DESIGN CHANGES/ISSUES
Link Arm Gear:
The biggest design modification that was implemented after the first test was the link arm gear, without the gear the Auto-jack frame wouldn’t remain vertical when lifted. Once the gear was added to the link arms the second lift (lift height vs. time) test could be successfully completed. One issue that was addressed was the issue of rapid lift during the first 1”-2” of lift, this was due to hydraulic cylinder stroke being fully extended. When the stroke is fully extended it takes an enormous amount of pressure to begin pulling in the hydraulic rod, which causes the rapid lift and the jack to jolt. This issue was mitigated during the lift trials by starting the test with the cylinder just slightly retracted to ensure the jolt and the rapid lift won’t occur. This test method allowed a smooth lift and a more accurate set of data.
Differential Plate:
The final design change was made on 04/10/2019 after the first test was initiated, after the first test it was evident that the jack exceeded the 50-lb initial design requirement. A modification was made to the top frame, this modification had no effect on the Auto-Jacks strength/structure it was only made to remove unnecessary weight. The modification consisted of designing a flat 12” x 12” x ¼” plate that was welded to the top of the frame, resting above the link arm gears. The long upper frame could then be cut down to a 12” x 12” section removing roughly 10-lbs of 1020 AISI square stock, this now allowed the jack to pass the weight test. After these modifications were made the final weight of the jack was just under 47.50-lbs which is 2.50-lbs lighter than the 50-lb weight requirement.
