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Pasnapbow-s The little brother to the pump action Snap crossbow.

#1 User is offline   Boot 

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Posted 13 October 2010 - 03:03 AM

The second in my backlog of un-posted projects, and slightly more interesting than my first homemade, (the Snap-Compact), this is my take on the original Snap crossbow, which was a take on Ryan Mcnumbers PAC bow... So... Props to all!

Again, skip the following if you don't care about the design and conceptualizing stages.

After working for a while on a pump action snap I found it to be exceedingly, and unintentionally similar to Carbons Snap-4, and so I ditched the project and began work on a fast and powerful secondary. Although the bow arms make it a bit too large to be a secondary, this rearrangement of the standard Snap-Crossbow cuts the length by pretty much a half (when a barrel is on both).

The idea came around when I was looking through the problems with the traditional Snap-Crossbow. The biggest (and possibly only) problem seemed to be its size compared to other blasters. In terms of power it was equal with spring powered blasters, and in terms of ROF, and "smoothness" of priming it was hugely superior. As such the only real goal in this build is to eliminate the size issue, and in that respect I think I succeeded.

(Read on from here, and look at the pretty pictures!)

The whole thing is (excluding the bow arms) slightly longer than a BBB, but unlike a BBB its entire length acts as a stock, putting the handle and trigger at the front of the blaster in what is kind of like a bull-pup configuration.

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Although in the pictures it is not done, all it lacks is a wire connecting the hole in the front handle to the actual clothes pin in the rear, and an RSCB which will screw into the metal insert on the top of the blaster (below)

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Unlike a standard pump action Snap crossbow, this one primes kind of like a recon. The non-dominant hand is placed behind the trigger and handle, and grips a priming slide. This slide operates just like the standard pump action crossbows, it engages the bowstring (which has vinyl tubing over it)

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Pulled back:

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Primed and ready:

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The great thing about this setup is, although it's not quite as fast as a regular pump action setup, it forces you to tilt the bow a bit each time, automatically reloading the RSCB.

In terms of connecting the RSCB, a metal PPR "threaded female adaptor" is placed directly into the plunger tube, and screws/ cuts into PPR creating a perfect airtight seal (while also reducing dead-space). I also used rubber washers, first done I think by Fome (?) to ensure an airtight seal on all my bolts.

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Everything else about this blaster is the same as the standard Snap crossbow. The catch surface is on the back of the plunger rod, and catches on my terrible trigger (the clothes pin used is of the "circle" variant so I had to bend the "spring" out of the way of the plunger tube and replace it with rubber bands).

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Plunger at rest:

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Primed:

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Despite this, and the fact that the trigger is in fact crooked :( (although not as badly as the picture makes it seem) the bow arms, and well filed catch nail make priming incredibly smooth, and misfires non-existent.

There are a couple more little discoveries that went into making this blaster which I think are entirely original (but if not props to you :D ), and the first is the handle:

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Don't recognize it? The smooth finish and nice curve isn't varnish or anything; to create the handle I made a single cut...

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...on half of a coat hanger. The curve fit's any hand fairly well. Just break a hanger in half, and cut each half in two. Glue the two ends together and attach. At least for me, these are much easier and cheaper to buy (if only a small number of handles are necessary), and the handles themselves are great. Comfortable, incredibly easy to make (literally easier than the old PVC handles), and cheap. I got a pack of 5 hangers on sale (making for a total of 10 handles) for 9 yuan, or about $1.50. You also get some nice thick wire from the hangers for trigger connections and such. These have become my standard handle, used anywhere except pre-made things (like nitefinders and BBB's).

The second is the material for bow arms themselves. As mentioned in my post in the Mod's and PJ's thread, my new barrel material resembling C-PVC in dimensions is amazing bow material. PPR is quite widely available in a range of sizes here, and is basically a type of high pressure gas line. The thick stuff I use for barreling is rated to 500PSI, and as a result is almost rubbery in texture. it is soft enough to be bent, but holds its shape very well. I tied the 6m section they sell it in in a "Fish" shape (as in bent in a loop) to carry home, and on returning a good two hours later the material sprung back to its original perfectly straight shape. There is also a thinner version with the same outer diameter (and an inner diameter that fits my McMaster foam Mega's ok) for when I don't want the bow to be as ridiculously powerful as it is.

With a single 12 inch PPR barrel, and a finally lubed E-tape seal (I still haven't found rubber of any usable sort for seals since my Snap-Compact, but I did get some Silicone spray) the bow is getting over 100 feet. It gets 6 1/2" of draw, and is about 15" long (with 12" of PPR for bow arms). It works great.

I believe that bow arms are a huge advancement in nerf. One of my biggest problems is getting springs, and I'm sure any newcomer to nerf (not just ones in China) experience the same problems. Now, if you can get pluming parts you have about 80% of the materials you need to finish a basic snap (well... cross Snap), and begin innovating.

And sorry, no video this time. As you may have noticed all my images for this build are a bit out of date. I uploaded everything (Cough using a proxy cough) for all of my projects at the same time because Photo bucket is partially blocked here in China, and doing it again would take too long. I promise though, that everything else has a video (or two :P ) and that the best is yet to come.

This post has been edited by Boot: 13 October 2010 - 03:04 AM

QUOTE
If you try to shoot over 45 feet with a magstrike accurately you fail

I beg to differ
0

#2 User is offline   Carbon 

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Posted 13 October 2010 - 05:23 AM

Nice solution for the LARGE SIZE problem of the 7.5. A pushrod system has been called a relocated clothespin in the past (linked so you can see how others have approached it). The main problem I see is that your handle will need to be longer in order to allow for the pushrod, and your thumb may get in the way as well, depending how it runs.
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#3 User is offline   lionhawk 

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Posted 13 October 2010 - 05:11 PM

Very nice job on the gun. The gun looks like it is a lot less bulkier than the pump-action crossbow. Bow-arms are certainly changing something in the nerf community.
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#4 User is offline   utahnerf 

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Posted 13 October 2010 - 05:40 PM

Great job, you've got lots of great ideas in your guns. I've gotta say, you are pumping out the guns, bro. Props.
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#5 User is offline   ChaosRaisin 

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Posted 13 October 2010 - 06:10 PM

Hey, great job man. Just wondering, What kind of string is the bowstring?
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#6 User is offline   Boot 

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Posted 14 October 2010 - 02:57 AM

View PostCarbon, on Oct 13 2010, 09:23 PM, said:

A pushrod system has been called a relocated clothespin in the past


Yes, that's exactly what I did (just with a thin wood dowel which is a bit less durable), and at least for me it fits perfectly. The thumb goes under it while the thumb under the cocking slide fits comfortably between the trigger extension and the plunger tube,

View Postlionhawk, on Oct 14 2010, 09:11 AM, said:

Very nice job on the gun.

View Postutahnerf, on Oct 14 2010, 09:40 AM, said:

Great job, you've got lots of great ideas in your guns. I've gotta say, you are pumping out the guns, bro. Props.


Thanks to both of you, and to utahnerf, the best is yet to come (although this the the last of my designs made completely from scratch. The next in the series of 7 should appear in the modifications thread soon :lol:

View PostChaosRaisin, on Oct 14 2010, 10:10 AM, said:

Hey, great job man. Just wondering, What kind of string is the bowstring?


Thanks, the bowstring is just nylon cable rated to I believe 80 pounds. its quite thin, but strong enough if you protect it from wear (from the priming handle) with some sort of sleeve like the vinyl tubing I used.

Good to see this is generating some interest, if anyone has questions or comment (or flames, I guess) feel free to post :D
QUOTE
If you try to shoot over 45 feet with a magstrike accurately you fail

I beg to differ
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