Q: Shooting beer cans (as in projectile, not target)

Discussion in 'General Slingshot Discussions' started by erajomppa, Apr 25, 2016.

  1. erajomppa

    erajomppa New Member

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    Straight to the point! I <strike> want </strike> will build a BIG slingshot that will use aluminium beer cans (or soda cans) as projectiles. I tried searching if someone might have done something like this before, but it turned out to be quite hard, since people seem to be using beer cans mostly as targets for slingshots, not as ammunition. :rolleyes:

    This idea comes from when I was innocent teenager and made a spud gun (picture no. 2 for reference) with my friend that was able to shoot projectiles like soda cans and oranges up to 200m (that was an orange, no distance data from cans :( ). Now I really want to replicate the results with mechanical energy.

    I sratched out the idea for the frame (picture no. 1). I want to use the standard plumbing pipe as a barrel as it is really ideal size, 70mm inner diameter and the 33cl cans have 66mm outer diameter. I might consider rectangular barrel, but I have some crazy ideas for the beer cans that will only work with circular barrel. But I wont reveal those ideas for now ;) Enough to say I want to use the pipe.

    I have some concerns about launching the projectile. Should I use a sled? I demonstrated this problem in the lower section of the first picture. By just using rope, would probably lead to problems. What do I need to take into consideration when I design a sled for this contraption? I think weight of it at least needs to be added into the weight of the projectile when thinking about power.

    And now perhaps the question that I should have asked first :D I ordered 5m of theraband gold. That ought to be plenty more than I need right? (Picture 3:) I input the data to the calculator and I got the following: 40cm long strips, 3 per side, total width 18cm (per side). this means 6 pieces of 6x40cm strips of TBG in total. So per side that makes 3 pieces of 6cm wide, 40cm long strips. But what do you think, I dont have experience with this big slingshots?


    For those still bothering to read, here is some background: I am now a 3rd year mechanical engineer student and I´v always been interested in building stuff like spud guns and crossbows etc. But I´v never really been into slingshots, since I´v only ever bought some shtty ones. The rubber was so hard to find that I just stuck with materials I got easily like old skis for crossbows. But now I´v been watching practically nothing else on youtube for the past week other than slingshot channel. And boy am I hooked! :cool: I just bought 5m of TBG from ebay and I´v gone to the hardware store to look through some materials for this big ass project and also for making a smaller one to begin with. Also got myself a few extra tools that I will need, like a hole puncher and a rolling cutter. Now I´m just gonna be a anxiously waiting for the mailman for the next week or so :D


    PS: What would you even call this (not the name, but the type of slingshot it is?): Ballista? crossbow? slingshot? slingbow ballista?
     

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  2. onnod

    onnod Im from Holland, isnt that weird?

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    I wouldn't use a sled, the cans have a flat bottom so I think the rope will be fine on its own. I'd put the knots on the outside because otherwise you'll scrape the bands which will reduce their life greatly.

    5m of TBG should be enough i think :) 40 cm bands on a 150 cm draw sounds good in my book. I don't have much big slingshot experience either, so I hope joerg or others with experience could shed some light as well.

    For the name, I guess slingshot balista ;)
     

  3. erajomppa

    erajomppa New Member

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    I express myself best in this situation be painting a picture, in paint:
     

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  4. Diaboloslinger

    Diaboloslinger New Member

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    How 'bout this:?

    [ame]https://www.youtube.com/watch?v=e4oKMmrljTk[/ame]
     
  5. erajomppa

    erajomppa New Member

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    That thing is awesome! It also nicely demonstrates how much energy there is inside of a bullet (blank) :cool:

    Here's to hoping I can replicate the results of that with mechanical means!
     
  6. JoergS

    JoergS Administrator

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    Biggest problem with your setup is that PVC pipes collapse when you cut them into halves. Even a long slit does that. If you want to use a circular barrel, you must use metal, in fact steel is your only choice.

    Maybe you can mount the top and bottom half pipes to wooden reinforcements though.

    The calculator is designed for handheld slingshots up to 20mm steel and is in fact useless for your project.

    1,50 m barrel length is not much for almost 400 grams of ammo... but if you use the 5 meters of TBG for a single band set, it will do the job. 8 full width bands per side, 30 cm long. Mind you we are talking roughly 250 to 300 kg of a draw force, waaaayyyy to much for puny PVC pipes as a barrel. Solid wooden beams are called for.

    Of course you will need a winch for the cocking.

    A sled will do no good, as the force will accelerate it with the ammo and it will most likely disintegrate or destroy your whole launcher.

    Thick rope (10 to 12 mm climbing rope) will work best. Don't worry, the cans will survive - they are quite sturdy in longitudinal direction.

    Just be careful, the forces involved are significant and if something breaks, your life will be in danger.
     
  7. seppman

    seppman Folding-Ladder Expert

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    You guys have overseen the biggest problem: he wants to shoot beer cans! FULL beer cans! BEER! Blasphemy! Use soda, that miiiiight work with the tips from above. But beer will only bring you straight to hell!
     
  8. erajomppa

    erajomppa New Member

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    Thanks for the info, this puts me into the ballpark of what to expect :cool:

    Barrel structure aside for the moment, what length would be more called for here? 2 meters? I just threw the 1,5m out of thin air, since it sounds manageable. 2m is getting big, but building it 50cm longer wont be my biggest concern.

    From the beginning I did not want to put the pressure on the pipe, just use it as a "guidance rail" inside wooden frame that takes the forces of the draw. I can see that I have to reinforce it with wood from BOTH top and bottom, just bottom wont work.

    I need to make a more realistic design and after that think if I really want/need the pipe there to guide the projectile. Just using wood would be more simple and more reliable.

    Yeah, it wont be a toy for the kiddies (not to mention the beer and all).

    But yeah, before I go any further with the design I need to think about the barrel length and the rubber. If I'd use 2m length, should I stick with 8x 30cm strips per side?

    PS: I do want to make one regular slingshot from the 5m I bought, so thats 20cm. So the total rubber I can manage right now is 4,8m (still heck of a lot). But ebay is open 24/7 if I need more right?
     
  9. erajomppa

    erajomppa New Member

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    What about cider? ;)
     
  10. Diaboloslinger

    Diaboloslinger New Member

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    Whoa...Wait!!!
    Sepp's right!!!
    I can't endorse this project.
    How 'bout a wine cooler shooter?
    Or promise to only shoot Mountain Dew...That will probably melt the target on impact...
     
  11. erajomppa

    erajomppa New Member

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    I brew beer myself and I dont take wasting (my) beer lightly, with all the effort I put into making it.

    That being said, it would sound so lame to say "I can shoot soda cans with this" :D

    EDIT: even Mountain Dew, which I like btw so dont y'all start dissin mah tastes! :p
     
  12. erajomppa

    erajomppa New Member

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    So this is my idea for a very simple trigger. It is a piece of plywood that is tied to the rope that comes from the pulley. You hook the drawn rope with it and pull it back with the pulley, then the secondary rope above can be pulled to release the rope under tension and fire the weapon.

    I think it might take some force to operate the trigger, but it ought to work.
     

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    Last edited: Apr 26, 2016
  13. JoergS

    JoergS Administrator

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    If you go to a 2m draw, 30 cm bandlength isn't long enough. The rubber stretches (safely) to five times the relaxed length. So you have to go to 40 cm instead. Happens to match your 4,80m supply.

    I'd cut the rubber into six loops 80 cm each, saves you from another attachment at the rope side. So you have three loops per side (total six bands per side).

    Draw weight goes down to about 180 kg, far more manageable. The increased draw length will compensate for that.

    Your trigger looks a bit too simple... there will be a ton of friction on the sear, don't forget. Maybe you want to look at the Leach Trench Catapult trigger, I made a replica and it works great at much the same draw weight.
     
  14. erajomppa

    erajomppa New Member

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    Did a fast google search and I think I found the one that you mean, looks simple enough and very effective. I could make that out of metal to make it more sturdy (rather than using plywood).

    180kg draw force ought to be plenty enough to make a can fly a few dozen meters ;)
    Maybe I could try one of those stunts that the two guys do on youtube where they pass a beer to each other in the most absurd ways. (Yeah, not really gonna do that!)

    Cheers mate, your feedback is a ton of help!
     

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  15. erajomppa

    erajomppa New Member

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    These guys:

    <iframe width="1280" height="720" src="https://www.youtube.com/embed/1b8W1tFFs3M" frameborder="0" allowfullscreen></iframe>

    EDIT: doesnt seem to want to work embedded...
     
  16. erajomppa

    erajomppa New Member

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    I gotta try to scavenge some scrap metal from the school workshop. If I ask nicely maybe they will let me cut and put it together there. I only got a Dremel at hand and I might need a bit bigger caliber tools for that. Though I might not make it quite as heavy duty as yours :D


    Also I made some planning with CAD program. I think I will go with two 2"x4" planks, one on top of the other 70mm apart. Then some 25mm thinner slats on the sides. Maybe add some aluminium corner profile like Jörg has in his "Torpedo shooter 2500".
     

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  17. erajomppa

    erajomppa New Member

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    Shopping spree :D

    I got myself a winch! As I do not possess as good materials and tools for woodworking as Jörg, I saved myself a whole lot of trouble and just bought one. Maximum load 350kg.. ought to cut it ;) It is quite compact! I like the removable handle, makes it less cumbersome to transport.

    Next I found something from the yacht section of the hardware store. I dont know what this is is (3.-4. pictures) but it might work with slingshot? I doubt it will be safe for a big one like I'm about to build but for something a bit smaller? There is a small pin that you pull that releases the main "hook". There is quite a lot of movement in the release state and that might also cause some issues? I dont know, I did not buy it but took pictures of it. It was around 5€

    Last but not least (5. - 7. pictures)! I found commercial version of Jörg's simple one piece trigger! It was mislabeled as a "gate latch" but we can clearly see what it really is :D
    You can clearly see the shape of the "latch", it is nicely balanced and under tension it will latch onto a rope and wont fall until "trigger" is pulled. Very nice find for only 2,5€! Will definitely find something to use this with! Not the beer can ballista though.
     

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  18. erajomppa

    erajomppa New Member

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    Alrighty! There has been progress, finally. I'v had so much to do that I was too exhausted to get myself to write about the little things I made so far. So now Im just gonna bundle them all here.

    Okay, so the trench catapult trigger mechanism is completed and it works nice. I accidentally screwd up the angle on my first try with the release handle and had to drill a new hole for a new axis. The old hole ended up being very usefull as a place for a safety pin (M8 bolt). I also bought one sailing hook thing with a pull-pin that releases it (one of the pictures has it. can be bothered to pinpoint it). The part says it can handle 1000DaN = 1000kg = 2000 pounds. Should be enough for this if my trench catapult mechanism fails on me.

    THIS WEEKEND I will hopefully be able to make it happen. I cant build it back home because I have no room for it (or to shoot it) so I'm building it here at my parents' house. I gotta go back on sunday so hopefully I can get it done tomorrow (saturday). I finished the barrel halves today (friday), they look very nice. Gotta sand them though.

    What else, what else... The rope is 8mm, can handle 1600kg no problem.. Yeah, I'll probably update again tomorrow. Now to sleep.. Its way past bedtime ;)
     

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  19. JoergS

    JoergS Administrator

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    You ARE serious about this! Congrats. Many people just talk, you actually make the darn thing. Very cool!

    Won't it be a bit tricky to hook in the trigger, given that the barrel is quite narrow though?