Jenga Pistol

The game of Jenga was possibly designed to be a more contemplative and strategic game. But sliding those blocks out carefully without knocking over the stack is just entirely too fiddly a task to perform. I figured it would be much more fun to just be able to shoot the blocks out with some sort of pistol.

The pistol works by hurling a wooden captive bolt forward inside the pistol, powered by rubber bands. The bolt has a pin on the front, which protrudes out of the muzzle of the gun by about 2 cm at most. This is enough to transfer the momentum of the bolt to the Jenga block in front of the gun, not unlike how the game of croquet works.

I actually designed the pistol so that the rubber band pulls the bolt back again from its front most position after impact. The main reason for this is that if I need to make a shot where I shoot out the sole supporting member of the Jenga stack, that the bolt withdraws a little bit after impact to get out of the way of the Jenga stack coming down to fill the gap. With a bit of practice, this maneuver turns out pretty easy to pull off, without collapsing the stack.

Other than the rubber band and pulley, the bolt and trigger are the only moving parts of the gun. The bolt has this little keyhole-like cavity cut into it to hook the rubber band into. I was perhaps being exceedingly clever in doing it this way, but it's the only way that I could think of that would allow easy replacement of the rubber bands, and allow the rubber bands to pull the bolt forward, and then back a bit at the end of its stroke.

The trigger piece is two pieces of wood glued together. It has a hook for holding the ends of the rubber bands. This also serves to pull the trigger up against the bolt from the rubber band tension.

When the bolt is pulled back, it automatically hooks onto the trigger. I actually carved a very slight hook shaped incline into the corner of the bolt where the hook catches onto it, to make the gun less likely to trigger accidentally. Cocking the gun is a simple matter of pulling the block all the way back.

The other little tricky bit is the pulley. There's a little wooden block glued to the rails (facing the camera in the shot at left) to keep the rubber band from moving too far sideways on the roller. Without this block, the rubber bands were prone to get stuck between the roller and the piece of wood holding it.

I varnished all the moving parts, and put a few drops of oil on the pieces the bolt slides against to let the bolt move more freely. I originally designed the gun to use just one rubber band, but with two, it shoots harder, which is more fun. It's enough to get the bolt going to about 12 meters per second, and accelerate the impacted Jenga block to about 6 meters per second.

Building the Jenga pistol

One of the trickier bits of the Jenga pistol is the bolt. The bolt is made out of one piece of maple, including the pin that sticks out on the left. You can also see a hole that I plugged in the bolt. That hole was already in the piece of wood, and I was going to use it for the keyhole shaped rubber band holder, but then I decided to move that part further back, so I put a plug in the hole.

Before cutting the bolt block to its final length, or even cutting out the pin part, I cut the dados in the top and bottom. The block is really too small to safely use with a dado blade, so I cut the dado by making a series of cuts with a normal saw blade and a zero clearance insert. I have my other fingers reaching on top of the fence, so that if something snapped or the piece got thrown out of my fingers, my fingers still would not reach the saw blade.

After cutting the dados top and bottom, I cut out the pin. I made four cuts from the end, and then the cross cuts all with the band saw to leave a square pin in the middle, 4 cm long.

I rounded the pin with a file. a carving knife would work too, but the file is slightly easier.

The bolt is pulled forward by a rubber band that hooks into a keyhole shaped cavity on the bolt. The The rubber band goes around an idler roller near the front of the gun, and is hooked in the back onto the trigger.

The guide roller consists of a little plastic spacer, which turns on a shaft that is made of a nail. The nail is cut to the right length, an the front of it flattened to widen it so that it becomes stuck in the hole I drilled for it.

To make the keyhole shaped hole, I drilled a hole in the side of the block, and then a smaller hole from the bottom of the block. I used brad point drills for both of these to get fairly clean holes

Finally, to get the keyhole shape, I used a fine saw to cut out the side of the hole that comes from the bottom.

After that, I drilled a smaller hole deep into the main larger hole, and stuck a small wooden pin in it to hook the rubber bands onto.

The pistol grip of the gun has a slot cut into it from the top all the way to where the bottom guide rail for the bolt goes. I glued in a block of wood above that rail to close the rest of the gap. This piece also provided support for the screw holding the top rail.

The top rail has a dovetail on either end, which mates with the block that forms the muzzle and with the handle block. It's held down by a screw on either end. The screw at the tip has to be put in at an angle though. If it were put in straight down, it would protrude into the hole of the muzzle block that the bolt's pin goes through.

Finally, to make the pistol more comfortable to handle, I put a slight chamfer on all the outside edges, and then sanded the edges smooth a little bit.

I also smoothed the guiderails for the bolt with a cabinet scraper, to make the bolt slide more easily. After varnishing everything, I put a few drops of oil on them to make the bolt slide more easily.

Don't you think this is COOL ? NO MORE BORING JENGA ! HURRAY !