Mechanism  :-Dhobi prashant  :-Kale kalesh  :-Jain suraj

Geneva mechanism

figure of Geneva mechanism

 A Geneva mechanism is commanly used mechanism for producing an intermittent rotary motion from a uniform input speed. rotary motion from a uniform input speed.  The driven member,or star wheel,contains evenly spaced slots into which the roller of the driving crank slides into.  The number of slotes determines the ratio between the dwell and motion periods of the driven shaft.

 The mechanism requires a minimum of Three slots to function and additional slots can be added. Three slots to function and additional slots can be added.  As the drive wheel turns it enters the slots of the driven,or star,wheel and the mechanism enters its motion period. mechanism enters its motion period.  As the pin leaves the slotes the driven wheel has been indexed and it continues to stay stationary untill the pin rotates bask around. stationary untill the pin rotates bask around.

 Geneva mechanism can come in a variety of form and sizes increasing the number of slots in the mechanisms driven wheel decreases the angular displacement by each rotation of the driving wheel.  The other characteristic of geneva mechanism is the “locking” feature.  That is when the driven wheel is not being turned by the driving wheel,it is locked in turned by the driving wheel,it is locked in place and is unable to ratate. place and is unable to ratate.

Watt’s mechanism

figure of watt’s mechanism figure of watt’s mechanism

The Watt’s Mechanism is a simple mechanism consisting of a piston used to sense the external pressure. The piston is connected to a link and the link is, in turn, connected to a V- Shaped chain. One end of the V- Shaped Chain is connected to a point which is pivoted and fixed. The other end of the V- Shaped Chain is free to move over a vertical scale.

The point, worth noting, in the Watt’s Mechanism is that the free link that moves over the scale generates a straight line. This is the primary reason, why the Watt’s Mechanism is also called as the Straight Line Mechanism.

ADVANTAGES OF THE Watt’S MECHANISM: The measurement of altitude of an aircraft by the use of a Watt’s Mechanism has many advantages, some of which are listed below. 1. Less dependence on the use of the Pitot – Static System, the susceptibilities of which have been said earlier. 2. Altitude Measurement Sensors have been replaced by the system, which eradicates the problem of burdening of ice.

3. The problem of fluid contamination in the Pitot – Static System is eradicated as there is no use of fluids in the Watt’s Mechanism. 4. There are no small gaps or crevices in the Mechanism, which makes it impossible for foreign matter to settle on the system.

DISADVANTAGES OF Watt’s MECHANISM: Like everything and everyone, the Watt’s Mechanism has its own kind of disadvantages which have been mentioned below. 1. The process is completely composed of mechanical components which are susceptible to sudden failure. Constant and thorough inspection is required.

Scott russel mechanism

Figure of scott russell mechanism

 A scott russell linkage converts linear motion to linear motion in a perpendicular to the to linear motion in a perpendicular to the input. input.  The linkages are often used in front wheel drive vehicles with solid rear axles to drive vehicles with solid rear axles to control lateral movement. control lateral movement.  The engineering design of locomotives improved over the years and by the year improved over the years and by the year 1830, the linkage straight line motion 1830, the linkage straight line motion finally disappeared. finally disappeared.

 It lingered on for many years with stationary engines,especially those with vertical cylinder. engines,especially those with vertical cylinder.  The main defect of the straight line motions was their ungainly size and weight especially was their ungainly size and weight especially for fast engines compared to a compact for fast engines compared to a compact slider mechanism. slider mechanism.

 Scott russell linkages are still used today in front wheel drive motor vehicles with solid front wheel drive motor vehicles with solid rear axles to control lateral movement. rear axles to control lateral movement.  A scott russell linkage on the rear axle of a 2002 Nissan sentra Nissan sentra.

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