Having built several cardboard vehicles up to this point, I decided to build my 3rd tank with working tracks. On my previous 2 cardboard tanks I had used bicycle inner tubes cut to size & super glued together. This method worked ok but in order to gain the needed friction for the track against the driving hub required tension on the track. Also on my other tanks I had used home made pulley's and rubber bands which required quite a bit of space inside the tank to provide the torque to turn the tracks. With the tension on the tracks to keep the friction needed to turn them reliably the amount of torque required from the pulley's was possible but at the cost of speed & space inside the tank. This led me to wanting to find a better track solution that was still simple enough to make without have to spend 10's upon 10's of hours making track links. I looked at several track designs on youtube but the simplest one appeared to be using cardboard for the tracks with the layer over the corrugation removed to provide a grooved track for corrugated cardboard driving hubs to turn. To eliminate all the volume pulley's would consume I decided to use plastic gears to drive the tracks from the electric motor.
Step 1: Building the Tank Chassis, Installing Motor, Gears, & Battery Box.
I start by deciding how big the tank needs to be & cut both sides of the chassis out of heavy cardstock. I then figure out how large the wheels need to be & measure out the spots where the axles will pass. I then use a hole punch & punch out the holes for the 7 axles. I used wooden dowels for the axles & drill out beads to fit over the axles & slide them up almost against the chassis providing just enough space for the axle to move freely but not far side to side. I reinforced the card stock chassis with jumbo craft sticks hot gluing them in place. The front drive axle I find what size gear I need and drill the hole in the center of it large enough for it to slide over the dowel. I then make a smaller dowel and add a secondary gear to it to provide much more torque. Then I mount the motor with hot glue making sure the motor gear is contacts the shaft gear properly as the hot glue sets up. Now I hot glue in the AA battery box with built in switch & solder the wires to the motor. Remember with gears you want the smallest gear on the motor shaft, then mesh the small motor gear with a larger gear on another shaft. On that same shaft you want a smaller gear connecting to a larger gear on the primary drive shaft. Basically you are reducing the high rpm from the motor shaft to a slower rpm (but with more torque) on the secondary shaft. Same goes for the secondary shaft to the primary drive shaft (slowing each shaft down giving far more torque). A tank needs all the torque you can get because tracks are hard to turn & in order for them to have any hope of not snagging up or binding you need that torque.
Step 2: Making the Tracks, Wheels, Driving Hub Gears, Fitting Tracks in Place.
Now I find a good piece of corrugated cardboard & decided how wide I need the track to be. I then cut out a piece of cardboard for the track & carefully peel off one side layer off the corrugated part. I bend the cardboard between each corrugation to make the track more flexible. I make the center 10 track wheels using card stock with 2 layers of thin sheet foam in between. I trim the excess foam to where it's slightly larger than the outer card stock wheel circle so as the foam is what contacting the inner track. I hot glue those to the 5 central axles. The driving axle I use a sheet of copier paper and cut a strip the same width as the track. I use elmers glue to glue in on the driving axle wrapping it around and around and adding enough to make theproper size drive wheel. I make the one on the opposite side the exact size by wrapping the same amount of paper around. Once the elmers glue dries I then hot glue a piece of the corrugated cardboard around the paper driving wheel which has enough circumference to allow for 6 corrugations on the hub proper spaced to fit into the corrugated track cardboard. I do the rear axle basically the same. I then wrap the cardboard track around the wheels leaving it enough slack so as it should turn fairly easy. I hot glue it together & do the same for the opposite side. The tracks required quite a bit of cut and reglues to make it work just right. At the rear the track kept slipping past the 5th bottom axles wheel on one side so I had to re hot glue that hub farther out by using a small piece of cardboard straw to extend it out & hot gluing it over the wooden dowel. I did the other side the same most to make the sides match since the other side was not suffering from the track slipping off. I had to glue card stock circles bigger than the hubs over the upper hubs which helped keep the track in place. To keep track from going inward toward the tank body I simply cut a piece of card stock & curved it out and hot glued it in place as a spacer to keep the track away from the tank body. After lots of tweeking I finally managed to get the chassis working reliable enough so I could move on to the tank body.
Step 3: Painting Chassis, Cutting Out Body Panels, Painting Tracks & Body.
Before starting on the body panels I went ahead and painted the chassis & wheels using 2 coats of brush on acrylic paint. Now I start on the body panels using card stock & hot gluing them in place. I cut out the hole for the batteries & the hole for the turret. I also cut out a small hole over the gears to give a spot to grease the gears when necessary. I then paint the tracks with a thin layer of acrylic brush paint (don't want to use too much since track has to remain easily flexible). Now I paint the body using 2 coats of acrylic brush on paint. It's beginning to look like a T34-88 at this point.
Step 4: Making the Turret and Barrel.
I use card stock to make the turret. I start by sketching the base of the turret & then make the top part of the turret just a bit smaller than bottom. I cut out a hole in the center of top and bottom of turret and hot glue a old cardboard roll in place. I then cut the sides of the turret out of card stock & hot glue them in place. I make the tool box on the back of the turret & hinge the upper part so the bottom of it can swing it and out from the turret. I also fix the lid to open on the box. Now I begin working on adding the barrel to the turret. I use an in pen tube for the back portion, a cardboard straw for the front portion which I hot glued into the pen tube. To make the rear most part of the barrel larger I simple wrapped a thin piece of copy paper around it using glue to hold it in place. The muzzle on the tip of the barrel I made out of a piece of card stock. With all hot glued securely into the turret I could finish the details like the shell loading portion of the barrel that sits inside the turret, the loaders seat, shells, all made of card stock & cardboard. I also finished up the portion of the turret around the barrel with card stock cut to fit around where the barrel enters the turret & hot glued them in place while bending & holding them in position.I also removed most of the original cardboard tube that ran down through the inside of the turret .leaving just enough to allow the turret to fasten securely down into the tank body but still being easy to remove.
Step 5: Painting Turret & Finishing Up Details in Interior of It & the Tank.
I can now paint the turret & barrel applying a couple of coats to turret and probably 4 coats on the barrel. I finish up painting the details on the interior of the turret like the seat, barrel loading groove, & the shells. I paint the 2 seats in the body of the tank as well as the control lever and foot lever controls.
Step 6: Making the Side Fuel Tank Containers & All the Other Details.
Now I begin making the fuel tanks. I used the card stock & cut it to the length I want the tanks to be and wrap it around a cylinder of proper size (in my case a elmers glue stick housing) & hot glue it together. I then cut circles out & hot glue those onto the ends. I used a piece of string which I painted metallic silver to give them a cable look & hot glued those in place at one point on the bottom of the tank for each string. I then hot glued the tanks to the tank body at where the strings meet on the bottom of the fuel tank. I use my hole punch to punch a circle out of the thin sheet of foam to serve as the fuel tank cap. I paint the cap silver. I fix a panel above the battery holder & cut vents in it hot gluing a piece of screen under the vent holes. I then cut out a cover to go over the switch & added a small piece of wood that holds the flap down against the tank by simple rotating it in place. Next I build a led spotlight on the front lookout ports of the tank. I used a 3V nickel sized coin battery & made a slider tray it fit in which allows it to be slid just a fraction of a inch to the right side of the front of the tank which activates the led spotlight. I now added rest of the little details like the shovel and ax I made using toothpick & card stock. I added a cable carrier bag on the back & painted more of the string silver to coil up & place in the carrier bag. I also added little pieces of cable to the front tow hooks on the tank running them back to a hook I made on each side of the tank to hold the cables to. I also used more of the corrugated track pieces to make spare track pieces to place on the front and side of the tank. I made a small cannon port on the left side of the front out of card stock & ink pen pieces. I painted the rest of the details on the tank too at this point. I used a bit of silver metallic on most of the green parts as well as on the red fuel tanks giving it a worn metal look especially on most of the edges. It just gave the tank a more realistic worn look.
Step 7: 360 Look at the Tank.
Now with it finished I did a test run. Last step will show a link to youtube video of this beast on the move.