Automated Lilypad Raft Storage

University of Wisconsin - Madison: Senior Design Capstone

Main Skills Used:

Project Management

CAD (Solidworks)

Automation (Rockwell Automation)

Iterative Prototyping

Project Background

As part of my senior design capstone course, my team was tasked with developing a rolling mechanism to store and deploy a foam “Lilypad”—a large, buoyant pad used for recreational swimming on lakes. The project was funded by an electric pontoon boat startup seeking an innovative way to enhance time on the water by integrating Lilypad storage directly within the pontoon. The challenge centered around designing a mechanism for a space-efficient, cylindrical storage solution while ensuring the boat's stability and functionality.

(Pontoon boat pictured is not associated with the client)

Design Criteria

In collaboration with the client, the following design criteria were established for the mechanism:

The fully rolled pad must fit within the pontoon’s designated geometry.
The rolling mechanism must operate with a smooth and continuous motion.
The pad must be deployed and stored through a hatch located above the waterline.
The mechanism should be automatically actuated via user controls.

Initial Prototype

The initial prototype was constructed using 3D-printed components and craft materials to evaluate the motion mechanics. This design incorporated a torque arm, actuated by a hand crank, to rotate the pad around a central axis. The torque arm was left unrestrained in the radial direction, allowing it to accommodate the increasing roll radius as the pad was rolled up.

Key insights gained from this prototype included:

Friction relief was necessary between the roll and the outer cage to prevent resistance caused by the pad pressing against it during unrolling.
A spring mechanism was required to keep the torque arm extended, maximizing its effective length.
A minimum radius was needed to define the inner diameter of the roll for optimal performance.

Second Prototype

This iteration addressed the previously identified issues by implementing the following improvements:

Rollers (bearings) were added to guide the pad along the cage, reducing friction.
Stronger materials were incorporated to withstand higher torque loads.
A spring mechanism was integrated to keep the rolling arm extended.
An axial cylinder was added to define and maintain the inner diameter of the roll.

It was determined that the rotating arm was an over engineered solution and that the inner diameter cylinder alone was sufficient to address torque concerns. A comma-shaped design was then developed as the attachment point for the pad. This design successfully facilitated the rolling and unrolling process, as the pad's stiffness allowed it to push outward from the inner radius.

This design was incorporated into the full size model with the addition of clamps for testing.

Final Full Size Prototype

A full-scale prototype was constructed using a repurposed garbage truck tarp motor system for actuation, paired with an aluminum axle. A toggle switch and Pulse Width Modulation (PWM) controller were integrated to enable variable speed control and bidirectional operation. Lightweight aluminum conveyor rollers were incorporated to provide friction relief and structural support for the outer cage. Since the pontoon geometry was proprietary to the client, a simplified mock-up box was built to replicate the interior width and height dimensions for testing.

This prototype was delivered to the client to help them better evaluate the torque load required for rolling the stiff foam pad.

Automation Project

As part of my continued education at UW-Madison, I enrolled in an Advanced Industrial Automation course. This course focused on Rockwell Automation systems using Rockwell Trainers provided by the university. As part of the coursework, I simulated motor automation with sensor feedback and HMI control while integrating safety features. Additional details are outlined in the project report.

Guinter_Project_Report.pdf

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