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Gearing Systems : Worm Gears

A wormset consists of two different types of gears, the worm and the worm gear. The worm is the gear that has only one tooth that is continuously wrapped around its circumference a certain number of times. The worm will mesh to the worm gear perpendicularly. Refer to the image below.

Worm gears

For every rotation of the worm one tooth of the worm gear will move. This means that the gear ratio of a wormset would be one over the number of gears on the worm gear. Due to this, a wormset is a great way to rapidly gear a motor down, and do it within a small package.

Another advantage of a wormset is that they are impossible to backdrive. This means that the worm can drive the worm gear but the worm gear cannot drive the worm providing convenient locking mechanism. However because of this there are large sliding and thrust loads, which will cause a wormset can be rather inefficient with an average efficiency of 40 to 85%.

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