Crimson Racing Wiki

Driveshaft

Subteam: PowertrainSubsystem: DriveTrainAssembly: Drivetrain AssemblyCars: CR22, CR25, CR26I, CR26E

Purpose

Transmit torque from the differential to the rear wheel while allowing suspension travel and steering-free articulation.

Function

A half shaft with a tripod joint at each end. The tripods accommodate the angle and length change as the suspension moves.

Design Process

Taylor Race FSAE half shaft blanks are ordered off the shelf at 20 in, then measured, cut to length, grooved for tripod retaining rings and assembled in house. A custom measuring jig is used to prevent the risk of exceeding half shaft travel range.

Analysis

RCV tripods are most similar to the GI GKN tripod joint. Right hand driveshaft angle 10.2 deg, left hand 11.4 deg, with estimated loss through each driveshaft below 0.5%.

Manufacturing Process

Half shafts are purchased from Taylor Race Engineering, then cut to size and slotted on the lathe. Measuring half shaft length carefully is critical to prevent pullout while driving, and length must be measured through the entire travel of the suspension to account for future ride height changes. The half shaft measuring tool and long Vernier calipers work well. Taylor Race C-clips retain the tripods on the shaft. Assembly: install the lowest C-clip on one end, slide the tripod onto the splines, follow with another C-clip, and repeat for each end. One side of each half shaft takes a fixed plunger pressed in with a hammer. Drop Delrin spacers inside the shaft followed by a spring and the floating plunger, using enough spacers that the floating plunger can be pressed flush while keeping about 1.5 to 2 in of travel. Grease the tripods with GKN tripod grease, making sure the bearings and rollers are fully coated. Insert the floating plunger side into the spool first, then the fixed plunger side into the spindle. Cover each tripod joint with plastic wrap secured with zip ties.

Full Material List

4130 steel half shaft blank, RCV FSAE tripods lubricated with GKN tripod grease.

Reoccuring issues

Fault Vault, 2023-07-17, CR22, Manufacturing, Compromised Failure. The right halfshaft was moving and making a strange noise, traced to worn tripod inserts letting the tripod bind and shift in the spindle. Shakedown 7-15-23 logged the same as "unacceptable drivetrain noise", isolated to the right halfshaft by running the car on blocks. A stiffer spring on the plunger was tried. Past tripod failures were also partly attributed to using CV-2 grease; the system now runs GKN tripod grease as the manufacturer recommends.

Improvements

Moved to GKN tripod grease as the manufacturer recommends, after past failures were partly attributed to CV-2 grease.

Still to document

Nothing in CrimsonStorage covers these yet.