In my previous article, I explained worm gears with their advantages, disadvantages and applications. In this article, I will be giving you a brief introduction to spur gear.
Spur gear is the most common type of gear used. It is used for transmitting power between two parallel shafts.
In this type of gear, the teeth cut on the cylindrical face are parallel to the axis of the gear. You can understand this well by taking a look at the following image.
Though several types of profiles can be used for cutting teeth on a spur gear, we commonly use involute teeth profile. The gear found in the image above uses an involute tooth profile.
A spur gear drive is a combination of two spur gears properly meshed with each other. It is used for transmitting rotational motion between parallel shafts. It offers a definite velocity ratio. From my previous article about gears,
Spur Gear Drive
If the driving gear is smaller the than the driven gear, then rotating velocity is reduced in the driven gear. If the driving gear is larger than the driven gear, rotational velocity is increased in the driven gear. If both the driving and driven gears have the same number of teeth, there is no change in the rotational velocity. In the image above, both the gears have the same number of teeth Hence, their velocity ratio is one and they rotate at same speeds.
In a spur gear drive, the smaller gear is called pinion and the larger one is called gear. When designing a spur gear drive, the pinion is made harder than the gear. This is because, the pinion has to run more no. of cycles when compared to the gear.
Materials used for making spur gears:
The following are some of the common materials used for making spur gears:
- Cast iron
- Steel (Plain Carbon, C45 and alloy steel)
- Nylon, Fibre Reinforced Plastics (FRP)
Modes of Failures in a Spur gear:
The following are some of the common modes of failure in a spur gear:
- Tooth Breakage (mostly because of fatigue loading)
- Surface Failures (Because of abrasion, pitting, seizure and scoring)
For a list of advantages, disadvantages and applications of spur gear, read this article.
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