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Crossbow/mechanical marblegun/harpoongun

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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Do you like this design

yes
2
18%
no
1
9%
Like it?? I wanna build it!!!
4
36%
Like it?? I wanna build it!!!
4
36%
 
Total votes : 11
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Crossbow/mechanical marblegun/harpoongun

Unread postAuthor: Brian the brain » Tue May 30, 2006 5:23 pm

This design has been discussed before so I decided to post it here for all to see.

I've built this a long time ago.It shot a marble halfway into a solid wood door.Half of the marble was in I mean.Glass jars where fun to shoot.THey blew apart in a cloud of glass.

The advantage is, you can easily repeat shots and the gun is silent.

Disadvantage is the accuracy.
The pulleysystem I designed doubles the distance you can pull the string therefor doubling the speed but halving the power.So I just doubled the amount of rubber bands to get it back up to my maxcimum pulling force.Well not maximum but to the point I started doubting the structure would hold.I estimate it took about 40 kilograms of force to pull back the string.
Still my pneumatic gun is more powerful.(over 300 psi)
This design would work with a strong spring( or a number of them) aswell.

Without the upper aluminium strip it would be just a harpoon gun.This would be much more dangerous because of the projectiles weight and pointed shape.Accuracy wouldn't be an issue anymore.

If anybody is interested in copying this design or modifying it, I offer my help.(pretty proud of it)
  • 0

Attachments
marble translation.JPG
trekkersysteem.JPG
This is the trigger system.THis diagram shows the simple version.In reality my "catch"was triangular and spring assisted to pop back into the firing position.When loading you could just pull the spring back and it "clicked" into locked position.
Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Brian the brain
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Unread postAuthor: Benny » Tue May 30, 2006 5:54 pm

great trigger design brian, turns out im making a crossbow, im about 2/3 through it. :D
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Unread postAuthor: Brian the brain » Tue May 30, 2006 6:03 pm

The trigger is very smooth.If you shape the upper part of the "catch" less dome-like it will automatically fall back when you pull a string past it.Attach a spring to it so it wants to stay in the protrayed position and it will automatically lock too.
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: Atlantis » Tue May 30, 2006 6:09 pm

I built one of these out of KNEX with rubber bands and yarn just to get a feel of how it works. I hope to make a full sized version out of wood and nylon string. What string did you use for yours?
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Unread postAuthor: Brian the brain » Tue May 30, 2006 6:33 pm

Just some black string I bought at a hardware store.Nothing special.Looked like a very long shoelace.Be sure to buy more then enough length.It's hard to tie a knot in the correct place at the first try.I made a small pad out of tape in the center to keep it from slipping over the marble.It worked only occasionally.I later cut a small section of electric pvc pipe and drilled a hole through it sideways and slipped it over the string, so it would "grab" the marble with the front.After all these years I still wish I never scraped it.I should have converted it to a harpoon gun.Never did...
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: Flinchy » Tue May 30, 2006 6:57 pm

interesting design you have there. i myself have been thinking of building my own fully functional crossbow, rather than one that just shoots marbels.
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