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Program: The Installation of Bevel Gears


Part 4 - Analyzing the Contact Pattern

This brings us to the issue of analyzing the contact pattern. Let’s first look at an ideal contact pattern.

This contact pattern is from a tooth without load. The length and position are important. Here we see that the contact is covering approximately 30-40% of the tooth surface and is located central to the toe. This would be an acceptable pattern of a gearset without load. But what if the pattern is not correct?

Here’s an example of a pattern without load that is not located central to the toe. With this pattern, the gear will most likely not function properly and it could fail in operation.

In theory, the contact pattern should be elliptical in shape. However, it’s important to keep in mind that the shape of the contact pattern is not as important as its location.

When assessing the contact pattern, it’s important to look at both the concave and convex sides of the gear and pinion. For the most part, the pattern on both sides of the teeth should be the same. If you find that the contact pattern is incorrect, most likely the pattern will be wrong on both sides. This can occur due to three main errors. These are profile error, cross contact and shaft angle error.  Let’s look at each of these three problems.