From The Ergoweb® Learning Center

Ergonomics- Brake Assembly – Install Drums On Compact/Midsize Cars

Task Prior to Abatement (Description)

Ergonomic case study for brake assembly installation workers. This is a fictitious job but reflective of common work situations on an auto assembly line.

Worker position: The worker stands adjacent to the auto assembly line.

Position brake drum: The worker gets the brake drum from the top rack of an overhead conveyor and positions the drum over the axle lugs and seats onto the brake shoes.

Secure drum: A tool is used to to insert a lock washer onto one of the axle lugs which holds the drum onto the axle during shipping.

Task Prior to Abatement (Illustration)


Ergonomic Risk Factor (Mechanical)

The narrow base of the tool produces concentrated pressure on hand tissues.

Ergonomic Risk Factor (Posture)

Reaching overhead is required to get the drums from the top rack.

Extreme forearm twist (forearm pronation) is required to get the drums from the left side of the rack.

Extreme wrist ulnar deviation is required in order to use the tool for lock washer insertion.

Ergonomic Solution (Engineering Controls)

Lower the conveyor to deliver brake drums at a height of 51 inches (just above the height of the axle on the assembly line) to minimize reaching.

Rotate the racks so that the drums can be grasped from the right side of the racks to lessen forearm twisting.

Bend the handle of the tool 60 to 75 degrees to reduce ulnar wrist deviation.

Lenghten the handle of the tool to at least 6 inches and cover the handle with a compliant material to reduce mechanical stress on the hand.

Ergonomic Solution (Illustration)


Armstrong, Thomas J.; Fine, Lawrence J.; Joseph, Bradley; and Silverstein, Barbara. Analysis of Selected Jobs for Control of Cumulative Trauma Disorders in Automobile Plants. Ann Arbor, Michigan: The University of Michigan, 1984.