2.15.2009 (Sunday) – Day 25 –
When we decided to build Science City’s 10′ by 12′ Robotic Labyrinth using a center pivot point it became obvious that we needed a game table that could remain rigid across the surface and still be light weight. That Balancing Act was described previously by using an aluminum skinned composite with an extruded polystyrene foam core.
Over the last few weeks I’ve been searching for information about aluminum composite panels and other variations of this general search criteria. Most of the hits seem to be related to insulated building panels with wooden skins while others discuss composite materials like carbon fiber and fiberglass materials.
Finally I came across the Bluebird Electric Bodywork web page that offered some clues into the relationships within their composite design. Of particular interest is the effect the thickness of materials have on stiffness. The site provides some interesting general engineering information about the design and core material types but it left me wanting to find more proof of the claims.
The Aluminum Panels
The desired size of our game platform halves are 6 foot by 10 foot panels designed to fit through doorways. We can easily order 4 foot by 10 foot sheets of aluminum which leaves us with a seam formed by a 2 foot by 10 foot section. Welding aluminum without seriously warping and distorting the sheet is beyond my current skill level. This is a big reason we are pursuing the 3M Aerospace Adhesive engineers to find their best adhesive for the job. The product they suggest is Scotch-Weld Epoxy Adhesive 2216 in the Gray compound.
A couple of years ago I stopped in a West Marine store in Miami and found their book section. I like books about building things and found the book titled “Aluminum Boat Building” by Ernest Sims which I bought. I pulled that book out tonight and noticed Appendix 2 is about adhesives for marine applications. It was Appendix 1 that really caught my attention. That section is about a relatively new process called Friction Stir Welding (FSW) developed in the UK by “The Welding Institute”. This process uses heat generated by a rotating tool which only heats the aluminum up to a plasticized state staying below the melting point. I don’t know of any companies in the Kansas City area yet that offer this process. I did some searching on the Internet and found the Missouri University of Science and Technology in Rolla is doing research on this process.