[dtengineering]

Do you see a metal backing in figure 4-4?

Neither do I. Bumpers MUST be constructed using the cross-section shown in figure 4-4.

The structure referred to in R29 is the robot structure. So you can put whatever kind of "metal backing" behind the bumper you want... but that metal backing is part of the robot, is included in the robot frame perimeter measurement, and in the robot weight. It's NOT part of the bumper.

Jason