Motion Transformation Systems

The mechanical fxn of relaying a motion from 1 part to another while altering the nature of the motion.

5 Systems1) 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 TranslationorTranslation to Rotation

Reversible

Rack and Pinion

• 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=D3MrUngdlCQ

Screw Gear SystemsType 1 • the screw is the driver• rotational is transformed into translational• e.g. jacks for lifting cars

Screw Gear Type 1Scissor Car Jack

http://www.youtube.com/watch?v=QeB2YxMqogI

Screw Gear SystemsType 2• the nut is the driver• rotational to translational• e.g. pipe wrenches

Screw Gear Type 2Pipe Wrench

http://www.youtube.com/watch?v=HYspwtCZ1yo

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=KnASJHtbGB0