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19XT 2WD/4WD Shifter

I designed, optimized, and manufactured a fully custom 2WD/4WD for JHU's Baja SAE team.

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Project Overview

I began my process by performing a detailed trade study evaluating different types of clutches used in commercial off-road vehicles as well as previous Hopkins Baja vehicles.

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I ultimately decided on a system architecture based on dog tooth clutches connecting power between the rear and front drivetrain. This 2WD/4WD shifter features a spring system to ensure that, in the instance that the system fails, both dogs stay engaged and allow our vehicle to operate in 4WD.

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The dog clutches engage and disengage quickly by use of a linear actuator, allowing the driver to focus on driving the vehicle.

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19XT Shifter Assembled

Custom Dog Tooth Clutches

To promote engagement at high shaft speed differentials, these dog tooth clutches feature a sloped trailing edge. To transfer torque, the "dogs" slide along splined shafts axially before meshing together.

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The driven dog features a bearing cup in order to maintain concentricity with the output shaft, and its tooh profile has been designed for 30° backlash for minimal slop while promoting engagement.

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Driven Dog Assembled

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System Integration

Dog Clutch FEAs

Sealing Case

Past shifters have suffered from frequent reliability issue and were difficult to maintain. My design solved those problems with a sealed, weatherproofing case. I accounted for ease of assembly with wrench clearances and designed them with simplicity in mind. I also reduced the total weight of this year's shifter by 23% and improved performance under stricter design factors and an increased 54% loading capacity.

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Shifter Sealing Case

Results

Upon the completion of much shaft stress analysis, hand calculations, spline design, and days on the mill, lathe, waterjet, CNC, and EDM... I present to you the 4WD shifter!

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This year, our car has won the following achievements:

  • 6th Place Overall across the 2023 Season

  • 4th Place Design Award at Baja Ohio

  • 4th Place Dynamic Events Award at Baja Ohio

  • 8th Place Hill Climb at Baja Oregon

  • 10th Place Overall at Baja Oregon

  • 10th Place Overall at Baja Wisconsin

Check out the 4WD system in action!

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