The Scotch Yoke (also known as slotted link mechanism[1]) is a reciprocating motion mechanism, converting the linear motion of a slider into rotational motion, or vice versa. The piston or other reciprocating part is directly coupled to a sliding yoke with a slot that engages a pin on the rotating part. The location of the piston versus time is simple harmonic motion, i.e., a sine wave having constant amplitude and constant frequency, given a constant rotational speed.
Scotch Yoke Mechanism Project Report Pdf
The term scotch yoke continues to be used when the slot in the yoke is shorter than the diameter of the circle made by the crank pin. For example, the side rods of a locomotive may have scotch yokes to permit vertical motion of intermediate driving axles.[2][3]
The Scotch yoke is not used in most internal combustion engines because of the rapid wear of the slot in the yoke caused by sliding friction and high contact pressures[citation needed]. This is mitigated by a sliding block between the crank and the slot in the piston rod. Also, increased heat loss during combustion due to extended dwell at top dead centre offsets any constant volume combustion improvements in real engines.[4] In an engine application, less percent of the time is spent at bottom dead centre when compared to a conventional piston and crankshaft mechanism, which reduces blowdown time for two-stroke engines. Experiments have shown that extended dwell time does not work well with constant volume combustion Otto cycle engines.[4] Gains might be more apparent in Otto cycle engines using a stratified direct injection (diesel or similar) cycle to reduce heat losses.[7]
Scotch yoke mechanism is a type of a reciprocating motion. It makes use of a slotted slider based system to convert circular motion into linear motion and vice versa. This mechanism is used to drive the piston. The widest usage of this mechanism is in pumping systems for oil, gas and other liquids. So here we study this mechanism by fabrication of a small piston driven by this mechanism. We use a motor to drive the circular disc. The disc has a small yoke in order to connect with the reciprocating arm. The arm has a slotted area just wide enough to adjust the yoke. The other end of the arm is fitted in a piston cylinder. The whole setup is fabricated to get the desired motion at least friction. This can also be used as a small part of other larger projects where linear motion is needed.
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