Video Gallery > Video Program Transcript

Program: The Installation of Bevel Gears

The Procedure for Checking Contact Pattern

To begin the process of checking the parts, apply a small amount of marking compound to a piece of cardboard.

Then spread out the compound on the piece of cardboard with the brush. This is done to achieve the proper consistency - not too thick and not too thin.

This would be an example of not enough marking compound. This is too much. And this would be the proper consistency.

Next, apply a uniform coating on the teeth. The coating should be just thick enough to cover the surface. There should not be any lumps or bare spots. Here we see an example of too much marking compound. Here we see not enough.

And here we see the desired amount.

Once the marking compound has been applied to the tooth surfaces, roll the parts together in both directions. 5 to 10 rotations in each direction should be enough.

And here we see the contact pattern that results.

You may want to document the contact pattern. The easiest method with Prussian Blue is to shoot a close-up photograph using a digital camera.

Another method of documenting the contact pattern is achieved by pulling a tape of the pattern.

While Prussian Blue is readily available – and suitable for a visual indication of the contact pattern, it does not always work well for pulling contact pattern tapes. If your chosen method for documenting the contact pattern is the pulling of contact pattern tapes, Arrow Gear recommends that you obtain gear marking compound.

Because of this, we will be using marking compound in the following example.

Pulling Contact Pattern Tapes

To pull a tape of the pattern, place the tape on the tooth surface.

Then smooth the tape with a cotton swab – being careful not to smear the marking compound.

Next, remove the tape, and place in on a piece of paper. You will need to do this for both the concave and convex sides of the gear tooth.

This illustration defines the concave and convex sides of the gear.