Information about Weight Machine
A weight machine is an exercise machine used for weight training that uses gravity as the primary source of resistance, and a combination of simple machines to convey that resistance to the person using the machine. Each of the simple machines (pulley, lever, wheel, incline) changes the mechanical advantage of the overall machine relative to the weight.
A stack machine—also called a stack or rack—has a set of massive rectangular plates that are pierced by a vertical bar which has holes drilled in it to accept a pin. Each of the plates has a channel on its underside (or a hole through the middle, as shown in the diagram) that aligns with one of the holes. When the pin is inserted through the channel into the hole, all of the plates above the pin rest upon it, and are lifted when the bar rises. The plates below do not rise. This allows the same machine to provide several levels of resistance over the same range of motion with an adjustment that requires very little force to accomplish in itself.[1]
The means of lifting the bar varies. Some machines have a roller at the top of the bar that sits on a lever. When the lever is raised the bar can go up and the roller moves along the lever, allowing the bar to stay vertical. On some machines the bar is attached to a hinge on the lever, which causes swaying in the bar and the plates as the lever goes up and down. On other machines the bar is attached to a cable or belt, which runs through pulleys or over a wheel. The other end of the cable will either be a handle or strap that the user holds or wraps around some body part, or will be attached to a lever, adding further simple machines to the mechanical chain.
Usually, each plate is marked with a number. On some machines these numbers give the actual weight of the plate and those above it. On some, the number gives the force at the user's actuation point with the machine. And on some machines the number is simply an index counting the number of plates being lifted.
The early Nautilus machines were a combination of lever and cable machines. They also had optional, fixed elements such as a chinning bar.
The plate-loaded machines will often have a very high mechanical advantage, due to the need to make room for large plates over a large range of motion following a path that causes them to converge at one end or the other. Also, the motion will generally not be vertical, and the net resistance is equal to the cosine of the angle at which it is moving relative to vertical.
For example, consider an incline press machine that is a single-lever machine that has the plates halfway up the lever from the handles to the fulcrum, and begins moving the plates at a 45-degree angle from vertical. The lever will provide a leverage advantage of 2:1, and the incline will have an advantage of 1:√2/2, for a net mechanical advantage of (4/√2):1 ≈ 2.8:1. Thus 110 lb (50 kg) of plates will apply to the user only about 40 lbf (18 kgf or 170 N) of force at the beginning of the motion.
On the other end of the spectrum may be a bent-over-row machine that is designed with the user's grip between the plates and the fulcrum. This amplifies the force needed by the user relative to the weight of the plates.
Stack machines
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The weight stack from a Cable machine: each plate weighs 6 kg.
The means of lifting the bar varies. Some machines have a roller at the top of the bar that sits on a lever. When the lever is raised the bar can go up and the roller moves along the lever, allowing the bar to stay vertical. On some machines the bar is attached to a hinge on the lever, which causes swaying in the bar and the plates as the lever goes up and down. On other machines the bar is attached to a cable or belt, which runs through pulleys or over a wheel. The other end of the cable will either be a handle or strap that the user holds or wraps around some body part, or will be attached to a lever, adding further simple machines to the mechanical chain.
Usually, each plate is marked with a number. On some machines these numbers give the actual weight of the plate and those above it. On some, the number gives the force at the user's actuation point with the machine. And on some machines the number is simply an index counting the number of plates being lifted.
The early Nautilus machines were a combination of lever and cable machines. They also had optional, fixed elements such as a chinning bar.
Plate-loaded machines
Plate-loaded machines[2] (such as the Smith machine) use standard barbell plates instead of captive stacks of plates. They combine a bar-end on which to hang the plates with a number of simple machines to convey the force to the user.[3]The plate-loaded machines will often have a very high mechanical advantage, due to the need to make room for large plates over a large range of motion following a path that causes them to converge at one end or the other. Also, the motion will generally not be vertical, and the net resistance is equal to the cosine of the angle at which it is moving relative to vertical.
For example, consider an incline press machine that is a single-lever machine that has the plates halfway up the lever from the handles to the fulcrum, and begins moving the plates at a 45-degree angle from vertical. The lever will provide a leverage advantage of 2:1, and the incline will have an advantage of 1:√2/2, for a net mechanical advantage of (4/√2):1 ≈ 2.8:1. Thus 110 lb (50 kg) of plates will apply to the user only about 40 lbf (18 kgf or 170 N) of force at the beginning of the motion.
On the other end of the spectrum may be a bent-over-row machine that is designed with the user's grip between the plates and the fulcrum. This amplifies the force needed by the user relative to the weight of the plates.
See also
Notes
1. ^ However, there are several ways for these stacks to become misaligned, requiring a great deal of force, and possibly tools, to allow the pin to be removed. Always use caution around weight stacks. Never pin the weights in a raised position. Follow all instructions posted on the machine or in the gym.
2. ^ Plate-loaded machines are referred to as racks but not as stacks.
3. ^ On most plate-loaded machines the bar-ends will be designed so that the weights remain secured by gravity throughout a controlled motion, but, as injuries do occur, can occur mid-lift, and can result in uncontrolled motion of the machine, always clamp the plates in place.
2. ^ Plate-loaded machines are referred to as racks but not as stacks.
3. ^ On most plate-loaded machines the bar-ends will be designed so that the weights remain secured by gravity throughout a controlled motion, but, as injuries do occur, can occur mid-lift, and can result in uncontrolled motion of the machine, always clamp the plates in place.
An exercise machine is any machine used in exercise. These range from simple spring-like devices to computerized electromechanical rides to recirculating-stream swimming pools.
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Weight training is a common type of strength training for developing the strength and size of skeletal muscles. It uses the force of gravity (in the form of weighted bars, dumbbells or weight stacks) to oppose the force generated by muscle through concentric or eccentric
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simple machine is any device that only requires the application of a single force to work. Work is done when a force is applied and results in movement over a set distance. The work done is the product of the force and the distance.
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In physics and engineering, mechanical advantage (MA) is the factor by which a mechanism multiplies the force put into it. Following are simple machines where the mechanical advantage is calculated.
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- The beam shown is in static equilibrium around the fulcrum.
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Arthur A. Jones (November 22, 1926 – August 28, 2007) [1] was the founder of Nautilus, Inc. and MedX, Inc. and the inventor of the Nautilus exercise machines, including the Nautilus pullover, which was first sold in 1970.
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The Smith machine is an item of equipment used in weight training. It consists of a barbell that is constrained to move only vertically upwards and downwards on steel runners.
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pound or pound-mass (abbreviations: lb, ℔, lbm, or sometimes in the United States: #) is a unit of mass (sometimes called 'weight' in everyday parlance) in a number of different systems, including English units, Imperial units, and United
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kilogram or kilogramme (symbol: kg) is the SI base unit of mass. The kilogram is defined as being equal to the mass of the International Prototype Kilogram (IPK), which is almost exactly equal to the mass of one liter of water.
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A pound or pound-force (abbreviations: lb, lbf, or lbf) is a unit of force. Pound is also the name of a unit of mass. One pound-force is approximately equal to the gravitational force exerted on a mass of one avoirdupois pound on the
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The unit kilogram-force (kgf, often just kg) or kilopond (kp) is defined as the force exerted by one kilogram of mass in standard Earth gravity.
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The newton (symbol: N) is the SI derived unit of force, named after Sir Isaac Newton in recognition of his work on classical mechanics.
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Definition
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cable machine is an item of equipment used in weight training or functional training. It consists of a rectangular, vertically-oriented steel frame about 3 meters wide and 2 meters high, with a weight stack at each end.
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The Smith machine is an item of equipment used in weight training. It consists of a barbell that is constrained to move only vertically upwards and downwards on steel runners.
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The leg press is a weight training exercise in which the individual pushes a weight away from them using their legs. The term leg press also refers to the apparatus used to perform this exercise.
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