Crawler articulated tractor
When I finally got track pieces I had to use them properly. I wanted to start with something bigger in order to ease the building process. I chose crawler tractor. Originally, I wanted the tractor to have removable tracks so wheels can be put on instead but I finished with solid attached tracks.
I started the build by the tracks. But all my variants were rather stiff which reduces the motor efficiency. I finally managed to find a compromise using a tension mechanism after many iterations. The assembly forced me to make the tractor articulated where each pair of tracks has its own motor. The steer mechanism ended up to be realized by a servo and a gear.
Three points hitch is realized using a modeller servo. I further added lights and started the final assembly. The micro controller unit is placed under the hood. I had to place the battery box as a part of the cabin. I added a line tracking sensor in order to make the tractor a little bit more self-sufficient. The sensor is calibrated using my own remote controller. This way you can adjust the calibration to different materials and light conditions. The line following combined with the articulated steering that is placed quite distant to the sensors was not finally so difficult.
I wanted to use the hitch and the tractor looked quite lonely. Thus, I built simple machinery. Moreover, I did not want to overweight the hitch. This resulted in semi carried tiller. It has tilting arms and lift-able rear wheels used for transportation. The tractor met my expectations. It is also quite strong and fast thanks to the two drive motors.
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