Transcript Geneva mechanism

Mechanism
130460119026:-Dhobi prashant
 130460119038:-Kale kalesh
 130460119034:-Jain suraj
figure of Geneva mechanism
 A Geneva mechanism is commanly used
mechanism for producing an intermittent
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.
 As the drive wheel turns it enters the slots
of the driven ,or star,wheel and the
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.
 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
place and is unable to ratate.
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 Altitude Measurement Sensors have been replaced
by the system, which eradicates the problem of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.
Figure of scott russell mechanism
 A scott russell linkage converts linear motion
to linear motion in a perpendicular to the
input.
 The linkages are often used in front wheel
drive vehicles with solid rear axles to
control lateral movement.
 The engineering design of locomotives
improved over the years and by the year
1830, the linkage straight line motion
finally disappeared.
 It lingered on for many years with stationary
engines ,especially those with vertical cylinder.
 The main defect of the straight line motions
was their ungainly size and weight especially
for fast engines compared to a compact
slider mechanism.
 Scott russell linkages are still
used today in
front wheel drive motor vehicles
with solid
rear axles to control lateral
movement.
 A scott russell linkage on the rear
axle of a
2002 Nissan sentra.