6505, assign3, case studies, part 2

6505, Assign3, Part 2

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Fluid Mechanics in Lifting DevicesCase Studies, Part 2

A PDF version of this presentation is available at Slidesharehttp://www.slideshare.net

http://www.slideshare.net


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Lifting devices - Introduction• Any device that can be used to raise or lower a loadIncludes:

• Lever

• Cranes

• Elevators

• Escalators

• Jacks

• Block and tackle

• Forklifts

• Hydraulic rams

These will be the focus of this presentation


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Lifting Devices - Brief History• Levers were probably used by ancient humans to lift loads

• Animal power

• The Egyptian Screw - invented by Archimedes

• Archimedes also invented other lifting devices

Me again! I created a continuous spiral inside a cylinder. It was used to lift water out of mines and ships

• Ancient Egyptians used an irrigation device called a "shaduf" that used a counterweight

• Assyrians - developed simple one wheel pulley system

Pulley


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Lifting Devices - Brief History• The windlass - invented by the Chinese

• Screw jacks - invented by Da Vinci in the 15th century• DaVinci also made one of the first discoveries of hydraulics, viz, velocity of flow is inversely proportional to cross-sectional area of a stream

• 1600's, Blaise Pascal develops his principle of transmissibility of pressure from point to point (Pascal's Principle)


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Lifting Devices - Brief History

• 1812 - Bramah pioneered the use of the hydraulic jack for lifting heavy load

• 1840-50 - the hydraulic jack is used to test the chains to be used for suspension bridges

• 1847 - hydraulic cranes used at Newcastle (England) harbour, soon to be used in other ports

• 1858 - hydraulic jacks successfully used in the launch of the ship Great Eastern

1795 - The first hydraulic press (used for pressing cotton bales) patented by Englishman Joseph Bramah


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Hydraulics and Elevators• 1800s saw the development of modern elevators (lift) including the use of hydraulic systems to operate the lift

• Early hydraulic lifts used steam and hydraulic plungers to make the lift move up and down

• Modern hydraulic lifts have a hollow plunger fitted to the elevator cab

• The plunger was fitted onto a hollow cylinder that extends into the ground the distance that the elevator will rise

• Water or oil is pumped into the cylinder at the required pressure to move the elevator vertically

• To lower the elevator, the fluid is released from the cylinder and gravity moves the elevator downwards

• Valves are used to control fluid flowing into and out the cylinder

• The valves were initially controlled by ropes and later lever controls

• Limited to low rise buildings - less than five stories - speeds less than 5 m/s

• Hence only suitable for non-intensive duty


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In certain situations where it is not possible to extend the building foundations downward, the ‘holeless‛ hydraulic lift is used . A telescopic piston is used instead of a plugging one.

Advantages of hydraulic lifts are:• Because is no need for a counterweight there is optimal utilisation of a lift shaft• There is no overhead machine room. Hence the power is supplied at lowlevel• Only one or two walls are required to be load bearing • The motive power for the lift can be placed away from the actual elevator. Some elevators have the motor pump unit located up to 15metres from the lift shaft.

Total installation costs of hydraulic systems are less than that for electric traction alternativesHowever, the performance efficiency of hydraulic systems is generally not as good as electric traction elevators


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The basic layout of a direct acting hydraulic

elevator. The depth of the hole required to

accommodate the hydraulic cylinder and the

cost of well boring limits these elevators to

low rise situations.

In a side acting hydraulic elevator the cylinder is

connected to the side of the car which

removes the need for a bore hole. Guides are used

to prevent the car from jamming in the shaft. In

situations of high volume / loads two cylinders are

used, one on each side of the shaft


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• 1870 - rope gears are used with hydraulic elevators

• Instead of a plunger, a smaller piston/cylinder combination is used that could be mounted vertically/horizontally anywhere within the building

• The ropes have the effect of multiplying the stroke of the piston


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Since 1870 there have been many innovations in elevator design, including:

• 1880 - use of the electric motor with revolving pinion gears that engaged brackets

• 1889 - directly connected geared electric elevator

• 1903 - gearless traction electric elevator - this was a fast, simple low cost elevator that ushered in the development of skyscrapers


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Significance and Impact of Elevators

• Enabled the construction of multi-storey buildings. In fact many buildings were designed around the capacity of the elevator

• Enable elderly and disabled people to access services in multi-storey buildings. For really tall buildings (Empire State Building) the elevator was the only efficient way of accessing the upper levels of the building

• Possibly influenced the development of building fire sprinkler systems as fire tenders are limited to the heights that their hoses can reach

• Enabled the development of modern cities, as the multi-story buildings often houses large number of people


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Cranes


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Cranes and HydraulicsCranes (or versions thereof) have been an important factor in the building of civilisation

Ancient Egyptian Cranes

Greco_Roman Tripostos


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Hydraulic Cranes1946 - The first hydraulic crane produced by British crane manufacturer F. Taylor & Sons

1959 - Taylor and Sons merged with Coles, another British crane manufacturer. The new company began production of the first mobile hydraulic cranes using ex-army vehicles. The boom on these cranes were powered by a hydraulic pump.

Eventually the company had to produce its own vehicles for mobile hydraulic cranes.


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• 1952 - introduction of the A2 mobile crane, which used a Chevrolet truck to transport and support the boom. It used hydraulic lifting cylinders and a hooked winch

• From this time onwards there were a number of significant improvements in hydraulic cranes including

• Increasingly precise winches

• Telescopic booms

• More efficient and powerful hydraulic pumps

• Incorporating more advanced materials into the crane's construction


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Some crane developments of the 1960s:

• Liebherr develop climbing cranes that used hydraulics in the masts

• Demag Zug develop a hydraulic crane with a 2.5 tonne lifting capacity. The use of hydraulic systems enable several different movements to be performed simultaneously and rapid luffing of the boom

• The effectiveness of telescopic cranes is mainly due to their use of hydraulics

• The hydraulic systems transfer forces from one part of a machine to another

• The hydraulic systems can be designed to act as force magnifiers

• Because there are few moving parts and friction is reduced by using oil-based fluids hydraulic telescopic cranes have high efficiency ratings

• Most modern telescopic cranes are able to reach to heights of about 60 metres. If a trussed jib is attached to the final boom extension these cranes can reach even higher


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• 1980's hydraulic cranes are a regular feature of most building sites. Crane technology continues to develop. Making larger cranes is seen as an important priority. Example the Hydra Husky 36/40TSC

There is a change in the way cranes are valued and used.

• Prior to WW2 cranes for valued for reliability

• Post WW2, other factors became more important, such as• Maximum carrying results for lowest cost and maintenance

• The comfort of the driver


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Significance and Impact of Cranes

• Improved imports/exports - cranes can be loaded and unloaded quickly. Improves ability to transport perishable goods

• Safer shipping - larger harbours/breakwaters and ports can be built

• Improved worker safety - less injury from lifting heavy loads

• The ability to construct larger/taller buildings and other constructions

• Enable work on aircraft to be carried out rapidly and efficiently

• Less time required to construct civil engineering projects


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Want to know more...

• http://science.howstuffworks.com/transport/engines-equipment/hydraulic-crane.htm

• http://www.deckrane.com/info/truckcrn.pdf

• http://homepage.ntlworld.com/tonyonthemoon/Coles-type-0-database-list.html


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Innovation in Lifting Devices

Active Chassis Systems - Elevators

• The precision of the guide rails used in an elevator shaft have a major effect on the quality of the ride

• Aligning guides in very tall buildings is costly and difficult

• Aswell, buildings are not completely static structures. Winds and temperature changes effect the alignment of the building and as a consequence the alignment of the elevator guide rails

• The Active Chassis System enables the elevator car to compensate for deviations in the guides resulting in a smoother ride for passengers

• The Active Chassis System was originally developed to enhance the suspension of automobiles


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Innovation in Lifting Devices

• Active Chassis Systems make use of sensors and actuators

• When the sensors detect deviations in the elevator car's ride, the actuators modify the car's suspension by increasing or decreasing hydraulic pressure in the suspension

• The overall result is that passengers have a smooth ride

• As well, there is less of a need to realign the guide rails in the elevator shaft


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Brier B,The Other Pyramids, http://www.archaeology.org/0209/abstracts/pyramids.html, accessed 25/5/12

Degreef, J.D., Cranes and Old Kingdom Building Technology, http://www.egyptologist.org/discus/messages/8/6026.html?1041105841, accessed 25/5/12

Cranes (machine) http://en.wikipedia.org/wiki/Crane_(machine), accessed 25/5/12

Vitrina Cu Machete, http://vitrinacumachete.wordpress.com/, accessed 26/5/12

Metcalfe, P & Metcalfe, R, Active Chassis Systems, Excel Senior High School, Engineering Studies, Pascal Press, 2009

Active Suspension, http://en.wikipedia.org/wiki/Active_suspension, Accessed 26/6/12


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End of Part 2

6505, assign3, case studies, part 2

Business

hydraulic elevators

hydraulic cylinder

hydraulic jacks

hydraulic cranes

hydraulic press

hydraulic plungers

holeless hydraulic lift

use of hydraulic systems