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PULLEY SYSTEMS - VELOCITY RATIO - 2 | |
V. Ryan © 2010 | |
The diameter of the driver pulley wheel is 200mm and the driven pulley wheel is 600mm. This means for every single revolution of the larger driven pulley wheel, the smaller driver pulley wheel rotates three times. This due to velocity ratio. The ratio can be worked out mathematically in different ways. The two most likely methods are shown below |
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PLEASE NOTE - WHEN WORKING OUT VELOCITY RATIO - THE
NUMBERS ARE ARRANGED IN THE SAME ORDER OF THE PULLEYS - IN THIS EXAMPLE
THE DRIVER COMES FIRST, FOLLOWED BY THE DRIVEN IN AN EXAM YOU MAY BE ASKED TO PUT THE DRIVER OR DRIVEN NUMBER FIRST. |
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An alternative method is to call the ‘DISTANCE MOVED’ as simply being DIAMETER. This makes the calculation easier to understand, although using this terminology may not be accepted in an examination. | |
This means that the larger pulley wheel (the driven pulley wheel) revolves a third of the rpm compared to the smaller driver pulley wheel. In effect the driven pulley wheel is slower and revolves a third as many times as the driver. This means if the rpm of the driver pulley wheel is divided by 3, the output rpm of the driven pulley wheel will be found. |
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