## Posts Tagged ‘rotating machinery’

### Pulley Diameter Determines Speed

Saturday, April 8th, 2017
 Soon after the first pulleys were used with belts to transmit mechanical power, engineers such as Leonhard Euler and Johann Albert Eytelwein discovered that the diameter of the pulleys used determined the speed at which they rotated.   This allowed for a greater diversity in mechanical applications.   We’ll set up an examination of this phenomenon today.     Last time we introduced this basic mechanical power transmission system consisting of a driving pulley, a driven pulley, and a belt, which we’ll call Situation A.   A Driven Pulley’s Larger Diameter Determines a Slower Speed         In this situation, the rotating machinery’s driven pulley diameter is larger than the electric motor’s driving pulley diameter.   The result is the driven pulley turns at a slower speed than the driving pulley.     Now let’s say we need to speed the rotating machinery up so it produces more widgets per hour.   In that case we’d make the driven pulley smaller, as shown in Situation B.   A Driven Pulley’s Smaller Diameter Determines a Faster Speed         With the smaller diameter driven pulley, the rotating machinery will operate faster than it did in Situation A.     Next week we’ll introduce the Pulley Speed Ratio Formula, which mathematically defines this phenomenon.  Copyright 2017 – Philip J. O’Keefe, PE Engineering Expert Witness Blog ____________________________________

### The Difference Between Driven and Driving Pulleys

Friday, March 31st, 2017
 Last time we introduced two historical legends in the field of engineering who pioneered the science of mechanical power transmission using belts and pulleys, Leonhard Euler and Johann Albert Eytelwein.   Today we’ll build a foundation for understanding their famous Euler-Eytelwein Formula through our example of a simple mechanical power transmission system consisting of two pulleys and a belt, and in so doing demonstrate the difference between driven and driving pulleys.     Our example of a basic mechanical power transmission system consists of two pulleys connected by a drive belt.   The driving pulley is attached to a source of mechanical power, for example, the shaft of an electric motor.   The driven pulley, which is attached to the shaft of a piece of rotating machinery, receives the mechanical power from the electric motor so the machinery can perform its function. The Difference Between Driven and Driving Pulleys          Next time we’ll see how driven pulleys can be made to spin at different speeds from the driving pulley, enabling different modes of operation in mechanical devices. Copyright 2017 – Philip J. O’Keefe, PE Engineering Expert Witness Blog ____________________________________