
What was the wife's reaction after your one slingshot was off a bit and nicked her car?
I did similar things in high school, though not as elaborate. Made it through with all things, including eyes and fingers, intact.
How many injuries have you and your friends suffered?
If not, why not?
If you were blocking sigs, you wouldn't have to read this.
What legal issues have you encountered? If your authorities are anything like they are in the more "progressive" states of the USA, they consider anything that looks like a firearm or throws any solid object (or not so solid), via any means of propulsion, a dangerous weapon.
Gamingmuseum.com: Give your 3D accelerator a rest.
Jörg,
With the recent controversy regarding assault weapons in the US and the plans to reduce clip sizes, I'm wondering if you would think your, um, devices would be more dangerous if they could shoot multiple objects rather than just one at a time?
myke
Mimetics Inc. Twitter
Have you tried to measure the projectile velocity (and calculate the energy) that your devices produce?
Have gnu, will travel.
This is at least the 2nd time I've seen this guy show up on slashdot. While I'm all for people building stuff in their garage (I do it for sure) I see nothing impressive in this gentlemans designs. Nothing new or interesting. I built something very similar to his nailgun when I was in 7th grade and found a box of large nails at a construction site. His hobby is great, but he needs to come up with something far more insightful before I consider it news worthy. Why is this making it on slashdot?
As opposed to 'safe' projectiles?
If you fire anything fast enough, it wouldn't be considered safe
Partly for the slingshots, but mostly for hearing Jörg giggle after every shot.
suitable for 3D printing or milling?
If you've already done this, where are they?
William
(who made a crossbow using a truck leaf spring when he was a teen-ager and used his father's ratchet lever hoist to cock it --- was fortunate to be to on the opposite side of the tree when the stock split and things went flying)
Sphinx of black quartz, judge my vow.
Thiss Gye is uh Moreon!
Are you in Zombie Squad? Do the slingshots work against Zombies?
This space for rent.
I think ACME Corporation makes stuff like this. Although they're pretty generic and typically failure prone. Look into the Ajax Corporation too.
http://www.cracked.com/article_16647_5-insane-devices-from-kids-cartoons-that-actually-exist.html
Outsource a design to be manufactured. I'd love to buy one.
Why is all the good stuff already modded 5, when I have mod points?
How do you keep the French from surrendering to you?
John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
This is a suggestion: Credit to Wendel for doing this back in the 70s.
Get high pressure tank, narrow and long.
Build fins and nozzle that screw into tank neck. Insert burst plate designed to go 10% below tanks burst rating.
Fill tank 3/4 with water.
Stand tank on fins.
Build bonfire around tank.
The last step for Wendel was 'get arrested by airmen in helicopter while putting out scattered fires, deny anything to do with ultimate water rocket, just good citizens abating a hazard. Get away with it.'
Their rocket made about 30,000 meters and was seen by the Russian launch detection satellites.
John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
...there's something unsettling about a German saying "Achtung!" and then firing a weapon. Maybe it was that three day war movie marathon on Spike.
"Computers are useless. They can only give you answers."
-- Pablo Picasso