This testing procedure is for all the requirements set forth in the Evaluation Sheet in Appendix G. These do not have to be performed in order since all these are independent tests. Some can be done simultaneously such as string tension and shear force on the ratchet teeth and pawl. Most of the tests will require little time except for the stringing of the racquet and the ratchet endurance test. 8 hours is allocated to testing the time it takes to string the racquet for 3 trials. The testing will be conducted in a garage equipped with a workbench and the tools necessary to make minor adjustments to the design.

• First pull the tension on a line of string using the device and compare it to the conventional drop weight stringer 3-5 times. Record the tension and ease of string.

  • Note any deflection seen in the pressure arm, struts, or ratcheting component and adjustment tubes.

• Translate the drop-mass along the pressure arms.

  • Note the ease of use and whether or not the mass could be translated.

• Pull the string tension to 30, 60, and 90lbs for a total of 3 trials.

  • Note the ease of use and whether or not the string slips inside of the clamp.

  • If string does slip, re-adjust sandpaper to maximize gripping power.

• While pulling the maximum tension, record whether the stringer is tipping or is close to tipping.

  • Clamps may need to be implemented

• Pull maximum tension on the stringer, then measure the amount of deflection in the arms using a straight-edge and a ruler.

• Rotate the swivel arm past 360° and record if successful or unsuccessful

• While stringing a racquet determine the greatest angle of the string when the ratchets are adjusted to the closest position to make the strings parallel. Then measure that angle either through the level app, or by taking a picture and solve for the angle.

• While stringing a racquet and having the drop-mass drop below parallel with the ground, ratchet both ratchets simultaneously if possible.

  • ​Record ease of use and whether synchronized ratcheting was successful or unsuccessful

• Translate and measure the ratcheting components along the shaft axis of rotation.

• Pull the maximum tension and let stand for 10, 20, and 30 minutes. Record Observations and note any deformation.

• After becoming familiar with the new stringing device perform the stringing operation 3-5 times as before and record the time and ease of stringing. 

  • ​Minor adjustments may have to be made, make them until 3-5 adequate trials have been conducted.

Risk

• String Slippage

  • Device could flip over

  • Tension not symetrical

• Drop-Mass stopper could fail

  • ​Made of plastic

  • Could land on racquet and cause irreversible damage

There is some risk involved in this design. The string could slip and cause the drop mass to fall. This could cause the entire device to flip if it is not clamped to the table. Another risk is the drop mass stopper as seen in Appendix I, Fig. 3. This is made of plastic and may snap under the load of the drop mass as it rests against it. A final major risk is the string snapping. This will also cause the drop mass to fall and potentially destroy the device.

          With so many specialized parts the need for every one of them to work is very important, but paramount is that they work together.  A slight design or manufacturing error causes the whole device to not perform as expected. Then it’s about making minor adjustments through the testing process to mitigate these errors. As the manufacturing and testing is being implemented, new ideal designs arise, but can’t be implemented due to time and the nature of the course.