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Direct Propulsion Pistol

It's about time for a new homemade!

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#1 hamoidar

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Posted 16 November 2012 - 12:58 PM

First, I want to say that all credit goes to Meaker IV for the trigger design!


This gun is the brainchild of my cardboard nerf pistol, which was a prototype. It is still made of an easy to machine material (particle sheet), and is easy to build.
Again, I did not make templates, but the design is super flexible, and really depends on your personal preference. Enough said, let’s get to work:

Parts:
Particle sheet (MDF?) About one (1) square foot needed.
Some 1/8” metal round
Hot-glue
˝” thick cutting board
Small extension spring
A tiny bit of 1/8” Polycarbonate (about two (2) square inches)
Rubber o-ring
And…that’s it.

Tools:
Dremal
Dremal bits
Drill
Hot-glue gun
Band saw or scroll saw (you could use a handsaw…or a Dremal)
Sandpaper

(You could really use a Dremal for everything, that is, except the glue)


Begin with…
A properly adjusted camera:
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In all seriousness, you need to cut out something which looks similar to the panels pictured:
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Next, you will need two Polycarbonate scraps which fit on the end of the gun:
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Glue the aforementioned Polycarbonate pieces to the front of the body panels:
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Now, cut your o-ring into sections which fit across the long edge of the Polycarbonate:
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I did not get good pictures of the catch, but it is simple:
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Here is another picture:
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Next, you need to cut out the trigger. DO NOT CUT OUT THE CENTER SLOT!!!
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Test-fit the trigger and catch:
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Now, add the barrel parts. The pieces need to be just over ˝” wide, as well as ˝” away from each other:
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Next, add the trigger guide, and the support beam:
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Add the second trigger guide:
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Connect the 1” long section of particleboard as shown.
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Place a bead of hot-glue in the spot pictured:
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Here is how the trigger/catch should work:
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Glue on the second body panel:
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Cut a 1” long section of 1/8” metal round; and notch the ends:
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Put the rubber band(s) on and you are done:
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You load the darts from the top:
Posted Image

Questions? Comments? Flames?
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#2 Mully

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Posted 16 November 2012 - 01:22 PM

Question: how far does it shoot?
Comment: looks like a real gun, I don't think the cops would like it if you sprayed it black.
Flame: very cool, very creative, very......interesting:)

Mully
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#3 hamoidar

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Posted 16 November 2012 - 02:01 PM

Question: how far does it shoot?
Comment: looks like a real gun, I don't think the cops would like it if you sprayed it black.
Flame: very cool, very creative, very......interesting

Mully

It shoots about 35ft flat, using two rubber bands.
I didn't paint it for a reason.
Thanks! P.S. That's not a flame. :)
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#4 Mully

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Posted 16 November 2012 - 02:22 PM

35'? Using cardboard? That's really good :)
Anyway, you're right, not a flame, my bad.

Mully
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Don't post as if you were in a chat room. We don't need to see a chat conversation between 2 parties exchanging information that doesn't benefit everyone else. Reread the Do's and Dont's of the New Members Guide. High signal, low noise.

Edited by Mully, 16 November 2012 - 03:34 PM.

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#5 Zorns Lemma

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Posted 16 November 2012 - 02:41 PM

What advantages do you see this providing over a pneumatic energy delivery system?

Could you somehow integrate a magazine and then change the priming mechanism so you could quickly unload a lot of darts at short range, in more compact fashion than say a Maverick, and with greater consistency than flywheels?
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#6 hamoidar

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Posted 16 November 2012 - 03:58 PM

What advantages do you see this providing over a pneumatic energy delivery system?

Could you somehow integrate a magazine and then change the priming mechanism so you could quickly unload a lot of darts at short range, in more compact fashion than say a Maverick, and with greater consistency than flywheels?

This blaster has a few advantages over pneumatic systems, as well as some disadvantages. For one, there is less of an energy loss due to friction between plunger tube and plunger head, as the gun does not have such components. Pneumatically actuated blasters typically have a rather large amount of dead space, which can reduce range, while guns operating with a direct propulsion system do not.

Note: sometimes a small amount of dead space can be beneficial, as the air acts as a spring, compressing until the pressure overcomes the friction holding the dart in place, therefore creating a high pressure burst of air.

One of the biggest advantages is in this system’s ability to be adapted to any size, or shape, as it has very few limitations in the way it can be situated in a shell.
One of the disadvantages of this system would be the stresses present in a more powerful blaster. In order for the range of such a gun to be competitive with pneumatic blasters, it would need to have a blisteringly fast dart-pusher, which would create an enormous impact with each shot.


In answer to your other question:
I have thought about the possibility of a magazine fed blaster which uses a direct propulsion system. Meaker IV and I were throwing around some ideas in the cardboard pistol thread, but we never came to a concrete conclusion. Overall, I think that it could be done, but it would take a large amount of planning/work.

The gun would not have to be much larger than it is now in order to be clip fed. Making it able to fire quickly would not be difficult, as there are many options for a priming system. An example would be a slide made of polycarbonate, which has slots for the dart pusher rod.

Overall, I think that the any future direct propulsion blasters will need to operate using a spring instead of a rubber band. Springs are much more reliable, and much easier to connect than rubber bands. Of course, I have seen some members use surgical tubing as a spring, with good results.
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#7 Meaker VI

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Posted 16 November 2012 - 04:14 PM

Excellent work! That looks even more simple than the cardboard one. I'm glad the trigger worked out.

What happens if you add more rubber bands? Do you see a range increase?

Couldn't you add a clip by just putting a box filled with darts on top? Right, the dart pusher. You'd need to figure out a work-around to that, I've got one idea but it'd be hard to explain.

Is the hot-glue for holding the dart in place, keeping it from dropping out, or ... ?

Side note - this system is basically the same thing as a crossbow. We have bow-powered blasters getting great ranges, and this does away with the mass of the plunger completely (and uses elastic instead of bow arms; bungies or surgical tubing could also work). There's certainly potential to get 100'+ ranges out of the darts, we just need to figure out how to do that safely and reliably. My guess is a longer draw stroke than traditional blasters use.
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#8 hamoidar

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Posted 16 November 2012 - 05:25 PM

Excellent work! That looks even more simple than the cardboard one. I'm glad the trigger worked out.

What happens if you add more rubber bands? Do you see a range increase?

Couldn't you add a clip by just putting a box filled with darts on top? Right, the dart pusher. You'd need to figure out a work-around to that, I've got one idea but it'd be hard to explain.

Is the hot-glue for holding the dart in place, keeping it from dropping out, or ... ?

Side note - this system is basically the same thing as a crossbow. We have bow-powered blasters getting great ranges, and this does away with the mass of the plunger completely (and uses elastic instead of bow arms; bungies or surgical tubing could also work). There's certainly potential to get 100'+ ranges out of the darts, we just need to figure out how to do that safely and reliably. My guess is a longer draw stroke than traditional blasters use.

Thanks! The trigger works great!

The gun functions fine with two rubber bands, any more and the dart pusher goes flying.

Yes, the hot glue holds the dart in place.

A bow is a great idea! I would solve so many problems, and would work with the current trigger system.
If you used a rope stopper, (like Ryanmcnumbers rainbow pump) you could potentially use a very strong bow, without the stress of the dart pusher impact.
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#9 zx532

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Posted 17 November 2012 - 04:08 PM

The gun functions fine with two rubber bands, any more and the dart pusher goes flying.


In order to stop the dart pusher from flying into the front and damaging it, couldnt you have the opening at the back of the blaster instead of the front? you would still need to reinforce both sides, but the dart pusher would be hitting a solid part of the original material, instead of something cut and glued together.
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#10 hamoidar

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Posted 17 November 2012 - 06:00 PM

In order to stop the dart pusher from flying into the front and damaging it, couldnt you have the opening at the back of the blaster instead of the front? you would still need to reinforce both sides, but the dart pusher would be hitting a solid part of the original material, instead of something cut and glued together.

It's really just a problem with the size of the dart pusher. When you have more than two rubber bands, one or two will come off of one side when you fire the gun. The o-ring pieces keep the dart pusher from damaging the gun body.
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#11 Ambience 327

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Posted 19 November 2012 - 10:01 AM

To prevent the rubber bands flying off, wouldn't it be a simple matter of adding some form of band-stop on the ends of the dart pusher? (i.e. a small washer or something similar to hold the bands on)
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#12 Meaker VI

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Posted 19 November 2012 - 12:22 PM

It's really just a problem with the size of the dart pusher. When you have more than two rubber bands, one or two will come off of one side when you fire the gun. The o-ring pieces keep the dart pusher from damaging the gun body.


You could use a longer dart-pusher, and then bend the ends to prevent the rubber bands falling off.
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