# Design

## Design of a Zip Line

Every zip line consists of a trolley attached to a steel cable that is typically covered with a vinyl coating. For safety, the rider should be wearing a helmet, gloves, and a harness which is used to keep the rider attached to the trolley. Gravity propels the rider from start to finish.

The first step when designing a zip line is to identify the parameters involved. Some of the questions that need to be answered are:

• How long of a distance will the zip line span?
• How high should the start and end points be?
• What is the topography of the ground relative to the zip line cable?
• What will the start and end points be attached to and how can they be secured?
• How much tension should there be to give the zip line an appropriate slope?
• What will the weight limitations be?

WARNING: Always consult with an industry professional before attempting to design or build your own zip line.

The zip line illustrated below covers a horizontal distance of 255 meters (m) and has a vertical drop of 16 m to the lowest point. The start point is 13 m above the ground and the end point is 11 m above the ground. Both points have been securely anchored using trees. Notice that the topography of the ground has a slightly downward grade from the start point to the end point. There is an elevation drop of 12 m. This helps achieve a sufficient slope, approximately 4 degrees in this example, without causing the cable to be extremely high off the ground at the start point. For safety reasons, a weight range of 70 to 250 pounds is acceptable for a zip line this size.

Figure 1. Example measurements (heights, lengths, and elevations) for a zip line. Note: The drawing is not shown to a proportional scale.