Degree Name

BS in Mechanical Engineering


Mechanical Engineering Department


Jim Widmann


JumpSport, a major trampoline company, has requested Cal Poly to design a custom play-structure consisting of large diameter balls with two types of connectors-long rod connections and very close connectors (for a ball-to-ball type connection). By the end of the project, appropriate testing will be carried out on the connections and a full-scale model will be constructed.

After an extensive design process, our team of three decided on a rod connection style for both the long and short connectors. These consist of a hook that latches into a loop protruding from the ball where the hook is attached by a power screw. The hook/power screw assembly is covered by a sleeve and plunger style cover assembly. The sleeve rides the threads of the power screw to tighten or loosen the fit of the plunger surface to the ball. Thus, the plunger acts to cover the hook while creating a suction to the ball so that the connection stays tight. For the short connector length is equal to approximately four inches so that adequate space is provided for a hand or foot to fit between the balls. The long connector is approximately four feet in length. This length is equal to the sum of one ball diameter and two short connectors so that at any time the created play-structure can be easily altered.

The prototypes will be produced by the team-Gary Johnson, Rosalie Mangione, and Steve Rose. The initial parts will be machined and an at home molding process will be used to replicate parts. Purchased parts in conjunction with these self-made parts will be assembled by the team.

Structural testing was conducted on both styles of connectors. The ball used to adequately measure the desired features are produced by Mondo. This Mondo product uses a plastic we intend to use except for a larger diameter. Testing on the Mondo products allows us to obtain the necessary test results without the need to produce a ball with the correct diameter. These tests include but are not limited to maximum weight capacity, tensile and shear tests on the loop alone, etc. This data was used to determine Young’s Modulus for the Mondo ball’s plastic. This information was useful in relating our calculated data to our tested data.

In the end, a full scale prototype was made and assembled using an alternative to the Mondo ball so as to meet the diameter requirements. The reason for a full scale prototype is to model the connection points also designed by the team. From this full scale prototype we learned that simply adhering loops to the balls is not an appropriate substitution because it cannot even handle the static loads of the structure simply supporting itself. However, this prototype did yield useful information about the ergonomic qualities of the structure. Connecting a ball that will be suspended in the air proved difficult for two adults and would be impossible for young children alone. Due to these problems, a decision cannot yet be made without further testing using more appropriate materials. However, as the project stands currently, it is not a viable product.