Intro: RC M48A3 Patton Tank
What you see here is a hand crafted and fully functional model of the M48A3 Patton main battle tank. As you may know, a fully functional tank can move, turn its turret, aim, and fire. This RC model can also perform these functions. Apart from functional properties, the RC tank also has very detailed aesthetic aspects, resembling the real tank.
The building of this tank is divided into five sections. The five sections are as follows: Frame construction, tracks, body, turret, and electro-mechanical components.
Step 1: Frame
The frame of a tank is a structure whose function is to hold the wheels, the body, and the turret of the tank together. For this model, real measurements were scaled down to make the frame. The frame consists of two panels, held together by short planks, all corresponding to the real measurements. The overall length of the tank is 21 inches, and its width not including the tracks is 11 inches.
The section holding the turret is made from a piece of wood cut in a curved shape, which will be further explained during the turret step.
Additionally, holes are drilled into the side of the frame for the wheels.
Step 2: Track System, Part 1
The first part of the track system consists of the road wheels (the ones carrying the weight), the drive wheel (the one powering the system), and the idler wheel (responsible for track tension and control). Using a two inch whole cutter, wholes were cut out of half inch thick pieces of wood. the cutout piece was used as the wheel. A piece of wood was used as the arm of each wheel, onto which wooden axles were attached. The wheels were fixed loosely onto the axle with metal washers. The purpose of the space between the two wheels is to guide the tracks, as will be shown in part 2. The purpose of this arm, as will be discussed in part 3, is for the suspension system.
The idler is the same system, but without an arm, instead it has a metal axle fixed permanently into the frame.
The drive wheel is made from quarter inch circles connected together with thick nails. The whole setup is then put on a long bolt, and fastened with nuts. The bolt is then put inside an aluminum tube, which is inserted into a larger aluminum tube fastened to the frame. A lubricant can be put between the two tubes, and the smaller tube can be either welded or fixed to the axle. What this will do is it will create a stable drive wheel that can easily turn the whole track system.
Step 3: Track Systems, Part 2
The tracks that go over the wheels are made on the basis of a bicycle chain. Narrow, 2.5 inch long panels of wood are cut, with a hole in the middle. The hole is fastened to a bolt, which is then fastened to the chain with hot glue. Note: Fastening the bolts to the chain with a nut would mean prevent the chain parts from moving freely, and wouldn't prevent the wood from rotating. Ample hot glue can do the job. The protrusion created by the chain is what will allow the tracks to be guided by the road wheels, and the bolts are what will be used by the drive wheel to power the track system.
Three pieces of wood with a notch in each as shown are put at the top of the track frame to support the track.
Each side needs about 50 pieces of wood.
Step 4: Track Systems, Part 3
The last component of the tracks is the suspension. In this case, a dowel was glued onto the road wheel arms, with a mechanism shown in the first picture placed on top. A hole is drilled in the middle of such mechanism, and another one is put on the top end of the suspensions system. The top segment is fixed to the tank, and a nail with the end cut off is fixed to it. The nail sits loosely inside the bottom segment, only guiding it. The bottom mechanism rotates freely on the dowel fixed to the arm. A spring is then inserted onto and between the mechanisms, finishing the suspension system.
The system is basically like a shock absorber, except without any of the fluid.
Once completed, the tracks can be placed on, and the track system will be complete.
Step 5: Body
The body consists mainly of panels attached to the frame, as well as some preliminary support for the turret placement (the turret ring). The front of the tank is simple enough, requiring only paneling and some slight curves to resemble the real tank, the rear however is a different story. In order to better resemble the engine deck of the M48A3, a raised platform was created and rear access hatches were made. The access hatches serve to install and repair the transmission which will come in a later step.There are two more access hatches that serve the purpose of providing access to the interior of the tank for repair and maintenance. handles are installed on these hatches with pieces of wood.
As for the track fenders, thin basswood will do the trick. The fenders were made in sections, attached together using hot glue. They increase the resemblance of the tank to the real thing. Each fender required 1 piece of basswood, 24 inches by 3 inches.
Step 6: Turret
The turret falls into the turret ring made in the body step, using guides to keep it tight against the circular shape of the ring. These guides consist of wheels on axles to soften the rotation, as well as stationary supports for a stronger guidance. These guides collectively do not support the entire diameter of the turret ring, as part of it is supported by the wheel that turns the turret.
The shape of the turret is created with wooden panels, which are attached together in a circular shape, then filed and sanded down to achieve a round turret.
What remains after the walls of the turret are completed is the detailing and the roof. These are done with bits of material found here and there, together making a commanders cupola with the .50 cal machine gun, gunners view port, ammunition loading tube, fuel tank, and camouflage net stowage cage.
Step 7: Electronics, Part 1
The transmitter was made by combining the transmitters from two old RC cars into one. This is very useful as the software is already there, and you only need to connect the wires to corresponding motors. More on how to connect the wires will be explained in part two, the receivers. In order to be able to conveniently control both the turret and the tank, two transmitters need to be fitted into one case. This can be done by cutting appropriate holes in the bottom of the transmitter, and installing one of the transmitters. Details are model specific, but for this transmitter, there are two control knobs which control each track individually. There are two buttons, each responsible for the rotation of the turret in one direction, and there is a third knob on the back for gun elevation/depression adjustment. As well, a button on the back fires the gun. The installation is only a matter of fixing the parts in place, and connecting the power.
In order to operate the tank, a little practice is required, since one of the knobs controlling the right track does not move up and down, as seen in the picture. Despite this difficulty, when combining both knobs, the right knob serves as the steering control. When, for example, you are going at a steady pace on the left track, moving the right knob to the right will decrease the right track speed, and therefore make the tank turn right. The reverse works as well.
Step 8: Electronics, Part 2
The motors powering the tank are two high torque motors, using 18 volts of electricity. The power for these motors comes from two drill batteries, whose casing has been removed to fit them into the front of the tank. 6 1.5 volt batteries are required to power the receiver taken from an RC car. Power is done.
The receiver is fixed to the bottom of the tank, and the corresponding motors to the RC cars driving and turning motor are each individually fixed to the drive motors. Something to note about RC motors is that they can turn both ways, and for that you need a system where when one side is positive, the other side is negative. 4 transistors can easily perform this function with the cables coming out of the resistor. The significant power boost can also be achieved using high voltage transistors.
As for driving moving the power from motor to track, a simple torque increase gear ratio was used to move power to the tracks.
Step 9: Electronics, Part 3
The turret of the tank is easily the most crowded area in the entire tank. That is because it contains many functions in a small area. In general, there are two functions that are performed: gun control and turret control.
Gun control is achieved through the use of some stepper motors as well as a normal motor. Stepper motors are used for gun elevation/depression, as well as reloading. Although servos could have been used, stepper motors deliver angular accuracy very easily. In other words, gun elevation/depression can be controlled numerically. Stepper motors are used as well for gun reload, which simply involves a rack gear, which is used to move the gun cock back and forth. As for firing, the trigger is pulled using a small motor, who's motion is time restricted (made to move for only a certain amount of time), and a piece of rigid plastic that is attached to the motor axle.
The gun itself is an inexpensive spring powered BB gun. Although it is a very small gun, it feels massive inside this tiny turret.
Another mechanism in the turret is the rotation motor. The motor axle is powering a wheel underneath the turret floor, while the motor itself is inside the turret. This means that the turret rotation is self-contained and is not operated from inside the tank. The motor is tensioned with a spring, in order to overcome any imperfections in the turret ring.
The electronics are powered by 4 1.5 volt batteries, making a total of 6 volts. This is enough to power the bread board, which contains the programing for the gun movement and turret movement, as well as the receiver from the RC car. Ironically, the batteries closely resemble the ammunition rack on the real tank.
Although the receiver only controls two motors, the programing allows that two motor control to be used for turning the turret, moving the gun, and firing.
Step 10: Conclusion
Fellow comrades, this tank is a remote control replica of an American M48A3 Patton tank, it is made mostly of wood apart from a few structural points which require metal. The functions of this tank include moving, turning the turret, elevating/depressing the gun, as well as shooting plastic BB's, all of which are done remotely. It also features realistic details resembling the real tank.
Good luck building.