Herringbone gears resemble two helical gears that have been placed side by side. They are often referred to as "double helicals". In the double helical gears arrangement, the thrusts are counter-balanced. In such double helical gears there is no thrust loading on the bearings.
Thursday, 26 November 2015
WHAT IS HELICAL GEAR ?
Helical gears have their teeth inclined to the axis of the shafts in the form of a helix, hence the name helical gears.
These gears are usually thought of as high speed gears. Helical gears can take higher loads than similarly sized spur gears. The motion of helical gears is smoother and quieter than the motion of spur gears.
Single helical gears impose both radial loads and thrust loads on their bearings and so require the use of thrust bearings. The angle of the helix on both the gear and the must be same in magnitude but opposite in direction, i.e., a right hand pinion meshes with a left hand gear.
These gears are usually thought of as high speed gears. Helical gears can take higher loads than similarly sized spur gears. The motion of helical gears is smoother and quieter than the motion of spur gears.
Single helical gears impose both radial loads and thrust loads on their bearings and so require the use of thrust bearings. The angle of the helix on both the gear and the must be same in magnitude but opposite in direction, i.e., a right hand pinion meshes with a left hand gear.
what is spur ?
Parallel and co-planer shafts connected by gears are called spur gears. The arrangement is called spur gearing.
Spur gears have straight teeth and are parallel to the axis of the wheel. Spur gears are the most common type of gears. The advantages of spur gears are their simplicity in design, economy of manufacture and maintenance, and absence of end thrust. They impose only radial loads on the bearings.
Spur gears are known as slow speed gears. If noise is not a serious design problem, spur gears can be used at almost any speed.
Monday, 23 November 2015
what is gear?
Gears are used in tons of mechanical devices. They
do several important jobs, but most important, they provide a gearreduction in motorized equipment. This is key because, often, a small
motor spinning very fast can provide enough power for
a device, but not enough torque.
For instance, an electric screwdriver has a very large gear reduction because
it needs lots of torque to turn screws, but the motor only produces a small
amount of torque at a high speed. With a gear reduction, the output speed can
be reduced while the torque is increased.
A gear or cogwheel is
a rotating machine part having cut teeth,
or cogs, which mesh with another toothed part to
transmit torque, in most cases with teeth on the one gear being of
identical shape, and often also with that shape on the other gear. Two or
more gears working in a sequence are called a gear train or, in many cases, a transmission; such gear arrangements
can produce a mechanical advantage through a gear ratio and
thus may be considered a simple machine. Geared devices can change the
speed, torque, and direction of a power source. The most common situation
is for a gear to mesh with another gear; however, a gear can also mesh with a
non-rotating toothed part, called a rack, thereby producing translation instead
of rotation. A gear is a wheel with teeth that mesh together with other gears.
Gears change the
• speed
• torque
• direction of rotating axles.
WHAT ARE TYPES OF TURBINE USED IN INDUSTRY?
Types of Turbines
There are many different kinds of turbines:
- You have probably heard of a steam turbine. Most power plants use coal, natural gas, oil or a nuclear reactor to create steam. The steam runs through a huge and very carefully designed multi-stage turbine to spin an output shaft that drives the plant's generator.
- Hydroelectric dams use water turbines in the same way to generate power. The turbines used in a hydroelectric plant look completely different from a steam turbine because water is so much denser (and slower moving) than steam, but it is the same principle.
- Wind turbines, also known as wind mills, use the wind as their motive force. A wind turbine looks nothing like a steam turbine or a water turbine because wind is slow moving and very light, but again, the principle is the same.
WHAT IS TURBINE?
A windmill is the simplest kind of turbine: a machine designed to capture some of the energy from a moving fluid (a liquid or a gas) so it can be put to use. As the wind blows past a windmill's sails, they rotate, removing some of the wind's kinetic energy and converting it into mechanical energy that turns heavy, rotating stones inside the mill. The faster the wind blows, the more energy it contains; the faster the sails spin, the more energy is supplied to the mill. Adding more sails to the windmill or changing their design so they catch the wind better can also help to capture more of the wind's energy. Although you may not realize it, the wind blows just a bit more slowly after it's passed by a windmill than before—it's given up some of its energy to the mill!
The key parts of a turbine are a set of blades that catch the moving fluid, a shaft or axle that rotates as the blades move, and some sort of machine that's driven by the axle. In a modern wind turbine, there are typically three propeller-like blades attached to an axle that powers an electricity generator. In an ancient waterwheel, there are wooden slats that turn as the water flows under or over them, turning the axle to which the wheel is attached and usually powering some kind of milling machine.
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