Standard Gears
Nearly all models will require at least one gear, as rarely will
all of the axles be running at the same speed and be in the same
position. Gears can be used to reduce speed, and there are four
basic Lego gears. I will use the names 'small', 'medium', 'normal'
and 'large' to describe them.
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The small gear has eight teeth
and a radius of half a Lego unit. |
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The medium gear has 16 teeth
and a radius of one Lego unit. |
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The standard gear (don't ask
me why I call it a standard sized gear!) has 24 teeth and
a radius of one and a half Lego units. |
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The large gear has 40 teeth
and a radius of two and a half Lego units. |
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In order to reduce or increase
the gear speed, you must combine one or more of the gears
shown. In the example on the left, by turning the near handle
you turn the eight toothed cog, which turns the 24 toothed
cog which turns the other handle (the blue dot is a marker).
The ratio for the decrease in speed in 24:8, which you can
cancel down to 3:1. This means that the large handle turns
around once for every three turns of the smaller handle. Another
important thing to note is that the gears will turn any gears
touching them in the opposite direction, an important consideration
if you are building a model. |
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Here is another
example. The handle is again connected to a small cog, but
this time it turns a 40 toothed cog. The ratio of speed is
this time 40:8 which cancels down like a fraction of 5:1. |
| But standard gears aren't
all perfect. In the two examples above, only three of the
four main cogs have been used. This is because the medium
sized one will only combine with itself on a beam. You can
see this by looking at the radii of each cog. You cannot mesh
a small gear and medium gear as no Lego beam has holes which
are 1.5 spaces apart. There is a way to get around this though,
and that is by meshing them on a beam, like in the picture
opposite. You will need to position a half bushing between
the two crossblocks to making the spacing correct. As a general
rule, the sum of the radii of two meshing gears must equal
the distance between their centres. |
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| Another way to join two gears
in which one is a medium sized gear, is to attach them vertically.
You will need to make sure that there is a 1/3 plate between
the two beams in order to space it properly. The gap is a
little wider than it needs to be, but is still enough to fit. |
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