How Do Worm Gear Reducers Work?

Tuesday - 02/01/2018 21:18

How Do Worm Gear Reducers Work?

Worm gear reducers mesh two very different mechanical parts, but, dissimilar as these paired components unquestionably are, they do create a unique relationship.

They function as potent gearing reducers, moving parts that lock together to greatly reduce the speed of a gear train.

Calculating Reduction Ratings

Imagine the first part of the gearing configuration, the brass worm, as a single-tooth gear. It's a slender screw-like cylinder that locks perpendicularly against a spur gear. Now, in calculating the ratio of the unit, the reduction integer, the number of teeth on the spur gear determines the ratio, for the worm component's tooth count is always set-in-stone as one.

Therefore, a circular gear with eighty teeth will have a reduction ratio of 80:1. So, with that simple equation in mind, all that's required to scale this ratio is a larger wheel. The diameter of the gear increases, the number of teeth subsequently multiplies, and the reduction ratio grows proportionally because the worm gear, at least mathematically, is still locked reliably at one.

Studying Worm Gear Reducers in Motion

Before saying anything else, we need to define the rotating sequence occurring within this gearing arrangement. Torque is transferred from the screw or worm to the circular gear. That's the progression used in this part, which is why it's known as a speed reducer. Incidentally, it's next to impossible to reverse this sequence, so the mechanism is also known as a self-locking speed reducer.

Anyway, as torque is transferred from the worm to the wheel gear, our reduction formula causes the powertrain to slow down. Again, this rating is easy to determine. Just count the number of teeth on the spur gear and divide by one. There is one notable drawback we should be aware of at this time, and that's the potential for losses, but we can skip ahead for more on this hindrance factor.

Lubricating Against Losses

There's an obvious disadvantage here, which is the perpendicular arrangement required to make worm engineering function properly. The spur gear isn't properly meshing or sliding against the screw-like shaft, so friction is an issue. Advanced low-viscosity lubricants solve this problem, plus high-quality design standards maximise the contact area between the two components.

Entirely capable of delivering ratio gains that peak at around 300:1, worm gear reducers are essential dual-part gearing assemblies. They dramatically drop powertrain velocity while simultaneously multiplying torque, thus providing two important functions. Their 90° offset also enables compact drive shaft switchovers while mechanically reassigning braking functions to the non-reversing gearing arrangement.

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