TESTING
The self-reversing ball screw was put to the test in multiple categories shown in the video below. the First Test being whether or not the threaded shaft switches the path of the ball nut smoothly and efficiently. As presented, the ball nut does as expected very smooth and efficient when held in place with only one finger with some chatter between the ball and the path due to the lack of load.
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The second test consist of a load perpendicular to the shaft. The load eliminates the chatter between the ball and the path, rotates and switches directions very efficiently. This type of load is recommended with the product.
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The third and final test is an axial load. The self-reversing ball screw does not reciprocate as intended due to the geometry of the ball nut. As the load is applied, there is not enough force to keep the ball from switching paths and reversing early as represented in the final 10 second of the video. Therefore, this actuator is not ideal for the project that it was intended for but could be very useful on other applications.
Duty Cycle
A stopwatch accurate to a tenth of a second is used to specifically time the interval in which the pruner spends cutting a 2 inch branch. The time starts immediately after the trigger of the motor is engaged and stops immediately after the blade has cut through the whole branch but has yet to start its return. The stopwatch is then used to time the interval in which the blade starts a cut and returns to the open position. The formula D.C. = (Tc / To) *100, where Tc = Time of cycle and To = time in between cycles is then used to calculate the official duty cycle.The results of the test are a pass fail outcome in which the duty cycle is higher or lower than that of the competition.
Testing Configurations
Movement Test
Weight and Dimension Test
The test is of the overall dimensions of the drive train. Even if the drive train fits within its parameters, it still must be under 1.25 pounds. The test is very simple and data is a pass fail concept. By effectively assembling the pruner and weighing the object as a whole, the ergonomics will prove to be better than last year’s project. The duration of this project is about an hour considering the assembling of the pruner as a whole.
General Test
The general test of this pruner is its ability to cut branches up to 2 inches in diameter. A caliper measures the size of the branch ensuring the branch is to maximum specification. The branch is rigidly attached while the pruning device is engaged. The test is passed if the device completely amputates a tree limb. Any branch under 2 inches is assumed to be manageable for the pruner if the first attempt passes.
