#### Ratio Tester

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Example Uses

**Winch:** As an endgame, you need to winch up the robot by spinning a cable around a circular drum. For radius, enter the drum's radius. For load, enter the weight of the robot (154lb max = 125lb robot + 15lb bumpers + 14lb battery). Since this is an end game task, change Voltage Applied to 10V to account for battery drop throughout the match. Then specify a desired loaded linear speed that the winch should climb, a maximum allowable current draw to keep the breakers from tripping, or a maximum allowable stall load to protect the motors. Change the number and type of motors to find a combination that gives acceptible values. Then use the ratio tester to find a set of reductions (e.g. spur gears, chains, belts, planetaries) that approximates the desired ratio.

**Elevator:** You need to lift a load with a motor connected to a linear elevator system. For radius, enter the radius of the pulley, sprocket, or drum driving the elevator. For load, enter the weight of the elevator carriage. Then specify a desired loaded linear speed that the elevator should raise, a maximum allowable current draw to keep the breakers from tripping, or a maximum allowable stall load to protect the motors. Change the number and type of motors to find a combination that gives acceptible values. Then use the ratio tester to find a set of reductions (e.g. spur gears, chains, belts, planetaries) that approximates the desired ratio.

**Arm:** You need to lift a load using an arm driven by a motor. For radius, enter the length of the arm (specifically the distance from axis of rotation to arm's center of mass). For load, enter the weight of the arm + the load it needs to lift. Then specify a desired loaded rotational speed that the arm should rotate, a maximum allowable current draw to keep the breakers from tripping, or a maximum allowable stall load to protect the motors. Change the number and type of motors to find a combination that gives acceptible values. Then use the ratio tester to find a set of reductions (e.g. spur gears, chains, belts, planetaries) that approximates the desired ratio.