Like many products in the power transmission industry, roller chain sprockets inevitably wear out. Sprocket wear is not necessarily a cause for concern. Excessive or rapid wear of any component, however, is a concern. The most likely cause of sprocket tooth wear? Elongated or elongated chain. This article will highlight some other reasons as well as examine the phenomenon of roller chain stretching.
Ideally, the material used for small sprockets or those with fewer teeth should be hardened and machined solid steel, a very resistant material. At best, a sprocket will outlast the roller chain, likely going through two or three chain applications before needing to be replaced. However, once a sprocket begins to show signs of wear, if it continues to run, it will begin to negatively affect the chain, creating a vicious cycle of wear.
Prevention and implementation of best practices will go a long way toward minimizing component wear.
Roller chain extension
Over time, the roller chain will stretch with regular use until it needs to be replaced. Each roller chain has an expected lifespan based on specifications and usage conditions. When the chain runs, it creates friction on the bushings and pins. This friction will cause these parts to slowly wear out. As parts wear, the distance between rollers connected by a pin connection increases.
This process normally occurs slowly, even when the chain elongates prematurely. There is no single cause for stretching. This can occur through a number of factors. In fact, in a typical drivetrain, with average load, running at a reasonable speed, the chain will still stretch. The best way to slow down the stretching process is through lubrication, the more thorough the method, the better.
As we noted, as the roller chain lengthens, the distance between the rollers increases. This phenomenon affects the way the chain wraps around the sprocket. When working properly, the roller will fall into the groove between the teeth and then roll off the drive side of the pinion tooth. The rollers of a stretched chain do not seat properly, hitting the face of the tooth instead of landing in the esophagus. This force will begin to wear down the teeth, creating a hook shape.
A stretched roller chain will always negatively affect the sprockets. Before replacing the sprockets, if they appear to be wearing faster than normal, use a chain stretching tool to measure how much the chain has stretched. This measurement will immediately tell you whether stretching is the cause of sprocket tooth wear. Chain elongation is acceptable up to 3% for drives with sprockets with less than 67 teeth. When the transmission has a sprocket with more than 67 teeth, elongation of up to 1.5% is allowed.
Correct installation of the chain drive
Another extremely important factor in minimizing sprocket tooth wear begins during installation. By taking the time during installation to ensure each step is performed correctly, you significantly reduce the chance of a transmission problem causing wear on the pinion teeth.
Sprocket alignment can be the biggest key here. Axial and angular alignment is essential for smooth and efficient chain operation. With misaligned or misaligned sprockets, the chain side plates can repeatedly hit the side of the sprocket teeth. The same goes for when the faces of the sprocket are at different angles to each other. Instead of the chain rolling off the face of the tooth, it will disengage at an angle that will exert abnormal forces against the teeth.
Transmission misalignment, misaligned sprockets, out-of-parallel sprockets, whatever term you want to use, will have negative effects on transmission performance. For the sprockets and roller chain to function as intended and not wear excessively, your installation practices must be greater than or equal to how you expect the drivetrain to function.
Materials for sprockets and roller chains
It is worth discussing the materials and manufacturing processes of both roller chains and sprockets. Sprocket and roller material will have a direct impact on their transmission performance. Both the correct hardness and the types and qualities of the steel used are very important.
Let's consider the sprocket first. Several aspects can influence sprocket wear. Sintered steel can wear out more quickly than solid 1045 steel. When the chain contacts the sprocket, the interaction can be quite severe depending on the speed and load. It is not difficult to imagine these forces exerting their influence on inferior materials. Additionally, an inadequately hardened tooth profile will begin to lose shape once surgery begins. Curing precision and product quality assurance will go a long way toward alleviating these problems.
The same goes for the chain roller. If a roller is too hard during the manufacturing process, it will create a harmful interaction between the sprocket teeth and the roller chain. There is a delicate balance, even under adverse conditions, that must be maintained for components to function as intended. Any errors during production will inevitably cause failures.
While it is difficult to analyze manufacturing processes and materials as a customer, supplier transparency can alleviate many concerns.
Prevention for next time
After replacing worn sprockets and stretched chain, it is crucial to prevent this from happening again. Before turning on the unit, re-evaluate the installation practices applied to this specific unit. Each step during installation is as critical as the ones before and after it. The importance of lubrication methods is also a drum we will continue to beat. Well-lubricated transmissions perform better than those that implement the bare minimum.
Rapid wear or unusual wear patterns on the sprocket teeth are signs that there is a serious problem with the chain drive. Start by inspecting the roller chain stretch first. Installation, maintenance techniques and product quality are also factors to be reviewed. This problem is highly preventable.
