Alt-BEAM Archive
Message #01353
To:
From: James Wilson jameswilson@globalserve.net
Date: Sun, 07 Mar 1999 12:26:55 -0500
Subject: [alt-beam] Re: I have 100 Gearmotors For Sale
It is very simple to determine the gear ratio. The number of teeth is
irrelevant, for our purposes the number and size of the teeth can be
completely ignored. The only thing that is of interest is the diameter. I
will walk you through the thought process:
If gear A has a diameter of 1 and gear B has a diameter of 4 there are two
possible gear ratios.
1) Gear A is driving Gear B so pick a point on the perimeter of both
gears that are touching, now drive A, (because the circumference of a circle
is pi times diameter we can ig nore the pi and just compare diameters ) the
distance traveled by the point on the diameter of A will always be equal to
the distance the point on B traveled the ratio of revolutions is now very
simple to calculate the smaller or A has to go around 4 times to make B go
around once thus a ratio of 4:1
2) Gear B is driving the process is the same but reversed thus 1:4
So for multiple gears simply start by finding each of their diameters,
determine where the power is being applied and select a point on the
diameter where each gear touches each other and divide and multiply the
appropriate numbers.
specific example
1/8" driving 7/8" give a ratio of 7:1 3/16" driving 7/8" gives a ratio
of 14:3 but the driver in the second ratio is coupled to the driven in the
first couple so if the 1/8" gear rotates 98 times the final 7/8" gear will
rotate 3 times thus 98:3 or 39:1.
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