MEASURING VIBRATION SOURCES (HARMONICS)
BrakeView's software is designed to be friendly, however that doesn't mean that it isn't powerful. With BrakeView's harmonic analysis, you can understand exactly what's going on when components cause vibrations in the vehicle.
Harmonic analysis turns this rotor...
...into this analysis:
BrakeView's harmonic analysis of an actual
brake rotor.
The upper graph shows a strong 2nd order runout
on both the inboard (blue) and outboard (yellow) sides of the
rotor.
The lower graph shows that there is a strong 1st and 3rd order
thickness variation.
WHAT IS HARMONIC ANALYSIS ANYWAY?
"Harmonic Analysis" sounds pretty impressive doesn't it? Don't let it scare you - it's a fancy mathematical way of describing things that move (or shake) back and forth. If a brake rotor was shaped like a saddle, it would press on the outboard brake pad twice per revolution. That's a 2nd order runout. (2nd order means 2x per revolution). If a perfect rotor was tilted, it would press on the outboard brake pad once per revolution. That would be a 1st order runout. (1st order means once per revolution.) With those sentences, we just did "harmonic analysis" using words!
BrakeView can look at your measured data and tell you "how many times" the bumps occur in each revolution along with how big the bumps are... now that's real harmonic analysis!
NOW FOR A LITTLE DEEPER LOOK...
This ugly shape in the center is made out of 4 different "pure shapes" that are added together.
The four shapes around the edges each represent a "harmonic". A harmonic is something that occurs a certain number of times per revolution. This center shape is made up of four different harmonics. In this example, the harmonics are 2nd order (lower left), 3rd order (upper left), 17th order (upper right) and 31st order (lower right).
BrakeView will take your measured shape and tell you exactly how much of each harmonic is present in the data. This is shown in a bar graph. The taller bars indicate that there is "more" of that particular harmonic. For our current example with 4 harmonics, the bar graph would look like this:
The 4 bars indicate that there is significant "amplitude" (or "height") at these frequencies. In the measurement world we use the term "undulations per revolution" (or "upr") to describe frequency. This is the same as saying "cycles" per revolution, but using big words like "undulations" allows you to impress your friends.