seminar topic for mechanical engineering ppt

1. G.ARUN YADAV
13P61A0307
MECH-A
IV-II

2. CONTENT
 Introduction
 History
 The First Hovercraft
 Basic Structure Of Hovercraft
 Principle Of Working
 Advantages of Hovercraft
 Disadvantages of Hovercraft
 Records
 Conclusion
 References

3. INTRODUCTION
A Hovercraft is a vehicle that
 Flies like a plane but
 Float like a boat
 Drive like a car
 It can hover over or move across land or water surfaces
while being held off from the surfaces by a cushion of air

4.  A Hovercraft can travel over all types of surfaces including
grass, mud, muskeg, sand, quicksand, water and ice
.Hovercraft prefer gentle terrain although they are capable of
climbing slopes up to 20%, depending upon
surface characteristics.

5. HISTORY
 The first design by Swedish designer “EMMANUEL
SWEDENBORG” in 1716.
 The project was short-lived because it was never built, for soon
Swedenborg soon realized that to operate such a machine
required a source of energy far greater than that could be
supplied by single human equipment.
 Until the early 20th century Hovercraft was not practically
possible, because only the internal combustion engine had the
very high power to weight ratio suitable for Hover flight.

6. The First Hovercraft
 Christopher Cockerel thought of using a
load of stuff you might find about the
house to make a hovercraft.
 Cockerel took a set of scales and a long
rod and arranged them so the rod was
vertical.
 He then affixed a vacuum cleaner to the
rod so it pointed down.

7.  Next he made a hole in a can and affixed a can that was
smaller than the first in such a way it allowed air in-
between the two cans. Cockerel made the vacuum
cleaner blow instead of suck, blowing air through the gap
in the two cans, and it worked.
 The scale went down as far as it could!.

8. Basic Structure Of Hovercraft

9. Parts Of Hovercraft
o Propeller:- It pushes the hovercraft ahead by pushing air
behind.
o Fan :- Primary purpose is to inflate the cushion contained
within the skirt beneath the craft as well as to provide thrust
with which to propel the craft forward.
o Skirt :- Part that allows the hovercraft to clear obstacles.
Generally speaking, the higher the skirt, the larger the obstacle
that the craft will clear.
o Lower hull :- It is the basic structure on which the Hovercraft
floats when the engine is stopped while moving over water. It
supports the whole weight of the craft.
o Rudders :-They are similar to that used in an aircraft.
Rudders are moved by hydraulic systems. By moving the
rudders we can change the direction of the craft.

10. Principle Of Working
 To lift the craft by a cushion of air to propel it using propellers.
 The air sucked in through a port by large lifting fans which are
fitted to the primary structure of the craft.
 They are powered by gas turbine or diesel engine.
 Fan is used to inflate the skirt and rest is ducted down under
the craft to fill area enclosed by the skirt.
 At the point when the pressure equals the weight of the craft,
the craft lifts up and air is escaped around the edges of the
skirt.
 So a constant feed of air is needed to lift the craft and
compensate for the losses.

11. SOME PICS OF HOVERCRAFT

12. ADVANTAGES OF
HOVERCRAFT
 Travel over any surface.
 Shortcutting routes.
 Travel rivers up as fast as down, irrespective of the
current.
 Travel in dry water-beds.
 No collision with debris, logs etc.
 Access to 75% of coastal area instead of only 5% with
conventional vessels.
 No turbulence or impact in water as no propeller churns
up the water so sea life remains untouched

13.  Hovercraft are very fuel efficient (CO² friendly) as Hovercraft
do not have to plough through the water but "fly" above the
surface. At maximum speed fuel consumption of a Hovercraft is
approx. 70% less than of a fast patrol boat with similar payload
capacity

14. DISADVANTAGES OF
HOVERCRAFT
 They move a lot of air and can relatively loud (Noise
Pollution).
 Steep grade can be issue.
 Potential of skirt damage.
 Not exactly agile(e.g.:cornering).
 The hovercraft is bulky and its high speed make it
difficult to control while on land.

15. RECORDS
 World's Largest Civil Hovercraft- The BHC SR.N4 Mk.III, at
56.4 m (185 ft) length and 310 metric tons (305 long tons) weight,
can accommodate 418 passengers and 60 cars.
 World's largest military hovercraft - The Russian Zubr class
LCAC at 57.6 meters (188 feet) length and a maximum
displacement of 535 tons. This hovercraft can transport three T-80
main battle tanks (MBT), 140 fully equipped troops, or up to
130 tons of cargo. Four have been purchased by the Greek Navy.
 Hovercraft land speed record-56.25 mph(90.53 km/h48.88 knots).
John Alford (USA) at Bonneville Salt Flats, Utah, USA on 21
September 1998.
 Longest continuous use - The original prototype SR.N6 Mk.I
(009) was in service for over 20 years, and logged a remarkable
22,000 hours of use. It is currently on display at the Hovercraft
Museum in Lee-on-the-Solent, Hampshire, England.

16. CONCLUSION
Hovercrafts are generally simple mechanisms in
theory. Yet the process from theory to manifestation is not as easy as
it may seem. A plethora of problems exist and must be faced in order
to attain a well functioning hovercraft. The plans and designs must be
flawless. One must take under consideration the weight and the shape
of each component in order to avoid problems such as instability and
dysfunction. One thing is certain; when building a hovercraft, be well
aware of the demands of construction. Be prepared and willing to
embrace failure for it is the only way to success. Only after failed
attempts will you be able to finally design an effective hovercraft.

17. REFERENCE
 www.google.com
 www.wikipedia.org