Wednesday, December 12, 2012

Portland State University Engineering Department

So I've been doing the career change thing for the past few years now, and I've finally made it to Portland State University. The past two years of full time plus at Portland Community College have been good, but I'm happy to finally have the foundation of my lower-division credits, and move on.

Now that I'm actually in the engineering department I get to take the meatier classes. There are three big categories of mechanical engineering: solids, heat transfer, and fluids. The first two are what they sound like, and fluids have to do with gasses and liquids. For the first two years of prerequisites, we really only dealt with solids, as they are a bit more straight forward. It turns out that fluids are a topic that enjoy since my big interest is in the renewable sector; learning how fluids work is very applicable for wind and hydroelectric power.

My first 3D-printed VAWT
Since I'm eager to apply what I've been learning to actual projects, I applied to and got hired on by the university as an undergraduate researcher in the Wind Energy and Turbulence Lab under Raul Cal. My personal research project is to develop a working model of a vertical axis wind turbine (VAWT). Having this research project is great, as it gives me learning goals outside of just finishing homework or taking a test. I've been using rapid prototyping to develop my models, so I've been doing all sorts of tutorials for SolidWorks (3D modeling) and using the engineering department's 3D printer. Most people in the lab are PhD candidates, so I'm getting exposed to concepts above and beyond the undergraduate level, reading scholarly articles, helping out in the wind tunnel, etc.

The wind tunnel and turbines (the turbines are about six inches tall)

I have seven terms down and another five to go. I can't to get out in the world and start working, but at least school is interesting!

Friday, June 1, 2012

Designing a Better Bike Polo Mallet

My big pastime is bike polo, so naturally I find myself thinking about the sport a lot. It is still a developing sport, so there are constantly innovations in gameplay, tactics, and equipment. In a materials science class we were talking about plastics, and it got me thinking about polo mallets... there is a lot to be desired about their design. ABS tubing has been used in bike polo mallets for years now. It is cheap, easy to find, and light, but it wears quickly and shatters into jagged edges. This means that we have to make new mallets all the time, which is a pain. In addition, the jagged edges make for inconsistent shots, so people started using solid caps on the ends of the mallets to try and even things up.

Wanting to use some of the engineering principals that I've been learning about, I decided to design a better mallet head. The main design goals were: light weight, durability, and performance.

I started out just testing materials for their wear characteristics, from HDPE, to Bakelite, to molybdenum phenolic. Finally I settled on UHMWPE (Ultra High Molecular Weight Polyethylene) as it had the best wear-resistance to weight ratio.

After settling on a material, I made some prototype mallets out of tube stock with an attachable cap, but the added weight of the cap and the machining time proved prohibitive. To try and save on weight, I tried drilling out the sides of the mallet head, but that weakened it too much and introduced lateral flex.

To get around this, solid stock was machined out and internal butting was introduced to find a balance between weight and stiffness. By drilling a blind hole, we automatically had an integrated cap, which provided both a good striking surface and added strength. With this design, I took the mallet to the club and after group testing, several rounds of improvements, and a host of manufacturing problems due to the blind hole, I went into production with the Portland Bike Polo Mallet Head. The mallet heads have now been shipped world-wide and have a 5th place finish at the World Championships under their belt.