Grappling Hook Launcher

Picture of Grappling Hook Launcher

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.  

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-CCCP-20 days ago

This is just a QEV air gun.

stormneel1 year ago
wait what about the motor to ascending you faster so you don't have to climb
crreed (author)  stormneel1 year ago
I mean sure, you could use one, I personally have not designed one.
jorth crreed1 month ago

Strip down a winch for a truck or ATV combine with a few pulleys and a harness. ta-da then combine them

hbutler110 months ago
Do you need a check valve
DanTDM hbutler12 months ago

Not at all.

have u tried to use a big co2 tank the ones they use for paint balling

DanTDM3 months ago

I am The Diamond Minecart.

gorillazo7 months ago
If I were to follow your plans as closely as part availability would allow but used a larger barrel for tennis balls or t-shirts, do you think I'd have issue with distance or power?
kevin12345689 months ago
Can u build me one?
OS_Epsilon1 year ago
Are you willing to make one for me?
I tried to build this myself, but it won't work. I was wondering if you could build it for me. I know this defeats the purpose of this website, but I was wondering if you could do it for me.
crreed (author)  Chillawolff1 year ago
Send me a picture of what you built and I will try to help you out
de05092 years ago
I get that the sound is one aspect to be taken into account for grappling hook guns. it is mostly used to sneak, but I would really like to ask if it would be good to use water bottle rockets to carry both the hook and the rope? water bottle rockets have large momentum and should be able to carry a sturdy hook and stronger rope to huge distances, provided the rope supplied is long as well.
crreed (author)  de05092 years ago
Water bottle rockets would never have enough force to carry much of anything besides itself
de0509 crreed2 years ago
Sir, Id rather have half my monthly allowances in exchange for your badass gun but I beg to differ. law of conservation of momentum will cause the bottle to have equal (sum of) momentum with the water thrown backwards. And we know that water is heavy and they splash very hard backwards, thus momentum forward is powerful as well. Also, people had been shooting water balloons(water is heavy) using a water bottle rocket. I may be too young to create such a gun, but Im at the gathering-ideas phase.
crreed (author)  de05092 years ago
the water is minimal you put in the rocket. A gallon of wate ris about 8.33 lbs and the amount in a rocket is no where near that, more like a few ounces (as the bottles they launch are usually about 20oz and we can essentially consider the plastic massless). Although they have a high velocity, the water weight is minimal so the momentum is relatively low. However, the momentum is not particularly relevant, more of the force that is required to launch the projectile (the grappling hook). I havent done the math but the force is fairly high in order to launch a 3.5lbs object over 80 feet at a 70 degree (or greater angle). So you could probably calculate this all out and see, compared to a bottle rocket which is esentially massless once in flight, that the two forces are greatly different.
water bottle rockets are extremely louder than this...then you would be soaked with water...
iBite-kun2 years ago
I don't understand the purpose of having both a fire extinguisher and a CO2 tank. Why?
The fire extinguisher on it's own has no pressurized CO2 inside since you emptied it. Therefore you need to add some to it, hence the CO2 canister.
or you could fill it with compressed air or propane
does the fire extinguisher act as a secondary?
crreed (author)  iBite-kun2 years ago
The CO2 in the canister is at a very high pressure (greater than 1000psi). This is too much for the launcher so only about 200psi is put into the fire extinguisher at a time which then, in turn, is used to launch the grappling hook.
Ruminator2 years ago
Outstanding Ccreed, any idea what the muzzle energy is at 150psi?
xprosario2 years ago
Osama is alive, paparulo.
ro'keefe2 years ago
out of curiousity, what is the approx cost of this? im a college student (NCSU engineering!!) and dont have a ton of extra money, but this is just awesome and i really want to make one
crreed (author)  ro'keefe2 years ago
really depends on how thrifty you are and if you can find old parts. to build it completely new would be about $125-$175

twhitfield2 years ago
Anyone know if commercially available guns are unreasonably expensive? I'm thinking that this would make a good addition to a rescue team/firefighter tool set...not so much for climbing but with a "soft" grappling hook this could be used to get ropes to people stranded in flood water, etc. Just a thought for real world application....
A few kayakers I know, including myself, use the tennis ball throwers from pet stores for this. Accuracy is high, max distance is pretty consistent (and far), and the portability/reliability is unbeatable.

Just punch a hole through a tennis ball, put your line all the way through the ball, tie a stopper knot ( on the tail of the line and start practicing.

Remember to never stand in the bight (don't position yourself where you could get tangled in the line). Also, only use line appropriate for your purpose. If you want to throw a safety line, make sure the line is a safe one (weight-tested, in good condition, etc.), you are just throwing a service line so that the distant party can then pull the heavier rescue line across, make that clear to them before throwing, and make sure they understand.
tinker2342 years ago
wow hey ideas on how to make a small pistol verison small motor like mythbusters did
crreed (author)  tinker2342 years ago
Ive never seen it but it seems like it would be near impossible at this point to make one the size of a pistol unless you could find some very strong spring or other compressible device to create a spring force of some sort.
gnarf_ crreed2 years ago
pistol crossbow?
mythbusters super hero epide also just so you know it might be posable to make it smaller
PSI, volume, flow rate, and dumping rate all vs. weight of hook/projectile.

Maybe a couple CO2 carts and a good dump valve (thought the pierce hole of a CO2 cart might be the limiting factor.)
jthomas422 years ago
If you go to or any local fire extinguisher service place, they have whats called a hydro test adapter that has the proper threads to screw into the unit. On the adapter is a 1/4 F Npt thread to attach an air chuck used when testing these portable units. all you will need is the model of the unit of the fire extinguisher you are using and that is found on the sticker. most units have a 585 psi range they are tested and rated to.
tinmanm2 years ago
I see you are using tissue paper as a packing for the grappling hook. Try a small amount of water 1/4 cup just ennogh to fill the valve. This works great for my air cannon that shoots ping pong balls.
MIT! nice, dude. the 'ible is great!
jtepper2 years ago
This is pretty cool! I have also used the extinguisher tanks for a number of nerf related projects. I find that in most cases, the male CGA-580 nut can be used with an appropriately sized o-ring. I have also been able to simply drill out the port in the fitting to 5/8" and solder in 1/2" copper pipe.
timnterra2 years ago
I'm not familiar with the "QEV" in your design. Does it function on the back-pressure from the closed blow gun valve?
crreed (author)  timnterra2 years ago
When pressure is released from the blow gun, it forces the diaphragm in the valve to switch directions and allow the air to flow from the tank to the barrel. If you google "QEV Valve," there are many good articles describing how it works.
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