The Physics Bus has been modified to run on waste vegetable oil. This isn’t hard to find -- it’s the ‘fryer grease’ that many fine establishments use to cook their french fries, donuts, or tortilla chips. They throw it out when it loses its good taste. We put it in the bus to make it run for free!
In order to work as engine fuel, veggie oil needs to be heated. This is because it is thick at room temperature and can even ‘gel up’ on cold days. Syrupy fuel is difficult to pump, impossibly slow to filter, and cannot be made into the fine mist that is necessary for combustion in the cylinders. At the ideal temperature of 180 degrees Fahrenheit, veggie is as good as diesel.
The main veggie tank, an old 55 gallon “racing fuel” barrel, has a coil of copper tubing inside it. Hot water from the engine flows through this coil heating the tank. The hot veggie oil gets pumped from the tank through a line which is inside of the hot coolant hose. This way it gets hotter and hotter as it gets nearer to the engine.
Former Aztlan Academy/Physics Factory student Marty volunteered to install the tank.
Once the veggie oil gets to the engine compartment it makes a pit-stop at what we call the "baby tank". This tank, a retired pressure cooker, has one gallon of veggie oil in it at all times. The tank is equipped with an electric heating element: with the flip of a switch this tank can be heated to operational temperature in less than 5 minutes.
Now that it is nice and hot, the veggie oil can be filtered easily. At this point it could be filtered through any normal diesel truck filter, but this type of filter, generally made of paper inside, would become clogged as soon as the bus cooled down. Instead we use a filter with a fine metal mesh screen inside. This way it can be cleaned and reused.
Mentor John Katz installing the oil filter.
After the oil goes through the filter, it is ready to go into the engine where the diesel fuel used to go. And the Physics Bus is on its way to your school!