As surprising as it is, there really is no where on the internet where I found any decent instructions on how to make a grappling hook gun. Figuring it would not be that hard to make, I decided to design and make one myself. After running into many problems, obstacles, and a few prototypes, I think I finally have a really solid version that definitely will impress all who use/see/build it. Naturally there are sure to be plenty of upgrades and other ways to accomplish what I did but I will share the parts and methods I used to make this particular launcher.
Although I call it a grappling hook launcher, it is basically a souped up version of any pneumatic gun. I took the best aspects of many different spud guns to make one of the best possible systems doing my best to avert creating any weak spots and not using any dangerous PVC (which shatters when over pressured and does not work well in the cold). This system is designed to be robust and efficient in every aspect of its construction. It is not hard to build and the most trouble anyone would have is gathering all the materials needed.
I tried my best to used parts locally avaliable (Home Depot, Lowes, etc) but a few i needed to order online. Feel free to ask me any questions you may have.
For everyones information, if you are really that concerned about why I didn't film myself climbing the rope, you are missing the purpose of the video, to show you how it works. The hook and rope combined for my gun weight 2lbs 2.1oz for anyone concerned that this device isnt practical. Also, I launched the hook at 150 psi and you could go much higher to achieve greater heights.
A little background on myself; I am current a Mechanical Engineering Student at the Massachusetts Institute of Technology (MIT) and have been building things for 14 years. My personal blog has most of my creations (some of them made by following Instructables). Enjoy.
Step 1: Parts and Materials
Parts Needed for Launcher Assembly
-Dry Chemical Fire Extinguisher
-N-Strike Raider Rapid Fire CS 35 Nerf Gun
-Black Spray Paint
-Air Tool 3/8" Hose
-20 oz CO2 Canister
-Paintball Coil Hose
-1.5 feet 3/4" Copper pipe
-8 inch tie downs
-(3) 6" Hose Clamps
-(4) Adjustable 5/8" Hose Clamps
-Pressure Gauge (mine had 1/8" threads on it)
-J-B Cold Weld
-3/4" garden hose to NPT thread adapter
-3/4" to 3/8" Reducer
-3/8" Close Nipple
-3/8" to 1/4" Reducer
-(4) 1/4" Close Nipple
-1/4" Check Valve
-175 psi Safety Valve
-(4) 90 Degree Elbows (male x female)
-(2) 1/4"x1/8" Reducing Bushing
-(4) 1/4" thread x3/8" barb Hose Barbs
14mm, 15mm, 16mm, 18mm
2 Adjustable wrenches
Copper Pipe Cutter (hack saw would be fine too)
Phillips and Flat head Screwdriver
Drill with set of bits
Dremel with bits (Sanding, a few grinding and the cutoff wheel)
Exacto Knife to cut hose
Propane Torch (Soldering copper pipes)
Some other basic tools that I'm sure you have
Step 2: Plans
So the concept behind this is simple, create a safe, strong and powerful launcher. Originally (as seen in the photo) I built the device out of SCH-80 PVC but I always have the thought of it exploding in little shrapnel too scary and ABS (which just splinters) was too hard to find. Also, PVC doesn't fair very well in the cold. Which also leads to the air source, CO2 (which all the paintballers know can get very cold). So instead in the second version, I made everything I could stronger (a lot of metal). You could get away with building this out of PVC but I didn't want to take the risk of anything exploding if i went up in the 150-200psi range (although my current saftey blow off valve is rated at 175 psi). (Message me personally if you want the plans for this gun as it is much easier to make if your looking for a quick project).
The final version begins with the CO2 coming from a paintball cylinder. It enters the gun through a check valve (to ensure it does not come out once it enters the tank) and then a Quick Exhaust Valve (QEV). The tank has a gauge on it to show pressure, a blow off safety valve which releases air over 175psi to ensure nothing bursts (although the system can probably handle up to 300psi). When the air is fully charged, a blow gun is used to change the direction of flow in the valve to allow the air in the tank to exit through the barrel and hence launching the projectile.
Step 3: Tank
First discharge the fire extinguisher wherever you want (fun part). Next, place the head of the extinguisher in a vice, clamp and twist bottle to the left to loosen it from the base (make sure you already discharged tank before this). Once the nozzle section is separated from the tank, all you need is the rubber gasket at the top of the stem. Carefully remove it with some needle nose pliers and save it, the rest of the assembly can be discarded as we will not need it for the rest of out project.
Next, take the gasket we previously removed and fit in on the NH side of the adapter (this side will have about 3 threads spaced farther apart) and slide it as high as you can get it. You are now ready to cold weld the tank and adapter together. Follow the directions of the cold weld and mix it together. Apply generously to the NH sides of the threads and insert into tank. Let tank dry upside down so cold weld goops up at the bottom (following gravity) of the seal which which we want. Place something heavy on top and leave for 24 hours to set.
Put the other parts on only after the weld has completely dried. I would keep a wrench on the 3/4" adapter so you dont put the torque on the weld itself when you put on the other fittings.
Step 4: CO2 Tank
Step 5: Barrel
Step 6: Blow Gun
Step 7: Connecting Everything on the Tank
Step 8: Connecting Entire System
Step 9: Nerf Gun Disassembly
Step 10: Securing Tank and Stem to Frame
Step 11: Attaching Blow Gun to Frame
Step 12: Inserting Barrel
Step 13: Grappling Hook
Step 14: Finish and Fire!
Step 15: Modifications
A simple device made out of PVC to use a tire valve (air pump) to connect to the system if you do not want to use CO2. I'm not sure how it will work with a check valve but it can be used in whatever air cannon project you want.
Another crude grappling hook. It probably does not support weight but it looks pretty cool. I used 1/2" copper with endcaps on each side. On one side, I drilled a hole and added the hooks. I coated the endcaps with camera film to make them smoother when it exits the barrel.
I added the CO2 tank to the gun by just strapping it down with the hose clamps and a towel underneath so I did not scratch the tank. There are probably many ways to affix the tank so keep the ideas coming.
I threw on a shoulder strap so one could carry it while keeping their hands free. I do not have any pictures of it but basically I just took one off of a laptop bag and then attached it using, yet again, more hose clamps (strong zip ties may work as well).