When all the data from the above threads was recorded, what was the status of the air compressor? When the air compressor loads, a very distinct chug is created..... The Air Compressor just happens to be at the same rotational velocity as the engine crankshaft....Most of my recordings are of trains that have been in run-8 for extended periods of time, and I've never been able to hear the air compressor over the engines (if it were running at all). I have heard the air compressor on a GP38-2 when idling. I find GE air compressors greatly overpower the engine itself in low throttle positions.
trainiac, here is something to play around with:Interesting! I tried the frequency analyser on it and it didn't give very clear results from the original recording...
http://free-os.t-com.hr/redmist/ler.mp3
This is idle recorded from a little wooden bridge about 2 meters above the exhaust.
It's a 12-645 turbocharged engine
but when I increased the speed 3.35 times (to bring it up to the equivalent of 900 rpm) it created the same peaks at the same frequencies as for the 16-cylinder engines, including one at 90 Hz (6 beats per rev). The only difference from the 16-cylinder is the amplitude of each frequency.
Here's the sped-up version of the recording
http://trainiax.net/freq.wav
--Michael Eby
--http://trainiax.net
--http://trainiax.net
