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Check this out!

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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Check this out!

Unread postAuthor: boyntonstu » Sun Jul 26, 2009 8:46 pm

http://www.youtube.com/watch?v=tyBmatkX4S0


I am impressed by the air blast!

Now imagine it with 5 rubbers and a trigger built like a spear gun.


Joerg and I have been cooperating on this project.


I am designing a trigger system that will safely hold the piston back with 300 pounds of force.

Any ideas?


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Unread postAuthor: THUNDERLORD » Sun Jul 26, 2009 9:13 pm

I modded a few "releases" similar to THESE (But cheaper) into crossbow triggers in the past, by removing the bolt running to the wrist strap.
I drilled a hole through the side and bolted them between thick sheet metal.

A better idea would be to find a bolt with same threads and mount the release to a simple "L" shaped metal mount.
(I had a mag. fed repeater in mind, hence the sheet metal, with slot)

For my bullpup crossbow, I bent a 1/4" rod into a trigger and ran it back to the release.

The releases I've seen are aluminum, so a synthetic string needed to be used (similar to short piece used on bow cables) or a strong plastic cover on metal cable.

Other than that, I imagine a trigger mechanism similar to the ones the most basic spearguns use: Just a notch in the metal spear, and a lever clips into it as the surgical tubing hose clamped to the handle is drawn back.
(I was in Hawaii one time and they sold this type speargun in corner stores) :shock:
Except, a seperate lever(s) could be combined for lighter trigger pull.

Cool to see the concept progressing. :) 8)

Got to go for know...got to get ready for work while it's there. :( 8)

EDIT: Yikes! those I linked are $60+.
The ones I used were like $20- (on sale).
Work fine too. Sometime I plan to post a pic of my use of them.

EDIT2: Dang!, forgot to mention, for an even more primitive trigger, "Mythbuster's" one time used vise-grips for the release on a slingshot testing rock impact on windshields with a slingshot.
Just a larger steel version of the archery releases...I was wondering,"Why didn't I ever think of that???"
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Last edited by THUNDERLORD on Sun Jul 26, 2009 9:27 pm, edited 1 time in total.
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Unread postAuthor: FORE!!!! » Sun Jul 26, 2009 9:26 pm

no ideas but nice weapon u got there,looks like alot of fun but it also looks a lil unsafe, i imagin if that rubber snaps or gives u wont have any front teeth,good luck
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Unread postAuthor: boyntonstu » Sun Jul 26, 2009 9:47 pm

THUNDERLORD wrote:I modded a few "releases" similar to THESE (But cheaper) into crossbow triggers in the past, by removing the bolt running to the wrist strap.
I drilled a hole through the side and bolted them between thick sheet metal.

A better idea would be to find a bolt with same threads and mount the release to a simple "L" shaped metal mount.
(I had a mag. fed repeater in mind, hence the sheet metal, with slot)

For my bullpup crossbow, I bent a 1/4" rod into a trigger and ran it back to the release.

The releases I've seen are aluminum, so a synthetic string needed to be used (similar to short piece used on bow cables) or a strong plastic cover on metal cable.

Other than that, I imagine a trigger mechanism similar to the ones the most basic spearguns use: Just a notch in the metal spear, and a lever clips into it as the surgical tubing hose clamped to the handle is drawn back.
(I was in Hawaii one time and they sold this type speargun in corner stores) :shock:
Except, a seperate lever(s) could be combined for lighter trigger pull.

Cool to see the concept progressing. :) 8)

Got to go for know...got to get ready for work while it's there. :( 8)

EDIT: Yikes! those I linked are $60+.
The ones I used were like $20- (on sale).
Work fine too. Sometime I plan to post a pic of my use of them.

EDIT2: Dang!, forgot to mention, for an even more primitive trigger, "Mythbuster's" one time used vise-grips for the release on a slingshot testing rock impact on windshields with a slingshot.
Just a larger steel version of the archery releases...I was wondering,"Why didn't I ever think of that???"



The problem is multiple rubbers.

I have to be able to draw 50 pounds into a nock, and do it 4 or 5 more times for 300 pounds of force and 600 psi.

I am thinking of a hold down on the top that will allow the string to pass beneath into the nock.

A spring loaded 1/4" diameter nub from below into a hole in the nock area.

The under trigger would be the opposite of a medieval crossbow that will pull the nub down from the hole instead of pushing the string up.


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Unread postAuthor: THUNDERLORD » Sun Jul 26, 2009 10:04 pm

boyntonstu wrote:...The problem is multiple rubbers....


Just found THIS!!!

States there: "..Reduces cocking tension to 16 lbs. Imported..."
A (small!!!) electric motor could be used!!!
The price is OK too, (last I saw the mechanism was attached to thier most expensive model and it was temporarily sold out).


...The under trigger would be the opposite of a medieval crossbow that will pull the nub down from the hole instead of pushing the string up.


IMO having the piston moving towards the firer, eliminating the transfer tube and having the trigger connected to the release (in front) would be better design.
Not sure if I fully understand your explaination on the other details,
But the rod would be attached to the trigger release before the bands are cocked individually (unless something like the hand crank I linked was used)???
Dang really out of time now. :(
Later Stu. 8)

EDIT: Just noticed "fully integrated into stock" version.
With that crank, the stock, and the bands connected to a short piece of archery string, and the Jorg's version air-bow, and a modded release(trigger)...Done(?)...Just lacks a motor! 8)
EDIT2: it would be easier to get the whole thing, remove the bow limbs and mod for airowgun. (using original trigger).(?)

EDIT3:D@MN!!! 3rd edit But noticed in vid, the bands are very short,
they could be attached up front and would be much longer that way...and have slight tension before drawn back. (wouldn't look as nice though...unless internally mounted but...).
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Re: Check this out!

Unread postAuthor: jackssmirkingrevenge » Sun Jul 26, 2009 11:32 pm

boyntonstu wrote:Now imagine it with 5 rubbers and a trigger built like a spear gun.


Imagine it with a spring, trigger, stock and cocking lever.

Oh.

Seems like a lot of work for something that is going to have the same function but likely less accuracy and power than a cheap springer.
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Re: Check this out!

Unread postAuthor: boyntonstu » Mon Jul 27, 2009 6:45 am

jackssmirkingrevenge wrote:
boyntonstu wrote:Now imagine it with 5 rubbers and a trigger built like a spear gun.


Imagine it with a spring, trigger, stock and cocking lever.

Oh.

Seems like a lot of work for something that is going to have the same function but likely less accuracy and power than a cheap springer.



Can ANY springer do this?

http://www.youtube.com/watch?v=ko1x5v_a85A

As for accuracy how about this?

http://www.youtube.com/watch?v=s0hhF91mrsc

Joerg showed that a single band works as a substitute for a compound bow..

Next, we build it into a gun with a good trigger and sights.

Do you get it?

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Re: Check this out!

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Unread postAuthor: inonickname » Mon Jul 27, 2009 6:48 am

What's with this thing you have going on with sticking tubes onto bows or slingshots?

I'm with jack, I can't really see this being better than a springer in many ways at all.
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Re: Check this out!

Unread postAuthor: jackssmirkingrevenge » Mon Jul 27, 2009 7:07 am

boyntonstu wrote:Can ANY springer do this?


Impressive, but most serious spring rifles would easily have put a pellet straight through the meat, bone and backstop. It would have been more interesting to see performance in terms of velocity and muzzle energy, or penetration in a more consistent medium like ballistic gelatin or water.

The thing is that springers use a lever to cock their mechanisms, while with a slingshot you're limited to the power you can retain directly in line with the shot.



Any reasonably good springer in competent hands can put all its shots in a 1 inch circle at 30 yards. A one-off shot at a rubber duck 5 yards away accompanied by the claim of "another direct hit" is hardly a valid comparison.

I don't want to sound scathing of such development, it's interesting to say the least, but I think a more scientific approach is in order.
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Re: Check this out!

Unread postAuthor: Ragnarok » Mon Jul 27, 2009 7:19 am

As Jack says, springers can have serious guts.

Interestingly, the guy DID a ballistic gelatine video. Unfortunately, the block wasn't nearly thick enough, and he over-penetrated, meaning that there's no actual results to compare with.

However, would still create questionable results even if they existed. It's known that spherical projectiles produce longer, but narrower impact channels than pellets for the same muzzle energy, so there's the whole question of "was it the projectile, or was it the respective accelerator?"

As for accuracy how about this?

Without a DOUBT. Put that thing against my springer at 20 yards, and I'd be able to shoot entire groups that would fit inside the hole a single shot from that questionable contraption would make.
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Does that thing kinda look like a big cat to you?
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Re: Check this out!

Unread postAuthor: jackssmirkingrevenge » Mon Jul 27, 2009 7:33 am

Ragnarok wrote:Interestingly, the guy DID a ballistic gelatine video. Unfortunately, the block wasn't nearly thick enough, and he over-penetrated, meaning that there's no actual results to compare with.


This one.

I'm very impressed with the results, however I'm pretty sure that the outstanding factor in this case is the extreme power Herr Sprave is putting into his shots by virtue of his physique, I'm sure that few members of this forum could get equal performance from the same slingshots.
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Re: Check this out!

Unread postAuthor: inonickname » Mon Jul 27, 2009 8:12 am

jackssmirkingrevenge wrote:The thing is that springers use a lever to cock their mechanisms, while with a slingshot you're limited to the power you can retain directly in line with the shot.


Yep, it's like the difference between using a winch to pull a car from a ditch, and doing it by hand.

Though with use of a lever mechanism cocking multiple cords and a trigger mechanism there wouldn't be an issue.
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Re: Check this out!

Unread postAuthor: boyntonstu » Mon Jul 27, 2009 8:16 am

jackssmirkingrevenge wrote:
Ragnarok wrote:Interestingly, the guy DID a ballistic gelatine video. Unfortunately, the block wasn't nearly thick enough, and he over-penetrated, meaning that there's no actual results to compare with.


This one.

I'm very impressed with the results, however I'm pretty sure that the outstanding factor in this case is the extreme power Herr Sprave is putting into his shots by virtue of his physique, I'm sure that few members of this forum could get equal performance from the same slingshots.


I agree with you about slingshots.

However, with a stirrup I am sure that everyone can dead lift 50 pounds to draw and cock a single rubber and repeat it 4 or 5 more times.

Actually, you can use a crossbow cocking rope, you need only 25 pounds of force to cock 50 pounds.

http://www.youtube.com/watch?v=sSFpWjc3k2c

Using multiple rubbers and a cocking rope, 300 pounds is very reachable without gym training.


Would you prefer 70 strokes with a shock pump?


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Re: Check this out!

Unread postAuthor: jackssmirkingrevenge » Mon Jul 27, 2009 8:23 am

boyntonstu wrote:Would you prefer 70 strokes with a shock pump?


Or one stroke withthis monster ;)

Using separate rubbers sounds like a good idea, if you can pile them on to a good enough trigger mechanism the power will certainly be there.

I still wouldn't be inclined to go down this route myself, having already tried before discovering the benefits of pneumatics, but a good project if it tickles your fancy ;)
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Re: Check this out!

Unread postAuthor: boyntonstu » Mon Jul 27, 2009 8:24 am

Ragnarok wrote:As Jack says, springers can have serious guts.

Interestingly, the guy DID a ballistic gelatine video. Unfortunately, the block wasn't nearly thick enough, and he over-penetrated, meaning that there's no actual results to compare with.

However, would still create questionable results even if they existed. It's known that spherical projectiles produce longer, but narrower impact channels than pellets for the same muzzle energy, so there's the whole question of "was it the projectile, or was it the respective accelerator?"

As for accuracy how about this?

Without a DOUBT. Put that thing against my springer at 20 yards, and I'd be able to shoot entire groups that would fit inside the hole a single shot from that questionable contraption would make.



Joerg measured 50 fpe.

Can any springer deliver 50 fpe?

This was with a SINGLE rubber.

How does 300 fpe sound to you?

The questonable contraption was just that, not a rifle with a good trigger and sights,

I will give you this, the recoil from the snapping rubber will affect the accuracy.

I am not sure by how much.

The rubber is going away from you at 200 fps.

OTOH You could shoot several dozen BB's in a single shot.


Can you shoot your springer as well as this guy?


http://www.youtube.com/watch?v=9ieWrWLjii0


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