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The Slingshot Channel Thread

All non-spudgun related discussion goes here such as projects, theories, serious questions, etc. All "off-topic" posts (aka useless posting, determined by moderators) will be removed.
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Unread postAuthor: JoergS » Sun Dec 19, 2010 4:46 pm

Took me 10 hours, but now it works!

I wanted to make a REALLY powerful slingshot crossbow. But of course there is only so much draw weight you can handle, and even the push-out forks have their limits. So I had to incorporate a winch.

So I used an entirely new concept. The entire trigger/lock part slides between two 40mmx20mm wooden rails. The winch rolls up a mountaineer type rope wich draws out the band. A rubber powered arm locks the winch every 45 degrees of turning (8 positions on a full turn) Trigger and lock have aluminum tubes glued into the wood so the force is evenly distributed and the screws do not wear out the wood.

The force vector of this slingshot is entirely straight, there is NO fork height at all. This makes the weapon incredibly strong.

I had little time to shoot it as it is dark, but it has a ton of power with the first test bands (20cm x 14cm x 7cm Thera Gold per side). A child can operate the winch, and there is much potential for even stronger bands.

A fantastic new toy!

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Here is a short video, it was too dark for more shooting... stay tuned.

[youtube]http://www.youtube.com/watch?v=dHVQ27a-ric[/youtube]

Jörg
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Unread postAuthor: jackssmirkingrevenge » Sun Dec 19, 2010 6:55 pm

Looking good, any muzzle velocity/energy figures?
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Unread postAuthor: JoergS » Mon Dec 20, 2010 12:45 am

Not yet, it was dark and my wife does not appreciate indoor shooting with this monster.
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Unread postAuthor: inonickname » Tue Dec 21, 2010 6:29 am

Looking great, just so you know it was featured here.

Your work is always of an amazing and high standard
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PimpAssasinG wrote:no im strong but you are a fat gay mother sucker that gets raped by black man for fun
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Unread postAuthor: wyz2285 » Tue Dec 21, 2010 7:12 am

cool thing :) But I never liked rubbers :wink: Kind like more a carbon fiber crossbow :roll:
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Unread postAuthor: JoergS » Sat Dec 25, 2010 11:47 am

Have finished the tripod today, minus the paint job.

Looks pretty good! Full and free motion, and the weapon can be detached just by lifting it out.

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It has beeing snowing since yesterday noon, and we are buried in snow. It is also freezing cold. So no destruction video yet!

Here is a pic of my snow covered car:

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And last not least, my 18 yr. old niece Julia, who lives with us, in a nice Zombie parody during our christmas feast. I think the greed is genuine! The bird smelled and tasted heavenly.

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(She is really quite pretty normally...)
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Unread postAuthor: POLAND_SPUD » Sat Dec 25, 2010 12:22 pm

your gun reminds me of this
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lol it would be more appropriate if your niece was fugly but instead she's nice
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Children are the future

unless we stop them now
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Unread postAuthor: Gaderelguitarist » Sat Dec 25, 2010 11:19 pm

Well I've decided my next project. Destroying an old alarm clock this morning with a sampling of my arsenal was more than enough motivation to build some new "toys".

I wonder about continuing the circular shape theme along the length of the priming rails. It might add some structural rigidity?

I also wonder about designing a system that would maintain the trigger and grip in their normal position, but would only move the locking fingers. Perhaps I'm over complicating it. Can't hurt to try.
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so many muchness
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Unread postAuthor: JoergS » Sun Dec 26, 2010 9:10 am

So I had one more ash fork from The Gopher. It was not easy to figure out what to do with it as it was clearly in need of a lot of shaping.

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So I debarked it first and removed the worst knobs.

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Then I decided to make a humble fork with a "bird's head" handle, for tubular rubber this time. I shaped the fork arms accordingly.

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But the handle had a long way to go before it was the way I wanted.

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After lots of rasp and file work, I had the final shape. It looked like a diver jumping in, or a dolphin! So I sanded it with 120 grit and decided on the finish.

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I used regular blue ink and gave it three soakings.

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The ink was of course not soaked up evenly, which is what I wanted in order to highlight the grain. But I did not expect how well it turned out!

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It has just received the first poly coat, which will bring out the grain and color even more. Plus it will protect the wonderful frame forever.

Thanks, Gopher, your four frames have been a lot of fun!

Jörg
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Unread postAuthor: JoergS » Mon Dec 27, 2010 12:40 pm

It was too cold for a destruction video, but I wanted to show the cannon thing in action.

Here:

http://www.youtube.com/watch?v=eObHehevODE
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Unread postAuthor: JoergS » Tue Dec 28, 2010 10:19 am

OK, following the "Cutlass" and the "Shield", now I completed my first 100% efficient no-handslaps slingshot.

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The frame of the slingshot is made from thin 6mm plywood, now very stable due to the hexagonal construction. It is a box now, completely shielding the entire hand.

The handle is made from round rod and there is a long M8 screw that runs through the whole slingshot. The "forks" are M8 screws as well, forming the cores for the round 20 mm wood rods.

Due to the thin wood, it weighs about 450 gramms only.

It may look strange, but it is a very good shooter.

Now my wife wants a new bird house for the garden :-)

Jörg
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Unread postAuthor: jrrdw » Tue Dec 28, 2010 2:42 pm

Nice work as all ways. I like the sling shot cannon, really nice.
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Unread postAuthor: JoergS » Thu Dec 30, 2010 1:30 pm

OK, as you may know I am planning to make a petanque ball shooting carriage mounted slingshot cannon. The goal is to shoot the 3" (8cm) (800 gramm heavy) steel ball with 70 m/s, almost 2000 Joules of energy.

So I wanted to do it like the Mythbusters and started out with a 1:10 model of it. This means the ammo has got to be 8mm steel as the petanque ball is 80 mm steel.

I have to say that working on such small mechanisms is not easy, in fact it is a lot easier to work big size. I am not totally happy with the precision of the job, but it is functional, even dangerously so. It fires 8 mm steel balls through a few layers of tough cardboard (moving boxes).

I have changed the lock mechanism, made it more sturdy by adding two more lock arms on the opposite side. This gives the lock arm much less play.

Have completed the model weapon now, including a second winch to adjust the shooting angle. This needs some finishing work and is ready to sit on my desk!

The "real" version will be almost 4 meters in total length.

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Here is the video:

http://www.youtube.com/watch?v=TZ9keWOP2To
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Unread postAuthor: DYI » Thu Dec 30, 2010 4:33 pm

The goal is to shoot the 3" (8cm) (800 gramm heavy) steel ball with 70 m/s, almost 2000 Joules of energy.


I'm no slingshot expert, and I just estimated instead of including the mass of the bands in the calculation (I don't know the force/extension relation for Thera band anyway, although I'm sure you've had an empirical equation for it for years now), but that's going to require somewhere between 10 and 20 full sized gold bands in parallel (so, between 5 and 10 for each band), isn't it? Also, a maximum draw force of over 2kN.
I like it :D

Those bands are going to get pretty expensive though, aren't they? I paid $25 for 3m of blue bands, and you're going to need between 10 and 20 metres of gold. Or are you getting a bulk discount from the manufacturer? :lol:
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Unread postAuthor: jrrdw » Thu Dec 30, 2010 5:05 pm

80mm is pretty big, but we want to see a slingshot cannon that will launch say......a bowling ball. A 16 pounder would make a mess. :twisted:
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