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Program: Arrow Gear’s Advanced Design and Development Assistance Capabilities

Part 1 - Introduction, Understanding Contact Pattern, Conventional Methods vs. Arrow Gear's System

Arrow Gear Company is among the world’s top producers of precision gears.

Throughout all areas of our company, we have integrated the latest technologies and are equipped with the most advanced machining capabilities.

But our expertise is more extensive than the actual process of machining gears. Resulting from our history of over 50 years in the gear business, we not only understand how to manufacture gears, but also how to engineer them to ensure peak performance and create cost savings for our customers.

In this program, we’d like to provide more information on our extensive expertise in the area of gear design.

Understanding the Contact Pattern

A critical attribute of a gear’s design is its contact pattern.

Simply stated, the contact pattern is the area in which the gear teeth come in contact with each other as the gears rotate. This area of contact is easily checked in this way.

The teeth are coated with a special marking compound and then run together in a tester. Tape is then applied to the tooth surface and transferred to a piece of paper.

Looking at the tape transfer, we can see the area of the gear tooth that is in contact – and this is what we refer to as the contact pattern.

When a gear is installed in a gearbox – and is actually powering the designated application, there are varying degrees of pressure or load on the gear teeth. When the gear teeth are under load – the contact pattern will change.

Here we see a contact pattern from a gear with a very light load. And here is a contact pattern from the same gear with a very heavy load. So there is a general rule of thumb, which states that, the heavier the load, the larger the contact pattern.

Now here is where the issue of contact pattern becomes so important. For a gear to perform properly under load, the contact pattern must be a certain shape and at a certain location. Typically, an ideal tooth contact pattern should be this type of oval shape and be located in this area – which is referred to as being located centrally to the toe of the gear tooth. While this may seem simple, it is a rather complicated subject – although one that Arrow Gear is very knowledgeable in.