First Design Problem

The first design problem with the submarine was to attach two sets of MirageDrive oscillating hydrofoils together.  The original connecting method connected the input links on each side of the MirageDrives with a single connecting link.  This formed a four-bar linkage, as shown below:

Old Design - 4 Bar Linkage

New Design - 5 Bar Linkage

This old linkage design prevented smooth motion through the hydrofoil cycle, resulting in a rocking motion.

Design Approach

A 3D model of the MirageDrive was created using Pro/ENGINEER to:

	Visualize and understand the problem
	Analyze proposed design solutions

The problem with the old connectors

Pro/ENGINEER Mechanism analysis illustrated that the required length for the connecting length changes through a hydrofoil cycle as a function of the pin separation.  That implies the cause of the rocking motion is due to the incorrect connecting link method.

The required link length as a function of the pin separation is shown below:

Link Length vs. Pin Separation

The new connector linkage

Solution of First Design Problem

A five-bar linkage was designed by adding a rotating arm to the original connecting setup.   The purpose of the rotating arms is to account for the required change in length.  Click here for an eDrawing of the assembly of the connecting linkage.

Second Design Problem

The second design problem was mounting the hydrofoil sets to the submarine hull while keeping the support completely fixed.  The submarine hull has a foam core which is weak in compression, so a large surface area is needed for mounting.  Past senior design groups were unsuccessful in achieving an adequate bond area.

The purpose of the hoops is to:

	Constrain the end mounts and pin of the MirageDrive
	Distribute loads on the hull over a large area

Solution of Second Design Problem

The best way to distribute the forces would be to build a frame inside the hull.  The frame consists of two hoops, one at the front of the foil sets and one at the rear.  Each hoop has a tab that extends at the top and bottom of the hull to hold the foil set.

The hoops

The MirageDrive on the hoops

A housing, which attaches to the tabs, surrounds each MirageDrive and supports it at the pins and end mounts as shown below.

The final design

FEA Output for front hoop

Material Selection

Finite element analysis was employed to qualitatively select the hoops materials.  A design decision has to be made between chopped glass fiber or glass fiber fabric with wood core.  The chopped fiber couldn't withstand the applied forces and hence glass fiber with wood core was selected.  Points of stress concentrations were reinforced by adding strips of carbon fiber.

See the anticipated

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Last Updated on 09/01/2005