scotch yoke mechanism project report pdf

[prateet]

The Scotch yoke (also known as slotted page link mechanism ) 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 a sine wave of constant amplitude, and constant frequency given a constant rotational speed.
This setup is most commonly used in control valve actuators in high-pressure oil and gas pipelines.
Although not a common metalworking machine nowadays, crude shapers can use Scotch yokes. Almost all those use a Whitworth linkage, which gives a slow speed forward cutting stroke and a faster return.
It has been used in various internal combustion engines, such as the Bourke engine, SyTech engine, and many hot air engines and steam engines.
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.
Under ideal engineering conditions, force is applied directly in the line of travel of the assembly. The sinusoidal motion, cosinusoidal velocity, and sinusoidal acceleration (assuming constant angular velocity) result in smoother operation. The higher percentage of time spent at top dead centre (dwell) improves theoretical engine efficiency of constant volume combustion cycles. It allows the elimination of joints typically served by a wrist pin, and near elimination of piston skirts and cylinder scuffing, as side loading of piston due to sine of connecting rod angle is mitigated. The longer the distance between the piston and the yoke, the less wear that occurs, but greater the inertia, making such increases in the piston rod length realistically only suitable for lower RPM (but higher torque) applications.
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. 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. Gains might be more apparent in Otto cycle engines using a stratified direct injection (diesel or similar) cycle to reduce heat losses.

[pawan]

Theory of machine:
It is a branch of engg. Which deals with study of relative motion between the various parts of machine & forces which acts on them.
Application or scope:
It is very essential for an engineer in designing the various parts of a machine.
Mechanism:
o It is like skeleton & has definite motion between various links.
o It is model of machine.
o It is related to the motion.
o It may be many links e.g. Engine indicator, typewriter etc.
Link or kinematics page link or element:
Each part of machine which moves relative to some other part is known as cinematic page link or element. A page link may have consisted of several parts which are manufactured as separate unit.
Characteristic of link:
o It must be a resistance body.
o It should have relative motion.
Types of links:
o Flexible link
o Rigid page link

Kinematics pair:
Kinematics pair has two elements or page link together which have relative motion between them. The motion between them completely or successfully constrained.
Classification of Kinematics pair:
1. On the basis of contact:
Lower pair
Higher pair
2. On the basis of type of constraint:
Closed pair
Unclosed pair
3. On the basis of type of relative motion:
Sliding pair
Screw pair
Turning pair
Spherical pair
Rolling pair
Inversion of mechanism:
When of the links is fixed in a kinematics chain ,it is called mechanism .so we can obtain as many mechanisms as the number of page link in a kinematic chain by fixing ,in turn , different page link in a kinematics chain . This method of obtaining different mechanism by fixing different links in a kinematic chain.
Types of inversion:
1. Four bar chain or quadric cycle chain:
o Beam engine
o Coupling rod of locomotive
o Watt s indicator mechanism
2. Single slider crank chain:
o Bull engine or pendulum engine
o Oscillating cylinder engine
o Rotary engine
o Crank & slotted quick return mechanism
o Whitworth quick return mechanism
3. Double slider crank

o Elliptical trammels
o Scotch yoke mechanism
o Oldham s coupling
Scotch yoke mechanism
When of the links is fixed in a kinematics chain ,it is called mechanism .so we can obtain as many mechanisms as the number of page link in a kinematics chain by fixing ,in turn , different page link in a kinematics chain . This method of obtaining different mechanism by fixing different links in a kinematic chain.

This mechanism is used for converting rotary motion into a reciprocating motion. The inversion is obtained by fixing either the page link 1 or page link 3. In figure page link 1 is fixed. In this mechanism, when the page link 2 (which corresponds to crank) rotates about B as center, the page link 4 (which corresponds to a frame) reciprocates.

[rajsekharg87]

Hi im sandesh..i was completed mimi project on scotch yoke mechanism..but i cant complete project report..i need to complete projet report on 20 th oct 2016..