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19mm Steel Projectile

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: Zen/// » Tue Jan 15, 2008 6:22 pm

Ive only made fins out of tape....

When it goes through something it rips off the fins instead of trying to carve the fins through w/e you are penetrating ( A waste of energy )
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Unread postAuthor: TurtleVVisperer » Wed Jan 16, 2008 12:12 am

EDIT: holy crap I didn't see where the page numbers were on this forum, I thought the latest post was on page one! Sorry for not keeping up.

c19o wrote:Haha nice, I'm currently making a hardened steel APFSDS round similiar to yours except longer. I finally got a welder to make it :D

OH MAN, you get extra credit for saying APFSDS. I've only ever heard one other person say that before...
jackssmirkingrevenge wrote:ooh, messy :) what are you firing it out of?

Combustion potato cannon, 2inch barrel, probably about 4ft barrel length I'm guessing, old spice aerosol deodorant for fuel, currently a push-button sparker for ignition, but I'm working on wiring my stun gun up.

rna_duelers wrote:I like a lot!High Speed Camera,you are on verge of the next generation of spudgun history.High Speed recording of potatoes in flight.

Were did you get your HighSpeed from and how much did it cost you?

Damage pictures of the dart would be nice if you could :D

I can't wait till it gets warmer outside! I can't motivate myself to go outside and test stuff right now. It's 10 degrees Fahrenheit here. But soon enough, I hope to have more high speed photos involving spuds.

As for the camera itself, that's a long story. But to shorten it significantly- I'm using a digital SLR camera (not a high speed video camera) to take high speed stills. The logic behind how it's done is easy enough to understand if you know what a camera shutter is.

One- in a completely dark room, hold the camera's shutter open.

Two- Do an event involving motion, like shooting an egg.

Two point five - The motion must cross a laser beam I have set up which, when broken, is detected by a homemade sensor which sets off an
external camera flash.

Three - Because the room was dark, the camera with the shutter open received no exposure until the flash went off illuminating the object at the exact moment it broke the laser beam. The flash I'm using has a duration of about 30 microseconds, so I get very clear results of very fast moving things.

So to answer your question about price- The camera is the most expensive thing. Everything else is under $50 total (homemade) I'm using a Canon Digital Rebel XT (350D) which I got new on eBay for about $600. It is THE BEST sub-$1,000 DSLR camera you can get- for now... or at least when I bought it summer '07 it was. Not sure now.

Any SLR will work, but digital is best because of the instant feedback. I'm sure I'll be posting more pictures and more info later on, but if you're interested, I wrote a very detailed paper about how to do it yourself.
-G'night for now.
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Unread postAuthor: Novacastrian » Wed Jan 16, 2008 1:00 am

Wow, i have the same camera- i only paid 100$ :D It takes great shots of anything. I think the best shots i have taken have been of lightning. Thanks heaps for the info in regards to your setup, i may have to try that one day :P
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Unread postAuthor: clide » Wed Jan 16, 2008 4:13 pm

TurtleVVisperer wrote:It is THE BEST sub-$1,000 DSLR camera you can get- for now... or at least when I bought it summer '07 it was. Not sure now.


Although probably not best on the camera side of things, <a href="http://gizmodo.com/341634/casios-exilim-pro-ex+f1-hands+on-1200-fps-demo-video-and-sample-60+shots+per+second-gallery">this camera</a> will be pretty nice for high speed action when it comes out. 1200 fps will probably be a bit slow for really high speed shots, but it would be quite good at high energy/low velocity impacts, and still a ton better than 30 fps video cameras.
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Unread postAuthor: TurtleVVisperer » Wed Jan 16, 2008 5:06 pm

Novacastrian wrote:Wow, i have the same camera- i only paid 100$ :D It takes great shots of anything. I think the best shots i have taken have been of lightning. Thanks heaps for the info in regards to your setup, i may have to try that one day :P


How i the world did you get it for 100? A friend? Anyways, it is so much fun isn't it. I'm in love with SLRs now.

clide wrote:Although probably not best on the camera side of things, <a href="http://gizmodo.com/341634/casios-exilim-pro-ex+f1-hands+on-1200-fps-demo-video-and-sample-60+shots+per+second-gallery">this camera</a> will be pretty nice for high speed action when it comes out. 1200 fps will probably be a bit slow for really high speed shots, but it would be quite good at high energy/low velocity impacts, and still a ton better than 30 fps video cameras.

That thing would be so much fun to have! Although I'd still buy an SLR over it, if I were looking for a video camera it would definitely be that. I just wish the resolution was better 1200fps... only 96 pixels tall. Still, for an HD video camera, it has some CRAZY AWESOME features.
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Unread postAuthor: paaiyan » Thu Jan 17, 2008 9:08 am

I have the same Rebel XT. Wonderful camera. Well, my parents have it, but I'm the only one that uses it. SO when you leave the shutter open, what do you set the aperture on?
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Unread postAuthor: noob of noobs » Thu Jan 17, 2008 4:47 pm

On the topic of the round, how did you put the flights on straight?
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Unread postAuthor: TurtleVVisperer » Fri Jan 18, 2008 8:45 pm

paaiyan wrote:I have the same Rebel XT. Wonderful camera. Well, my parents have it, but I'm the only one that uses it. SO when you leave the shutter open, what do you set the aperture on?


I do a few test exposures before hand by passing my hand in front of the laser to simulate the shot. Then I look at the picture and adjust accordingly. Because when things explode they explode in all directions, it is sometimes hard to get all of it in focus, so on the egg pictures I used f/20. Not only did that increase the depth of field, but also, because I placed the flash so close to the egg, it would have overexposed the egg had I chosen a larger aperture.

noob of noobs wrote:On the topic of the round, how did you put the flights on straight?


"flights on straight?" I don't understand, you mean the fins? For the fins we just marked where we wanted them with a sharpie, then welded them on by hand. They aren't perfectly on straight, but that is just from lack of practice welding.
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Unread postAuthor: Lentamentalisk » Thu Jan 24, 2008 7:06 pm

on the topic of fins, I suggest that before welding on fins, you find the CoG (center of gravity), and mark that. NEVER have any part of fin in front of that point. Your fins are far too long. Make sure to take into account the extra weight that the fins will be adding to the projectile. Usually fins dont take up more than the last 1/4th of the dart. I dont know how much you know about fins, but the way they work is that they create more surface area for the air rushing past to hit against, keeping that part behind. The fins move the CoP (center of pressure) towards the back of the projectile. If the CoP is in front of, or near the CoG, then the projectile will tumble like crazy. You can test the stability of a projectile (assuming to rifling) by looping a string around the shaft at the CoG, and then holding it in front of a fan. If the projectile turns to face the wind, then it will be stable. If not, then you better duck for cover when you shoot it ;-)
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