Hovercraft












During my mechanical design course, I worked on a team of five to design and build a 5 HP hovercraft. Below is our report's executive summary. To view the complete design report (with CAD drawings and parts) please see the attachment.


Executive Summary:
Team Awesome was formed on the premise of designing and building a human rideable hovercraft. The goal for
the project was to build a large ‘floating platform’ capable of holding multiple people and running independent of
any external power source. With the design goals of simplifying fabrication and construction, minimizing cost, and
maximizing safety, the team built an operational transmission driving a 22” lift fan from a 5HP gas engine and
fabricated the larger craft frame attaching to this transmission module, but issues with skirt design and fabrication
currently limit the craft’s hovering performance.

To fully implement these ideas within the budgetary constraints of the project, a significant design emphasis was
placed on low cost and free parts. A standard design process would be to determine ideal payload, then calculate
pressure and flow rate, choose an appropriate fan, and purchase an engine appropriate for the fan’s power
requirements. However, due to the cost of parts, we instead setup a series of relationships to calculate minimums
for each of these components and fit the design to parts we could acquire.

In this vane, the first engine chosen was pulled from a 1985 Kawasaki 750 Turbo donated to the team by an
alumnus. The initial fan selection and transmission design were both designed for this motor. Despite cost cutting
efforts, however, we were unable to get the cost for the necessary transmission within our budget. After
additional searching, the Kawasaki was ultimately replaced by a 5HP Tecumseh vertical shaft lawn mower engine
that we were also able to freely acquire.

A lift fan for the craft was selected for this engine and the transmission designed around it. The 8 blade 25 degree
pitch No.3 lift fan is connected to the engine via a belt drive geared to run the fan near 3600rpm. The transmission
is constructed of steel tube with one high precision bearing housing attached to hold the fan shaft. This
transmission structure was built after a full loads analysis of all the power transmission points and a FEA of the
structural components were conducted. The design is strong enough in all aspects by respectable safety margins
and is now operational.

The body of the hovercraft has been designed as a separate frame and deck, which the transmission and engine
assembly can be bolted onto and removed from. The chassis is built with a frame of steel tubes to which a
plywood deck is mounted. A skirt has been fabricated and attached to this deck, but the high stiffness of the skirt
material in conjunction with fabrication difficulty has resulted in a wrinkled skirt that does not create an adequate
seal between craft and ground necessary for hovering operation. Replacing this skirt with another solution,
however, should result in a fully functional hovercraft.

This project has been organized, at the highest level, by a series of two gates. The first gate in this process was an
analysis, design, and construction of the entire transmission module, complete with demonstration. This gate was
achieved on time, though the transmission module has since been modified. The second gate involved the
fabrication of the rest of the craft and integration of the transmission module, leading to our current design.

While members of the team have worked through all elements of the project, Dan Greely and Chester Macklin
have led fabrication efforts, with Joe Funke and Heena Mutha providing calculations verifying design choices, and
Bryce Lee has directed the structural design and analyses. Possibly the most important lesson learned is that
identifying and addressing critical elements early is of utmost importance. The team spent large amounts of time
working on solutions that turned out to be too expensive, and we also did not adequately prepare to deal with
fabrication difficulty of what turned out to be one of the most important elements of the hovercraft, the skirt.
From these lessons, we conclude by offering possible redesigns to improve performance.
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Heena Mutha,
Mar 28, 2010, 11:46 AM
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