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ESLT Blaster - 3D-Printed

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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.

3D Printed Version

3D Printing Files
STL Format (3D Printed Parts)

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'
Menards or Sprinkler Warehouse - 3/4" PVC WYE X SWING
6338K412 - SAE 841 Bronze Flanged-Sleeve Bearing for 1/4" Shaft Diameter, 3/8" OD, 3/8" Length
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
2614T52 - Extreme-Temperature Silicone Rubber Plain Back, 3/16" Thick, 2" Width x 1'
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
90272A155 - Zinc-Pltd STL Pan Head Phillips Machine Screw 6-32 Thread, 1-1/4" 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
-3D Printer w/ no less than 7x7x2" print area
-Scrollsaw or Hacksaw
-Drill press and/or power drill
-Dremel w/ cutting wheel or Mill
-7/64”, #27, 1/4", 3/8"” drill bits and ½” spade bit
-#6-32 tapping bit
-1/4-20 tap and die set
-Scissors and/or file
-Countersink (Any size, really)
-Electrical tape
-Super Glue
-Safety Glasses
-Leet skillz

Very helpful, not critical:
-Custom tooling plates

Fabrication & Main Assembly
First, print out all of your pieces. I usually do the main handle and front assembly pieces separate, which ends up being most of the printing time. The rest of the pieces I can do in two separate prints. It should be a total of 14 pieces if you're printing a stock. They're all fairly easy pieces to print with the exception of the handle. The ideal setup would be having two extruders, one doing the actual handle, the other printing support material that doesn't stick to ABS. Since I don't have the capability, the areas with support material come out pretty ugly but are still definitely usable. If the surface is rough, just add some tape to the outside to make it more comfy. 

Make sure you drill out any holes that print undersized, and tap all holes that are 7/64".

Handle assembly is fairly self-explanatory.

Cut a small piece of 1/4" aluminum rod for your catch stick and insert the 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. 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. Insert your bushing holder into the other side of the swing x wye.

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.

*Your plunger rod adapter will obviously be printed.

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. Get 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.

3D Printed Stock
The flat back piece does not necessarily have to be printed, which is why it's a separate piece. I usually cut mine out of 3/8" sheet. For the foam back piece (8865K53), I used a belt sander to shape the back however I wanted. Works really well and only takes a couple minutes. Make sure you drill some vent holes to allow air to escape behind the plunger rod.

ESLT Firing Demo