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MARCH
Steg-O-Saw-Us comprises of a framework made out of 1-inch mild steel box section. Once the framework had been welded together we were then able to calculate where the front and rear wheel supports needed to be drilled. The front wheel supports not only locate the wheels but are also used to tension the 3 inch toothed belts shich we used as tracks. The main problem that we faced at this stage was the total combined weight of the robot. In order to overcome this problem the rear wheels were machined out of a piece of 8 inch x 4 inch aluminum, the front wheel 1/4 inch plates had to be drilled to minimize weight and the front wheels were made out of 4 inch ABS plastic. Once the frame, wheels and tracks were assembled we discovered that when pushed at walking speed the tracks came off from the rear wheels. We agreed amongst ourselves to machine a large enough lip on the outside of the rear wheels to prevent this from happening.
APRIL
With the framework now completed, the two Bosch 750w motors could be fitted by means of a 3/8-inch industrial chain connected to the rear wheels. The speed controllers, batteries and the radio gear were also bought this month and could be fitted to the robot. The photo below shows the two 4QD 120-24 speed controllers in the process of being connected to the batteries and the motors. The batteries used are Yuasa 12v 17ah types, which give 24v output for approx. 30 minutes. Specialist wiring is used to connect the batteries to the speed controllers via the isolation switch. Because of the nature of their use the wire is copper section sleeved with glass fibre, making it heat and flame proof.
Its time to test the design, speed and strength as the audition date approaches. Steg-O-Saw-Us proved to be fast and powerful but all was not what we had hoped for. The maximum speed had been estimated at 10 mph but was actually 15mph and it exceeded our expectations of strength by pulling a 2 1/2 ton transit van and with a running start could push 100 kilo's. Unfortunately we discovered a problem with the tracks. If we tried to turn too fast one of the tracks came off. In order to attempt to solve this problem we mounted pieces of PTFE either side of all of the wheels preventing the track from moving. All seemed to be working well and we were ready to attend the auditions. It was whilst on the see-saw during the audition that the left hand track came off- the PTFE had been worn away by the track allowing it to become trapped between the front wheel and the remainder of the PTFE wedge. Although the robot has performed over and above our expectations and was able to qualify for the next round of auditions for Robot Wars the track design needed to be rethought and re-tested.