Tank

The Instructions page of this website teaches how you can remove the top, remove the bottom, extract the disc, make strips for tank treads, and make a big tube. If you're not sure how, click those links. Three cans ought to be enough if you measure everthing carefully. Otherwise, just use more cans, overshoot on the widths, and trim it later; as shown in the video.

If you intend to make many tanks in your life, it's helpful to make partial-cans ("can elevators") that you can use repeatedly to make correct-width cylinders and strips. Look at the bottom of the sleeve in these photos as an example.

Make the Turret. Trim excess material from the bottom of the can top with scissors.

After making the side cuts, carefully fold the flap over-and-back along the same fold-line until it comes off by itself near the rim of the turret-top. Round out the bottom edge of the turret opening.

Rounded corners lets the turret slide easily around the top of the tank body as the turret rotates in place. Otherwise, it may catch.

You may want to plant a flag in the top of the turret. If so, first pop a hole in the top with your pushpin where you want the flagstand to be. Then enlarge the hole to toothpick-size with the punch. Punch from the outside-to-inside direction.

Later you will jam your flagstand-toothpick though this hole. If desired, for stability, you can thread the toothpick-end through the side of a straw-segment concealed underneath the turret; this helps keeps the flag upright.

There is a better way to keep the flag locked in place and upright; you could substitute a toothpick clip/nut for the straw-segment.

Now you want to make the center hole in the can top. It's for receiving the toothpick that will serve as the central axis of the tank body.

[Eventually, the barrel straw will be pierced by the toothpick that connects/joins the turret to the body.]

Use a pushpin, and then the punch, to make a toothpick-sized hole in the top-center of the turret.

Make sure you punch this time from the inside-to-outside (i.e., interior to exterior) direction. If you get the direction wrong, you can't really shove the end of the axis-toothpick through the hole later.

Now tilt up the hatch.

Make the Long Tank Body Piece. Now we've gotten to the fun part. It takes two cylinders to make the tank-body. Basically, you'll form them into approximately square shapes ("profiles"), using the tank tool, and then insert one into the other cross-wise to make a kind of enclosed box.

Our first task is to wrap the shorter cylinder (66 mm high) around the tank tool so that it encloses its trapezoid-shaped cross-section.

Wrapping the trapezoid to create its profile can be tricky. The tank tool is dimensioned to fit loosely inside the cylinder; otherwise, it is too difficult to insert. Once you've got the tool in the cylinder and have molded the metal into shape, you can rid yourself of that extra room by folding part of the cylinder over itself underneath the rear of the tank body, thereby creating a small, flat flap.

Before you do this, make sure that the bends you've put into the cylinder make it fit snugly against the tank tool. The trick is this: pull the material taut against the tank tool; then press-in your crease as best as you can. That's pretty easy to do until you get to the final bend. Incidentally, the first (gentle) bend in the cylinder (the one at the leading front edge of the tank body) should be made while it's off the tank form.

The technique for getting a snug fit on the final bend is to use the flat part of your scissors. Use it to mark, with a 90-degree bend, the place where the can will fold over on itself. You'll fold the excess part of the cylinder back over itself at that mark near the tail end of the tank-body, rolling the material forward as you press in; then use the flat side of your scissors to press the flap against the tank tool so it locks in place; but not too sharply or it will crease the metal so it cracks open. See the video. The cylinder should now be wrapped snugly around the tank tool.

Incidentally, this is an important point: by "crease" and "fold," I don't mean what that usually means. I mean to put a very small curved bend into the metal, since an actual hard, sharp crease will cause the metal to crack and break along the fold line. The nature of metal is that it can take a limited amount of bending and still spring back to its original position, but if you bend it beyond that limited amount, it partially keeps the shape into which you've moved it. The amount of bend that it keeps depends on how far you stretched the metal past its bounceback point. So, you want to make your bend slightly more extreme than the one you're shooting for; this way, it will bounce back into the position you want. This sounds harder to do than it is.

Sometimes, you may not have perfectly measured the correct width of the cylinder, so you'll need to trim the excess. If the cylinder is wider than the tank-body, then trim it using the tank tool as a guide. Scissor off the cylinder where it overhangs the trapezoidal tank-body shape on each side.

When you're finished, the edge of the metal should line up nicely with the edge of the tank tool.

The better way to handle the excess material overhanging the tank form, however, is to fold the material over the edge and tape it into position on one side. To fold the flaps, you'll need to cut small wedges around the corners. This picture of the geometry of my light switch cover with foldable flaps should give you an idea of what I'm talking about:

If you're going the flap route, you'll want to start with the tallest cylinder possible, so that you'll have plenty of material to fold over and tape-up.

Opening the Well. Our next task is to put a large central hole in the top so that the barrel has room to swing in a circle. So we have to find the center. Align the center finder or one of your bottom discs in the center of the top of the tank-body. Just use your fingers as spacers. Verify, by feel, that the four "corners" of the center finder (North, South, East, and West) are an approximately equal distance from the edge.

Poke a hole in the top of the tank-body through the centered disc. Then poke other holes around the center hole to divide the top into compass quadrants or octants. These other holes will mark where to position your cuts in the next step.

Cut an X (the quadrant cuts) in the top with scissors or with the edge of a pushpin. The X is centered in the middle and extends to the marker holes. Make sure stop at the border of the main well of the tank-body. (You'll feel the edge of the well with tip of the bottom blade of your scissors when you're making the "X" cuts). Make another "X" cut at a 45 degree angle to the first one (the octant cuts), so that you have an 8-slice pie.

Clip off the inner ends of the pie segments about halfway out.

You just need to cut off enough of the pie wedge to provide an opening in the center. This opening will provide clearance for your fingers as you later fold the pie slices back in on themselves. These folded-in flaps will widen the well opening to provide clearance for the barrel to rotate. They will also help attach each profile to its sister.

Poke a hole in the bottom of the well (at its center, where the pushpin hole in the tank tool is located).

Slide the cylinder off the tank tool. The pie-segments will usually bend slightly into the center well as you do this, so lift them out of the way as necessary to get clearance.

Make the Short Tank Body Piece. Make the second part of the tank-body just like you did the first, with the cylinder wrapping around the tank tool in the perpendicular (90 degree) direction.

Since the top of the tank tool is now narrower than the bottom in the direction of the fold, it helps to slide the tank tool a bit to the side as needed when you make your top creases. This way, there's always hard plastic to crease against. Notice how I've shifted the tool to my left to put a better crease in the left side?

Assembling the Box. Slide the long tank-body cylinder through the short tank-body cylinder so that the corners line up on the top. Carefully fold the eight flaps back in on themselves, making sure that the corners of each body-piece stays in proper alignment with its sister at the top of the tank. They should be under a bit of tension. You'll maintain this tension by holding the corners of the tank with your other hand, once you've locked the other two corners in place.

Important note — after creasing the first pizza segment in, you'll be tempted to pull your finger straight out. Don't. It'll get caught by the neighboring pizza slices. Instead, carefully drop your finger to the bottom of the tank well and move it to the center before extracting it. As the video shows, by creases, I mean 180-degree folds of the two layers, together, back towards the wall.

Now line up the holes in the bottom of the two tank cylinders and poke it with the punch. This time, punch from the exterior to the interior, since that's the direction the toothpick will be inserted in the next step.

Install the Treads. Pass the tank tread through the slot in the bottom of the tank tool.

Tape the ends of the tread into a loop. Feed it back through the slot so that the taped part is concealed in the slot. Do the same on the other side.

To keep the second tread from sliding around towards the tank center, you'll want to clip a section of the bottom of the outer cylinder of the tank tool and then fold it in on itself and around the inner edges of the second tread. Do this on both sides of the tank tread where it enters the tank-body.

To be honest, the dimensions of a soda can aren't quite right for making treads easily, although it can be done easily enough. When I'm not feeling lazy, I'll lengthen the tread by attaching a connecting strip having the same width as the tread. I'll bind them together the same way as I re-circle the any other tread strip — by winding tape around the joint. So long as you rotate the extended section to the interior of the tank, no one will know the difference and the treads will look more "natural."

Make the Blast Shields. Take two of the can tops and remove the disc from each. Using a pushpin and the punch, make a toothpick-sized hole in the very center of the disc, each poked from the inside to outside direction.

Insert the toothpick through the discs, making sure that the edges of each disc lines up with its brother. Now put the two discs over the bottom part of the toothpick so that the toothpick locks in at an axial orientation.

If you are meticulous, you can superglue the disks to each other so they don't make the toothpick tilt off-axis.

Insert the other end of the toothpick through the hole in the bottom of the tank so the blast shield lies flush against the bottom of the tank body. [Pro tip — it's easier if you install the tank treads before you install the blast shield.]

You may want to add a straw segment or a toothpick clip to act as a nut to keep the toothpick from slipping. [Pro-tip: It's best to superglue this nut, and any top nut in the center of the turret, in place. The turret will tend to come loose otherwise.

One of the functions of the shield is to act as a counterweight to the barrel. If necessary for balance, tape pennies (a.k.a. "Non-Magnetic Kinetic-Energy-Absorbing Security Enhancers") to the underside of the shield.

Make the Barrel. The barrel is just a big tube. The Instructions page demonstrates how to make it. When you're tearing the strip off the can to make the barrel, you need to think about where to cut the cylinder edge. The cut position determines what colors and shapes will be displayed on the barrel.

Cut the strip to the appropriate length before you roll it up. A barrel that's too long just looks strange.

Attach the Straw to the Barrel. The straw is permanently affixed to the barrel like this:

Make the crossholes in the barrel by first piercing the side in one spot with a pushpin. Then push the pushpin forward so it pierces the opposite side, while maintaining its perpendicularity with the barrel. You may have to pinch the tube closed a bit to do this; try to make the tube a bit oval here, while not letting the tube collapse.

Enlarge that first hole with the punch. Then push through so the tip of the punch passes through the opposite hole. Again, don't let the tube collapse. Repeat this process with the straw segment.

To join the straw to the barrel, first put your toothpick through a crosshole in the barrel. Load the straw in the barrel so all the crossholes are aligned. Shove the toothpick through all the crossholes. This will take a bit of force, even though you enlarged the toothpick with the punch. Finding all the crossholes with a toothpick tip that you can't see will take a bit of "feel." Now clip the toothpick off using nail clippers, or just snap it off.

[Pro tip: very flexible or very stiff straws work badly, but McDonald's straws have a nice blend of rigidity and "grab"]. For an extra sturdy connection, you could have made two crossholes along the barrel about a quarter-inch apart. That should keep the straw segment from moving in the barrel as you manipulate the barrel during play.

This is even easier with a strip of elastic fabric. Just pierce the tube perpendicularly, as described above, but with the elastic strip in the middle substituted for the straw segment. Later, you'll run the central-axis toothpick through the other end of the elastic strip. The elastic only needs to stick out a few millimeters from the end of the tube.

Another method is to fold a segment of coffee straw into thirds with two bends, so that a loop of plastic is made with the crossed ends. Place the segment in the end of the barrel and pierce the two ends of the folded loop with a toothpick segment and the central shaft. You can't see it through the metal, but the straw encircles both toothpicks.

Attach the Straw to the Central Shaft. Let's first prepare the straw to receive the toothpick. Make two crossholes in the end of the straw, as you did before. Check that the holes will align the barrel so that its seam faces downard, out of view. The distance isn't a key factor — just make the barrel the extend out the turret as far as you like.

We'll need to expand these holes into two parallel slots that will allow the straw to move freely as the barrel is tilted up and down. Don't make these slots too wide. The plastic plastic needs to grip the toothpick and keep the barrel in a particular position, without weight of the barrel lifting it up the shaft. On the other hand, it needs to give the straw freedom of motion around the shaft.

I'll be honest. There's a bit of an art to guaging how best to make the slots. Grip trades off with mobility. Finding the right balance between these two goals takes practice. You'll have to test the barrel's motion for good function, and you might not get the dimensions right on the first or second try.

The "right" length for the slot will be a function of its geometry. Imagine the barrel in its fully flat position and then its fully angled position. Picture how much forward through the straw that the toothpick needs to travel in order to move from one configuration to the other. If you find that, during use, your turret tries to slide back, then your slot is either too short or is in the wrong position. Lengthen your slot a bit until it descends without pushing against the toothpick.

Also, by trying it on, determine how much straw you can safely remove from the back end so it doesn't press into the floor of the well when the barrel is fully elevated.

Sometimes, if the bottom of the barrel has an opening on its bottom surface where it contacts the edge of the well, it can catch on the edge of the well. If so, tape over the opening so it can slide smoothly around the well with the turret.

Mount the Turret. Thread the center toothpick through the turret and carefully press it into place against the top of the tank. To keep the turret from lifting up off the tank-body during use, thread the top of the toothpick with straw segments that grip the toothpick-shaft. The more straw segments you place, the tighter the grip will be. [Even if you use clear straw segments this messes up the appearance of the tank, but you'll have to decide whether appearance or functionality is more important to you. Later, we hope to be selling a more attractive top nut and bottom nut for the tank that can keep the center toothpick in firmer alignment through the tank-body.] If you can safely handle superglue, it helps to glue the straw to the toothpick on both the top and bottom of the tank.

Make the Flag. Make a flag and bend it on to the flagstand. Fold in a corner or two of the flag to keep it from falling off or opening. Trim off any overhanging bits with scissors. Jam it into the hole you made earlier when made the turret.

Mount the Lego-head. You've got a couple of options here. I've designed a MDF platform that can pop into the lid-mouth to receive the Lego-head. Or you could double up on the lids. Or you could tape/glue a piece of can-metal to the underside with a perfectly-sized hole in it for receiving the Lego-head. Or you could try to combine the double lids with the black can metal so the tank looks dark inside.

I've made the "neck" for the Lego-head by clipping the head off a pushpin, punching it into the platform, and then dropping the hollow Lego-head over it.

Here's the really lazy way to do it, though; just drop it on the axial toothpick:

Spitwad-Launching Tanks. Making the spitwad-launching variant of the tank is simple. Just cut another barrel-hole in the turret (like you did before) that's opposite the other barrel-hole, and trim the edges. You'll take another straw, preferably one with the accordian-style top, and connect it to another straw by passing the end of the accordian straw into the other straw. Shove a thumbtack, then thumbnail, then toothpick perpendicularly through both straws, and make that your slot area for the center toothpick. Pass the barrel over the normal straw and mount the straws to the center toothpick as before.

Load the barrel of the tank like you would load an ancient musket. Just wet the spitwad and shove it down the barrel with a coffee straw. My physics textbooks taught me that a 45 degree angle is optimal for launching the spitwad at the maximum distance.

Don't Make the Flamethrower Tank. Flamethrower tanks are not recommended. You're on your own, and I assume no liability for any negligence or injury. I expect that the process of making the flamethrower tank involves eye protection, gloves, a jacket, long pants, experimentation, a safe environment, and second-degree burns.

If you're "brave" enough to try this, please send me the video (3:47 mark)!