Vibration Analyzer, iPhone

A low cost vibration analyzer iPhone application was recently released on the iTunes store that opens the door to some interesting uses.
Two versions have been released, Vibration Lite which is free and Vibration which sells for $4.99.
The free version is limited in features but will give you a good indication of the potential of the device.
First off, I am not connected in any way with the Vibration application, just a customer that sees some interesting uses for the low cost vibration analyzer.
Vibration analyzing has been widely used in industry for years in preventive maintenance programs and it has a solid record in the reduction of machine downtime. The devices used in industry are very expensive and companies that own them are not interested in letting them out to play on the weekends. It would be difficult to compare the expensive industrial model to the low cost iPhone application but it does offer some features that allow vibration data collection with minimal investment.

A few interesting uses in our RV aircraft.
The iPhone could be placed and aligned in the x, y, and z axis in a standard repeatable position on each model of the RV series and used to record the vibration patterns of the aircraft, these patterns could be compared to similar models. The data comparisons could be used to determine how our aircraft stacks up to others in smoothness and place seat of the pants numbers on the before and after of prop balancing.
Other uses would include establishing a vibration signature for your aircraft and comparing it on a regular basis, this could be used to identify rubbing or chafing areas such as lose exhaust parts and may provide a early warning on failing moving components.
Any thoughts on other uses?

Hmmm....Will it work with an Ipod Touch, too? My wife's son gave her one for Mother's Day & one of these days she won't be looking.

Prop balancing obviously comes to mind immediately.

Charlie

At present the device is not practical as a balancer for rotating members, I have contacted the developer and suggested the addition of an external trigger source. The external trigger could be light sensing and trigger off a reflective flag on the back of the prop spinner. The trigger would be plugged into the external phone / mike jack providing a reference of the imbalance. Without the reference it would be hit and miss to locate the proper position to apply the offset weight.

With a little development this could be a low cost prop balancing device.

Screenshot? Does it give a power spectrum/FFT kinda thing? In theory that data COULD be taken at different speeds or even on the ground to do fluter analysis, fatigue analysis, etc. But at that point, you'd be better off using real DAQ equipment, since you'll be spending so much on Finitie element modeling. We do the exact same types of analyses at work on helicopters, but it aint cheap. As was said above, it might be a nice check for whether your fuel tank or engine mount bolts have broken/cracked/come loose. I doubt if it'd be sensitive enough to see a loose exhaust....but who knows.

I suspect you'd saturate the accelerometer if you strapped an iPhone to like the engine mount to do any prop balancing. I know people have played with Wii remotes in race cars and the like, and those accelerometers saturate at like 3 G's.

EDIT: I found the app online, and there's a BIG but in the descreption:

"According to the documentation, the maximum sample rate for the accelerometer is 100Hz, limiting the maximum frequency to 50 Hz."

50 hz is the highest frequency vibration that the thing can theoretically find, realistically, it's under that, I'd bet. 50hz is the first vibration mode at 3k rpm, or the second at 1500 rpm. You could balance the prop for the first mode at useful rpms, but you'd potentially be missing out one some other important vibrations, and I bet the sensitivity stinks at that high a frequency, anyway.

Take a look at this. Upto +-40gs

http://www.freescale.com/files/sensors/doc/data_sheet/MMA3201D.pdf

Typical Applications
Vibration Monitoring and Recording
Impact Monitoring
Appliance Control
Mechanical Bearing Monitoring
Computer Hard Drive Protection
Computer Mouse and Joysticks
Virtual Reality Input Devices
Sports Diagnostic Devices and Systems

I can build one by using one of this chips with a microcontroller to send the data to a pc. It's very inexpensive. On the computer side. FFT on a thousand channels can be done simultaneously with a modern graphics card.

Not sure how usefull...

...but it is sure fun to play with! I am going to use mine in the airplane and see if I can find the sweet spot at various power settings for MP and RPM.
Fun stuff.

Interesting discussion on the use of the iPhone vibration analyzer application for propellor balancing.

http://dld-llc.com/xmb/viewthread.php?tid=4

vibration and noise

Since much of the vibration/noise in a piston single is under 100hz, would a noise logging/recording program/iPhone app do about the same thing, just perhaps not quite as well?