What are the "Whoop" sounds engines make whenever they start up?

Trains Magazine General Discussion
1

In the first second or 2 in this video you can here the “whoop” sound: http://www.youtube.com/watch?v=89xJfGhvIdc&feature=related

It has always bothered me what sound this is, and I hope somebody can answer it for me.

Thank you.

2

It’s the air compressor kicking on.

3

air compresser motor turning on… it is a GE trademark sound so to speak…

csx engineer

4

Thanks.

5

I have wondered about that sound too. I had assumed it was some type of power operated clutch engaging a load because it is a momentary sound. How does the air compressor make that sound?

6

The compressor on an EMD locomotive is driven by the engine, so you never hear this sound in that case. On the GE, it’s powered by a motor and not the prime mover. Therefore, whenever the motor engages, ‘whoop’!

7

That whoop makes Amtrak’s P42s sound,as well as look like Shamu.

8

I always wondered what that sound was…I erroneously attributed it to the turbocharger. I hear it all time, thanks for the clarification… [:)]

9

I use to think that noise was something to do with the toilets on the Amtrak superliners, becase whenever I would flush one I would here that noise.

Im still wondering when you say that GE’s have seperate motors to drive the compressor do you mean a 2nd desiel engine or an electric motor? Do P42’s or GE’s in general just have one main prime mover in them? or do P42’s have a 2nd one for HEP? and another for the compressor?

Thanks

Joe

10

http://www.youtube.com/watch?v=UFe91kGMMbA

There’s a video I got of it near CN’s Neenah, WI yard. The ‘whoop’ can be heard around :26 or so. It’s kind of nice, IMO…but then I like newer GEs.

11

Electric motor.

12

I always thought the sound was from the huge GE cooling fan turning on after being off for a while…guess not.

13

the air compresser has its own electric motor that is hooked up to it… not a desiel engin… EMD power has its air compresser hooked up to a shaft off the prime mover that is always turning as long as the engin is running… and then uses a magnet vavle to “load” or “unload” the compresser as needed to maintain PSI in the main air resovars… since the compresser is always turning and the pistons are always moving in this type of setup they use the magnet valve to close a port on the compresser cylinders to allow the compressed air to be pumped into the air system… when the PSI is reached to where it isnt needed to pump air…the air that is in the cylinders isnt compressed and just vented back to atmohsphere… now with the electic motor drivin air compresser…it only comes on and compresses air when needed and isnt moving when not in use…saves ware and tear on the actul compresser and isnt takeing HP power away from the prime mover to turn the compresser shaft so more HP from the engin can be used to turn the main genorator and secondary altentar which makes power for the traction motors and all secondary electrical systems respectivly…

csx engineer

14

you will also notice in the clips posted that you will hear a high speed thump thump sound after the “woop”…that is the air compresser pumping…

csx engineer

15

The whoop is the compressor clutch engaging…it is a centrifugal clutch on a flywheel that engages the compressor a few seconds after it spins up.

The thumping sound that follows is the actual compressor.

16

And here I always thought it was the Amtrak car attendants having a party. Silly me.

Dave Nelson