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ESLT Blaster - Non-3D Printed Version

Extension Spring/Latex Tubing Blaster

Bullpups are the new hottest thing in the NIC these days so I decided to build one that's better than the rest. Ice9 gave me the idea a while back to use latex tubing to power a blaster. I've been changing the design constantly over the last six months or so and probably will keep doing so. I'll try to update new files and pieces in this write-up as the blaster improves. I'd like to thank Kane for access to his printer and for letting me adapt his snapoid-level catch to something that can be easily made, and works flawlessly.  You'll see different pictures of different revisions, so make sure you read the descriptions for the pictures. This blaster was designed around having a 3d printer, so a lot of things will force you to be creative and come up with a different way of building it.

Many items are featured on these blasters have been changed, and will continue to change. Use this thread for reference. The original thread including some recent updates is located here.

Non-3D Printed Version*

*Disclaimer - I haven't actually built a completely non-3D printed version of this blaster so a lot of the pictures won't make sense. Read the descriptions and please ask if something is unclear. A lot of the directions will be up to you to figure out. This is more of a guideline and not a step-by-step writeup. I'd also recommend also reading the 3D printed version of this.

Parts List
Hardware store - Schedule 40 Solid Core Pipe-1 1/2"x10'
Hardware store - Schedule 40 Solid Core Pipe-1 1/4"x10'
Hardware store - Schedule 40 Solid Core Pipe-1"x10'
Hardware store - SDR 26 PVC Pipe-1 1/2"x10'(thinwall)
Hardware store - CPVC Pipe- 1/2"x10'
4880K44- Standard-Wall White PVC Pipe Fitting 1-1/4 Pipe Size, Tee
Menards or Sprinkler Warehouse - 3/4" PVC WYE X SWING
Hardware store - 3/4" PVC Plug (must be round)
6338K412 - SAE 841 Bronze Flanged-Sleeve Bearing for 1/4" Shaft Diameter, 3/8" OD, 3/8" Length
8619K461 - Rigid HDPE Polyethylene 1/4" Thick, 12" X 12"
8619K431 - Rigid HDPE Polyethylene 3/8" Thick, 12" X 12"
8619K471 - Rigid HDPE Polyethylene 1/2" Thick, 12" X 12"
8619K491 - Rigid HDPE Polyethylene 1" Thick, 12" X 12"
5233K66 - Masterkleer PVC Tubing 1/2" ID, 5/8" OD, 1/16" Wall Thickness x 1'
8974K31 - Multipurpose Aluminum (Alloy 6061) 1/4" Diameter X 6' Length
9686T74 - Nylon Eyebolt with Nut-Not for Lifting, 1/4"-20 Thread, 1/2" Eye ID, 1" Shank, 7/8" L Thread, Packs of 25
94812A116 - Nylon 6/6 Hex Nut, Off-White, 1/4"-20 Thread Size, 7/16" W, 15/64" H, Packs of 100
9691K56 - U-Cup Seal 1/4" Height, 7/8" ID, 1-3/8" OD x 5
8572K55 - White Delrin ® Acetal Resin Rod 1/2" Diameter x 5'
90272A144 - Zinc-Pltd STL Pan Head Phillips Machine Screw 6-32 Thread, 1/4" Length
90272A148 - Zinc-Pltd STL Pan Head Phillips Machine Screw 6-32 Thread, 1/2" Length
90272A157 - Zinc-Pltd STL Pan Head Phillips Machine Screw 6-32 Thread, 1-1/2" Length
90480A007 - Zinc-Plated Steel Machine Screw Hex Nut 6-32 Thread Size, 5/16" Width, 7/64" Height x 100
4880K977 - Standard-Wall White PVC Pipe Fitting 1-1/2 X 1 X 1-1/2 Pipe Size, Reducing Tee
9657K82 - 1 Pack Steel Compression Spring, Music Wire, 10" Length, 1/4" Od, .022" Wire Dia

5234K33- Super Soft Latex Rubber Tubing 1/4" ID, 3/8" OD, 1/16" Wall, Semi-Clear Amber x 1'
9432K125 - Precision Music Wire Extension Spring, 5.0" L, .750" OD, .075" Wire Diameter, Zinc-Plated Steel, Packs of 3

Essential Tools
-Drill press and/or power drill
-Dremel w/ cutting wheel or Mill
-7/64”, #27, 1/4", 3/8"” drill bits and ½”, 5/8" spade bits
-#6-32 tapping bit
-1/4-20 tap and die set
-Scissors and/or file
-Countersink (Any size, really)
-Electrical tape
-Super Glue
-Computer, printer, and full sheet label paper (templates)
-Safety Glasses
-Leet skillz

Very helpful, not critical:
-Custom tooling plates

Non-3D Printed Version Templates

If you're printing templates, make sure you set it to print true. Do no scale it to any extent, or you'll end up wasting a bunch of plastic.

Fabrication & Main Assembly
First, print your templates on a piece of label paper. Cut each piece out and stick it to the appropriate materials. The thickness for each part is on the templates. There are a couple options for your handle. You can make it pretty much any thickness you want, I usually go for 1". If you don't want to buy expensive 1" material, you can do a sandwich of three 3/8" or 1/4" pieces, or a combination of both. Before I started making exclusively 3D printed handles, I used two 3/8" printed pieces on the outside, so I could have a nice round edge. If you're reading this, I assume you don't have the capability of printing stuff. I usually used to grind the shit out of whatever material on the belt sander to make my handles. A router would also work. This part is entirely up to you. Do whatever you want to do for your handle.

There is one piece on the templates that is supposed to be curved on one edge. This is your catch plate. It might not even be critical to have this piece rounded. Once again, you'll have to figure this out on your own, but there are options. Another piece not listed on the templates is a 2 3/8" long piece of 1/2" rod or bar. You'll need to make a 1/4" hole that is centered which will act as your plunger rod adapter for the eye bolt.

*The plunger rod adapter is not to scale in this picture. It should be 2 3/8" long.

Make sure you drill holes in the top of the main handle, and the front piece which will attach your handle clamp to the handle. Having a small vice is really helpful for this. Tap the hole when you're done.

After you have your pieces cut out, you can assemble your handle. This should be pretty self-explanatory so I'm just going to let you look at the picture.

Depending on what size you want your trigger and catch to be, you might need spacers to keep them centered. You can either cut these out of sheet or order specific spacers off McMaster. The thicker the trigger, the better it generally feels in my opinion, so if you have a 1" handle, I'd go with a 1" trigger.

For the catch spring you have a few options. You can cut the front piece entirely out of a solid 1" piece and drill a hole for the spring. You can also do the layering method and have the middle piece have a notch cut out for the catch spring.

Next you'll need to make your handle clamp. Cut a piece of 1.5" PVC lengthwise in a "C" shape. Test to see how well it attaches to 1 1/4". You'll probably want this piece at least 9" long. Clean it up with scissors or on a belt sander. Line up your hole with the handle and drill four #27 sized holes where they meet up. Countersink them, insert screws, and attach it to your handle.

Cut two notches in the front of it to allow space for the wye spacer. 

Now it's time to cut your front tube. All the pictures up to this point are of a blaster with a different method to attach the pump grip, using two slots instead of one. With two slots, it becomes very difficult to make them long, which they need to be for this blaster. You also won't be able to use an extension spring with this method so I'm going to show you the way I'm doing it now.

If you don't have a mill, your best option is probably using a dremel. 

When you're cutting the smaller slot in the back, it's a good idea to attach your handle clamp to the front tube so you can cut both slots at once. The front tube should go 4 3/8" through the front of the handle clamp. The back slot should line up perfectly with end of the front piece on your handle. You'll also need to drill a 1/2" diameter hole between the end of the tube and slot. Leave at least 3/8" on the end of the front tube to allow for barrel spacer to fit.

Secure your handle clamp to your front tube with two 1/4" screws on each side.

Plunger Rod & Tube
Cut a piece of 1/4" aluminum rod, 12 1/4" long. Use the die to cut threads 1.5" long on each side of the rod. This can be tricky and it may look ugly when you're done threading. If you're holding it in the vise when threading (most likely have to), it'll leave vise marks in the aluminum. You'll have to sand or file these down so the rod can slide through the bushing. 

Using a 1/4" tap, tap all three of the plunger head discs. Cut out a disc of rubber for your plunger head cushion, and poke a hole in the middle to pass through the rod. Assemble the plunger head as shown in the picture. You'll want the smallest disc in the middle, the next biggest in the front, and the largest in the back. You can either use a u-cup or skirt without changing pieces. Make sure you have a nut in front and back.

Put your plunger head aside, and start building your plunger tube. Cut a piece of 1 1/4" PVC to 8.75" long. Now take your swing x wye, wrap it in e-tape, and push it into your plunger tube. Try to get this seal as good as possible. Now you'll need to get your 1" round plug, or anything that will plug in a 3/4" coupler. You'll need to drill a centered hole in the plug, 3/8" diameter. It's very important this is centered so good luck. Before I printed them, I did this on the lathe.

Slip in your bushing and make sure everything seals the best you can get it. None of these blasters seal perfectly but it doesn't seem to make a difference in the performance.

Now lube up your plunger tube, insert your plunger rod, and put on the catch piece, plunger rod adapter, and eye bolt as shown in the picture. You'll also want a nut behind the catch piece.

*The plunger rod adapter is not to scale and will be much longer than in this picture.

Final Assembly & Miscellaneous
Now that everything is mostly assembled, take your plunger tube and rod assembly and join it with the rest of the blaster. At this point you'll want to decide if you want to use an extension spring or latex tubing. If you're doing an extension spring, you'll have to attach it to the eye bolt before you put the plunger rod inside the front tube. It's pretty much impossible to add the spring when it's mostly assembled.

Secure the plunger tube to the handle clamp with two 1/2" long screws, one of each side. It should go through the swing x wye as well. 

Now it's time to make your blaster prime. On the templates sheet you'll see a piece with four holes that says "tube" for the thickness of the piece. This is your tube spacer which will connect the 1" PVC and the pump grip. You can probably use 1.5" PVC for your tube spacer. I obviously print mine, but I've done similar things using 1.5" as a tube spacer before and it works quite well. 

After you've cut out your tube spacer, get your reducing tee which you'll be using as your pump grip, and stuff 1.5" thinwall in each side. Place your tube spacer on the top of your pump grip with the front edge of the tube spacer being flush with the end of the pump grip. Tape or temporarily glue it on top and use it as a guide to drill holes that line up with the spacer. 

Next you'll need to cut a piece of 1" PVC, 7 3/4" long. Do the same thing with the tube spacer on the piece of 1" except you'll want to use a 7/64" bit, and tap the hole. The screws will anchor into here. Cut a slot on the bottom of the piece of 1" to allow enough space for the catch piece.

Now, insert your latex tubing if you aren't using an extension spring, followed by inserting the 1" piece of PVC. Line up the tube spacer, 1" PVC, and pump grip. Secure them with four 1/2" screws which should fit perfectly without going too far in the piece of 1" PVC.

Almost done. Secure your rear and front barrel spacers with 1/4" screws

Insert barrel, pvc wye, and vinyl tubing (fits in PVC stub)

To complete you blaster, you'll need to cut a 2" long piece of 1/2" rod (delrin or nylon). This will act as your "spring rest". Either the latex or extension spring will rest on this. Drill a hole towards the top of the 1/2" and insert a screw to prevent it from falling out.

Tensioning the latex can be difficult. You'll want to tie a knot over the 1/2" rod while making sure you have a considerable amount of pre-tension. You'll have to mess with this a bit until you get the amount of tension you desire.

ESLT Firing Demo