I’ve always thought tanks were cool, ever since I studied WWII in middle school. I then wanted to have a remote control tank that was quite large. The only solution to this problem was to build one. I did hours of research on the ‘net, looking for others who have large R/C tanks. I came up with only a couple and they required special tooling or materials that I didn’t have. In traditional FastMHz style, I’ve built this tank with a lot of improvisation!
The photos above show various angles of the tank. Everything that you see with the exception of the tracks are made of plywood that I got from the local Home Depot and Lowes. The tank is primed and painted with spray paint.
The hardest part of building a tank that actually works is the construction of reliable and functional tracks. I went through a few tests with various materials, including leather belts that would normally be used to hold pants up. They worked, but VERY unreliably and very inefficiently. Looks like I’d have to spend some dough…but on what?
The answer: Snowmobile drive belts!! After hours of Googling for various materials, I found these almost by accident. They are perfect because they are flexible and have a tread on them already…well, the teeth that make the tread were originally on the inside, but I turned them inside out. At $29 each, it was a steal. Normally these belts are used to take power from an engine to the snowmobile’s drive system, so they are tough.
To turn these belts into tank tracks, I took an old lawnmower V belt and chopped it into 2cm chunks, and riveted those onto the inside of the belt as seen Above Right. The lawnmower belt chunks ride in the space built into the wheels, holding the tracks on. This tank has NEVER thrown a track and it MOVES! It can do 360s like crazy.
This system is known as a Friction Drive setup. The largest wheel is on the motor and spins inside the belt. Simple friction drags the belt along to move the tank. The black material on the drive wheel is rubber taken from an old tire inner tube and adhered with contact cement and CA glue. I had already tried sandpaper and was thinking of Velcro until it dawned on me that rubber against rubber would probably work best. The Friction Drive system also acts as a clutch, preventing the motors from stalling should the tank get stuck.
The smallest and topmost wheel is the tension wheel. It is attached with an aluminum plate for strength. This wheel pulls the track tight and allows easy removal of the tracks for maintenance. The black part is made of hardboard and distributes the tension on the back wheel bolt across the other 3 wheel bolts.
Electrical and Drive Systems:
Ahhh, the electrics. The tank operates on 24 volts, with 7AH of capacity in the GelCell batteries seen Above Left. The batteries are in the back of the tank, wired in series. The blue object is an Airtronics surface FM receiver. The right photo shows the two Victor 883s and motors. These motors are windshield wiper motors I got surplus for $19 each.
These motors are designed for 12 volts, but I wanted more speed, so I am running them on 24. They take it quite well, though they get hot when run hard and long. The solution was a fan and baffle cooling system. One fan (Right Bottom) blows in, while one blows out. The index cards and duct tape form baffles which force the air past the motors and speed controls. If I run the tank very hard, the exhaust is quite warm.
Victor 883 Specs:
Surge Current: Rated: 100A for < 2 second, 200A for < 1s, Actual: > 300A
Continuous Current: 60 amps
Reverse Delay: None
Frequency: 2000 Hz
Weight: 4 oz
Cooling: Active fan (12v or 24v)
Signal type: Standard R/C Type PWM
Price: $320 = $150 + $10 for PWM cable x 2
Where to get: www.ififirst.com
Victor 883s are great because they work with standard hobby radios, but are capable of much more voltage than hobby ESCs. This is the same ESC that I used in my E-Maxx project.
Power Source: 24 volts; Two 12 volt 7AH GelCells
Cooling System: CPU Fans
Radio: Airtronics 4 channel FM
Motors: 2x 12v Windshield wiper motors (worm drive)
Speed Controllers: 2x Victor 883s
Material: 99% wood, aluminum plates for idler wheels
Power Draw: > 300 watts
Runtime: ~ 30 minutes on flat terrain
Weight: > 30 LBs
Cost: > $600 USD