GEARS
FEATURE SPONSOR
GEARS REVOLVING & EVOLVING
A teenager in court for dangerous driving is asked by the attorney for the prosecution… “What gear were you in as you turned into the high street?”
“A hoody, jeans and trainers” replied the teenager.
GEAR, GEARS, DRIVETRAIN, GEARBOX A gear is normally but not exclusively a rotating machine part with teeth or cogs.
When two gears mesh in a rotating machine they impart motion from one to the other, the motion will change direction. Rotation speed and torque can remain the same, increase or decrease depending on the gears relationship to each-other.
When two gears mesh in this way we have a transmission or a drive train. Put a number of these gears into a housing, with an input shaft and an output shaft and what we have is generally known as gearbox.
TYPES OF GEARS EVERYWHERE There are many types of gears and they are used in infinite number of applications. Without even knowing or thinking about it we use gears in our everyday lives and we have done so for hundreds of years. Wrist watches are probably closest to home for most of us, food mixers or the gearbox in our car.
There is not a day goes buy in our modern lives where we are not directly or indirectly affected by gears. So, for a technology that’s been around for so long why all the song and dance when it comes to the wind turbine?
WIND POWER - HISTORY
Windmills have been around for thousands of years. The Greeks as far back in the first century is one of the earliest known instance of using a wind-driven wheel to power a machine.
I can’t guarantee there were gears involved but changing rotation speed, direction and torque through pulley wheels and belts is a similar principle. The gear tooth and mesh replace the belt but the mechanical advantage gained from different sized wheels or gears is the same basic principle.
If you ever get a chance to visit a more recent working windmill used for grinding grain it is well worth the trip. In these you can see on a massive, open and expanded scale how motion is imparted from the sails through the main shaft and a series of wooden or iron gears depending on the vintage of the machine, to drive the grinding stones.
WIND TURBINE GEARBOX This is just an expanded version of what takes place in a wind turbine gearbox. The gearbox is the heart of the turbine it converts the slow rotation and the high torque on the rotor side of the gearbox through the transmission in the gearbox to high speed low torque at the generator side.
UNDERSTANDING TORQUE If you have difficulty understanding torque, visit one of the gear manufacturers stands at a trade show. If they have a demonstration gear on display, try to rotate the input shaft by hand. Once you have exhausted yourself and suffered a hernia, move around to the output shaft and try the same. This you will find incredibly easy.
You are still moving the same components, weighing exactly the same but due to the low torque at the output shaft and the mechanical advantage of the drive train you are able to do this easily.
We can now see clearly why a gearbox is used in the wind turbine’s drive train and what it does let’s take a look at how it has developed in the very short time that our industry has existed as a real producer of energy.
WIND TURBINE HISTORY In the very early part of the 1980s wind turbines went into what could be really called serial production for the first time to be used as commercial generators of energy.
At the time the industry was an infant and in many ways still is when compared to others. Many gearboxes were little more than adaptions of gearboxes used in industrial or agricultural applications. These gearboxes were relatively simple affairs with two or three stage spur gear drives between input and output.
These worked but were not without their problems, size, weight, noise and reliability being among these. As our industry has progressed, turbine size increased and regulations have become more stringent, the development of the gears and the gearbox has needed to keep pace and adapt.
GEARBOX DEVELOPMENT
98
www.windenergynetwork.co.uk
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