2010- 2009
2008
Polyglot 12: R- Air Compressor
- Stanford CS145
- Retina
- Electoral College
- Obama vs McCain
- Perpetual Motion
- Book Safe
- Cráneo de Cristal
- Back to School
- Artificial Neuron
- Search Appliance
- Orthogonal Viewer
- Porcupine
- Bitmaps in JavaScript
- My Brain
- Domino Logic
- Faster is Better
- Transfer
- Car Fire
- Helsinki
- Jessa Gamble
- Maker Faire 2008
- Downhill Walker
- Youngme / Nowme
- Python Parallel Port
- MobWrite 2
- Class Clown
- Mask
- Progress
- Angel Island
- Scapegoat
- Localhost
- Disneyland
- Technical Difficulties
- Wooden Brain
- 2007
- 2006
- 2005
- 2004
- 2003
- 2002
Air Compressor
8 December 2008
My database course at Stanford is finally over! I learned a lot and I think I did well. To celebrate I built an air compressor.
One piston on a crank shaft would produce intermittent air flow since most cylinders are single-acting. Two pistons offset 180° would be better, but there would still be 100% pressure fluctuations twice per revolution. Three pistons offset at 120° would fill in these dips and smooth out the airflow. Presumably the more pistons one has, the better. Wrong. Somewhat surprisingly three pistons provides significantly smoother airflow than four pistons
- Two pistons:
![[Two pumps at 180 degrees]](/news/2008/piston2.gif)
- Three pistons:
![[Three pumps at 120 degrees]](/news/2008/piston3.gif)
- Four pistons:
![[Four pumps at 90 degrees]](/news/2008/piston4.gif)
(Black is the sum of the functions. Graphs computed at http://gcalc.net)
With the math complete, it was time to build it. I bought three bike pumps from a sporting goods store and some brass plumbing from a hardware store (freaky moment: the clerk didn't know how to give me 2 meters of tubing, had to order it in yards). Bearings arrived from VXB (their linear motion and large inner diameter bearings are so sexy).
Rather than use Meccano, I chose the challenge of using wood for everything except the camshaft. The primary motivation was to reduce the running noise of the compressor. Definitely a learning experience; in future I need to optimize wooden structures for simplicity rather than for minimal usage of material. Never the less, the result looks good and works well. Enjoy the movie:
(The music is "Morning Nightcap" from Lúnasa.)
The geek is back.
