Correction to last post Integrated to dispalcement not velocity.

Now I remember... Andy is the "non-vibration" guy who is building a 'balancer'....

Andy, what kind of work do you do exactly? Where did you ever get the idea to build a balancing machine from scratch? As for phase, you do realize that phase lag is not some arbitrary or simply calculated value. It relates the actual location of the heavy spot to the peak amplitude location (high spot). The 'high spot' typically lags the 'heavy spot'. If you have "instrument lag" as well (only on analog instruments?) that is added to the physical lag. But on modern digital balancing equipment there is not instrument lag as there used to be with the old analog instruments, for instance the IRD 350 that I started with.

I actually have an IT background, netadmin, a little programming, throw in some electronics and some CNC machining. No formal training in anything. I also do a little XRF analysis and instrument repair. I'm actually a self taght madman, hell bent on building my own balancer, because I want to, and I can. Of course lag is not just a number I've pulled out of my head. by running a few sine waves from a signal generator, one can easily find the lag due to hardware. And yes, digital instruments can have lag too, depending on the type of DSP used, certain DSP algorithms are the number crunching equivilant to an RC combo. Then throw in some test weights at known phase angles, then one can find the lag that you speak of. When I say generic lag, its a number good enough for semi accurate balancing of any rotor, large or small, as the physical lag will obviously change with mass, diameter, and the properties of the material of the device under test.

I decided to build a balancer after building the third smallest turbojet in existence(at the time). With an idle speed of 60,000 rpm and a theoretical safe speed of around 200,000 rpm(I only ran it up to 130,000), balance was a little critical. Later after building a larger turbojet, I definately needed something to balance with. Why did I design and build turbojets??? I dunno, it sounded like fun(I was 26). It was far better than smoking weed and drinking like most friends and idiots that age were doing. Being the stubborn self taught lunatic that I am, I designed, fabricated, and machined everything including a centrifugal compressor and several turbine wheels. Same for the balancer, stubborness, and willing to learn led me in that direction, and I found the problem more intriguing than building jet engines. By that stubborness I now have my own accelerometer, my own hardware, and my own software, that I intend to produce and sell as a low cost alternative to what is out there. I, choose to challenge myself in a country where everyone wants to throw some cash or a debit card at every problem they stumble upon, or hire a consultant to make the bad go away. I create much of my own problems, BUT, the fundamental difference, is they are MY problems, the ones I want to solve. I go against the norm as much as I can, as ingenuity and creativity can't be found by doing what others want you to do, or by spending time doing what others think one should do wih their time.

So I don't know much about Vibration analysis, but it won't take long, hopefully with a little help from everyone here. I mean, I know this isn't some ground breaking research here, or something that is going to change the world of dynamic balancing. It's an alternative, a niche.

What do you do Rusty?

This message has been edited. Last edited by: Andy Paul,

A small factor to consider in selecting balancing unit would be the "familiarity" factor.

While you could generally balance in any unit (displacement, velocity, or acceleration), subject to some of the other considerations discussed above, I think more people use displacement for balancing and commonly refer to the lag angle between weight and displacment effect vector as indicator of where the machine is in relation to resonance based on simple SDOF model. (far below resonance we expect lag of 0; at resonance we expect lag of 90; and far above resonance expect a lag of 180). More importantly, some people use their knowledge of the machine type and where they expect it's running in relationship to resonance to determine best location for trial weight based on initial vibration phase measurements.

It is a trivial mathematical excercize to discover the same relationship in other units (for example lag between weight and velocity effect vector would be -90 far below resonance, 0 at resonance and 90 far above resonance). But most people don't talk or think in these terms.

Wow Andy... very impressive and very interesting. I hope you don't think I was "challenging" your place here, or your right to build whatever you want to. I was just curious.

I've been a mechanical engineer for 26 years now, a vibration guy for 20 years, and self-employed as a vibration consultant (for lack of a better word) for 12 years.

No, I didn't take it that way. Well maybe a little. I am a little thin skinned when people ask why. I tend to ask why not. I have had a few people in the industry tell me I'm wasting that time. Nah. Spending your day in a cubicle is wasting time!

I myself should have stayed in school, I would love to return to become an EE. The I would be dangerous! Im 32, so I do have some time.

Pete, I follow, peak velocity occurs 90 degrees apart from peak displacement and acceleration.

Im going to pick up a couple of vibration books.
It's clear I need to understand much more than imbalance to successfully balance.