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Mark 8

A Homemade Blaster for Beginners

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#1 Meaker VI

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Posted 20 September 2013 - 06:21 PM

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This is what you're building. ~7" of plunger draw with ~36" length of surgical/latex tubing for power. It includes an RSCB clip/barrel assembly. Yes, at ~40" long (primed) with barrel, it is somewhat long; but it's light and - most importantly - really easy to build.

This whole thing also available as a .pdf download (download moved to NH local at the end of the post), by the way (which includes a cover page and credits). An all-text version of the post is available at the bottom, which I recommend you read if you're a totally new builder and completely unsure of what to do here. The .pdf is designed to be printed (in BW or color) and used as instructions so you can build on the fly. File was Edited 9-23-13 to include the clothespin on the cut list and to better align the check-boxes on the shopping list.

Credit goes to:
Carbon - SNAP Catch
Rork - Plunger head, improvements on the SNAP
Boltsniper - the inspiration for my modification to the SNAP setup, which is not that original but I hadn't noticed it posted elsewhere
RSCB - The RSCB, for which I've provided a fool-resistant writeup here as well

Edit: A poster in this thread has provided a cheaper means of power than latex:

I have a solution to the expensive late(x) ... problem. I use glider high start tubing, used to launch model gliders. It costs less than four dollars for 10 METERS. Performance is fantastic. Hobby King


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Exploded view - For a seasoned builder, everything you'd need to know is in this image.

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Parts list - In case it isn't clear, I got everything at Lowes except the clothespins, which I had lying around (hijacked from the kitchen where they usually live lives as bag clips). I could have also gotten everything at Homedepot, and have for past builds.

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Shopping list - print and take with you to the store

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Cut list - These need to be included in more write ups. Knowing beforehand what length to cut all your parts to is great. Also cut the tails off of your clothespin while you're cutting stuff.

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Front Bushing - figured it'd be good to start with the easiest thing to build.

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Plunger - the next easiest part to construct.

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Mark 8 Blaster Body pt. 1

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Mark 8 Blaster Body pt. 2 -

Disclaimer: You can use just tape to hold the catch on, but you should reinforce that sucker ASAP. Once you've got the blaster working, run a few zip-ties, wire ties, or wraps of cord/twine around the taped-on jaw or put some glue in there.

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Mark 8 Catch Detail

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RSCB build instructions (Optional) - Langley asked further down, you could replace all this with a coupler and two barrels (with 1/2" PVC sheaths). Tape them together in so they face opposite directions and you have a flip-barrel with 2 shots at the ready. For full-disclosure, I glued most of my RSCB together and cut the elbow/T down where they attach for a lower profile.

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Mark 8 Final Assembly

 

Text-only version:

 

1) Acquire the Parts (& Tools)

I'm working on the assumption that you have nothing. As such, I'm giving you a complete shopping list, if you already have any of the items here, sub them in. I'm also giving you the shopping list including materials to build the RSCB shown on the blaster. If you don't want that or already have a 'Y' fitting for a hopper, sub out the 1/2" PVC fittings except the coupler.

Parts:

I got all of the parts for this blaser, except the clothes pin, at Lowes. I have found them all at Home Depot as well, and I wouldn't be surprized if you could find them all at an ACE or McClendons (local WA-based hardware store).

PVC Aisle:

The PVC/CPVC is usually bought in 10 foot lenghts in its own aisle and is white. My local store also sells 5 foot lengths, but they're more expensive than a full 10 footer. PVC is sold in a few different types; typically you'll find Schedule 40 and 200 PSI. These labels will be stamped on the side of the pipe and the shelf label. 200 PSI "Thinwall" is rarer, but this is most likely because it isn't used for the same thing - Schedule 40 is used mostly for indoor drain pipes, 200 PSI seems to be more landscaping-oriented. My Lowes stores both in the same aisle, some stores might store them in different places; in either case check the pipe you're buying to be sure that it is what you want.

CPVC is sometimes kept by the copper, which may be in a different area of the store, and is used as plumbing supply pipe. It is off-white.

Fittings are the parts that join pieces of pipe together. They are usually near the pipe, but may be in a different aisle or on the back of the aisle the PVC is on. I've been in some stores where they were in several aisles. Always check the fitting to several others in the bin and your pipe to ensure it's the one you want, they often get mixed up into the wrong bin. If your store carries pipe, they should also carry most of the fittings you'll need. Every fitting will be a slip-fit type - if it has threads it is not one you want.

Pipe:

1/2" PVC - Schedule 40 or 200 PSI 2$
1 1/4" PVC - Schedule 40 4.50$
1/2" CPVC - Bring a dart to check the fit if you want it for barrels too - In my experiance, the dart should slide freely in and out but not fall out on its own. You will need to check multiple sticks in the same stack of pipes, they vary quite a bit. $5

Fittings:

1/2" PVC: Endcap, Elbow, 'T', and Coupler 2$. You won't need any of this if you have a 'Y' fitting and are planning to make a hopper instead of the RSCB I show.
1" PVC: Bushing - 1" to 1/2". 1$ This should fit inside your 1 1/4" PVC and has a spot for the 1/2" PVC to fit. If you can't find one, pick up a stick of 1" Schedule 40 PVC ($4) and carry on.
1/2" CPVC: Endcap, 'T' 1$

Hardware Aisle:

You'll need a pretty well stocked hardware aisle for this bit. Homedepot, Lowes, Do-it Best, McClendons, and ACE should all have stores that are sufficient, but larger stores will be better stocked. Unfortuneately, some of these parts are bought in large quantities and you only need 1-2. If you can find bins with grab & label bags with everything you need, do that instead. I'll use the prices for boxes of parts where applicible.

Specialty Washers:
1 1/4" Neoprene/Rubber washer 1$
1 1/2" Neoprene/Rubber washer 1$
1 1/4" Steel fender washer 1.25$

A note about the "#8" - the "#X" is a way of labeling standard screw sizes (diameters). You can sub in different #'s for what you have. They should work fine. Different lengths and types (I used coarse thread) could work too, provided you have the tools to make them work.

Regular washers:
#8 Washers - if you have any hardware lying around, you may have one of these you can scrounge, they're super-common. 1.50$

Screws:
#8 1/2" long Screws - type doesn't matter. I like Phillips and hex-head, phillips because my bit doesn't slip out and stab me as often as flat and hex-head because I can use a flat bit or a hex socket for superb accuracy and ease of install.6$
#8 1" long Wood or Gypsum/Drywall screws - usually gold or black in color and sold in 1 lb. boxes. Most wood/drywall screws should be #8, so don't fret if it doesn't say. 6$

Misc:
1-1/2" right-angle corner braces. Different from right-angle corner plates, which are flat. Should be somewhere in the hardware area. 3$
A Clothespin - You might not be able to find this at the hardware store, but they are plentiful at Walmart or Target and just about any other grocery store. Home Depot lists them as available in stores on their website, look in the closet/organization section or hardware. Wood ones work fine for me. Scrounge them if you can, you only need 1 for this blaster (but then, you can just build a whole bunch of blasters with them) $2.5
Latex Tubing - I think I used 3/8". It was pretty costly at $2/foot, and you need 2-3 feet. $6
Wire or Roofing nails - I used wire, I think it is 12-16 gauge. It's stiff enough that it won't bend easily when pressed in your hand, and about the diameter of a nail. If you need to use roofing nails, get them 1-1/4" long and have a file, grinder, dremel, or some rough pavement available (a concrete sidewalk or street should do). $4

Wood:
I used a 1 x 4 Furring strip. You can probably find something that will work for free in the scrap bin, but if not, get either a 1 x 4, 1 x 3, or 1 x 2 furring strip (1-2.75$). Furring strips are usually in the back, and are often nasty looking. Find one that is mostly straight and doesn't have any/many knots in it. Failing that, Lowes and Home Depot often have 'hobby wood' near their moldings. These are various sized pieces of 'hardwoods' (a term used for wood that comes from deciduous trees, has little to do with actual hardness) and have various costs, but will hold up better to wear than the furring strips. Get Oak, hickory, maple, or ash. Failing even that, I hear Trex (or equivalant plastic-wood decking) works well. Failing even that, just about anything roughly handle-shaped should work with the method I show: a shaped piece of MDF or particle board, PVC board, epoxy-filled PVC pipe, an appropriately sized stick...


Total parts: $50.00 +Tax

You should have extra PVC and hardware left over. My stores carry fender washers and brackets in packs of two or more, so if you were to pick up another of each of the PVC/CPVC fittings and some more latex ($8), you'll be able to bulid 2 blasters with the left over hardware and PVC (~$30 per blaster).

If you just bought the parts/length of materials needed for each blaster, you'd be building them for +/-$15.55 +tax each. The amount of materials you'd need to buy to have nothing left over is in the hundreds of blasters range though, so don't expect to get that low without subbing in stuff you have already. Or perhaps by stumbling upon one of the Legendary Hardware Stores of Old, that still let you buy screws out of buckets with scoops in them and then wrap them up in paper bags. Been at least a decade an a half since I've been in one of those, though Lowes lets you buy some nuts & bolts in a bag you label yourself.

Tools:

You won't need many tools for this blaster, I designed it to work with a minimal set.

That said, there is little getting away without a drill, but a good corded or battery powerd one can be had for $30. A less reputable one can be had from Harbor Freight for $20 (not including their often-available 30-40% off cupons). I reccomend a corded drill unless you have good reason to get the battery powered one - cords always have full power and short extension cords cost $5-10. Batteries need charging at inopertune times, eventually die permenantly, and cost much more ($10-60 and more). Another option is something called a 'pin vice,' which should run $5-10, but the trick is finding one. Look in hobby shops or online, if you get one you'll need a smaller bit (1/16") to drill pilot holes with. I'm 90% sure 1/8" bits will work in pin vices, check with the dealer.

You'll also need:

1/8" Drill bit
Scissors, a knife, or something else for reaming out PVC and cleaning edges. Don't use your mother's cutlery.
A saw - A hacksaw, wood (hand) saw, bandsaw, scrollsaw, some types of pocket-knife saws and blades, and even mason's line will work. If you don't own or know anyone who owns any kind of saw, get a Coping Saw. You should be able to find one for less than $10. Anything a scrollsaw can do you can do with a coping saw (and time, and maybe a clamp).
A screw driver that works with the screws you got
Tape - I used electrical tape (2$), though duct tape or clear packing tape ought to also work.
A ruler or tape measure
A pencil/pen/marker

You may need:
A file - to shorten/clean up your nail or wire, optionally to shorten some screws and clean up your handle/cuts
Pliers - especially if you're using wire, not so much if you're using a nail
Sandpaper - to clean up your cuts and handle
Lubricant - I used white lithium grease, but I don't claim to be a lube expert. Look at your product to be sure it is safe for plastic and rubber; white lithium and silicon are supposed to be good. I hear looking in the electrical aisle yeilds good results, I found mine in the tool department. Do not use WD-40 or any other kind of petrolium-based oil, it eats plastic (and rubber).

I used:
A scroll saw, scissors, files (on the wood), sanding block, drill, tape measure, pencil, pliers, and screwdrivers. I could have easily used any other saw, I had the scroll saw set up already and it was easier to use than a regular saw in my cramped shop.

2) Cut to Length

You'll need to use your saw and clean-up tools to cut the parts to the following lengths:

1/2" PVC - 12", 2 x 3/4", and 2 x 2". Grand total: 18" of 1/2" PVC
1 1/4" PVC - 14", cut at a slant on the end. The exact slant doesn't matter much, and is mostly so you can get into the pipe a bit with your screwdriver to attach the handle. I measured 12" and drew a mark, then connected the two marks and cut along that.
1/2" CPVC - 14", 12". Grand total: 26" of CPVC
1/2" PVC Coupler - cut in half
Wood/Handle material - 5", cut at any slight angle you like. While you're cutting things, shape it however you want with your saw/files/sandpaper or use this template.
Cut the tails off of your clothespin.
If you bought the 1" PVC because you couldn't find a bushing, cut 2 x 3/4" rings off that

You are done cutting, put your saw away.

3) Sub-Assemblies

Plunger Head:

Use the 1/2" CPVC endcap, one of each size of fender washer, a 1" screw, and a #8 washer.

In the center of the 1/2" CPVC endcap, drill a hole. It is easiest to do this by flipping it over and drilling from the back. Roughly center works fine for me, some people use a sharpie or other marking impliment wrapped in tape to mark close to the actual center, and thne use a nail, screw, or punch to make a dent in that mark to help the drill stay in place. In the end, you should have a more-or-less centered 1/8" hole in your endcap.

Take the screw, and on it place the #8 washer, the 1/2" washer (if you have it) the smaller rubber fender washer, the larger rubber fender washer, and lastly the metal fender washer.

Screw it into the endcap.

Plunger body:

Use the 12" CPVC, a 1/2" screw, and the plunger head. Later you will also use the CPVC 'T' and another 1/2" screw, but for now, set them aside.

Mark 2 1/2" down the shaft of your 12" piece of CPVC. Drill a hole through the CPVC, but not all the way through both sides. Use the scissors/etc. to widen the hole to about 1/4". This will be the catch hole.

Slip the plunger head onto the plunger shaft, on the end closest to the hole you just made. Drill a hole through both the side of the endcap and the plunger shaft and insert a 1/2" screw until it won't tighten any more. It will stick out, don't worry - as long as it is inside the plunger tube body it won't hurt anything. The forces on this plunger aren't such that you need any stronger attachement than this. If you were using a compression spring, like many homemade a using K25/26's, this would need some reinforcement.

Set the completed plunger aside for now.

Blaster body:

Use your 14" long 1-1/4" PVC, your handle, and 2 of your 1" long screws

Taking the 14" long 1 1/4" PVC piece, drill 2 holes about 1" apart into the sloped tail you cut earlier. Tilt the blaster on its side and mark on your handle where these holes will fall - the handle should be pretty far back on the blaster, the front of the handle should be no further than 2" from the back of the PVC.

Carefully drill the holes out of the handle. I did this carefully by hand, but I recommend using a clamp or vice if you have it. If not, hold the handle in such a way that, should the material fail or the drill bit come out, your body (especially your hands) will not be in the way of the bit. You don't need to drill very far into the material, go slow and take your time.

Ream out the holes in the blaster body a bit with your scissors from the inside; not much is needed, you're just trying to make it easier to sink the screws. Use a countersink if you have one of those.

Once that is done, take 2 of the 1" long screws and screw them through the PVC into the handle until they are tight.

Catch stop:

Use your 3/4" long 1/2" PVC ring, 1/2 of the 1/2" Coupler, tape, and the 1" PVC ring if you have that (you may need to slice through the side of it to get it around the coupler).

Check that your 1/2" PVC ring slides freely over your 1/2" CPVC plunger rod. If it does not, ream it out with scissors, sandpaper, or a file until it does.

Insert that 1/2" PVC ring into the 1/2 coupler. Bang it on the table a few times to make sure it's all the way in. Wrap with tape until it fits into the body of the blaster. It doesn't need to be snug, but shouldn't rattle around. If you have the 1" PVC ring, wrap the 1/2" PVC coupler until it fits into the 1" PVC ring ( or slice the side of the ring so it will fit over the coupler), then put a few wraps on the 1" PVC ring until it fits into the blaster body. In either case, it should be loose enough that it will fall out if you don't hold it in.

Catch:

Use your clothespin, nail/wire, bracket, catch stop, and the blaster body.

Drill a hole through the jaws of the clothespin.

Insert the Catch stop into the body of the blaster, using the plunger to provide stability if needed. Line the hole in the clothespin up with the catch stop inside the blaster, so that the clothespin fits in front of the handle. Drill a hole through the blaster body bottom and the catch stop, being careful not to drill into the plunger. Insert a piece of wire or a nail into this hole while you drill another hole into the side of the blaster (again avoiding the plunger) and put a 1/2" screw into it. It will not tighten all the way without pushing against the plunger, this is fine. Leave it out a turn or two, whatever it takes to not touch the plunger.

If it bothers you too much, use your file, sandpaper, grinder, dremel, or the pavement to shrink the screw down so it doesn't stick into the plunger when driven all the way in.

Remove the temporary wire or nail and tape the clothespin in place. Put the nail or wire back into the clothespin. If you are using a nail, grind down the tip of the nail so it is round and protrudes into the plunger about 1/4" - far enough so that it will catch, but also so that the clothespin will pull it all the way out when in the most open position. Tape the angle bracket to the outer jaw. If you're using a wire, wrap the wire around the clothespin and through one of the holes in the angle bracket. If you're using a nail, tape the angle bracket over the nail. You can improve this attachement by gluing or ziptying the bracket to the outside clothespin, but that can be done later. The blaster will function without a sturdier catch attachment, but once built, I recommend reinforcing it with glue, zip ties, wire ties, or twine to ready it for regular use.

Spring Stop/Barrel stub:

Use your tape, 2" long 1/2" PVC piece, and bushing. If you didn't get a bushing, use the other 1/2 of the 1/2" PVC coupler and the other 1" PVC ring.

Insert the 2" long 1/2" PVC into the bushing and bang on the table to ensure a good fit. Wrap the bushing with tape until it fits snugly into the front of the blaster body. Remove it and set aside.

If you don't have the bushing, insert the 1/2" PVC into the coupler and bang on the table for a good fit. Wrap in tape until it fits tightly into the 1" PVC ring. Bang on the table again to ensure a good fit. Wrap the 1" PVC ring in tape until it fits snugly into the front of the blaster body. Remove and set aside. Since PVC varies, you may need to slice the side of the ring to get it to fit over the coupler. If you do that, tape or glue over the slice so that air won't go through. Alternatively, don't use the coupler and just wrap the 1/2" PVC until it fits singly in the 1".

4) Final Assembly:

Put the plunger into the blaster body, with the head pointed toward the flat end of the plunger. Pull the tail out until it stops. Rotate the plunger to arrange the hole drilled earlier toward the catch at the bottom of the blaster. Push the plunger slowly forward until the catch locks. Attach the 1/2" CPVC T to the back of the plunger as shown, drill a hole and insert a 1/2" screw.

Pull the bracket/trigger to release the plunger. If it slides freely forward, pull the plunger back to see if the trigger recatches. If it does, congratulations! The blaster functions and you can continue. If not, remove the clothespin jaw with the catch pin (either a nail or a piece of wire) and file the pin down more. Replace it and repeat as needed until the plunger moves freely when the trigger is pulled but stops when the trigger catches the hole in the plunger.

Once the trigger/plunger is working, pull the plunger back and add lube to the inside of the plunger tube, at least an inch down into the tube.

Take the blaster assembly and insert the Spring stop/Barrel stub. Drill a hole through the assembly on either side of the blaster. Insert a 1/2" screw into each hole.

Pull the trigger and force the plunger all the way forward; then pull it back and push it forward to work the lube into the plunger head and along the sides of the plunger. With the plunger all the way forward, take the latex tubing and thread it through the CPVC 'T' handle. Wrap one end around the front barrel-stub and tie a double knot. Stretch the tubing, working it evenly from the tied side, and tie another knot around the front barrel stub as above.

Congratulations! The blaster is complete!

Now to build the ...

5) RSCB

Use the other 2" long 1/2" PVC piece, the 14" long CPVC piece, the 12" long 3/4" PVC piece, the other 1/2" PVC piece, and the 1/2" PVC 'T', elbow, and endcap.

If you're using 200 PSI 1/2" PVC, tape the last 2" of the CPVC and pound it into the PVC. If you're using Schedule 40, ream it out so that the CPVC fits at least 1/2" in and cut off the excess. Ream out the end with the PVC to create a smooth ramp. Attach this to one side of the 'T', the 12" long PVC to the oppisite side, and the 1/2" long PVC to the remaining side.

Attach the Elbow to the 1/2" PVC stub. Drill and screw into the 1/2" long PVC piece to keep the elbow and 'T' in line with eachother. Tape over the joint.

Attach the elbow to the barrel stub. Drill and screw to keep it from moving.

Load darts into the 12" long 1/2" PVC piece, attach the 1/2" PVC endcap.


6) Pick your Target

Pull back the plunger, pull the trigger, and let those darts fly!

Disclaimer: Do not point at animals, people, glass, etc. Do not aim at eyes or face. By using any portion of this writeup, you agree that I am not liable for anything you do. etc. etc.
 
Edit 12-21-2015: Used the upgraded forum software to upload and attach the Mark-8 PDF instructions directly to the site.

Attached Files


Edited by Meaker VI, 22 January 2016 - 10:08 AM.

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#2 iModify

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Posted 20 September 2013 - 07:41 PM

Great Job! This will help many new modders.
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#3 quertyman

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Posted 20 September 2013 - 07:44 PM

Wow, excellent writeup and good job making everything hardware store reachable. How on earth did you make those pictures? They are amazingly well made. As a suggestion maybe making a better mount for the latex tubing would make it a bit better looking and also I would suggest you use a better way of attaching the clothespin trigger on.
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#4 Mully

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Posted 20 September 2013 - 08:00 PM

How on earth did you make those pictures?

I'm wondering the exact same thing; excellent writeup! Very easy to understand, the way you did those pictures is really neat.

Edited by Mully, 20 September 2013 - 08:01 PM.

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S.C.U.N.

#5 Ivan S

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Posted 21 September 2013 - 01:17 AM

This is really impressive, especially the new catch design. Have you tried increasing pretension for more power? Do you know if the tubing's elastic limit would prevent you from increasing power past a certain point? It would be great to have a spring-like blaster which can be adjusted to fire arrows or shotgun blasts the way airguns can.
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#6 DartSlinger

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Posted 21 September 2013 - 01:48 PM

How on earth did you make those pictures? They are amazingly well made.

I second this. I believe he made them using Google Sketchup, but I'm not sure.

Fantastic write-up, man. This is very detailed and well done. This will definitely help people who are trying to get into homemades cheaply.

Oh, by the way, I've been in a hardware store where you could buy nails by the pound. It was a True Value, and it had the old manual scale and the fork-thing to scoop the nails with. No screws, though, so I guess it was only semi-legendary. Since you're ninety-seven, I guess you remember clean back to when people used wooden pegs instead of nails. Posted Image
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#7 koree

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Posted 21 September 2013 - 02:26 PM

This looks nice but I'm rather concerned about the nail/CPVC interface. Wouldn't the catch interface wear down really quickly?
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#8 Buffdaddy

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Posted 21 September 2013 - 02:35 PM

I suppose the easiest thing to do is fire it a hundred times, then compare before and after pictures.

But I agree, I could certainly see the catch interface wearing down faster than for a well made, traditional SNAP.

Idea for improvement: before attaching the plunger head, take a 1/2" OD nylon spacer from the hardware drawers, hammer it down the shaft with a metal rod, drill a hole through the plunger rod/spacer combo, and secure in place with a 5/8" long nail or similar item that will sit flush with the plunger. THEN you can carve out the catch hole directly in front of the spacer. That way, you have a nice solid surface that should last longer.
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#9 Meaker VI

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Posted 21 September 2013 - 05:24 PM

Thanks for the props everyone, I appreciate it.

Wow, excellent writeup and good job making everything hardware store reachable. How on earth did you make those pictures?


I made a Sketchup model of all of the parts of the blaster, laid out each 'view' I wanted, and then exported an isometric parallel-projection image with shadows, edges, and profiles turned on. For the overview, I also exported a CAD file of the lines and overlaid that onto a flat-color image, so in the .pdf the lines will scale infinitely. The images were exported as fairly large .png's before scaling down for the web/distribution, I think they started 2400 px wide at least. I encourage everyone to steal my method when making write ups.


As a suggestion maybe making a better mount for the latex tubing would make it a bit better looking and also I would suggest you use a better way of attaching the clothespin trigger on.


Obviously the trigger should be better attached, but for an absolute first blaster, I'm just trying to get people to build it. Zip ties and glue are both mentioned in the write up as better solutions, but to keep costs and approach-ability down, I omitted them as necessary.

Using the barrel-stub as a mount is actually super-sturdy and I can't think of an easier way to mount the tubing. On my blaster, the RSCB isn't attached to the mount other than by friction and I can just pop the RSCB off and detension the thing.

This is really impressive, especially the new catch design. Have you tried increasing pretension for more power? Do you know if the tubing's elastic limit would prevent you from increasing power past a certain point? It would be great to have a spring-like blaster which can be adjusted to fire arrows or shotgun blasts the way airguns can.


I didn't want to push the tubing too far. Yes you could get more tension out of it, I think you could easily use 24", but I can tell I've got plenty of pull left even primed. You could also always add more latex/bungies like in the old days. Keeping this approachable was paramount, and for ease of assembly I recommend 36" of tubing.

Oh, by the way, I've been in a hardware store where you could buy nails by the pound. It was a True Value, and it had the old manual scale and the fork-thing to scoop the nails with. No screws, though, so I guess it was only semi-legendary. Since you're ninety-seven, I guess you remember clean back to when people used wooden pegs instead of nails. Posted Image


Heh, the 97 year old thing is because I avoid putting my exact birthdate on forums. I'm post-college for reference.

This looks nice but I'm rather concerned about the nail/CPVC interface. Wouldn't the catch interface wear down really quickly?


I suppose the easiest thing to do is fire it a hundred times, then compare before and after pictures.

But I agree, I could certainly see the catch interface wearing down faster than for a well made, traditional SNAP.

Idea for improvement: before attaching the plunger head, take a 1/2" OD nylon spacer from the hardware drawers, hammer it down the shaft with a metal rod, drill a hole through the plunger rod/spacer combo, and secure in place with a 5/8" long nail or similar item that will sit flush with the plunger. THEN you can carve out the catch hole directly in front of the spacer. That way, you have a nice solid surface that should last longer.


Traditional SNAP catches will be more durable, yes. This is easier to make. This should last long enough, for me, the bigger issue is scratching on the plunger rod. There's any number of ways you could reinforce it, or you could instead use a wood dowel or (any other material) rod, but again, this was something already on the parts list.

I'll put a few hundred rounds through it and let you know how that goes.

Edit: While not yet at a few hundred, I did fire & dry fire it some 50 times yesterday. So far, no signs of wear to the catch, but the trouble is that one wrap of e-tape isn't near as strong as the spring on the clothespin. Sometimes it pulls out & away from the blaster, causing it to fail to prime. I'll add a disclaimer, about using zip ties and/or glue to hold that sucker down. However, as the goal was to get someone to build something, e-tape/tape is great to start with. Easy to do and easy to undo if it goes wrong. The other types of tape I'm recommending shouldn't have as many problems, and more than one wrap would have to work better too :P

Edited by Meaker VI, 22 September 2013 - 09:30 AM.

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#10 pinhead52

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Posted 22 September 2013 - 09:30 AM

This is a truly amazing writeup. It's clean, easy to follow, professionally done, and most importantly, accessible. Anyone with a basic toolbox and a few bucks can build one or two of these. Even the tools you used to make the writeup (SketchUp) are accessible to everyone. I hope this sets a new precedent for writeup quality on this board. This could be published.

On a side note, I don't think I noticed any mention of this being used for the homemade contest. Did you want to give the rest of us a chance?
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#11 Langley

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Posted 22 September 2013 - 09:38 AM

the checkboxes, though - those were a total fail!

That's how hard I had to work to even find something to criticize.


We sure do appreciate all of your hard work, 'Noah'.

Yeah, the checkboxes don't line up, so I guess there is that, but otherwise the write up looks amazing. I have some issues with some of the design decisions, but the diagrams and instructions are perfect. I did notice there was no explanation for cutting the 'tails' off the clothespin, so I think the cut list could be improved by showing the clothespin with a dotted line across it.

I know it drives up the price quite a bit, but I think adding epoxy putty to the design would be worth it. First, it would allow for a better way of securing the clothespin. I usually screw mine directly into the plunger tube, but I don't usually use wooden clothespins. The biggest advantage to using adhesive or screws to secure the clothespin is that this design could easily have a pump sleeve added without any other modification. Because of the way you set up the catch, you have room on the plunger tube for a thinwall pvc grip to slide over without it having to extend past the front of the plunger tube. See the Thumb SLAP for an example of what I'm talking about.

Second, epoxy putty could be jammed into the hole in the plunger rod to give the pin something to rub against other than CPVC. I've also tried this sort of catch and it will wear down very quickly. It will continue catching indefinitely, but the place where the pin catches on the plunger rod will drift, decreasing your draw over time.

I think this thing is begging to have some alternate stored energy mechanisms. As much as I hate to admit it, this thing would definitely lend itself to bow-arms, and because of the way the catch works, you could put any diameter spring in that would fit, and the pin won't get caught on the coils. You might have to combine a spring with bungees or latex tubing just to keep the plunger rod from rotating out of alignment though.

My only other issue is that, while the barrel stub might be a great place to secure the bungees with an RSCB, it doesn't allow you to put a flip-barrel on. It would be nice to be able to put a flip barrel on just for the sake of any builders that have difficulty getting the RSCB to feed properly.
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#12 Meaker VI

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Posted 22 September 2013 - 10:14 AM

On a side note, I don't think I noticed any mention of this being used for the homemade contest. Did you want to give the rest of us a chance?


I appreciate the compliments. As to this question, I have submitted this thread in the submissions thread for the contest, but I'm willing to pull it if doing so encourages more entries. I'll be discussing that later.

We sure do appreciate all of your hard work, 'Noah'.

Yeah, the checkboxes don't line up, so I guess there is that, but otherwise the write up looks amazing. I have some issues with some of the design decisions, but the diagrams and instructions are perfect. I did notice there was no explanation for cutting the 'tails' off the clothespin, so I think the cut list could be improved by showing the clothespin with a dotted line across it.


Wait, they don't? I'll get that fixed. I may need to fix the margins on a couple pages too, and I'll add the clothespin thing. I had meant to originally, but forgot to model & export it. Speaking of, most of the "complex" models I used are available on the 3d warehouse - the clothespin ( though it was out of scale), the scissors, the screws, even the PVC and fittings. Not CPVC though, but you can just color PVC off white and scale to make that.

I know it drives up the price quite a bit, but I think adding epoxy putty to the design would be worth it. First, it would allow for a better way of securing the clothespin. I usually screw mine directly into the plunger tube, but I don't usually use wooden clothespins. The biggest advantage to using adhesive or screws to secure the clothespin is that this design could easily have a pump sleeve added without any other modification. Because of the way you set up the catch, you have room on the plunger tube for a thinwall pvc grip to slide over without it having to extend past the front of the plunger tube. See the Thumb SLAP for an example of what I'm talking about.

Second, epoxy putty could be jammed into the hole in the plunger rod to give the pin something to rub against other than CPVC. I've also tried this sort of catch and it will wear down very quickly. It will continue catching indefinitely, but the place where the pin catches on the plunger rod will drift, decreasing your draw over time.


Agreed, though I've used gorilla super-glue before and that worked well and would be more accessible ( the gorilla stuff specifically expands when cured, making it great for those of us who are not Boltsniper and all perfect about our cutting and gluing). Is that thin wall 1.5"? Shoot. I'll need to get some of that. I've been using 2" , which could slide over anything but looks ghetto.

As for epoxy putty in the catch, it can't hurt, but I don't know that it'd help either. It makes the plunger heavier (sometimes significantly) and the stuff I find never really works well as glue so it might just slide back with the hole. Fortunately, you can always just retention to accommodate.

I think this thing is begging to have some alternate stored energy mechanisms. As much as I hate to admit it, this thing would definitely lend itself to bow-arms, and because of the way the catch works, you could put any diameter spring in that would fit, and the pin won't get caught on the coils. You might have to combine a spring with bungees or latex tubing just to keep the plunger rod from rotating out of alignment though.


I considered using bow-arms, but didn't because they're difficult to mount and can be confusing. I originally used this sort of catch on my version of Boltsniper's GNS, which has a normal compression-spring setup, getting it to catch consistently isn't hard because of the T handle.

My only other issue is that, while the barrel stub might be a great place to secure the bungees with an RSCB, it doesn't allow you to put a flip-barrel on. It would be nice to be able to put a flip barrel on just for the sake of any builders that have difficulty getting the RSCB to feed properly.


Replace the RSCB parts with a coupler. I feel I've illustrated how I build my RSCBs pretty well though, and I haven't had a problem with mine. I did leave out the cosmetic fix I did though - I like to cut the elbow and T down so it sits lower against the blaster.

Thanks for the comments and criticisms, I'll try to get those things addressed.
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#13 Langley

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Posted 22 September 2013 - 10:22 AM

I appreciate the compliments. As to this question, I have submitted this thread in the submissions thread for the contest, but I'm willing to pull it if doing so encourages more entries. I'll be discussing that later.


I really don't think that's necessary. You've set a good precedent with this writeup for other people to strive for, but there's still room for improvement. You've also offered to help other people with diagrams, which is one of the things that sets this entry so far ahead.
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#14 Carbon

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Posted 22 September 2013 - 04:00 PM

The SNAPbow has set a lot of standards for what's "expected" on a SNAP...as such, there's a lot of talk of increased wear due to the nail-on-plastic catch. However, I haven't found that to be nearly the concern with an extension spring. A K26 is a *lot* of power (and requiring a burly catch), but a lot of that power is lost due to internal friction. Crossbows, extension springs and latex tubing blasters have far less friction, which means a weaker spring can be used to get similar performance....which therefore means the catch doesn't really need to be nearly as strong. It's even less of an issue on this design than on a normal compression spring SNAP, because even as the catch wears, it'll still function (and it'll take a *really* long time before it wears long enough to cause a significantly decreased draw, or a malfunction). Latex tubing is an excellent power source, and this blaster does a great job of making it newb-accessible.

My only nit right offhand is the setup of the writeup with regards to pictures and the text: your pictures are great, and the inclusion of the text writeup as well is great (and vital to the search engine), but my preference would be to have searchable text next to your excellent diagrams. This way, to search a term would plunk you in the text at the bottom, then making you navigate back to the corresponding diagram up top. That's debatable as far as utility, though. Overall, excellent work.
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#15 Meaker VI

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Posted 23 September 2013 - 03:22 PM

My only nit right offhand is the setup of the writeup with regards to pictures and the text: your pictures are great, and the inclusion of the text writeup as well is great (and vital to the search engine), but my preference would be to have searchable text next to your excellent diagrams.


I've added text below every image.

As an aside, is there interest in/need for a writeup on how I did my writeup? I've included most of the actual details of how it was done (Except that I used variations on Franklin Gothic as the font), but not the more artistic/layout or design parts (which could get wordy). If so, where would I put such a thing? Here in Homemades?
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#16 pinhead52

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Posted 23 September 2013 - 03:33 PM

I would either just put it in General Nerf and PM a mod that it could be a sticky.

By the way, I was joking about you pulling from the competition. Having something this professional this early on will certainly up the ante for future submissions.
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#17 Endryo7

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Posted 13 October 2013 - 11:56 AM

Hello, I'm a newb that wants to build this, but I have one dumb question:
Can I put a hopper on this instead of a RSCB?
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#18 HasreadCoC

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Posted 13 October 2013 - 03:09 PM

Hello, I'm a newb that wants to build this, but I have one dumb question:
Can I put a hopper on this instead of a RSCB?

Yep. You can pretty much put a hopper on anything with a large enough air volume and some oomph. Most war-class 1/2"pvc-coupler'd blasters can use hoppers, RSCBs, etc interchangeably. If there are bow arms or bungies involved, it's just a matter of having that stuff attack behind the coupler you plug your dart feeding mech (such as a hopper) into.
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#19 Langley

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Posted 13 October 2013 - 10:18 PM

Mark 8.1?

Posted Image

The first thing I noticed is that you left out the air intake/speed holes.
Posted Image

I took a number of other diversions from the original plan. Instead of a 1/2" coupler, I used another 3/4 to 1/2 reducer bushing with the flange cut off. This required significantly less tape. I also cheated and used a rasp and some sand paper to ream out the 1/2" pvc because the scissors were taking way too long. Keep in mind that some people are stuck with pretty thick pipe (if you know what I mean). I also used a machine screw and nut to secure the washers on the plunger head, and I reversed the screw so that the head is inside the endcap, leaving more room for additional screws to attach the endcap to the plunger rod. I used two screws each on the tee and plunger head so that it would be strong enough for an internal spring (see below).

The biggest improvement I felt this design needed to make it vastly more usable was a stock. For the grip and stock I was only able to use what I had laying around, or I would have planned out a much nicer more ergonomic stock. Still, I think this gets the point across. Using three pieces of 1/2" PVC you can easily attach a stock using the same material used in the grip.

Posted Image


The added bonus is that you can turn the CPVC tee 90 degrees and use the gap between the top two lengths of PVC to keep the plunger rod aligned if you want to put in a spring instead of latex tubing or bungies.

Below is the same blaster with the addition of half of a spring from a heavy duty pneumatic screen door closer. The stock prevents the plunger rod from turning past the point where the catch hole doesn't line up. This variation gets significantly improved range over the latex tubing.

The screen door closer is about $12, but you can easily cut the spring in half and use it in two blasters, and it was much cheaper than the 10' of latex tubing I had to buy because they were out of the cut-to-length spool.
Posted Image

I need to make the plunger rod an inch or two longer, because it has to sit back farther in the spring configuration, and it rests right against the back of the plunger tube in the latex tubing configuration, leaving too little room to get my fingers in to pull the handle back. I also need to try it out with a pump sleeve. I screwed in the internal bushing from below, through the clothes pin instead of from the side as in the instructions to allow a 1-1/2" thinwall pump sleeve, but I don't have time tonight to try it out.
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#20 Meaker VI

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Posted 14 October 2013 - 10:53 AM

Mark 8.1?

The first thing I noticed is that you left out the air intake/speed holes.

I took a number of other diversions from the original plan. Instead of a 1/2" coupler, I used another 3/4 to 1/2 reducer bushing with the flange cut off. This required significantly less tape. I also cheated and used a rasp and some sand paper to ream out the 1/2" pvc because the scissors were taking way too long.

The biggest improvement I felt this design needed to make it vastly more usable was a stock. For the grip and stock I was only able to use what I had laying around, or I would have planned out a much nicer more ergonomic stock. Still, I think this gets the point across. Using three pieces of 1/2" PVC you can easily attach a stock using the same material used in the grip.


Excellent work.

Most of the goal of this project was to make it approachable and easy to build; so I kept the parts list down and didn't do some things that would result in better construction, but might be difficult for someone without any experience to do. Like cutting the flange off of a bushing - I did that at first, but then realized that I had to do it using a scroll saw and that doing it without would be a pain (unless you're cutting the bushing off at the flange, which would be easier). Without the superior fit that the bushing would provide, I didn't need speed holes (the rear spring-guide in mine isn't held in securely since there isn't any force on it; the tape is mostly just for centering). I left the rasp out as a requirement because I had success with the scissors and figured more people would have them. Rasps are actually really easy to find (and drill mounted rasps are equally easy), but you've got to know what you're looking for, they cost something when you don't already own one, and they still take a lot of work (except the drill mounted kind).

Building the stock out of 1/2" PVC and handle material the way you did is basically what I'd do, and fits well within the constraints I'd placed on the design initially. Interesting solution to making a spring work, I'd just relied on my own keeping the 'T' aligned before (which worked fine for me).

Hello, I'm a newb that wants to build this, but I have one dumb question:
Can I put a hopper on this instead of a RSCB?


Yes! If you have a Y, don't buy the 90* 1/2" PVC Elbow or the 1/2" PVC T. You also won't need to cut some of the 1/2" PVC parts (3/4" long 1/2" PVC, I think). You'll still need to make the barrel and blaster-barrel stub as I've shown, and the clip itself can be the same thing as on an RSCB (1/2" PVC w/endcap). Langley's post above shows the blaster with a hopper on it; I left that out originally since Y's aren't readily available.
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#21 MonkeyMeister

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Posted 11 December 2015 - 12:21 PM

Hello, I am relatively new to homemade, if I were to build this, what spring could I use instead of the latex tubing?


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#22 Langley

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Posted 11 December 2015 - 03:04 PM

Before you add a spring to this blaster you need to take into consideration that it wasn't designed for an internal spring.  At a minimum, you'll have to use additional fasteners on the plunger head and the bushing to bear the added strain, and you'll have to change the dimensions so there's enough space between the plunger head and the catch for the compressed length of the spring.  You're basically going to have to redesign the whole thing around whatever spring you pick. 
 
With all that said, you've got a few options.  The go-to spring for this kind of blaster is called a k26, and you can only order small quantities of them from McMaster Carr as far as I know.  If you get a pack of these, you'll be all set to build most of the other spring powered homemades on this site.  The k26 fits right over the cpvc and rests against the endcap used to make the plunger head, so it won't get fouled up by the screws.
 
You can also try and find springs at your local hardware store.  They're not guaranteed to stock anything in the right range of sizes for a nerf blaster, but it's probably worth a look.  The spring database has some info about some springs commonly found in chain hardware stores. 
 
Lastly, if you absolutely have to get something from a brick-and-mortar store you can try cutting the spring out of a pneumatic screen door closer like this one. This isn't recommended but I've played around with it a bit and it works.  You just have to cut the closer open with a hack saw while the plunger is retracted, and then the spring probably needs to be trimmed to a shorter length. 


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#23 Meaker VI

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Posted 14 December 2015 - 05:52 PM

Before you add a spring to this blaster you need to take into consideration that it wasn't designed for an internal spring.  At a minimum, you'll have to use additional fasteners on the plunger head and the bushing to bear the added strain, and you'll have to change the dimensions so there's enough space between the plunger head and the catch for the compressed length of the spring.  You're basically going to have to redesign the whole thing around whatever spring you pick.


Yeah, adding an internal spring would either turn it into a SNAP or make it an unwieldy length. An extension spring would work, and I'm sure I've seen one (I've used them!) that would work at Home Depot, but I don't remember the part name/number. Doing that would be dangerous though - fast moving metal spring mounted externally = certain doom.

The design purpose of the blaster was to make something you can buy all of the parts inexpensively from one well-stocked hardware/home improvement store. Secondly was to make it easy to build, hence the catch at the back instead of near the plunger like in a regular SNAP. Ordering a regular spring would be more expensive than buying a few feet of latex.

The jist of all that is this - build it like I show it first, unless you absolutely can't find latex tubing or bungee cord (after asking at the store, they probably carry it). Once you've built it, use the leftover parts, other guides here on the site, and some imagination to build something else (Like a SNAP).
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#24 TOTtomdora

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Posted 21 January 2016 - 04:35 PM

I apologise if this is considered a necro, but I'd like to ask for some help.

I made the blaster and used bungee (didn't have any at first, tried springs, which didn't work at all, and latex tubing is ridiculously expensive), but the trigger pull is incredibly heavy. As in, the corner piece would rather snap off than release the catch. Is this supposed to happen?

(Also, I should mention that the catch is a nail that's been cut down, I only had 1-1/2", and didn't want to buy an entire box of 1-1/4")


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#25 Meaker VI

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Posted 21 January 2016 - 06:34 PM

I apologise if this is considered a necro, but I'd like to ask for some help.

I made the blaster and used bungee (didn't have any at first, tried springs, which didn't work at all, and latex tubing is ridiculously expensive), but the trigger pull is incredibly heavy. As in, the corner piece would rather snap off than release the catch. Is this supposed to happen?

(Also, I should mention that the catch is a nail that's been cut down, I only had 1-1/2", and didn't want to buy an entire box of 1-1/4")

 

Your pull sounds too heavy, try to loosen the bungee or find a longer or less-strong one.


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