Milestone 6: Transmission Subassembly
Transaxle Subassembly
Subassembly Breakdown
The heart of this subassembly is the MWSC 3-speed Cub Cadet Transaxle. The transaxle contains a 13/15 Reverse/1st gear set and a 17/19 2nd/3rd gear set along with the 4.60:1.00 MWSC differential and axles. The shifter for the transaxle will be MWSC H-pattern shifter that will be modified with a custom shift lever and knob for improved ergonomics. This subassembly also includes the shifter gasket from MWSC, custom mounting brackets to attach the subsystem to the tractor's frame, and all appropriate mounting hardware.
Assembly Drawing
Assembly Drawing
Subassembly BOM
Shifter Mechanism Manufacturing Drawings
Shifter Assembly
Shifter Weldment
Shifter Rod 1
Shifter Rod 2
Shift Knob
Transaxle Mount Manufacturing Drawings
Formed Drawing
Bend Drawing
Transaxle Mount Spacer
Transaxle Mount FEA
In order to decrease manufacturing costs, this year's drivetrain design will utilize steel sheetmetal transaxle mounts rather than billet aluminum machined mounts like those found on Wildcat 3122. FEA simulations were conducted in SOLIDWORKS in order to ensure that the component would not fail.
FEA Scenario
Utilizing the assumptions that the fully assembled transaxle weighs 150 lbs. and that the weight will be equally distributed among all four transaxle mounts, the simulation was set up by fixing one face of the mount to simulate its attachment to a rigid frame. Then 37.5 lbs. was equally distributed in the downwards vertical direction between the two bolt holes that secure the mount to the transaxle.
Component Design
The transaxle mounts are constructed from bent 14 gauge mild steel. All seams are welded after the bending process.
Stress Results
The stress results illustrate a maximum stress of approximately 9,000 psi. This yields a factor safety of approximately 4.5 within the part design. Since this component will undergo unpredictable dynamic loading during tractor operation, the project team has elected to utilize this design rather than moving towards a lighter-weight design.
Displacement Results
The displacement results illustrate a maximum amount of deflection of 0.0163" during this loading condition. The loading condition used assumes that the transaxle is solely supported by these mounts. Therefore, the supportive forces provided by the bulkhead and tires are not taken into consideration which would reduce the loading that these components see. With this being said, this amount of displacement is still less then the amount of allowable shaft misalignment for the couplers used in this system. Therefore, the project team considers this component's design to meet all performance requirements.