| 1 bar linkage |
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| When a single bar is pivoted at one end, the other end will
turn round in a circle. This is the basis of the familiar crank.
The axle around which the free end of the crank turns is called,
appropriately, the crankshaft. |
There are many LEGO parts that can be used as a crank:
engine crank, pulley, gear,
liftarm, cam, etc.
Applications: windlass
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| A crank is actually a form of lever where the
force is applied in a circular motion (better known as torque). |
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| The force can be applied to turn the crankshaft as
by a motor and the free end of the crank can then be made to
perform work, like kicking a ball. |
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| Alternatively, the force can be applied to the
free end of the crank and the work is done at the axle (or
crankshaft) as in a windlass. |
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| This is also what you are doing when you crank up
an engine. But nowadays it is easier to just turn the
ignition key :-) |
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| 2 bar linkage |
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| The 2-bar link forms a hinge with the two bars opening or closing about the common
pivot point. Familiar as a pair of tongs. Most commonly used
as a jaw. Actually a 2nd class lever with the fulcrum at the
pivot point. |
How about the jaws of T. rex?
Use as grabber
Lever for pumping the large pneumatic pump. |
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| 3 bar linkage |
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| The 3-bar linkage is familiar as the Watts
linkage. |
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| Note that if the 3 links are closed, a triangle
results which is a
rigid structure. Although the closed 3-bar linkage is useless as
a mechanism as the parts are immovable, it is just great for strengthening your creations. |
Triangular tread drive. |
| It has been known since ancient times that if the
bars are in the ratio 3:4:5, a right angled triangle results.
There are not many right angled triangles you can make with
LEGO. Can you find them? |
Good old Pythagoras' Theorem? |
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| 4 bar linkage |
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| This is the most important linkage category. You
will find applications of the 4-bar linkage in almost if not all of the Technic
models. |
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| Inversions |
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