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.
Step 1: Materials
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.
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" MPT (Male Pipe Thread) to 1" slip street elbow
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 Orbit Model 57461 1" sprinkler valve
1 Blow gun similar to this
1 1/4" NPT hex nipple, like this
3 2"(ish) wood screws
Wood scrap for base, a 16" length of 2x4 should work fine
Launcher section Fig 3
4 13" lengths of 1/2" pipe
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
** these transitions usually can't be made with one adapter, just make sure the starting and ending dimensions are correct.
Memphis Net and Twine sku# 263 1lb minimum order is enough to make 7-8 nets
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.
PVC pipe cement and primer
PVC safe pipe joint compound (pipe dope) such as this
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
Saw, for cutting PVC pipe
Heat gun, propane torch, or candle for bending PVC
3/16" and 7/16" (or 5/8" see the **note in the pressure chamber section) drill bits
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
Step 2: Net Procurement And Math
I ordered my net from the Memphis Net & Twine Company. If you have your own favorite gill net vendor, you can probably order an identical item from them. I have NO financial ties to MN&T other than being a satisfied purchaser of their retail products.Here is the link to the product page on the MN&T website. Below is the exact info from my order information page, shipping is not included in the price. One pound of this net (minimum order) will make 7 or possibly 8, 9-1/2 foot square nets.Sku: 263Description: 3 in. sq. mesh, 12 ft. deepQty: 1lbPrice: $12.65If you would like to try an alternate net part number please read the Alternate Net Substitution section below.
Optional Net Math Section
You may have noticed that the catalog description lists the net as 12 feet deep while I have claimed it is 9-1/2 feet square, why the difference? Let us first deal with a hypothetical net that has 3" mesh and is 3 meshes deep. You might think 3 x 3 equals a 9 inch deep net, but that would be incorrect. Visualize the meshes as diamonds stacked point to point and NOT squares stacked like bricks. Reference Fig 1 and it becomes apparent that the depth of our hypothetical net is nearly 12-3/4 inches. To extend this example to MN&T sku# 263, 27 x 4.24 equals 114.48 inches, divide by 12 and we get 9.55 feet deep. So where does MN&T get the 12 foot depth figure? They are building a certain amount of droop, when used in a fishing application the diamonds will be longer vertically than they are wide.I have included a spreadsheet that will allow you to enter different figures to see what size net you will end up with, and how many nets you will get from a pound of that particular net. If the spreadsheet returns a zero for waste material, you may want to subtract one net from the total expected. The default numbers in the spreadsheet are for MN&T sku# 263 272.
Alternate Net Substitution
I will use MN&T catalog and part numbers in this example, but as long as you know the correct variables, any net vendor should work. Using the spreadsheet is important, if you don't own MS excel, consider downloading OpenOffice. An excellent free MS office replacement that will allow you to view and edit the Net Math spreadsheet. Please consult Fig 2 or have the spreadsheet open for this example. The top section of the spreadsheet contains a section called Mesh Count Estimator. This will help you calculate the mesh count you need to reach a desired net size. In this example I have entered 3.5 (3-1/2" mesh) in the Mesh size cell and 9.5 in the Desired depth cell. This should closely match the sku #263 net's overall size but with a 3-1/2" mesh instead of 3". The computed result, 23.03 appears in the mesh count cell. As fractional net meshes don't exist, just round to the closest integer, 23 in this case. Next, we will browse through the MN&T catalog for a 3-1/2" mesh net 23 meshes deep. Go to the multifilament net section of the MN&T web catalog, then select #208 twine size and browse through the 3-1/2" mesh part numbers to find a net closest to the 23 mesh count. Part number 272 fits our specification perfectly.Now enter all the information from the 272 page into the yellow cells on the Enter line of the net properties section of the spreadsheet. The Square depth cell tells us this net will be 9.43' square. This is also the spacing for the knots of your spreader string in step 9. The Knot cut point shows we need to count 46 knots and then cut between knot 46 and 47, the Cut length cell tells us knot 46 should fall at 161" on stretched netting. We can also assume that because the overall weight of the 272 net is slightly less than the 263 net, it should fit fine in the net holder. I would advise waiting to build the net holder part of the launcher section if you try any radically different mesh, twine, or overall net sizes. Once you have the net constructed, fold it up and make sure you have the correct size PVC holder.
Net Math.xls76 KB
Step 3: Build The Pressure Chamber
The pressure chamber is assembled first. It should be allowed to cure a full 24 hours before applying pressure. PVC pipe assembly is simple and is covered in other instructables as well as on youtube. A brief refresher on solvent welding PVC pipe. Use in a well ventilated area, make sure both pieces to be assembled are clean and free of burs, prime both pieces, put glue on both pieces, assemble with a twisting motion and hold for 15 seconds. For brevity's sake, solvent welding will be referred to as "gluing" PVC. The video shows how all the parts are assembled, make sure you have youtube annotation turned on.Pressure chamber supplies1 1" MPT (Male Pipe Thread) to 1" slip street elbow1 1" elbow1 2" to 1" reducer bushing1 2" cap1 2" coupler1 foot of 1" pipeMinimum 9" length of 2" pipe1 valve stemPVC primer and cementDrill and 7/16" bit (or 5/8" if you purchased the larger base valve stem)optional 1 pressure gaugeAssemblyDrill the correct size hole in the center of the 2" cap. 7/16" for the smaller (.453" base) valve stem, or 5/8" for the larger (.625" base) valve stem. Pull the valve stem through this hole.Cut a length of 2" pipe at least 9" long. Keep in mind that the longer it is the more time it will take to fill up if you are using a manual air pump.Glue the 2" to 1" reducing bushing into the 2" couplerGlue the 2" cap with tire valve to one end of 2" pipe. Glue the coupler to the other end.Glue a short piece of 1" pipe into the bushing, glue the 1" slip elbow onto that.Cut a piece of 1" pipe for the pistol grip, something between 3" and 6" should work. Glue the 1" MPT street elbow to one end of pistol grip pipe.Glue assembled pistol grip pipe into 1" slip elbow on pressure chamber. Ensure that the threaded fitting aligns with the axis of the pressure chamber and doesn't point off to the right or left.Optional: Drill a hole of slightly smaller diameter than the fitting of the air valve, locate the hole 3/4" into the pipe side (NOT the bushing side) of the 2" coupler. Use the air valve to cut threads into the hole, then thread back in using thread locker on the fitting.
Step 4: Build The Trigger Valve Assembly
Show All 9 Items
In this step we will modify an Orbit Model 57461 1" jar top sprinkler valve, making it a pneumatically actuated trigger valve. I found this particular model to have a number of advantages. It is the cheapest 1" valve I've found. The air valve is installed in the center of the cap allowing easy orientation of the trigger. Finally, the "jar top" construction makes it extremely easy to work on. Here is a link to a page devoted to modifying this exact valve, I left out the safety ball valve in this design. Here is a link to a visual explanation of how the sprinkler valve works.
Trigger Valve Supplies
1 Orbit Model 57461 1" sprinkler valve
1 Blow gun or similar
1 1/4" NPT pipe/hex nipple, like this
Dremel or drill
Remove solenoid and bleed screw, they will not be needed Fig 1. Save the solenoid for future diabolical inventions.
Disassemble valve by unscrewing the "jar" ring. Be careful, as under the top is a spring under tension.
Cut, grind, or drill out the center of the top, make sure to leave enough plastic to thread the 1/4" NPT fitting into Fig 2. Grind or cut down the lip of material around the center hole to the level of the ribs Figs 3 & 4. This will allow you to get the fitting deep and tight.
Use the 1/4" NPT fitting as a tap for cutting threads into the hole you just made, try to keep it as perpendicular as possible Fig 5.
Once you have the threads cut, put Teflon tape on one end of the fitting and thread that into the blow gun Fig 6. Apply some thread locker to the other end of the fitting and tighten the whole assembly into the valve top.
You are now ready to epoxy three places. A little dab in the bleed screw hole in the top, a little dab in the bleed hole at the valve outlet, and a good bit of epoxy around bottom and top of the brass fitting Figs 7 & 8. Try and leave the wrench flats of the fitting exposed and epoxy free in case you need to remove the blow gun at some point.
Let the epoxy dry and then reassemble valve. The lever side of the valve should be underneath the outlet of the valve. Make the securing ring is as tight as possible.
Step 5: Assemble And Test Valve and Pressure Chamber
Once your pressure chamber has cured for 24 hours, and your trigger valve has cured long enough for the epoxy to reach full strength, you are ready to assemble and test the trigger valve and pressure chamber.SuppliesAssembled pressure chamber from step 3Assembled trigger valve from step 4PVC pipe joint compound (pipe dope) such as thisSource of pressurized airWrench or channel lock pliersoptional 5 gallon bucket filled with waterAssemblyThread your trigger valve onto the pressure chamber for a test fit. The arrows on the side of the valve point in the direction of the airflow, they should be pointing away from the pressure chamber. The goal is to get the blow gun situated vertically in front of the pistol grip to act as a trigger. Use the channel lock pliers or adjustable wrench to get the trigger valve as tight as possible. If the sprinkler valve bottoms out before the blow gun trigger is vertical, you can file off small amounts of plastic from the end of the threaded street elbow until it fits perfect.Fill the chamber to 80 psi. Aim in a safe direction and briskly pull the trigger, you should get a loud POP and feel a bit of recoil. Here is a great troubleshooting guide if your valve does anything other than go bang.Once you have a successful test, remove the trigger valve. Apply the pipe joint compound to the street elbow threads and tighten down the valve once more. Optional: perform a leak test. Pressurize your chamber to 80 psi. Fill a 5 gallon bucket with water and dip the assembly, look for any bubbles. Tighten and add pipe joint compound to areas with leaks. If the PVC joints are leaking on the pressure chamber, you can apply a vacuum and suck super glue into the voids.
Step 6: Bend Launcher Arms
In this step we will build a bending jig, and use it to bend four launcher arms to a specific angle. Make sure annotations are turned on when viewing the video. Launcher arm supplies
4 13" lengths of 1/2" pipe2 1/2" PVC caps DO NOT PRIME OR GLUE THEMSand, at least two cups worthHeat gun, propane torch or candleWood scrap and 3 2" screws to make bending jigLeather glovesAssemblyChoose a launcher tube angle. A 17 or 19 degree angle will give you longer range but you may need the high performance tractors. A 21 or 23 degree angle will give you quicker opening shorter range netting, a safer bet if you are going to use soda bottle tractors. Choose and print out one of the PDF templates below. They should be printed in landscape mode on 8 1/2" by 11" paper at 100% scale.Build bending jig. My example bending jig is built on a scrap of 2x4 wood. Hold the template to the surface and put a screw in the pivot position Fig 1. Hold one of the arms against the pivot screw and sink screw #2 using the edge of the pipe as a guide Fig 2. Again, with the pipe held against the pivot screw, sink screw #3 using the pipe edge as a guide Fig 3.Cut four 13" lengths of 1/2" pipe, these are the launcher arms. Measure and mark, with permanent marker, 3" in from one end of each arm. This mark, the pivot mark, will indicate where to heat the pipe for bending, and indicate the point to line up with the pivot screw of the bending jig.Bend the launcher arms. Tap in place, but DO NOT GLUE, a 1/2" cap on end of the arm. Fill pipe with sand, and tamp to get as tightly packed as possible Fig 4. Fill the second 1/2" cap half full with sand and tap on the open end of the arm. The sand keeps the pipe from kinking. With both caps on the pipe the sand shouldn't slosh when shaken, if it does, add more sand. Put on leather gloves and heat arm as locally as possible on the pivot mark. Rotate the pipe rapidly for even heating and to prevent blistering the pipe. The arm is ready for bending when it will sag under its own weight held horizontally. Align pivot mark with pivot screw, the remaining short length should be captured by screw #2, immediately bend longer length of pipe over and lodge against screw #3. Allow to cool on the jig, if PVC is removed while it is still warm it will begin to straighten and lose the correct angle. Once PVC is room temp, remove from jig, remove both caps, and pour out the sand. The heating can also be accomplished with a candle, have a look at robert's instructable step #3. Both tk4717 and ome33 had good results with the candle technique.
Repeat for the remaining three arms.
17 degree.pdf(612x792) 201 KB
19 degree.pdf(612x792) 172 KB
21 degree.pdf(612x792) 210 KB
23 degree.pdf(612x792) 216 KB
Step 7: Build Launcher Assembly
In this step we will build the launcher assembly. When finished, the whole assembly is threaded into the outlet side of the trigger valve assembly. No pipe dope or Teflon tape is needed as this section of the gun isn't holding pressure, the air from the pressure chamber will only be present for an instant so small leaks aren't a problem. For that matter, just line up the PVC parts that need to be assembled and push together, don't bother twisting, as proper alignment is paramount for this section. It is helpful to use a good bit of glue as this gives you a few more seconds to tweak the alignment before it sets, just have some towels handy to wipe up the excess that is squeezed out.Launcher assembly supplies
4 bent launcher arms from step 61 1/2" cross2 1/2" tee4 1/2" street elbows4 1-1/2" pieces of 1/2" pipe the coupler joiners1 1-1/2" pipe 9" long 1 1-1/2" coupler** 1 1-1/2" to 1/2" reducing bushings** 1" MPT to 1/2" slipPVC primer and glueA nickelA drill and 3/16" bit** these transitions usually can't be made with one adapter, just make sure the starting and ending measurements are correct.AssemblyFig 1 is a view of all the components needed for this step.Assemble and glue the adapters needed to go from 1" MPT fitting to 1/2" slip. Glue this to the 1/2" cross, using one coupler joiner.Glue one 1/2" tee perpendicular to the axis of the cross with a coupler joiner. Repeat for the other side.Glue the 1-1/2" coupler to the 9" length of 1-1/2" pipe. Glue the bushings needed to go from 1 1/2" pipe to 1/2". Drill a 3/16" hole in the center of the nickel and force it into the 1/2" bushing that is at the base of the net holder. This nickel is an air flow restrictor, it allows a little bit of air in to the net holder to assist with net deployment. Pin this nickel in place by gluing in a coupler joiner. Glue net holder assembly to cross.At this point I would NOT glue the street elbows into the tees, or the launcher arms into the elbows. Line up the street elbows by sighting down the launcher arm as in Fig 2, Figs 3 and 4 show incorrect alignment. Once aligned, firmly tap the street elbows on the launcher arms and then tap those into the four tee outlets. This will allow you to adjust the angles, or replace the launcher arms, before final gluing.Align the arms such that the bottom two are parallel with the net holder tube. The top two arms should be twice the angle of your launcher arms. Example, if you used 19 degree launcher arms, the upper two arms should be at an angle of 38 degrees relative to the lower arms.Thread the launcher assembly onto the trigger valve/pressure chamber assembly from step 5, horizontal launcher arms down, angled arms up.
Step 8: Assemble Tractors
Tractors are what slip on to the launcher arms and are propelled with compressed air to pull the net outward. You can build two kinds of tractors. The simplest are just four empty soda bottles. They must be bottles that were used for a carbonated beverage as they were designed to withstand pressure. Other bottles, especially water bottles, are much flimsier and likely to burst. The bottles can be filled with a little bit of hot glue, silicon adhesive, or wax to give them a bit more momentum. The soda bottle tractors are free, nearly indestructible, but suffer slightly shorter range. The high performance tractors are more efficient, due to lower internal volume, so have greater range. They are a bit more fragile, SDR-21 (Class 200) PVC pipe may be hard to locate, and they take a little more time to fabricate.
4 per net 16 or 20oz carbonated soda bottles
Hot glue/silicone sealant/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" SCH-40 will NOT work!
4 per net 12" lengths of non-adhesive 1" ID foam pipe insulation
Dremel with sanding drum
When selecting soda bottles I would advise digging through a recycle bin with a launcher arm in hand. You want a bottle that slips over the launcher arm, and, ideally, will not slide off under its own weight. Make sure the bottles are identical volume, don't mix in a 16 oz bottle with three 20 oz.
For the soda bottle tractors, there is very little assembly. You may want to test your net gun with unweighted bottles, as you can always add weight later. Use a scale, or melt/pour identical pre-measured amounts into each bottle. I don't recommend adding more than 40 grams to each bottle.
For the high performance tractors, begin by cutting the necks off of the 4 soda bottles Fig 1. Use the Dremel tool to sand down the threads Fig 2 so the neck can be pushed into one end of a 3/4" coupler. Once it fits snugly, super glue in place Fig 3.
Take the 8" lengths of 3/4" SDR-21 (Class 200) and glue the soda neck couplers on one end and a 3/4" cap on the other Fig 4.
Cut four 12" lengths of pipe insulation. These will be slipped over the net tractors leaving 2-3 inches of cushion at the end . This will protect the tractor from shattering if it hits the ground. It will also minimize damage if the tractor accidentally hits something valuable, like a car, plasma TV, or a cranium. Wait until the tractors are tied to the net (next step) before putting on the insulation.
Step 9: Assemble Net
Show All 9 Items
A single net will be cut from the large net you ordered. We will build a net spreader, a string that runs the perimeter of the net and pulls it evenly into a square. The tractors are tied to each corner, through a loop in the spreader string, and a loop in the corner mesh of the net. This step involves a little knot work, I use the overhand loop, the bowline, and the double fisherman's bend. All of the dimensions in this step relate to MN&T sku# 263, if you use a different number you will have to change the following three dimensions. Substitute the Knot cut point value from the net math spreadsheet instead of knot 54.Substitute the Cut length value from the net math spreadsheet for the 162" value.Substitute the Square depth value from the net math spreadsheet as the overhand knot spacing for the net spreader string, instead of 9.55'.Net supplies
4 tractors from step 81lb Memphis Net and Twine sku# 263OR a substitute net computed using the net math spreadsheet in step 2At least 50' of nylon mason's twine (#15 or smaller), kite string, or some other thin durable rope. This will be the spreader stringUtility knife4 zip tiesAssemblyYou will receive a pound of net in a plastic bag. The net is pulled taught and wound into the bag like a rope. Find the free end and count off 54 knots and then cut between knots 54 and 55 Fig 1. The 54th knot should land at 162" Fig 2.Take your spreader string and measure 5' and tie an overhand loop. Tie three more overhand loops every 9 foot 6 inches. Leave another 5' of string after the fourth knot and cut. You should end up with 4 overhand loops evenly spaced with 5' of free string at either end Fig 3.Spread your net out in an area where it can lay flat and as square as possible. Tie an overhand loop in the corner of each corner mesh of the net.Weave the spreader string through the rim meshes of the net Fig 4. A spreader string overhand loop should line up with each net corner overhand loop Fig 5. The 5 foot 'tails' you left on the spreader string should meet in the middle of the remaining side. Measure a length of 9' 6" on this side and tie a double fisherman's bend in the middle Fig 6, cut off excess string.Cut four 2' lengths of string, these will be the tractor strings. Tie one end of the tractor string by making a bowline that passes through both the spreader loop and mesh loop Fig 7. Tie a second bowline at the other end of the tractor string, try and end up with 16" from bowline to bowline. Zip tie the free bowline to the bottle neck or the PVC tractor body Fig 8. You can try tying a knot here but I have yet to find one that holds well.If you built the high performance tractors, put the pipe insulation on now. Slide the insulation until it completely covers the tractor Fig 9. Make sure to leave 2-3" of foam at the cap end of each tractor to act as a shock absorber.
Step 10: Loading And Firing The Netgun
Now for the fun part. Please be safe in this step. If the launcher arms aren't glued, there is a chance they will fly off during firing, so make sure any spectators are behind you. Only load the net gun when there is NO pressure in the chamber. It is helpful to have an assistant when laying out and untangling the net.Firing and reloading supplies
Assembled netgunAssembled net Open area, preferably outsideCompressed air sourceLay net on ground in a square, pick a clean area, as getting leaves or other debris in the net will keep it from deploying correctly. Pick two tractors, hold them together, these are the tops. Walk the tops across the net so they are in between the other two tractors, these outside two are now the bottoms. Move the tractors together so they are in a row touching sides.
Starting at the base of the tractors, pull the net into a rope-like tube. Begin at the tip of this tube (farthest from the tractors), grab a 6-8" handful of net and fold back and forth in a zig zag fashion until you are up to the tractor strings. Do NOT keep folding in the same direction, rolling the net will keep it from deploying correctly.At the end of the zig zag fold you will end up with an 8 inch, or so, bundle of net. Smooth this bundle out, and insert into the net holder, it will fit snugly.Remember your top and bottom tractor order. Working left to right the first tractor slips on the bottom left launcher arm, second on the top left, third on the top right, and the fourth on the lower right.
Pressurize net gun to 80psi. You should have a at least 30 feet of downrange space free of anything that the net might get entangled in. Keep any spectators behind you in case an unglued launcher arm flies off.Aim net gun. Visualize yourself at the point of a skewed four sided pyramid Fig 1. The two lower launcher arms fire horizontally and outward, the upper pull up and out, your prey will be ensnared in the base of the pyramid. Pull the trigger. If everything goes well the net will be pulled into a square somewhere between 12' and 25' feet in front of you. Consult the troubleshooting tips (below) if net doesn't deploy as desired.
Once you are satisfied with the net deployment, glue your launcher arms in place. Make alignment marks with indelible marker or tape before disassembly, you will then have good alignment references when you glue it back together.If you decide to paint your net gun, do not paint the launcher arms. Even a thin layer of paint will cause the tractors to stick.
TroubleshootingNet deployed in a horizontal rectangle, not square. Add more up angle to the top launcher arms.Net deployed in a vertical rectangle, not square. Reduce the up angle of the top launcher arms.Net deployed like a big X, not a square. Caused by putting a tractor on the incorrect arm during the loading sequence. Make absolutely sure you keep the tractors in the correct order, put marks on them if it helps.Net never really opened up at all. Caused by debris in the net , wet net, or poor folding technique. May also be caused by low pressure due to air leaking out while waiting to fire.launcher arm flew off. Many possible causes.
Make sure the launcher arms are firmly tapped into the tees.Too much weight in soda bottle tractor(s) causing excessive back pressure. Try starting with empty bottles. Sticking tractor(s), make sure the tractors can move freely on the launcher arms. If one or more seem to be stuck, correct problem by replacing tractor or defective launcher arm.Too high pressure, start low (70-80psi) and then work up.
Step 11: Et cetera
Thanks for all the positive responses so far. I will post updates to the build and attachments here. I came up with the safety after negligently discharging a net while filling the pressure chamber. It is so easy to make, every responsible net gun owner should have one. I developed the tennis ball attachment while working on an older net gun design that had a 2" net holder, it is a lot of fun for the $3 it costs to make.
Mechanical Trigger Safety
A very simple mechanical safety that will prevent the net gun from firing in the event the trigger is unintentionally actuated. Supplies
Scrap 1/2" pvc pipeSmall rubber bandAssemblyCut a short length of 1/2" pipe, probably between 1/4" and 3/8", it will depend on the specifics of the blow gun. It needs to fit under the blow gun handle and be thick enough to prevent the handle from depressing the valve underneath. You made need to cut a wedge out of one side of the ring to allow it to slip under the handle.Loop rubber band around one end of ring, and through itself. Take the free loop of the rubber band and slide onto the body of the blow gun valve.To put ON SAFE, slide ring around brass valve underneath lever Fig 1. To take OFF SAFE, slide ring down and out of the way of valve and lever Fig 2.
Tennis Ball Launcher
The inside diameter of a 2" PVC coupler fits a tennis ball perfectly. If you own a ball chasing canine, this will forever associate the bang of compressed air with the joy of the chase.Supplies
1 1" slip to 1" MPT adapter1 2" coupler1 2" to 1" reducing bushing2" length of 1" PVC pipe (scrap from pressure chamber assembly)At least one tennis ballPVC primer and cementAssemblyFig 3 is a view of all the components needed for this attachment.Glue the bushing into the coupler.Glue the 1" pipe into the slip end of the of the 1" MPT adapter.Glue the exposed 1" pipe from the MPT adapter into the bushing. Let set for 24 hours.Unscrew and remove the net attachment, and thread on the tennis ball attachment. With tennis ball on the ground push the launcher attachment over the tennis ball until it is firmly seated Fig 4.Pressurize and fire. Repeat as necessary. If you have a slobbery dog Fig 5 you will appreciate not having to touch the drool covered ball.