OH GOODY, EVEN MORE ON GEARS!

Please Explore!


Of all the lessons utilizing LEGO® bricks, probably the ones on gears are the most prevalent. But hey, you can never study gears enough! They had a pretty profound impact on the world. So here goes....


GEARS are wheels with mating teeth cut in the rim or surface so that one can turn the other without slippage. The lever is basic to gearing. A pair of gears is essentially a set of spinning levers each with two equal arms acting in turn. Effective lever action is possible, however, only because a pair of mating gear-tooth profiles act against each other to produce the relative motion desired. Gears can be mounted on parallel, intersecting, or nonintersecting shafts. Consequently, they can:
  1. Change the plane of rotation.
  2. Increase or decrease the speed of Applied Motion.
  3. Magnify or reduce the Applied Force.
  4. Provide a drive without slippage.


The Theoretical Mechanical Advantage of any gear train is the PRODUCT of the number of teeth on the DRIVEN wheels ( gears ) DIVIDED BY the PRODUCT of the number of teeth on the DRIVER gears ( pinions):

TMA = Ng/Np



Hmmm...all fine and well, but I suppose I should elaborate....Let's look at some definitions! ( Oh boy Oh boy! )


GEAR SYSTEM
A system of two or more gears meshed together so that the motion of one is passed on to the other(s).
GEAR DOWN
To adjust gears in such a way that the DRIVER ( OUTPUT ) gear goes slower than the DRIVING ( INPUT ) gear. MORE POWER!
LOW GEAR
The arrangement of gears providing little speed but great power.
GEAR UP
To adjust gears in such a way that the DRIVER ( OUTPUT ) gear goes FASTER than the DRIVING ( INPUT ) gear. MORE SPEED!
HIGH GEAR
The arrangement of gears providing the greatest speed but little power.
REVERSE GEAR
The arrangement of gears providing reverse, or backward, motion.
SHIFT GEARS
To change from one gear arrangement to another.


And this all leads to blammo!

GEAR RATIOS


No not "radios," RATIOS! A "ratio" is a comparison. In the case of gears, ( if it has not been made obvious yet ) it is the comparison of TURNS OF INPUT to TURNS OF OUTPUT.
For example, a gear ratio of 5:1 ( an 8 toothed gear turning a 40 toothed gear in LEGO®) means that the input shaft must make five revolutions to produce one revolution of the output shaft. This also means that the output speed is five times slower, but the output torque is five times greater!

Funny how things work out that way.

INPUT SPEED:OUTPUT SPEED equals OUTPUT TEETH:INPUT TEETH

OUTPUT / INPUT


Okay, I challenge you folk in webland to look at the following gear trains and calculate the GEAR RATIOs! Or build your own and challenge your students to calculate the ratios! Oh my goodness applied mathematics!


Oh Goody, a GEAR TRAIN CHALLENGE!

Better Yet, TYPES OF LEGO® GEARS!


Go Back to Weird Richard

THANKS PAT FOR ORIGINAL TEXT
Copyright© 1996 by Richard Wright for PCS Education Systems, Inc. All Rights Reserved