# Vibration explaination

Hello everyone, Most pf the GM FSM’s have a section on vibration diagnosis they classify vibration several different ways one of which is calling them 1st order, 2nd order, 3rd order and so forth. Try as I may I just can’t grasp the concept. Do any of the more talented in the physics department feel they can add anything.

It must have something to do with frequencys having cooresponding frequencys. This is just a concept that I would like to have a better grasp on. GM certainly devotes a lot of pages on proper vibration diagnosis methods,there must be something going on I should be aware of

I found this nice site on the basics of resonance. http://www.intuitor.com/resonance/index.php

Hope this helps.

Simple High School Physics,thanks

To get a grasp of 1st, 2nd, 3rd, order vibrations, see if you can borrow a guitar, a banjo will do also if no guitars are available.

Pluck a string, the “A” string for example, you will hear a tone that is the string vibrating at 110 HZ, that’s the first order vibration. Now lightly touch the string right above the 12th fret, the half way point of the string and pluck it. The first order vibration will be damped out but the 2nd order won’t be and you hear a 220 Hz vibration which is “A” one octave higer than the open A. Now do the same thing touching the string at the 1/3 point, right above the 7th fret and you will hear the third order vibration of 330 Hz or a very slightly sharp “E” tone.

So a 1st order vibration could be considered the source and if you have a 3rd order vibration the way to fix it is not dealing with the 3rd but the 1st. Should you always look to determine what order vibration you are dealing with? This does seem the point.

The conditions for a 1st order vibration to exist are wider for 2nd,3rd,and so on. This makes sense in regards to how narrow the conditions become for the vibration to exist.

What made me start looking was the post about the YJ that had a vibration upon start but went away after moving,we were bouncing around ideas about u-joints and I was wondering if u-joints produce first order vibration,which should be present at all times,if I have this right.