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Saturday, 1 October 2016

Huge List of Darknet (Deep Web) Hidden Websites 2016

 



Huge List of Darknet (Deep Web) Hidden Websites 2016: Hello! guys so today i will be sharing HUGE list of Darknet (Deep Web) hidden websites with you all! :)
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Transmission

What is a "Transmission"?

The transmission is a device that is connected to the back of the engine and sends the power from the engine to the drive wheels. An automobile engine runs at its best at a certain RPM (Revolutions Per Minute) range and it is the transmission's job to make sure that the power is delivered to the wheels while keeping the engine within that range. It does this through various gear combinations. In first gear, the engine turns much faster in relation to the drive wheels, while in high gear the engine is loafing even though the car may be going in excess of 70 MPH. In addition to the various forward gears, a transmission also has a neutral position which disconnects the engine from the drive wheels, and reverse, which causes the drive wheels to turn in the opposite direction allowing you to back up. Finally, there is the Park position. In this position, a latch mechanism (not unlike a deadbolt lock on a door) is inserted into a slot in the output shaft to lock the drive wheels and keep them from turning, thereby preventing the vehicle from rolling.
There are two basic types of automatic transmissions based on whether the vehicle is rear wheel drive or front wheel drive.

On a rear wheel drive car, the transmission is usually mounted to the back of the engine and is located under the hump in the center of the floorboard alongside the gas pedal position. A drive shaft connects the rear of the transmission to the final drive which is located in the rear axle and is used to send power to the rear wheels. Power flow on this system is simple and straight forward going from the engine, through the torque converter, then through the transmission and drive shaft until it reaches the final drive where it is split and sent to the two rear wheels.
Power flow on a front wheel drive automobile






Power flow on a rear wheel drive automobile








On a front wheel drive car, the transmission is usually combined with the final drive to form what is called a transaxle. The engine on a front wheel drive car is usually mounted sideways in the car with the transaxle tucked under it on the side of the engine facing the rear of the car. Front axles are connected directly to the transaxle and provide power to the front wheels. In this example, power flows from the engine, through the torque converter to a large chain that sends the power through a 180 degree turn to the transmission that is along side the engine. From there, the power is routed through the transmission to the final drive where it is split and sent to the two front wheels through the drive axles. There are a number of other arrangements including front drive vehicles where the engine is mounted front to back instead of sideways and there are other systems that drive all four wheels but the two systems described here are by far the most popular. A much less popular rear drive arrangement has the transmission mounted directly to the final drive at the rear and is connected by a drive shaft to the torque converter which is still mounted on the engine. This system is found on the new Corvette and is used in order to balance the weight evenly between the front and rear wheels for improved performance and handling. Another rear drive system mounts everything, the engine, transmission and final drive in the rear. This rear engine arrangement is popular on the Porsche.
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Automatic Transmission Working System

If you have ever driven a car with an automatic transmission, then you know that there are two big differences between an automatic transmission and a manual transmission:
  • There is no clutch pedal in an automatic transmission car.
  • There is no gear shift in an automatic transmission car. Once you put the transmission into drive, everything else is automatic.
Both the automatic transmission (plus its torque converter) and a manual transmission (with­ its clutch) accomplish exactly the same thing, but they do it in totally different ways. It turns out that the way an automatic transmission does it is absolutely amazing!
6L50 transmission
In this article, we'll work our way through an automatic transmission. We'll start with the key to the whole system: planetary gearsets. Then we'll see how the transmission is put together, learn how the controls work and discuss some of the intricacies involved in controlling a transmission.

Purpose of an Automatic Transmission


Just like that of a manual transmission, the automatic transmission's primary job is to allow the engine to operate in its narrow range of speeds while providing a wide range of output speeds.
automatic transmission
Location of the automatic transmission.
Without a transmission, cars would be limited to one gear ratio, and that ratio would have to be selected to allow the car to travel at the desired top speed. If you wanted a top speed of 80 mph, then the gear ratio would be similar to third gear in most manual transmission cars.
­ You've probably never tried driving a manual transmission car using only third gear. If you did, you'd quickly find out that you had almost no acceleration when starting out, and at high speeds, the engine would be screaming along near the red-line. A car like this would wear out very quickly and would be nearly undriveable.
So the transmission uses gears to make more effective use of the engine's torque, and to keep the engine operating at an appropriate speed. When towing or hauling heavy objects, your vehicle's transmission can get hot enough to burn up the transmission fluid. In order to protect the transmission from serious damage, drivers who tow should buy vehicles equipped with transmission coolers.
­­The key difference between a manual and an automatic transmission is that the manual transmission locks and unlocks different sets of gears to the output shaft to achieve the various gear ratios, while in an automatic transmission, the same set of gears produces all of the different gear ratios. The planetary gearset is the device that makes this possible in an automatic transmission.
Let's take a look at how the planetary gearset works.

The Planetary Gearset

When you take apart and look inside an automatic transmission, you find a huge assortment of parts in a fairly small space. Among other things, you see:
  • An ingenious planetary gearset
  • A set of bands to lock parts of a gearset
  • A set of three wet-plate clutches to lock other parts of the gearset
  • An incredibly odd hydraulic system that controls the clutches and bands
  • A large gear pump to move transmission fluid around
­The center of attention is the planetary gearset. About the size of a cantaloupe, this one part creates all of the different gear ratios that the transmission can produce. Everything else in the transmission is there to help the How Gear Ratios Work do its thing. This amazing piece of gearing has appeared on HowStuffWorks before. You may recognize it from the electric screwdriver article. An automatic transmission contains two complete planetary gearsets folded together into one component. See How Gear Ratios Work for an introduction to planetary gearsets.

ring gear, planet carrier, sun gears
From left to right: the ring gear, planet carrier, and two sun gears
Any planetary gearset has three main components:
  • The sun gear
  • The planet gears and the planet gears' carrier
  • The ring gear
Each of these three components can be the input, the output or can be held stationary. Choosing which piece plays which role determines the gear ratio for the gearset. Let's take a look at a single planetary gearset.

Planetary Gearset Ratios


One of the planetary gearsets from our transmission has a ring gear with 72 teeth and a sun gear with 30 teeth. We can get lots of different gear ratios out of this gearset.


Input
Output
Stationary
Calculation
Gear Ratio
A
Sun (S)
Planet Carrier (C)
Ring (R)
1 + R/S
3.4:1
B
Planet Carrier (C)
Ring (R)
Sun (S)
1 / (1 + S/R)
0.71:1
C
Sun (S)
Ring (R)
Planet Carrier (C)
-R/S
-2.4:1

Also, locking any two of the three components together will lock up the whole device at a 1:1 gear reduction. Notice that the first gear ratio listed above is a reduction -- the output speed is slower than the input speed. The second is an overdrive -- the output speed is faster than the input speed. The last is a reduction again, but the output direction is reversed. There are several other ratios that can be gotten out of this planetary gear set, but these are the ones that are relevant to our automatic transmission.

So this one set of gears can produce all of these different gear ratios without having to engage or disengage any other gears. With two of these gearsets in a row, we can get the four forward gears and one reverse gear our transmission needs. We'll put the two sets of gears together in the next section.

Compound Planetary Gearset


This automatic transmission uses a set of gears, called a compound planetary gearset, that looks like a single planetary gearset but actually behaves like two planetary gearsets combined. It has one ring gear that is always the output of the transmission, but it has two sun gears and two sets of planets.
Let's look at some of the parts:

automatic transmission gear housing
How the gears in the transmission are put together
Left to right: the ring gear, planet carrier, and two sun gears

The figure below shows the planets in the planet carrier. Notice how the planet on the right sits lower than the planet on the left. The planet on the right does not engage the ring gear -- it engages the other planet. Only the planet on the left engages the ring gear.

automatic transmission planet carrier
Planet carrier: Note the two sets of planets.

Next you can see the inside of the planet carrier. The shorter gears are engaged only by the smaller sun gear. The longer planets are engaged by the bigger sun gear and by the smaller planets.

automatic transmission planet carrier
Inside the planet carrier: Note the two sets of planets.

First Gear


In first gear, the smaller sun gear is driven clockwise by the turbine in the torque converter. The planet carrier tries to spin counterclockwise, but is held still by the one-way clutch (which only allows rotation in the clockwise direction) and the ring gear turns the output. The small gear has 30 teeth and the ring gear has 72, so the gear ratio is:
Ratio = -R/S = - 72/30 = -2.4:1
So the rotation is negative 2.4:1, which means that the output direction would be opposite the input direction. But the output direction is really the same as the input direction -- this is where the trick with the two sets of planets comes in. The first set of planets engages the second set, and the second set turns the ring gear; this combination reverses the direction. You can see that this would also cause the bigger sun gear to spin; but because that clutch is released, the bigger sun gear is free to spin in the opposite direction of the turbine (counterclockwise).

Second Gear


This transmission does something really neat in order to get the ratio needed for second gear. It acts like two planetary gearsets connected to each other with a common planet carrier.
The first stage of the planet carrier actually uses the larger sun gear as the ring gear. So the first stage consists of the sun (the smaller sun gear), the planet carrier, and the ring (the larger sun gear).
The input is the small sun gear; the ring gear (large sun gear) is held stationary by the band, and the output is the planet carrier. For this stage, with the sun as input, planet carrier as output, and the ring gear fixed, the formula is:
1 + R/S = 1 + 36/30 = 2.2:1
The planet carrier turns 2.2 times for each rotation of the small sun gear. At the second stage, the planet carrier acts as the input for the second planetary gear set, the larger sun gear (which is held stationary) acts as the sun, and the ring gear acts as the output, so the gear ratio is:
1 / (1 + S/R) = 1 / (1 + 36/72) = 0.67:1
To get the overall reduction for second gear, we multiply the first stage by the second, 2.2 x 0.67, to get a 1.47:1 reduction. This may sound wacky, but if you watch the video you'll get an idea of how it works.

Third Gear


Most automatic transmissions have a 1:1 ratio in third gear. You'll remember from the previous section that all we have to do to get a 1:1 output is lock together any two of the three parts of the planetary gear. With the arrangement in this gearset it is even easier -- all we have to do is engage the clutches that lock each of the sun gears to the turbine.
If both sun gears turn in the same direction, the planet gears lockup because they can only spin in opposite directions. This locks the ring gear to the planets and causes everything to spin as a unit, producing a 1:1 ratio.

Overdrive


By definition, an overdrive has a faster output speed than input speed. It's a speed increase -- the opposite of a reduction. In this transmission, engaging the overdrive accomplishes two things at once. If you read How Torque Convertor Works?, you learned about lockup torque converters. In order to improve efficiency, some cars have a mechanism that locks up the torque converter so that the output of the engine goes straight to the transmission.
In this transmission, when overdrive is engaged, a shaft that is attached to the housing of the torque converter (which is bolted to the flywheel of the engine) is connected by clutch to the planet carrier. The small sun gear freewheels, and the larger sun gear is held by the overdrive band. Nothing is connected to the turbine; the only input comes from the converter housing. Let's go back to our chart again, this time with the planet carrier for input, the sun gear fixed and the ring gear for output.
Ratio = 1 / (1 + S/R) = 1 / ( 1 + 36/72) = 0.67:1
So the output spins once for every two-thirds of a rotation of the engine. If the engine is turning at 2000 rotations per minute (RPM), the output speed is 3000 RPM. This allows cars to drive at freeway speed while the engine speed stays nice and slow.

Reverse Gear

Reverse is very similar to first gear, except that instead of the small sun gear being driven by the torque converter turbine, the bigger sun gear is driven, and the small one freewheels in the opposite direction. The planet carrier is held by the reverse band to the housing. So, according to our equations from the last page, we have:
Ratio = -R/S = 72/36 = 2.0:1
So the ratio in reverse is a little less than first gear in this transmission.
Gear Ratios
This transmission has four forward gears and one reverse gear. Let's summarize the gear ratios, inputs and outputs:

Gear
Input
Output
Fixed
Gear Ratio
1st
30-tooth sun
72-tooth ring
Planet carrier
2.4:1
2nd
30-tooth sun
Planet carrier
36-tooth ring
2.2:1
Planet carrier
72-tooth ring
36-tooth sun
0.67:1
Total 2nd
1.47:1
3rd
30- and 36-tooth suns
72-tooth ring
1.0:1
OD
Planet carrier
72-tooth ring
36-tooth sun
0.67:1
Reverse
36-tooth sun
72-tooth ring
Planet carrier
-2.0:1

After reading these sections, you are probably wondering how the different inputs get connected and disconnected. This is done by a series of clutches and bands inside the transmission. In the next section, we'll see how these work.

Clutches and Bands in an Automatic Transmission

In the last section, we discussed how each of the gear ratios is created by the transmission. For instance, when we discussed overdrive, we said:
In this transmission, when overdrive is engaged, a shaft that is attached to the housing of the torque converter (which is bolted to the flywheel of the engine) is connected by clutch to the planet carrier. The small sun gear freewheels, and the larger sun gear is held by the overdrive band. Nothing is connected to the turbine; the only input comes from the converter housing.
To get the transmission into overdrive, lots of things have to be connected and disconnected by clutches and bands. The planet carrier gets connected to the torque converter housing by a clutch. The small sun gets disconnected from the turbine by a clutch so that it can freewheel. The big sun gear is held to the housing by a band so that it could not rotate. Each gear shift triggers a series of events like these, with different clutches and bands engaging and disengaging. Let's take a look at a band.
Bands
In this transmission there are two bands. The bands in a transmission are, literally, steel bands that wrap around sections of the gear train and connect to the housing. They are actuated by hydraulic cylinders inside the case of the transmission.

automatic transmission bands
One of the bands

In the figure above, you can see one of the bands in the housing of the transmission. The gear train is removed. The metal rod is connected to the piston, which actuates the band.

automatic transmission pistons
The pistons that actuate the bands are visible here.

Above you can see the two pistons that actuate the bands. Hydraulic pressure, routed into the cylinder by a set of valves, causes the pistons to push on the bands, locking that part of the gear train to the housing.
The clutches in the transmission are a little more complex. In this transmission there are four clutches. Each clutch is actuated by pressurized hydraulic fluid that enters a piston inside the clutch. Springs make sure that the clutch releases when the pressure is reduced. Below you can see the piston and the clutch drum. Notice the rubber seal on the piston -- this is one of the components that is replaced when your transmission gets rebuilt.

automatic transmission clutch
One of the clutches in a transmission

The next figure shows the alternating layers of clutch friction material and steel plates. The friction material is splined on the inside, where it locks to one of the gears. The steel plate is splined on the outside, where it locks to the clutch housing. These clutch plates are also replaced when the transmission is rebuilt.

automatic transmission planet clutch plates
The clutch plates

The pressure for the clutches is fed through passageways in the shafts. The hydraulic system controls which clutches and bands are energized at any given moment.

When You Put the Car in Park

It may seem like a simple thing to lock the transmission and keep it from spinning; but there are actually some complex requirements for this mechanism:
  • You have to be able to disengage it when the car is on a hill (the weight of the car is resting on the mechanism).
  • You have to be able to engage the mechanism even if the lever does not line up with the gear.
  • Once engaged, something has to prevent the lever from popping up and disengaging.
The mechanism that does all this is pretty neat. Let's look at some of the parts first.

automatic transmission in park
The output of the transmission: The square notches are engaged by the parking-brake mechanism to hold the car still.
The parking-brake mechanism engages the teeth on the output to hold the car still. This is the section of the transmission that hooks up to the drive shaft -- so if this part can't spin, the car can't move.
automatic transmission housing
The empty housing of the transmission with the parking brake mechanism poking through, as it does when the car is in park
Above you see the parking mechanism protruding into the housing where the gears are located. Notice that it has tapered sides. This helps to disengage the parking brake when you are parked on a hill -- the force from the weight of the car helps to push the parking mechanism out of place because of the angle of the taper.

automatic transmission park mechanism
This rod actuates the park mechanism.
This rod is connected to a cable that is operated by the shift lever in your car.

automatic transmission park mechanism
Top view of the park mechanism
When the shift lever is placed in park, the rod pushes the spring against the small tapered bushing. If the park mechanism is lined up so that it can drop into one of the notches in the output gear section, the tapered bushing will push the mechanism down. If the mechanism is lined up on one of the high spots on the output, then the spring will push on the tapered bushing, but the lever will not lock into place until the car rolls a little and the teeth line up properly. This is why sometimes your car moves a little bit after you put it in park and release the brake pedal -- it has to roll a little for the teeth to line up to where the parking mechanism can drop into place.
Once the car is safely in park, the bushing holds down the lever so that the car will not pop out of park if it is on a hill.
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The Basics Of Electromagnetic Clutches & Brakes


The Basics Of Electromagnetic Clutches & Brakes

Electromagnetic clutches and brakes seem simple, but complex variations fit them to multiple applications.
People use electromagnetic (EM) clutches and brakes every day and often don’t realize it. Anyone who switches on a lawn tractor, copy machine, or car air conditioner may be using an EM clutch — and EM brakes are just as common.
Electromagnetic clutches operate electrically but transmit torque mechanically. Engineers once referred to them as electromechanical clutches. Over the years EM came to stand for electromagnetic, referring to the way the units actuate, but their basic operation has not changed.
Electromagnetic clutches and brakes come in many forms, including tooth, multiple disc, hysteresis, and magnetic particle. However, the most widely used version is the single-face design.
Elements of EM
Both EM clutches and brakes share basic structural components: a coil in a shell, also referred to as a field; a hub; and an armature. A clutch also has a rotor, which connects to the moving part of the machine, such as a driveshaft.

The coil shell is usually carbon steel, which combines strength with magnetic properties. Copper wire forms the coil, although sometimes aluminum is used. A bobbin or epoxy adhesive holds the coil in the shell.
Activating the unit’s electric circuit energizes the coil. The current running through the coil generates a magnetic field. When magnetic flux overcomes the air gap between the armature and field, magnetic attraction pulls the armature — which connects to the hub — into contact with the rotor.
Magnetic and friction forces accelerate the armature and hub to match rotor speed. The rotor and armature slip past each other for the first 0.02 to 1.0 sec until the input and output speeds are the same. The matching of speeds is sometimes called 100% lockup.
Brakes lack a rotor, so magnetic flux acts directly between the armature and field. The field usually bolts to the machine frame or on a torque arm that handles brake torque. When the armature contacts the field, braking torque transfers into the field housing and machine frame, decelerating the load. As in a clutch, speed can change quickly.
Most industrial applications use single-flux, twopole clutches. These have one north-south flux path between the rotor and armature. However, mobile clutches and other specialty electromagnetic clutches can use a double or triple-flux rotor. These clutches have slots in both the rotor and armature that create additional air gaps between the two parts. These curved slots run parallel to the rotor or armature circumference, so they are often called banana slots.


Taking the path of least resistance, magnetic flux weaves between the rotor and armature two or three times when the faces engage. This weaving produces multiple north-south pole pairs. Each pair can increase the torque in a clutch. In theory, an additional set of poles at the same diameter as the first set would double the operating torque. In practice, however, each addition shrinks the diameter of all contact points. The serpentine path the magnetic flux takes also diminishes the available flux. But a double-flux design pushes up torque 30 to 50%, and a triple-flux design can bring a 40 to 90% torque boost over a single-flux unit.
The ability to increase torque without a heavier or larger clutch is especially important in weight-sensitive applications. Alternately, engineers may be able to specify smaller clutches to get the required torque.
For both clutches and brakes, turning off the power to the coil disengages the unit. As soon as power is cut, flux falls rapidly and the armature separates. One or more springs help push the armature away from its contact suRface and maintain a predetermined air gap.
All torqued up
So how much torque will a given brake or clutch supply? The main factor affecting the torque rating of a clutch or brake is the combination of voltage and current. The fields of EM clutches and brakes can be constructed for almost any dc voltage. The torque the unit produces will be the same as long as it is supplied with the correct operating voltage and current.
Electrical current controls the change in magnetic field strength, dB, as shown by:
dB = (µ0 I/4Π ) × dl sin (u)/r2
where I = net current, r = displacement vector from the coil to the point at which we want to know the magnetic field, u = angle between the vector and a current element dl, and 0 = magnetic moment of the dipole.
For instance, a 90-V clutch, a 48-V clutch, and a 24-V clutch, all powered with their respective voltages and constant current, would each produce the same amount of torque. However, applying 48 V to a 90-V clutch results in about half the torque output. This is because voltage and torque have a nearly linear relationship.

Because voltage and current are so important for maximum torque output, designers specify constant-current power supplies for critical applications. Less-expensive rectified power supplies keep voltage constant but let current change as resistance changes. Based on V = I × R, available current falls as resistance increases. An increase in resistance often results from rising temperature as the coil heats up, according to:
Rf = Ri × [1 + αCu × (Tf – Ti)]
where Rf = final resistance; Ri = initial resistance; αCu = 0.0039°C-1, copper wire’s temperature coefficient of resistance, ; Tf = final temperature; and Ti = initial temperature.
Because magnetic flux degrades with elevated coil temperature, torque declines by about 8% for every additional 20°C in the coil. Designers can compensate for minor temperature fluctuations by slightly oversizing the clutch or brake, with the advantage of being able to use a less-expensive rectified power supply instead of a constant-current source.
Designers must also distinguish between the clutch or brake’s dynamic and static-torque ratings. Applications with relatively low rotational speed — 5 to 50 rpm depending upon the unit’s size — need not consider dynamic torque. The static torque rating is usually closest to the application’s conditions.
However, a designer specifying a clutch or brake for a machine that runs at 3,000 rpm must determine the unit’s dynamic torque. Almost all manufacturers list products by static-torque rating, but dynamic torque can be less than half the static rating. Most manufacturers publish torque curves showing the relationship between dynamic and static torque for a given series of clutch or brake. (A sample curve is shown in the accompanying graphic.)
Timely torque
Torque is probably the designer’s first consideration when specifying EM clutches or brakes, but engagement time is important, too. There are actually two engagement times to consider. The first is the time it takes the coil to develop a magnetic field strong enough to pull in the armature. The second, the time-to-speed or time-to-stop for clutches and brakes, respectively, relates to the unit’s inertia.
Inertia depends on the mass and geometry of the rotating system. Web sites like inertia-calc.com can help designers determine a system’s inertia and the torque needed to accelerate or decelerate that load in a given time.
Most CAD systems can calculate component inertia, but the key to sizing clutches is calculating how much inertia is reflected back to the clutch or brake. To do this, engineers use the formula:
T = (WK2 × ΔN) / (308 × t)
where T = required torque (lb-ft), WK2 = total inertia (lb-ft2), N = change in the rotational speed (rpm), and t = time during which the acceleration or deceleration must take place. The inertia term accounts for rotating component’s weights, W (lb) and the radius of gyration (ft), K. Designers sizing a clutch or brake must first determine this inertia to calculate how much torque the unit can handle.
Compared to inertial considerations, the time needed to develop a sufficient magnetic field to actuate the brake or clutch is short.
Magnetic-field strength depends on the number of turns in the coil. The air gap between the armature and clutch rotor or brake face is a resistance the magnetic field must overcome. Magnetic lines of flux diminish quickly in air, so the greater the gap, the longer it takes the armature to develop enough magnetic attraction.
High-cycle applications often use floating armatures that rest against the rotor or brake face, making the air gap zero and response time consistent.
In fixed-armature designs, engineers must consider the air gap in new units as well as the gap in the future as contact surfaces wear and the gap grows. In high-cycle applications where accuracy is important, even a difference of 10 to 15 msec can affect performance. And in normal-cycle applications, a new machine with accurate timing can eventually see a “drift” in accuracy due to wear.
Consider a cut-to-length application where a photo eye reads a mark on the material to determine where to stop the material flow and make a cut. If the machine is not calibrated accordingly, it will produce slightly longer pieces over time than when it was brand new because wear widens the air gap, creating a slightly longer pull-in time.
To speed responses, some EM clutches and brakes use overexcitation. The unit’s power supply gives the coil a burst of voltage significantly higher than its nominal rating for a few milliseconds. Higher voltage lets the coil generate a more-powerful magnetic field more quickly, starting the process of attracting the armature and accelerating or decelerating the load.
Three times the rated voltage typically gives around one-third faster response. Overexcitation of 15 times the normal coil voltage produces responses three times faster. For instance, a clutch coil rated for 6 V should be overexcited to 90 V to cut response time to one-third of the original.
Once overexcitation is no longer needed, the power supply returns to its normal operating voltage. Overexcitation can be repeated as needed, but the high-voltage bursts must be short enough that they do not overheat the coil.
The benefits of burnishing
Although armatures, rotors, and brake faces are machined or even lapped as flat as possible at manufacture, peaks and valleys remain on the surfaces. When a new clutch or brake engages, the contact area is initially confined to the peaks on the mating surfaces. This smaller contact area means torque can be as much as 50% less than the unit’s static torque rating.
To get the full torque, users need to burnish mating surfaces. Burnishing cycles the unit, letting those initial peaks wear down so there is more surface contact between the mating faces. These cycles — 20 to over 100 of them, depending on the amount of torque required — should be lower in inertia, speed, or both, than the end application.
For some designs, like bearing-mounted clutches with the rotor and armature connected and held in place by a bearing, users can complete the burnishing on a bench top or burnishing station instead of on the machine. On the other hand, two-piece clutches or brakes, which have separate armatures, burnish better after installation. That’s because armature alignment and, hence, burnishing lines can shift slightly when the unit moves.
Such alignment shifts may produce small torque reductions that would only be noticed in torque-sensitive applications. Other applications may not need burnishing at all. If the system needs less torque than the clutch or brake provides out of the box, users can skip the burnishing step. In general, burnishing is more critical on higher torque devices.
How long does it last?
Normal operations wear down contact surfaces, just as burnishing does. Every time a clutch or brake engages during rotation, a certain amount of energy is transferred as heat. This transfer wears both the armature and the opposing contact surface.
Wear rates depend on size, speed, and inertia. For example, if workers changed pulleys on a machine from 1:1 to 2:1 so that it ran at 1,000 rpm instead of its previous speed of 500 rpm, the change would quadruple its clutch’s wear rate. That’s because reflected inertia increases with the square of the speed ratio. That is:
(WK2)r = WK2 × Δ N2.
In such situations, a fixed armature stops engaging when the air gap gets too large for the magnetic field to overcome. Zero-gap or auto-wear armatures can wear to less than one-half of their original thickness before failing.
Designers can estimate life from the energy transferred each time the brake or clutch engages.
Ee = [m × v2 × τ d]/[182 × (τ d + τ l)]
where Ee= energy per engagement, m = inertia, v = speed, τ d = dynamic torque, and τ l= load torque. Knowing the energy per engagement lets designers calculate the number of engagement cycles the clutch or brake will last:
L = V/(Ee × w)
where L = unit life in number of cycles, V = total engagement area, and w = wear rate.
Clutches subject to low speed, low side loads, or infrequent operation often use bushings on rotating parts. Although less expensive than bearings, bushings tend to fail before the air gap grows to the point of failure. At higher loads and speeds, bearing-mounted fields, rotors, and hubs are better options. Unless bearings are stressed beyond their physical limitations or become contaminated, they tend to have a long life and are usually the next area to fail after the air gap.
It is rare for a coil to stop working in an EM clutch or brake. Coil failures are usually due to heat-induced breakdown of the coil-wire’s insulation. Causes include high ambient temperature, high cycle rates, excessive slipping between the armature and contact surface, and the application of higher voltage than the coil rating permits.
Figuring on friction
The torque between an armature and clutch rotor or brake field is derived from the steel-to-steel coefficient of friction and magnetic force, but most industrial designs add friction material to change torque or wear characteristics.
The friction material is recessed between the inner and outer poles in both brakes and clutches. This ensures magnetic metal-tometal contact between the armature and coil shell or rotor but expands the contact surface area. The larger area slows wear and extends cycle life. In some applications, materials such as ceramics have greatly extended life in clutches and brakes to 25 or 50 million cycles.
Clutches in automobiles, agricultural equipment, and construction gear tend not to use friction material because they have lower cycle requirements than industrial clutches. In addition, mobile equipment is often exposed to wet weather that can swell friction materials and cut available torque.
While most friction materials primarily slow wear, they can also be used to alter the relatively high coefficient of friction of steel-to-steel contact. An engineer who needs a clutch or brake with extended slip time might specify a material with a lower coefficient of friction. Conversely, for slightly higher torque, common in low-rpm applications, designers might use high-coefficient-of-friction materials such as cork.
No matter what material designers choose, the wearing action creates particulates. Where particulates are problematic, such as in clean-room and food-handling applications, units should be enclosed to keep particles from contaminating the surroundings.
However, a more-common scenario is that the clutch or brake becomes contaminated by something in the environment. Oil or grease should be kept away from clutches or brakes because they reduce friction between contact surfaces, lowering available torque. The same is true for oil mists and airborne lubricant particles in the work area.
Dust and other contaminants that fall between contact surfaces can also reduce torque. Designers who know their clutch or brake will be in a contaminant-prone environment may choose to add a shield to protect contact surfaces.
Clutches and brakes that have not been used in a while can rust on the contact surfaces. This is generally not a major concern because the rust wears away within a few cycles, leaving no lasting impact on torque.
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Tuesday, 16 June 2015

Top 15 Advanced Operating Systems For Hackers


Today we are discussing about top 15 advanced operating systems which has great penetration testing or ethical hacking tools. the top Os on this list is my favorite Linux distro Kali Linux because it is very popular in pentesting and it is developed by the same team of BackTrack (Offensive security). i am not including BackTrack on this list because it is no more available officially on their website and the next version of BackTrack is Kali Linux. the listed operating systems are here based on Linux kernel so it is all free operating systems. (Included download links for all Os) :)

I am recommending you to read my earlier post to understand more about Linux distros related to hacking security: Linux Powerful Distros For Hacking Or Security: Kali, Tails And Qubes



1. Kali Linux


Kali Linux is a Debian-derived Linux distribution designed for digital forensics and penetration testing. It is maintained and funded by Offensive Security Ltd. Mati Aharoni and Devon Kearns of Offensive Security developed it by rewriting BackTrack. Kali Linux is the most versatile and advanced penetration testing distro. Kali updates its tools and it is available for many different platforms like VMware and ARM. if you want to know more about Kali Linux then i recommend you read my previous article: An Introduction To Hacker’s OS Kali Linux And Setup Tutorial.

Click here to download

2. BackBox 


It includes some of the most used security and analysis Linux tools, aiming to a wide spread of goals, ranging from web application analysis to network analysis, from stress tests to sniffing, including also vulnerability assessment, computer forensic analysis and exploitation.

The power of this distribution is given by its Launchpad repository core constantly updated to the last stable version of the most known and used ethical hacking tools. The integration and development of new tools inside the distribution follows the commencement of open source community and particularly the Debian Free Software Guidelines criteria.

Click here to download


3. Parrot-sec forensic os


Parrot Security is an operating system based on Debian GNU/Linux mixed with Frozenbox OS and Kali linux in order to provide the best penetration and security testing experience. it is an operating system for IT security and penetration testing developed by the Frozenbox Dev Team. It is a GNU/Linux distribution based on Debian and mixed with Kali. 

Parrot uses Kali repositories in order to take latest updats for almost all the tools, but it also has its own dedicated repository where all the custom packets are kept. This is why this distro is not just a simple Kali “mod” but entire new concept which relies on Kali’s tool repositories. As such, it introduces a lot of new features and different developing choices.Parrot uses MATE as a Desktop Environment. Lightweight and powerful interface is derived from famous Gnome 2, and thanks to FrozenBox highly customizable with captivating icons, ad-hoc themes and wallpapers. System look is proposed and designed by the community members and also members of Frozenbox Network, who are closely following the development of this project.

Click here to download


4. DEFT
Deft is Ubuntu customization with a collection of computer forensic programs and documents created by thousands of individuals, teams and companies. Each of these works might come under a different licence. There Licence Policy describe the process that we follow in determining which software we will ship and by default on the deft install CD.

Click here to download


5. Live Hacking OS


As i am said before Live Hacking OS is also based on linux which has big package of hacking tools useful for ethical hacking or penetration testing. It includes the graphical user interface GNOME inbuilt. There is a second variation available which has command line only, and it requires very less hardware requirements.



6. Samurai Web Security Framework


The Samurai Web Testing Framework is a live linux environment that has been pre-configured to function as a web pen-testing environment. The CD contains the best of the open source and free tools that focus on testing and attacking websites. In developing this environment, we have based our tool selection on the tools we use in our security practice. We have included the tools used in all four steps of a web pen-test.

Click here to download

7. Network Security Toolkit (NST)


Network Security Toolkit (NST) is a bootable live CD based on Fedora Core. The toolkit was designed to provide easy access to best-of-breed open source network security applications and should run on most x86 platforms. The main intent of developing this toolkit was to provide the network security administrator with a comprehensive set of open source network security tools. 

What we find rather fascinating with NST is that we can transform most x86 systems (Pentium II and above) into a system designed for network traffic analysis, intrusion detection, network packet generation, wireless network monitoring, a virtual system service server, or a sophisticated network/host scanner.

Click here to download

8. Bugtraq


Bugtraq is an electronic mailing list dedicated to issues about computer security. On-topic issues are new discussions about vulnerabilities, vendor security-related announcements, methods of exploitation, and how to fix them. It is a high-volume mailing list, and almost all new vulnerabilities are discussed there.
Bugtraq team is experienced freaks and developers, It is available in Debian, Ubuntu and OpenSuSe in 32 and 64 bit architectures.

Click here to download

9. NodeZero


 It is said the necessity is the mother of all invention, and NodeZero Linux is no different. There team is built of testers and developers, who have come to the census that live systems do not offer what they need in their security audits. Penetration Testing distributions tend to have historically utilized the “Live” system concept of linux, which really means that they try not to make any permanent effects to a system. Ergo all changes are gone after reboot, and run from media such as discs and USB’s drives. However all that this maybe very handy for occasional testing, its usefulness can be depleted when your testing regularly. Its there believe that “Live System’s” just don’t scale well in a robust testing environment.

All though NodeZero Linux can be used as a “Live System” for occasional testing, its real strength comes from the understanding that a tester requires a strong and efficient system. This is achieved in our belief by working at a distribution that is a permanent installation, that benefits from a strong selection of tools, integrated with a stable linux environment.

Click here to download

10. Pentoo


 Pentoo is a Live CD and Live USB designed for penetration testing and security assessment. Based on Gentoo Linux, Pentoo is provided both as 32 and 64 bit installable live cd. Pentoo is also available as an overlay for an existing Gentoo installation. It features packet injection patched wifi drivers, GPGPU cracking software, and lots of tools for penetration testing and security assessment. The Pentoo kernel includes grsecurity and PAX hardening and extra patches - with binaries compiled from a hardened toolchain with the latest nightly versions of some tools available.

Click here to download

11. GnackTrack


 GnackTrack is an open and free project to merge penetration testing tools and the linux Gnome desktop. GnackTrack is a Live (and installable) Linux distribution designed for Penetration Testing and is based on Ubuntu.

Backtrack is not only a single player in the field of ethical hacking, so you can try some other distribution as well, if you are Gnome lover than must try this, however backtrack 5 is also available on Gnome platform. Just like backtrack, Gnacktrack comes with multiple tools that are really helpful to do a effective penetration testing, it has Metasploit, armitage, wa3f and others wonderful tools.

Click here to download

12. Blackbuntu




Blackbuntu is distribution for penetration testing which was specially designed for security training students and practitioners of information security. Blackbuntu is penetration testing distribution with GNOME Desktop Environment. It's currently being built using the Ubuntu 10.10 and work on reference Back|Track.

Click here to download

13. Knoppix STD


 Knoppix STD (Security Tools Distribution) is a Live CD Linux distribution based on Knoppix that focused on computer security tools. It included GPL licensed tools in the following categories: authentication, password cracking, encryption, forensics, firewalls, honeypots, intrusion detection system, network utilities, penetration, packet sniffers, assemblers, vulnerability assessment and wireless networking. Knoppix STD version 0.1 was published January 24, 2004, on Knoppix 3.2. Thereafter, the project stagnated, lacking updated drivers and packages. A release date for version 0.2 has not yet been announced. A list of tools is available on the official website.

Click here to download

14. Weakerth4n


 Weakerth4n is a penetration testing distribution which is built from Debian Squeeze.For the desktop environment it uses Fluxbox.This operating system is ideal for WiFi hacking as it contains plenty of Wireless tools. It has a very well maintained website and a devoted community. Built from Debian Squeeze (Fluxbox within a desktop environment) this operating system is particularly suited for WiFi hacking as it contains plenty of Wireless cracking and hacking tools.

Tools includes: Wifi attacks, SQL Hacking, Cisco Exploitation, Password Cracking, Web Hacking, Bluetooth, VoIP Hacking, Social Engineering, Information Gathering, Fuzzing Android Hacking, Networking and creating Shells.



15. Cyborg Hawk


The most advanced, powerful and yet beautiful penetration testing distribution ever created. Lined up with ultimate collection of tools for pro Ethical Hackers and Cyber Security Experts. It has 700 + tools while Kali have 300+ and also dedicated tools for and menu for mobile security and malware analysis . Also it is easy to compare it with Kali as to make a better OS than Kali we have to outperform it. It is a new operating system based on Ubuntu linux, i am not tested this OS that is why i placed it in the last of this list.

Cyborg Hawk is developed by Team Cybord led by Vaibhav Singh and Shahnawaz Alam from Ztrela Knowledge Solutions Pvt. Ltd.
Recommended article: Top Ten Popular Hacking Tools
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