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I will show you how to build a net gun out of materials available at any big box home improvement store. This net gun is capable of firing a 90 square foot net 15 to 25 feet using 80-100 psi of compressed air. The net is reusable, assuming your prey doesn't destroy or run off with it. The launcher section is modular and can be removed in case you want to use a different design or add attachments. Thread on some 1" PVC pipe and you have a Christmas Cannon, or check step 11 for how to build a tennis ball launching attachment.
The net gun is similar to many pneumatic launchers, but instead of launching a single projectile, it launches four tractors that pull the net through the air. The tractors are based on the fact that the neck of a standard soda bottle fits very well over the outside of 1/2" PVC pipe. The cost to build this will range from approximately $40-$75.
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Signing UpStep 1Materials
Before you begin be aware that this project uses PVC pipe in an application it is explicitly not intended for. PVC is meant for water, not pressurized air or other gases. The problem is not the pressure, this project uses pressures less than half the working pressure of any PVC component, but the failure mode when pressurized by gas. If the PVC is compromised, by dropping, impact, or other means, it shatters into sharp pieces that are ejected by the pressurized gas. An excellent discussion and demonstration here, make sure to watch the video through to the end.
Nearly all of these items can be picked up at your local home improvement retailer. It is probably worth buying a full 10' length of 1/2" pipe, for all the other sizes see if you can buy shorter lengths or scrap. Alternatively, get some friends together, share the costs of the full length pipes, and build a lot of net guns. The tire valves are available at auto parts stores. The net is addressed in detail in the next step.
SUPPLIES
All PVC fittings are slip fit unless otherwise noted
All PVC pipe and fittings must be SCH-40 (SCHedule 40) unless otherwise noted
All PVC pipe should have a PSI rating of 200 or greater, absolutely no cell core ABS DWV pipe
- Pressure chamber parts Fig 1
1 1" elbow
1 2" to 1" reducer bushing
1 2" cap
1 2" coupler
1 foot of 1" pipe
minimum 9" length of 2" pipe
**1 valve stem, prefer a .453" as it corresponds to the readily available 7/16" drill bit
optional 1 pressure gauge
**There are two standard size automotive valve stems, one for a rim hole sized .453" the other .625". These two sizes correspond to fractional drill bit sizes of 29/64" and 5/8" respectively, the much more common 7/16" bit can be substituted in place of the less common 29/64". Additionally, most common drill indexes stop at 7/16" or 1/2" and do not contain the larger 5/8" bit.
- Trigger valve parts Fig 2
1 Blow gun similar to this
1 1/4" NPT hex nipple, like this
- Bending jig
Wood scrap for base, a 16" length of 2x4 should work fine
- Launcher section Fig 3
1 1/2" cross
2 1/2" tee
4 1/2" street elbows
4 1-1/2" pieces of 1/2" pipe (coupler joiners)
1 1-1/2" pipe 9" long
1 1-1/2" coupler
**1 1-1/2" to 1/2" reducing bushings
** 1 1" MPT to 1/2" slip
1 nickel
** these transitions usually can't be made with one adapter, just make sure the starting and ending dimensions are correct.
- Net
OR a substitute net computed using the net math spreadsheet and instructions in step 2
Nylon mason's twine (#15 or smaller), kite string, or some other thin durable rope
4 per net 16-20oz carbonated soda bottles
4 per net zip ties > 4" long
Hot glue/silicone/wax to pour in bottles to add weight
Optional additional items needed for high performance net tractors
4 per net 3/4" couplers
4 per net 3/4" caps
4 per net 8" lengths of SDR-21(Class 200) 3/4" thinwall PVC note: regular 3/4" SCH40 will NOT work!
4 per net 12" lengths of non-adhesive 1" ID foam pipe insulation. Pipe insulation is generally sold in 6' lengths.
- Consumables
PVC safe pipe joint compound (pipe dope) such as this
Teflon tape
Sand, at least two cups worth (for bending the launcher arms)
2 1/2" pvc caps (for bending launcher arms, not part of gun)
Epoxy for modifying sprinkler valve
Thread locker (Loctite)
- Tools & Safety
Heat gun, propane torch, or candle for bending PVC
Drill
3/16" and 7/16" (or 5/8" see the **note in the pressure chamber section) drill bits
Tape measure
Utility knife
Dremel tool, or similar, with a sanding drum
Wrench for 1/4" npt hex nipple
Large adjustable wrench or channel-lock pliers, for tightening the trigger valve
A compressor or pump capable of attaching to a Schrader tire valve and attaining at least 80 psi
Safety glasses
Leather gloves
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(my question mark is finnicky)
I mean, most tanks can be adjusted to have a low output.
Please link to the "just as cheap" pressure rated ABS. You are probably thinking of DWV (drain waste vent) cell-core ABS that is explicitly is labeled "not for pressure." In that case you are just substituting a different non-approved pipe for PVC.
I think you also misunderstand the "how people get hurt." The lowest pressure rating in this project is the 2" pressure chamber at 280psi. The problem isn't PVC pressure rating, though it would be for DWV ABS. PVC splinters when broken, if it is pressurized with gas, which stores kinetic energy like a spring, those splinters go flying, ouch. PVC is approved for fluids because a hydraulic failure will not end up with with bits flying everywhere. This is why pneumatic cylinders like fire extinguishers and SCUBA tanks are tested hydraulically by "hydro-testing." Again, it is hard to beat this video/discussion http://www.crazybuilders.com/item.php?id=000010&type=project_section&title=blast_box I link to in the first step.
tu eres muy muy simpatico.
Correct sch40 will not fit, just like it says in Step 8.
Do you need a 1/4" ball valve
No, you do not need a 1/4" ball valve.
Thx
http://www.homedepot.com/h_d1/N-5yc1v/R-100098062/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053