Milestone 5: Dropbox/Redcution Housing Subassembly

Dropbox/Reduction Housing Subassembly

Subassembly Breakdown

The Reduction Housing provides an initial gear reduction prior to the transmission input. This reduction is required in order to obtain the final drive gear ratios that required for optimal performance. The housing casting, gaskets, and internals are all sourced from Midwest Super Cub. The mounting bulkhead will be fabricated in house and the required hardware will be sourced from McMaster Carr.

ASSEMBLY DRAWING

SUBASSEMBLY BOM

BULKHEAD MANUFACTURING DRAWINGS

FORMED DRAWING

BEND LINE DRAWING

BOLT PATTERN

BULKHEAD FEA

Since one of the main design considerations for this project is to reduce the overall weight of the system relative to last year's design, Finite Element Analysis (FEA) will be conducted on all major brackets in order to determine where excess material can be removed from the design. The transaxle bulkhead is a rather large bracket within this system; therefore, the new bulkhead design was evaluated using FEA to reduce the component's weight.

FEA Scenario

For this FEA simulation, a conservative estimate was made that the entire transaxle with reduction housing weighs 150 lbs. This load was evenly split among the 8 bolt holes that mount the bulkhead to the front of the reduction housing. The load was applied vertically in the downwards direction. The mounting flanges on the side of the bulkhead were set to be fixed geometries to simulate the bulkhead being mounted to the frame. Von Mises stress(psi) and displacement(in.) were the simulation results that were analyzed during this process.

Initial Design

In order to reduce weight, the initial design utilized 16 gauge mild sheet steel which is 2 gauges lighter than last year's bulkhead.

Initial Stress FEA

The initial stress results indicated that a lot of material within the design was experiencing minimal stress and was therefore not required.

Initial Displacement FEA

The initial displacement results illustrated a maximum displacement of 0.00037".

Final Design

The final design is a skeletonized version of the initial design in which a majority of the unstressed material was removed and fillets were added to mitigate stress concentrations.

Final Stress FEA

The final stress results indicate a factor of safety of approximately 8. Due to this more material could be removed; however, the pulling team's frame designer has expressed a desire of using this component as a frame crossmember. In order to provide the strength required to fulfill this request, this bulkhead design was maintained.

Final Displacement FEA

The final displacement results indicate a maximum displacement of 0.0018". This amount of displacement was deemed to be more than acceptable by the pulling team.

Additional FEA

Further simulations were conducted in order to see what loading would produce a factory of safety of 2 (a more standard factory of safety for this application). The initial simulation set up was utilized as the loading was incrementally increased until the maximum stress in the part reached approximately half of the material yield strength.

Stress Results

A load of 600 lbs. applied in the downwards vertical direction was required to obtain a maximum stress which resulted in a factor of safety of approximately 2.

Displacement Results

With a load of 600 lbs., a maximum displacement of 0.0073" occurs. This amount of displacement is still considered to be acceptable according to the pulling team.

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