Motion Transformation Systems
The mechanical fxn of relaying a
motion from 1 part to another while
altering the nature of the motion.
5 Systems
1) Rack and Pinion Systems
2) Screw Gear Systems Type 1
3) Screw Gear Systems Type 2
4) Cam and Follower Systems
5) Slider-Crank Mechanisms
Rack and Pinion Systems
Rotation to Translation
or
Translation to Rotation
Reversible
Rack and Pinion
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at least 1 gear = a pinion
1 straight bar with teeth = rack
teeth on rack and pinion must be identical
frequent lubrication
the greater the # of teeth the slower the rotation
Rack and Pinion Animation
http://www.youtube.com/watch?v=D3MrUngdl
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Screw Gear Systems
Type 1
• the screw is the driver
• rotational is transformed into translational
• e.g. jacks for lifting cars
Screw Gear Type 1
Scissor Car Jack
http://www.youtube.com/watch?v=
QeB2YxMqogI
Screw Gear Systems
Type 2
• the nut is the driver
• rotational to translational
• e.g. pipe wrenches
Screw Gear Type 2
Pipe Wrench
http://www.youtube.com/watch?v=HYspwtCZ1y
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Screw Gear Systems
• type 1 (car jack) has the nut connected to the
screw so that the nut cannot rotate
• in both systems the threads of the screws and
nuts must match
• type 2 (monkey wrench) has the nut fixed so
that its only possible motion is rotational
Cam and Follower Systems
• transform the rotational motion of a cam into
the recriprocating translational motion of a
follower
• a back and forth movement like that of a
sewing machine
• cams = rotational axis is centred
• eccentric cams = rotational axis is off-centre
Cam and Follower
• the follower must be guided in its translational
motion
• the shape of the cam determines how the
follower will move
• a device such as a return spring is usually
necessary to keep the follower in continual
contact with the cam
Cam and follower
http://www.youtube.com/watch?v=ZbdsGf_t8hs
Slider-Crank Mechanisms
• used in internal combustion engine
• to transform the translational motion of the
pistons into the rotational motion of the crank
Slider - Crank Mechanisms
• the connecting rod contains 2 bushings to
attach it to the crank and piston
• the cylinder must guide the part moving in
translation
• frequent lubrication
Slider - Crank Mechanisms
http://www.youtube.com/watch?v=KnASJHtbGB
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