Mechanical Engineering

Most countries in the world use AC or Alternating Current, most circuits these days use DC or Direct Current. To control a modern circuit with mains power means putting a control circuit containing a rectifier between the power source and the whatis being controlled. The rectifier changes AC power into DC power.

There are a number of factors that would affect the answer to this question including torque, shaft speeds, load etc. This is why there are many methods of delivering force to remote locations (worm, belt, chain). I believe some of the advantages when working with belts are - reduced friction losses as the belt has more contact area - decreased energy loss through vibration (in effect a belt has vibration dampening) - belt breakage usually seperates the drive system causing little damge or danger unlike chain If someone can answer the physics side of this I would be most appreciative as most of these answers come from car knowlege (see variable belt drive vs. timing chain).

A pneumatic actuator converts energy (in the form of compressed air, typically) into motion. The motion can be rotary or linear, depending on the type of actuator. Some types of pneumatic actuators include: * Tie rod cylinders * Rotary actuators * Grippers * Rodless actuators with magnetic linkage or rotary cyclinders * Rodless actuators with mechanical linkage * Pneumatic artificial muscles * Speciality actuators that combine rotary and linear motion--frequently used for clamping operations * Vacuum generators A Pneumatic actuator mainly consists of a piston, a cylinder, and valves or ports. The piston is covered by a diaphragm, or seal, which keeps the air in the upper portion of the cylinder, allowing air pressure to force the diaphragm downard, moving the piston underneath, which in turn moves the valve stem, which is linked to the internal parts of the actuator. Pneumatic actuators may only have one spot for a signal input, top or bottom, depending on action required. Valves require little pressure to operate and usually double or triple the input force. The larger the size of the piston, the larger the output pressure can be. Having a larger piston can also be good if air supply is low, allowing the same forces with less input. These pressures are large enough to crush object in the pipe. On 100 kPa input, you could lift a small car (upwards 1,000 lbs) easily, and this is only a basic, small pneumatic valve. However, the resulting forces required of the stem would be too great and cause the valve stem to fail. This pressure is transferred to the valve stem, which is hooked up to either the valve plug (see plug valve), butterfly valve etc. Larger forces are required in high pressure or high flow pipelines to allow the valve to overcome these forces, and allow it to move the valves moving parts to control the material flowing inside. Valves input pressure is the "control signal." This can come from a variety of measuring devices, and each different pressure is a different set point for a valve. A typical standard signal is 20-100 kPa. For example, a valve could be controlling the pressure in a vessel which has a constant out-flow, and a varied in-flow (varied by the actuator and valve). A pressure transmitter will monitor the pressure in the vessel and transmit a signal from 20-100 kPa. 20 kPa means there is no pressure, 100 kPa means there is full range pressure (can be varied by the transmiters calibration points). As the pressure rises in the vessel, the output of the transmitter rises, this increase in pressure is sent to the valve, which causes the valve to stroke downard, and start closing the valve, decreasing flow into the vessel, reducing the pressure in the vessel as excess pressure is evacuated through the out flow. This is called a direct acting process. http://en.wikipedia.org/wiki/Pneumatic_actuator

*A valve thatrelieves pressure due to thermal expansion of liquid* You will see PSV's pressure safety valves on vessels with gas in them. You will see TSV's (Thermal Safety Valves) on pipelines/vessels full of fluid. The fluid in a blocked in pipeline in the sun will expand and quickly increase the pressure in the pipeline. The Thermal safety valve relieves this pressure due to thermal expansion. Essentially TSV's and PSV's Are the same physical device just used for different reasons, and so named differently. To complicate the issue you can also get combined temperature and pressure relief valves. These have two mechanisms 1. Normal spring to hold valve closed until set pressure is reached and valve opens. 2. Wax/oil filled probe, that as it gets to set temperature expands and opens valve. I have not yet seen these valves in the process industry, but there is one on my water heater at home. http://www.rmc.com.au/files/spec_sheets/HT501_1.pdf

An alloy is a metal that has been mixed with another metal. Aluminum alloys could contain zinc, copper, or silicon (not limited to). Gold alloys can contain copper or silver.

Aluminum alloy is created to be stronger and more corrosion resistant than plain aluminum.

Gold alloy is created to be cheaper.

Many more alloys exist.

Ultimate shear stress of Mild steel is 210N/sq mm

Passivation is removing the free iron and other exogenous materials from the surface so that a good passive layer can be formed. In the case of carbon steel, this is not possible. After cleaning with a good cleaner, there are a variety of coatings that can be used for carbon steel to provide a corrosion resistant layer, but passivation is not the correct process. For details see the link in the left column.

It depends on the type of engine, but its generally one of a few things. A turbofan like on a commercial plane have the bypass, or large amounts of air flowing close to the out side of the engine. A higher temperature engine may have a heat exchanger on the turbine blades that actuall takes cooler air and passes it over the vanes so they don't melt. Almost every turbine engine has some sort of oil cooler to help keep the moving parts from getting too hot. With many turbines the idea is to more or less protect the engine from heat than to cool it down. More heat with a turbine means more power.

Mild steel is ferrous with about .16 to .19 percent carbon.

A Standard can be defined as a set of technical definitions and guidelines that
function as instructions for designers, manufacturers, operators, or users of
equipment.


A standard becomes a Code when it has been adopted by one or more
governmental bodies and is enforceable by law, or when it has been incorporated
into a business contract.

SS400

A suction milking machine is divided into two different parts one side is the milking side the other is the pulsator side. When the machine is turned on a vacuum pump removes air for the system everywhere when it is not on the vacuum be the same on both the milking aide and the pulsator side.

The first bent-wire paper clip was patented by Samuel B. Fay in 1867. This clip was originally intended primarily for attaching tickets to fabric, although the patent recognized that it could be used to attach papers together. We have found no advertisement or other mention for the Fay paper clip before 1899, and it therefore appears unlikely that it had significant, if any, sales prior to the late 1890s. However, beginning in 1899 and for decades thereafter, the Fay design was widely advertised under many brand names for use in fastening papers.

Some can - because they are designed to be able to spread their weight (displacement) over a wide enough area that can be supported by the bottom of the vehicle and sealing the bottom of said vehicle, along with re-routing exhaust/intake. Most don't float because they are not designed to.

Gas turbines are a type of Internal Combustion engine, however; Assuming that you want to know the difference between a recpirocating piston engine and a gas turbine engine, the simple answer is that ICE's (Internal combustion engines) create work by moving a crank that is connected to a piston. An explosion in the piston chamber pushes a piston (or series of pistons) attached to a crankshaft, which turns the shaft. The gas turbine works by turning a shaft connected to a turbine. The turbine is powered by a compressed feul-air mixture. A stream of gas is compressed with air and forced through a chamber containing the turbine. The turbine turns the shaft as a result of complex mechanics that control the movement and flow of the compressed fuel-air mixture. The basic mechanical difference: A reciprocating piston engine uses a linear "back and forth" motion to turn a shaft, and the gas turbine engines relies on a constant circular motion to turn a shaft.

PSI = Pounds per Square Inch. Bar - is one atmosphere (14 PSI)

a gas compressor is a device that increases pressure and reduces its volume

It's 1. IMA = Distance in / Distance out. A single pulley doesn't do anything toward mechanical advantage, it changes the direction of the force.

Not always. A single-axeled pulley (the typical pulley) has an IMA of 1, having one axel. If there was a second axel, then the IMA would = 2, so on and so forth.

The easy way to do it is IMA = # of axels.

Neither tensile strength nor compressive strength is inherently "stronger." Some materials are stronger in tension; other materials are stronger in compression. For example, rope is much stronger in tension than in compression, but concrete is much stronger in compression than in tension.

First class levers are like see-saws. The fulcrum (turning point) comes between the effort and the load. So if you push down on the effort the load goes up. With second class levers the load comes between the effort and the fulcrum. This is good for catapulting things. Third class levers have the effort between the load and the fulcrum. An example would be a fishing rod. The fish on the end is the load, your hand on the rod is the effort and the hand at the end is the fulcrum.

hair dryer, cars ,lawnmower ,generator ,computer ,pool ,cleaner ,tv ,plane ,cell phone ,fans ,heaters ,remote contrl car ,boat

For DC:

Permanent magnet brush motor; (uses fixed magnets for stator fields); toys and automotive use

Shunt field motor; (field winding has many turns of fine wire in parallel with armature) small machines;

Series field motor; (field winding has few turns of heavy wire in series with armature); high speed, high torque;

Compound field motor; (has both series and shunt fields); large machinery, general purpose workhorses;

Brushless DC motors (use electronics to switch stator windings on and off, and have permanent magnet rotors) small fans and light loads.

For single phase AC:

Split Phase induction motor (2 different windings connected to supply, cage type rotor) low torque, general purpose;

Capacitor Start induction motor; (As per split phase, but with capacitor in series with starting winding) high starting torque, general purpose;

Capacitor start, Capacitor run induction motor; (as per capacitor start, but different capacitors used for starting and running) high starting and running torque, quietest running;

Shaded pole induction motor; (run winding and copper or aluminium ring around part of iron core of stator) small, cheap motors, low torque;

Universal motor; (as per series DC motor above) high torque, high speed, poor speed stability.

For 2 or 3 phase AC (star or delta connected)

Polyphase induction motor (2 or 3 identical windings on stator, cage rotor) general purpose;

Wound rotor induction motor (2 or 3 identical windings on stator, wound rotor connected in star to 3 sliprings and external resistance unit) very high starting torque, low starting current;

Synchronous motor; (standard stator, and wound rotor connected to DC supply for 'excitation' of rotor field) constant speed, power factor correction.

GAUGE , is one inch thick of steel or metal.

So, take this one inch thick of steel sheet and cut it into 12 equal thickness sheets , you get a 12 gauge steel sheet.

Similarly, take this one inch thick of steel sheet and cut it into 14 equal thickness sheets , you get a 14 gauge steel sheet. and so on .

So, a 12 gauge steel sheet is thicker than 14 gauge , 14 is thicker than 16 , 16 is thicker than 18 and so on.

Wrong!!! See my discussion on this...

Type 316 is an austenitic chromiumnickel

stainless steel containing

molybdenum. This addition increases

general corrosion resistance, improves

resistance to pitting from chloride ion

solutions, and provides increased

strength at elevated temperatures. Properties

are similar to those of Type 304

except that this alloy is somewhat

stronger at elevated temperatures.

Corrosion resistance is improved, particularly

against sulfuric, hydrochloric,

acetic, formic and tartaric acids; acid

sulfates and alkaline chlorides.

Fineness Modulus is used to know the size of aggregate grains (Particles) for various measurements used in Civil Engineering.

To characterize the overall coarseness or fineness of an aggregate, a concept of fineness modulus is developed. The Fineness Modulus is defined as

Fineness Modulus =

Σ(Cumulative Retained Percentage)

100

To calculate the fineness modulus, the sum of the cumulative percentages retained on a definitely specified set of sieves needs to be determined, and the result is then divided by 100. The sieves specified for the determination of fineness modulus are No. 100, No. 50, No. 30, No. 16, No. 8, No. 4, 3/8", 3/4", 1.5", 3", and 6".

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