Things You'll Need
Instructions
Tank
Build the base of the tank using bricks, flat plates and wheel bricks. Depending on the size and shape of your tank, the dimensions of the base may differ, but it should be about as long as you want to build the tank, and the width (including the wheels) should be about the size you want the model to be.
Attach the treads to the wheels on the base. Not all tanks have treads, and not all LEGO sets have tank treads, so you may have to make treads out of paper.
Build up the walls of the tank around the base. If you are making a tank which can fit Minifig characters, make the tank hollow. Otherwise, you can make the tank a solid piece. Build up the walls until they are taller than the wheels.
Cover the top of the tank base using plates to create armor. The plates should cover the tank treads on both sides of the tank. Attach two 4-by-5 hinge plates to the left and right sides of the tank, so the larger part of the plate hangs over the front of the vehicle. Place 2-by-2 bricks on the backs of the plates. Connect the two hinge pieces with a series of plates to create the front piece. Repeat on the back.
Attach the 4-by-4-stud swivel brick to the middle of the tank. Build a turret around the top of the tank attached to this piece. Do not connect the turret to the base of the tank, as it should turn freely on the model. Place a brick with Technic cross-slot holes at the front of the turret, pointing forward.
Thread several hollow rods onto your Technic rod. Cap the piece with a Technic spacer. Attach this to the front of the turret to make the gun barrel.
Heavy Artillery
Build a leg, about 6-studs long on the half of a 2-by-2 hinge plate. Make the leg the height of a single brick, and attach flat plates to the top edge.
Attach a 2-by-4-stud plate on top of a 4-by-4-stud plate, along the center. Place two 1-by-4-stud flat plates on either side, and attach the two leg pieces on top of that.
Attach a 2-by-2-stud plate in front of the hinge pieces, cover this with two layers of 2-by-4-stud plates. This makes the base of your vehicle.
Cover the base of the vehicle with a 4-by-4 swivel plate. Build a turret on top of this piece, placing a brick with a Technic cross slot on the front at the front and center. Most heavy artillery also includes front-mounted armor extending around the front of the turret.
Build the gun barrel using Technic rods, with a hollow piece and a spacer on the end. Attach this to the front of the turret.