Straight Line Mechanisms

 

Straight line mechanisms

- Straight line motion mechanisms are mechanisms, having a point that moves along straight line, or nearly straight line, without being guided by a plane surface -Generation of straight line motion using linkage mechanisms has always been common requirement in machine design practice. - Although exact straight line can't be generated using simple mechanisms though some simple mechanisms are designed such that they can generate approximate straight lines for short range of motion. - These approximate straight line mechanisms has important application in machine design. - These mechanisms were used extensively in classical machines such as steam engines. - Perfect straight line can also be generated using linkage mechanisms but those are relatively complex mechanisms. - There are two classes of straight line mechanisms: a) Approximate straight line mechanisms. b) Exact straight line mechanisms.  _the straight line mechanisms were mostly developed were mostly developed in industrial revolution days when many machines required straight line paths in their operation, whether it was guiding the piston of engines or for operating valves 1)

EXACT STRAIGHT LINE MOTION MECHANISMS Condition of exact straight line motions If point B moves on the circumference of a circle with center O and radius OA, then, point C, which is an extension of AB traces a straight line perpendicular to a provided product AB and AC is constant. Examples:

  Peaucellier exact straight line motion mechanism  

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Hart mechanism 2) APPROXIMATE STRAIGHT LINE MOTION MECHANISMS A few four bar mechanisms with certain modification provide approximate straight line motions Various approximate straight line mechanisms:

         

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watt's mechanism

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modified Scott Russell mechanism

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Grasshopper mechanism

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Techebicheffes mechanism

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reboert's mechanism

NAME SEC SEAT NO.

‫ب‬ ‫خط‬ ‫لسيد‬ ‫محمد‬ ‫لسيد‬ ‫كنوز‬ 5 118

 

Straight line mechanisms