Mechanisms

Now that the class is working on our Lego cars, we've been learning about gears and mechanisms.  There are obviously hundreds of different mechanisms used in engineering and for this assignment, we explored Cornell's Kinematic Models for Design Digital Library (KMODDL) http://kmoddl.library.cornell.edu/index.php

There were so many mechanisms to explore that it was hard to choose one to talk about. One of the mechanisms from this collection that I found interesting was the Slider Crank Mechanism.  

http://media-3.web.britannica.com/eb-media/90/4190-004-4DAAB8E9.jpg

The description said this mechanism "may be the most ubiquitous mechanism in the world" because it is found in every internal combustion engine.  Now, I'm not really a car person at all, so the extent of my knowledge about combustion engines is that the piston moves up and down because of pressure from the sparks created.  I know now that the up and down of the piston is aided by a slider crank mechanism.

http://www.allsubjects4you.com/reciprocating-engine_files/image002.jpg

First, I'll explain how this mechanism works on its own.  Basically, it changes rotational motion into linear motion.  The wheel or handle is rotating, and in the image above, point A is fixed and the rod from A to B moves around point B in a circular motion.  The other end is not fixed, but slides back and forth in some type of guide.  Now, this crank has four links, and it can be modified four different ways, changing the part that is grounded or fixed.  So hopefully you can see where the combustion engine comes in. The sliding part of the mechanism is the piston on top and the rotational motion is below the piston. It's clear that this mechanism is extremely important for engineering because of it's many uses.