Specifications

CT Corsair Final Report May 2, 2014

diagram of the entire scissor arm assembly. The free body diagram allowed the simplification to

be noticed that the failure loading of the upper arm should match the failure loading of the lower

arm. The reason behind the simplification is if the lower arm has a higher failure loading point

than the upper arm, then the lower scissor is overdesigned. In reverse, if the lower scissor arm

has a lower failure loading point then it becomes the weak link in the system. In order to

determine the failure loading point of the upper arm the arm was reconstructed in CAD, Figure

33. Then FEA analysis of the upper scissor arm model was done in ABAQUS.

The first step in the FEA analysis was to determine the loading scenario that best represented the

loading scenario in real life. After analyzing the free body diagram again, the best representative

loading scenario was to load the upper scissor arms at the bolt holes in pure compression along

the longest axis of the part. Once the loading scenario was chosen then a mesh convergence was

performed to determine the optimal mesh density for the part, which was 9038. Finally the

ABAQUS simulation determined that the failure for the upper scissor arm is 540 lbs.

After determining the failure load for the upper scissor arm, the loading of the lower scissor arm

was analyzed revealing that the lower scissor arm fails in tension at the bolt holes. The maximum

tension that the lower scissor arm must withstand is 540 lbs. because the upper scissor arm will

fail after this point. A design for the lower scissor arm was created in SolidWorks and then 3-D

printed out of ABS plastic to check for collision interferences on the simulator base.

In order to validate all of the ANSYS modeling a quarter scale model of the lower scissor arm

was machined and an FEA analysis was performed. The FEA analysis consisted of loading the

quarter scale model in tension along its longest axis until failure, exactly the same as the full size

part. Failure of the quarter scale model in ANSYS was determined to be between 550 lbs. and

600 lbs. To validate the FEA model the machined quarter scale model was placed in a tension

test machine and was pulled apart until it failed at 600 lbs. Both the real world model and the

ANSYS model failed at the same load validating the FEA model. After validation, the full scale

lower scissor arm design was validated in ANSYS with a failure loading of 5,000 lbs.

The failure loading of the lower scissor arm is considerably higher than the failure loading of the

upper scissor arm which allows it to be a success and overdesigned. Though the piece is

overdesigned, the design optimized the manufacturing and material resources that were

available. The team was limited to what could be manufactured in the machine shop and also

designed the part with ease of manufacturing in mind. Therefore, the part was overdesigned but

succeeds in the overall goal of producing a lower scissor arm that works.

The third deliverable of the project was to design a new motor mount for the gearbox and motor

combination. In order to design the new motor mount, the full assembly of the base in

SolidWorks was utilized. Both the model of the gearbox and the motor were imported into the

SolidWorks assembly which allowed the visual placement of the new motor and gearbox within

the model. Then certain key dimensions such as the distance from the top of the old motor mount

to center of the gearbox spindle and distance from face of the old motor mount to face of the

gearbox spindle were constrained. These dimensions were important because they placed the

spindle of the gearbox in the same exact place as the spindle from the old gearbox, allowing the