Gear drives are commonly applied in today's industries. People use them to meet various requirements. Of course, they have many advantages. For instance, they have high reliability. Their constant-use durability is very good. Besides, the precision is also high.
Although they have many advantages, their disadvantages still deserve our attention. These disadvantages may have negative effect on them. Now, let us talk something about those disadvantages.
First of all, there are some difficulties for the installation of the gear drives. Even the simplest floating-idler gear drives often require a certain amount of engine block and timing cover clearance work. Water intrusion, oil leaks, and metal shavings in the oil are the least of it. Fixed idler systems often necessitate installation of a new timing cover or spacer, which can have an impact on accessory belt alignment. Belt alignment issues often require a new water pump, new pulley or pulley spacers.
Second, they can not avoid the harmonic vibration. There is a close relationship between gear drives and the harmonic vibration. Even so-called "quiet drives" can not be free of a certain amount of harmonic vibration. And no matter how well engineered they are, all of them have a certain amount of clearance that causes their telltale gear whine. That gear whine is indicative of high frequency vibration, which can work its way through the camshaft and into the valve train. The vibration may have a bad impact on the camshafts and rocker arms.
Thirdly, their gains are relatively small. When compare them with a double roller chain, the gear drives do a better job at maintaining spark stability and timing accuracy in theory. However, their gains are pretty minimal. These gains are about 4/10ths of a percent power gain for a fixed idler gear drive, which occurs only briefly near the engine's redline.
In addition, they cost more than many types of chains relatively. All in all, you should not ignore gear drive disadvantages. The information about them may help you to learn about these products in an overall view.
