The Mini Emergency Line Gun Project




About: I'm Mario Caicedo Langer, from Colombia, former Navy officer and BSc in Naval Sciences. Right now I'm Technical Director and Technology Lead Teacher at STEM - Engineering for Kids Azerbaijan. Also, I'm artis...

Emergencies. They never advice. They catch you unprepared. And sometimes in some emergencies, we think "It would be good if someone had a gun like Batman's".

This project is for helping people in rescues: a home-made line gun capable of launching a flotable projectile to a man having problems in the water (Right now, In Colombia we have an winter emergency with storms, floods and avalanches, so I think this could be an useful idea for helping rescuers in his job). It could be useful to pass a line from one side to another, too. Or for grab the nearest tree or structure.

How it works? Like the weapon of an action figure. You insert the projectile, the spring compress, and the back part of the projectile gets caught in the trigger. When you press the trigger, the back part is released and the projectile is launched.

NOTE: because the position of the camera (and my bad aim), it looks like a short distance. But the steel cable is 9 meters (30 ft) long, enough for catch a tree branch if you are dragged by a river. (The next week I will do the experiment with a longest cable)

Without the steel cable, the projectile can fly about 20 meters (66 ft).

And why a spring? It's "easy" to recharge and you can do it over and over and over again. Air power could work, but if you want to recharge it, try to find an air compressor in a disaster area or in the middle of the forest. Gunpowder is another option, but imagine you are dragged by a river (powder and water are a bad combination) or inside of a burning building (powder and fire are a good combination, but very inconvenient, too).

This instructable is not the whole idea, but a concept. It's just the begining. is the home of the smartest minds of the world, and it would be great if this become an open project. Somebody carry on making a better spring launcher, and then another one improves the line system, and a third one implement a more resistant cord, and so on. Who knows? maybe one day every one of us could have a grappling gun in his emergency kit. Watch out, Batman!

Step 1: Disclaimers, Cautions and (because We Never Pay Enough Attention to the Warnings), Materials and Tools

CAUTION: Because of the short time of the contest, this is a non tested prototype made of ordinary stuff. Instructables and M.C. Langer are not responsibles for injuries, death or property damage due to the bad, wrong or reckless use of this instructable. Make this project under your own risk. Don't use it in a real or simulated danger situation. Don't aim or shoot the gun against people or animals. Don't try to imitate movies, TV shows or comics actions like balancing your own weight, stop freefalls or fight criminals. Always use personal protection when you work with springs. In emergency situations, always call the competent authorities (911 in US and 123 in Colombia).


  • SUGRU (orange)
  • Hard spring (impeller)
  • Small spring (for the trigger)
  • 1 1/2" PVC Pipe (big enough for covering the hard spring)
  • PVC Cap
  • Garden hose pistol
  • Three 90° iron angles
  • Nuts and bolts
  • Empty yarn cone
  • Plastic bottle (It will be the head. I use one from a deodorant)
  • Aluminum cylinder (I use one from a discharged military flare)
  • 1/2" PVC pipe and cap (Note: it will be great if this is replaced with aluminum pipe, or another light metal)
  • Thin steel cable.

Cord: I use thin steel cable. Paracord could be useful. I know in US you can find a better and lighter cord.

Tools and others:
  • Dremel rotary tool
  • screwdrivers
  • pliers
  • paint
  • superglue
And remember the rules:

1. If you don't have it, replace it!
2. Use protective equipment (dust mask and goggles)
3. Beware of drilled and soldered hot surfaces
4. Work in a good ventilated area.
5. Always have junk in stock
6. Enjoy!

Step 2: The Trigger

The trigger is easy. Cut an iron angle and insert a screw with a plastic piece (for activating the gun with your finger). Then, insert the small spring, and fasten with a nut.

Step 3: The Launcher

Take the PVC cap and make a hole in the middle, big enough for the PVC (or aluminum) pipe of the projectile. The pipe must go loose across the hole. Then screw the trigger to the cap. It has to be mobile. Couple the big PVC pipe into the cap, introduce the big spring and fasten the spring base, the cap and the PVC pipe with screws. Fix the end of the small spring to the cap, so you can press the trigger and it will return.

Step 4: The Handle

Disarm the garden hose pistol. We will need the handle. Adapt the yarn cone. Then, use the iron angles and a metal strip to strip the handle to the launcher.

Step 5: The Projectile

Take the aluminum case and attach in the center of the bottom the 1/2" PVC cap. Drill another hole on the bottom, insert the steel cable and fasten it inside the case. Insert the other end of the cable into the PVC pipe, and drive te cable to the gun. If you want, just use a piece of cable in the projectile, and made a loop for attach another kind of rope or stuff to the projectile.

Fix the PVC pipe to the cap using screws. Make a small cut in the middle of the pipe. When you charge the gun, the trigger will enter into the cut, keeping the projectile ready to launch.

Adjust the plastic bottle into the aluminum case. Because the primary objective of this gun is for acuatic rescue, the projectile must be watertight. Use SUGRU for sealing the holes and spaces between case and bottle. Adjust and fix using screws. I painted orange the projectile because highlights.

Step 6: Sugru, Painting and Charging

If you want, paint the gun. I use SUGRU because I wanted a more ergonomic (and colorful) handle.

For charging the launcher, introduce the projectile into the launcher and... use ALL your force!

Halloween Props Challenge

Finalist in the
Halloween Props Challenge

Second Prize in the
Sugru Life Hacks Contest



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    87 Discussions


    2 years ago

    I needed this months ago. Doesn't anyone read minds any more?

    Good job, thanks for the share. Semper Fi

    1 reply

    4 years ago

    Can it rewind itself


    5 years ago

    You should make a shooting video


    8 years ago on Introduction

    I've used something similar for years. I zip-tied a spinning reel to the underside
    of a slingshot and put a small weight on the end of the line. For me, its primary function is shooting the line over trees and then pulling antenna wire back for HAM Radio use; Works like a champ. I always use the slingshots that have surgical tubing for the kinetic energy... While it's only good for 50-75 yards, it is consistently accurate. I use fifty pound mono-filament line.


    2 replies
    M.C. Langerrncbme

    Reply 8 years ago on Introduction

    I have fity pound nylon monofilament. But a very thin line has a problem: could cut easier the rescuer hands. I want to use the monofilamente for a speargun like the one in Batman Returns.


    6 years ago on Introduction

    Amazing! What a sleek, wonderful creation. It would be interesting to have an adaptable projectile with different heads that could click in, such as a grappling hook, buoy, foam-tipped, or one with a little compartment (for getting emergancy supplies to hard- to reach areas).

    1 reply

    8 years ago on Introduction

    heavy line would mean a bit less distance tho, of course.


    8 years ago on Introduction

    Just a thought: You can duct tape a fishing reel to the front of a slingshot (wrist-rocket type, not the "Big Y" tree branch type) and launch lines 100 yds.


    8 years ago on Introduction

    i gotta say M.C. Langer, this is a pretty sweet idea! probably will save a few lives dude!