Hydraulic Jack 8 Ton
Mica Withington
For over 70 years, Metro Hydraulic Jack Company, a third-generation, family-owned and operated business, has been providing industrial hydraulic parts and equipment services to commercial, automotive, marine, refuse, and construction industries.
A jack is a mechanical lifting device used to apply great forces or lift heavy loads. A mechanical jack employs a screw thread for lifting heavy equipment. A hydraulic jack uses hydraulic power.[1] The most common form is a car jack, floor jack or garage jack, which lifts vehicles so that maintenance can be performed. Jacks are usually rated for a maximum lifting capacity (for example, 1.5 tons or 3 tons). Industrial jacks can be rated for many tons of load.
The personal name Jack, which came into English usage around the thirteenth century as a nickname form of John, came in the sixteenth century to be used as a colloquial word for 'a man (of low status)' (much as in the modern usage 'jack of all trades, master of none'). From here, the word was 'applied to things which in some way take the place of a lad or man, or save human labour'. The first attestation in the Oxford English Dictionary of jack in the sense 'a machine, usually portable, for lifting heavy weights by force acting from below' is from 1679, referring to 'an Engine used for the removing and commodious placing of great Timber.'[2]
A scissor jack use the mechanical advantage of a leadscrew and 4-bar linkage to allow a human to lift a vehicle by manual force alone. They are inexpensive and are common in manufacturer-supplied breakdown kits. The jack shown at the left is made for a modern vehicle and the notch fits into a jack-up point[3] on a unibody. Earlier versions have a platform to lift on a vehicle's frame or axle.
Electrically operated car scissor jacks are powered by 12 volt electricity supplied directly from the car's cigarette lighter receptacle. The electrical energy is used to power these car jacks to raise and lower automatically. Electric jacks require less effort from the motorist for operation.
A house jack, also called a screw jack, is a mechanical device primarily used to lift buildings from their foundations for repairs or relocation. A series of jacks is used and then wood cribbing temporarily supports the structure. This process is repeated until the desired height is reached. The house jack can be used for jacking carrying beams that have settled or for installing new structural beams. On the top of the jack is a cast iron circular pad that the jacking post rests on. This pad moves independently of the house jack so that it does not turn as the acme-threaded rod is turned with a metal rod. This piece tilts very slightly, but not enough to render the post dangerously out of plumb.
Hydraulic jacks are typically used for shop work, rather than as an emergency jack to be carried with the vehicle. Use of jacks not designed for a specific vehicle requires more than the usual care in selecting ground conditions, the jacking point on a vehicle, and to ensure stability when the jack is extended. Hydraulic jacks are often used to lift elevators in low and medium rise buildings.
A hydraulic jack uses a liquid, which is incompressible, that is forced into a cylinder by a pump plunger. Oil is used since it is self lubricating and stable. When the plunger pulls back, it draws oil out of the reservoir through a suction check valve into the pump chamber. When the plunger moves forward, it pushes the oil through a discharge check valve into the cylinder. The suction valve ball is within the chamber and opens with each draw of the plunger. The discharge valve ball is outside the chamber and opens when the oil is pushed into the cylinder. At this point the suction ball within the chamber is forced shut and oil pressure builds in the cylinder.
In a floor jack (aka 'trolley jack') a horizontal piston pushes on the short end of a bellcrank, with the long arm providing the vertical motion to a lifting pad, kept horizontal with a horizontal linkage. Floor jacks usually include casters and wheels, allowing compensation for the arc taken by the lifting pad. This mechanism provides a low profile when collapsed, for easy maneuvering underneath the vehicle, while allowing considerable extension.
A bottle jack or whiskey jack[6] is a jack which resembles a bottle in shape, having a cylindrical body and a neck. Within is a vertical lifting ram with a support pad of some kind fixed to the top. The jack may be hydraulic or work by screw action. In the hydraulic version, the hydraulic ram emerges from the body vertically by hydraulic pressure provided by a pump either on the baseplate or at a remote location via a pressure hose. With a single action piston the lift range is somewhat limited, so its use for lifting vehicles is limited to those with a relatively high clearance. For lifting structures such as houses the hydraulic interconnection of multiple vertical jacks through valves enables the even distribution of forces while enabling close control of the lift.
The screw version of the bottle jack works by turning a large nut running on the threaded vertical ram at the neck of the body. The nut has gear teeth, and is generally turned by a bevel gear spigotted to the body, the bevel gear being turned manually by a jack handle fitting into a square socket. The ram may have a second screwed ram within it, which doubles the lifting range telescopically.
Bottle jacks have a capacity of up to 50 tons and may be used to lift a variety of objects. Typical uses include the repair of automobiles and house foundations. Larger, heavy-duty models may be known as a barrel jack.[7]
An air hydraulic jack is a hydraulic jack that is actuated by compressed air - for example, air from a compressor - instead of human work. This eliminates the need for the user to actuate the hydraulic mechanism, saving effort and potentially increasing speed. Sometimes, such jacks are also able to be operated by the normal hydraulic actuation method, thereby retaining functionality, even if a source of compressed air is not available.
An inflatable jack, lifting bag, or pneumatic lifting bag is an air bag that is inflated by compressed air (without a hydraulic component) in order to lift objects. The bag can be deflated to be reused later. The objects can be of a smaller load such as an automobile[10] or it can be a larger object such as an airplane.[11]
Air bags are also used by rescuers to lift heavy objects up to help victims who are trapped under those objects. There are three main types of lifting bags for rescue: high pressure, medium pressure and low pressure systems. Low-pressure bags are operated at 7.25 psi for high vertical lift in a large surface area but lower lifting capacities. Medium-pressure bags are operated at 15 psi. High-pressure bags which have higher lifting capacities are operated at pressure between 90 and 145 psi. Two air bags can be stacked together to provide a higher lift. It is recommended that no more than two bags can be used in a stacked configuration, the bigger bag must be the bottom one, and no other objects are inserted between the stacked bags. Incorrect use of stacked bags may result in a bag (or other objects) shooting out to create a dangerous projectile.[12]
The farm jack also known as a railroad jack, high lift jack or kanga-jack was invented in 1905. It consists of a steel beam with a series of equally spaced holes along its length, and a hand-operated mechanism which can be moved from one end of the beam to the other through the use of a pair of climbing pins. Typical sizes for the farm jack are 4 feet (1.2 m), 5 feet (1.5 m)and 6 feet (1.8 m) referring to the length of the beam.
The jack's versatility stems from its use for such applications as lifting, winching, clamping, pulling and pushing. It is this versatility, along with the long travel it offers and its relative portability, which make the farm jack so popular with off-road drivers.
National and international standards have been developed to standardize the safety and performance requirements for jacks and other lifting devices. Selection of the standard is an agreement between the purchaser and the manufacturer, and has some significance in the design of the jack. In the United States, ASME has developed the Safety Standard for Portable Automotive Service Equipment, last revised in 2014, including requirements for hydraulic hand jacks, transmission jacks, emergency tire changing jacks, service jacks, fork lift jacks, and other lifting devices.[13]
Most likely yes. I don't see that there is an issue with the black o-ring, but if you'll notice, there's a second ring around that shaft, which is most likely nylon. I can't tell for sure, but it looks as though there might be an issue there. To fix your issue, you'd most likely need to replace both. You'd also need to check the barrel of the pump (what this rod goes into) to make sure it is round and there's no gouging or deformity in there.
The bigger unasked question is, is it worth your time/money to do so? Answer there is, probably not. You can get decent jacks as a replacement fairly cheap. I'd consider this jack a throw away item and be done with it. But that's up to you.
In a hydraulic jack, fluid pressure multiplies force in a cylinder to lift a heavy load. These jacks have many applications: machine shops, the automobile industry, material handling equipment, lifting platforms, railroad work, and hydropower plants. This article examines how hydraulic jacks work, how to use them properly, different types of jacks, and what to consider when selecting a hydraulic jack.
Hydraulic jacks operate based on Pascal's Law. This law states that a pressure change at one point in an enclosed incompressible fluid leads to the exact pressure change at every point. This law also governs the hydraulic jack press and the braking system for most vehicles. According to the law, pressure equals force divided by area. Therefore, force equals pressure multiplied by area. If pressure is constant and area increases, force also increases.
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