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blow-forward bolt

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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blow-forward bolt

Unread postAuthor: keep_it_real » Wed Feb 21, 2007 12:10 am

I made a blow forward bolt for my gun. The only problem is it's a little to big for the paintballs. As the bolt comes forward it slices off the bottom of the next paintball. The bolt is similar to the one clide made (go here: http://www.spudfiles.com/forums/viewtopic.php?t=160&)

Here is the gun I'm putting it on: http://www.spudfiles.com/forums/viewtopic.php?t=6109&

Sorry about the crappy pictures.

I'm also not sure how to hold the paintballs in place so two done slide down into the barrel. Maybe I could cut out a hole and put it some kind of leaf spring.
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Attachments
bolt 004.jpg
bolt is open
bolt 004.jpg (31.5 KiB) Viewed 1285 times
bolt 003.jpg
bolt is closed
bolt 003.jpg (24.72 KiB) Viewed 1285 times
bolt 002.jpg
too big
bolt 002.jpg (21.89 KiB) Viewed 1285 times
bolt 001.jpg
bolt 001.jpg (34.54 KiB) Viewed 1285 times

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Unread postAuthor: Insomniac » Wed Feb 21, 2007 1:10 am

Cool! Do you have any ammo that is a good fit???
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Unread postAuthor: noname » Wed Feb 21, 2007 1:14 am

If you have a lathe, turn down the front of the bolt and make the part where the paintballs fall into a better fit. The bolt will slide easier, and won't slice off paintballs. I'd also recommend chamfering the bolt, you'll get less chops.
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Unread postAuthor: Recruit » Wed Feb 21, 2007 2:46 am

:idea: :idea: :idea: It is a pneumatic bolt right? What you could do is hook up a computer fan that could fit PBs between the blades maybe rip out a few blades so they fit then hook it it up abve the bolt so only one Paint ball fall down to the bolt at a time. Now you hook it up so when you pull the trigger it turns the fan on you will need like a dimmer switch i you want ti go auto.
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Unread postAuthor: jrrdw » Wed Feb 21, 2007 5:46 am

Put a "scoop" type finger on the bolt to pick up the next paint ball??? Something like a piece of flat spring steel with a bend in it to scoop the next ball.

I also see where the barrel could cause you some problems with the sharp inside edge.
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Unread postAuthor: experament-u2 » Wed Feb 21, 2007 7:48 am

im very interested in the desgin could u kinda explain it tho iv looked at the semi auto link but i just cant get my head around it
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Unread postAuthor: keep_it_real » Wed Feb 21, 2007 10:41 am

The air pushes the bolt forward until the end clears the first o-ring type thing. Then the air floods into the piston through the holes all the way around the piston. Did you look at the animation on the semi auto link. It helps a lot.
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Unread postAuthor: judgment_arms » Wed Feb 21, 2007 1:17 pm

Very nice, now a few questions:
Did you use a lathe?
About how much did the parts cost?
What kind of rate of fire can you get out of it?
And, Does it fire from an open or closed bolt?

jrrdw wrote:...I also see where the barrel could cause you some problems with the sharp inside edge.

You need crown the breach, run your pocket knife around the inside edge at an angle to round it, then take some fine grit, about 150grit, sand paper and run over that to remove any burs left by the knife. The muzzle should also be crowned, it improves accuracy slightly.
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Unread postAuthor: iknowmy3tables » Wed Feb 21, 2007 3:05 pm

Hey just so happens I’m making a blow forward bolt, with similar proportion, Its really super ghetto though and has a less effective pop off design, meant to delay the passage of air.
The point is that mine is getto, and back to the subject to fix you problem a further step in addition to tampering bolt tip, is softening the impact , may be by adding a thin layer foam at an angle. But I’d just use marbles
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Unread postAuthor: keep_it_real » Wed Feb 21, 2007 6:26 pm

hmm i'll try all that stuff.

It was cheap, I got everything in the picture for like $5. I didn't use a lathe. I found a piece of 1" thin wall pvc thats slightly bigger at one end (what do you call it) this fit perfectly over the threaded t joint. Next I got some 1" cpvc which fit sorta well inside the 1" thinwall. I had to wrap it with a layer of duct tape. 3/4" cpvc fits inside 1" cpvc so that acts as the bolt. The 1" cpvc sort of acts as an o-ring. then I just cut some screws apart (you can see the end of a screw sticking out on the right side in the first picture). I attached the spring to this and then to the bolt in the same way.

You could get a good rate of fire I think. the semi auto I made is really slow because the ball valve is just open a little to refill the temporary chamber.

judgement arms: I don't really get your last question. It's open to let the paintball in then when you fire, it closes which blocks off the hopper and lets the air through the bolt. Is that what you were getting at?
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Unread postAuthor: judgment_arms » Wed Feb 21, 2007 7:14 pm

Ok, sorry about that, let me rephrase my question:
When your ready to fire, before you pull the trigger, is the bolt open, like on a Thompson Sub-Machine Gun, or closed, like a Browning Automatic Rifle or an AR15?
But judging from your description I’d guess it fires from an open bolt.
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Unread postAuthor: keep_it_real » Wed Feb 21, 2007 7:28 pm

ya it's open. do you have to caulk a closed bolt? If not, how do you get it to go backwards. Man that would be sweet.
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Unread postAuthor: judgment_arms » Wed Feb 21, 2007 7:38 pm

Don’t know how you’d make a closed bolt semi/full automatic airgun, I personally prefer the open bolt system. The open bolt system is simpler, and it gets the job done just fine, remember what Mr. Kalashnikov said: “all that is complex is not useful, all that is useful is simple”.
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Unread postAuthor: Recruit » Thu Feb 22, 2007 7:50 am

judgment_arms wrote:Don’t know how you’d make a closed bolt semi/full automatic airgun, I personally prefer the open bolt system. The open bolt system is simpler, and it gets the job done just fine, remember what Mr. Kalashnikov said: “all that is complex is not useful, all that is useful is simple”.


WHat about the A-bombs that ended WWII? They where not simply and did good in that they end the war but stilll very bad.
Any ways keep working on it.
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Unread postAuthor: judgment_arms » Thu Feb 22, 2007 9:45 pm

Ok Recruit,
One, you need to work on your grammar, so do I but.
Two, the incendiary carpet bombing runs would have ended it to, and there’s nothing simpler than dumping gas on something and touching it off!
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