Walter Lackey
Mechanical Engineering Technology
Differential
Design
Construction
The construction started with a 40 groove GT2 3mm timing belt pulley. In order to turn this pulley into The Differential Housing the center of the pulley had to be hogged out to allow the carriers to fit inside. The Gallery above shows this manufacturing process.
The function of a differential is to allow the drive wheels to spin at different speeds while turning, and to allow torque to automatically vector to the wheel with the least traction. These functions create increased driver control through corners and especially under hard acceleration.
The design started with side and spider gears from an R/C differential of unknown origin. The design follows conventional automobile differential design. therefore the major design challenges in of the differential were determining dimensions in the 3D printed carriers, and designing within our manufacturing capabilities at CWU.
Exploded view of Differential from Solidworks model.
The fastener holes were drilled by assembling the Differential, clamping it together and drilling through the whole assembly on a drill press. This method ensures the alignment of the holes through all components.
The side housings were machined from 2" aluminum stock on a CNC lathe. The smallest diameter on the image to the left is a bearing seat, which has a tolerance of (+-.002"). Even with the precision of a CNC lathe it took three attempts to achieve the desired dimensions.
The next phase of construction was to print the carriers so that they provide perfect clearance between the side and spider gears. The manufacturing in this step is as simple as hitting the print button, however, it still took four attempts before the gears meshed smoothly.
In factory form.
Clamped by its hub in a 4 jaw chuck
In factory form.
Step 2: Print Carriers
Step 4: Drill Holes for Fanteners
Step 3: CNC Machine Side Housings
Step 1: Hog Out Differential Housing
Step 5: Turn Bevel Clearence Bushings
One of the most important and tedious steps in the construction of the Differential was getting the length of this bushing correct. If the clearance is too tight the Differential will bind, if the clearance is too loose the Differential will have a reduced life span or simply not function. Due to tolerance stack-up, the specified length of the bushing had to be modified for final fitment.
