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AC4400 Cab noise/vibration ?

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BDA
  • Member since
    April 2018
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AC4400 Cab noise/vibration ?
Posted by BDA on Wednesday, November 9, 2022 4:55 AM

Hello all .

Can someone from the US tell me if as built or Dash 9 converted AC4400 C6M are noisy or vibration prone in the cab compared to the C44-9s .

I ask because some out here are said to be not the nicest thing to get around in compared to original C44-9 SD70 ACE etc . 

 

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Posted by SD70Dude on Thursday, November 10, 2022 3:32 AM

It would be hard to find something louder than a Dash-9 'rattlecab'.  They shake everything loose, including your mind.  

Our AC44 rebuilds are just starting to show up, but from what I've heard from CP guys theirs definitely didn't get any quieter after rebuilding.  

Greetings from Alberta

-an Articulate Malcontent

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  • From: Canterlot
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Posted by zugmann on Thursday, November 10, 2022 4:19 PM

SD70Dude
It would be hard to find something louder than a Dash-9 'rattlecab'.  They shake everything loose, including your mind.  

70M-2

60E & GP38 rebuilds.  Those were due to them using lots of metal & plastic panels around the cab and not enough sound deadening cushion-y insulation stuff.  And the 60Es had metal air ducts that made everything so much worse that they had to be reconfigured. 

Gevos used to do the death wobble when they shut down.  

 

  

The opinions expressed here represent my own and not those of

my employer, any other railroad, company, or person.

BDA
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    April 2018
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Posted by BDA on Tuesday, November 15, 2022 12:35 AM

I don't remember Dash 9 cabs being too bad , not like a 90MAC in earthquake mode .

I ask because some Dash 9 AC rebuilds here are something else compared to original Dash 9s .

Not sure why the AC conversion would make them worse than original DCs . I had wondered if the rebuilds would get isolated cabs but apparently not .

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Posted by M636C on Saturday, November 26, 2022 8:20 PM

BDA

I don't remember Dash 9 cabs being too bad , not like a 90MAC in earthquake mode .

I ask because some Dash 9 AC rebuilds here are something else compared to original Dash 9s .

Not sure why the AC conversion would make them worse than original DCs . I had wondered if the rebuilds would get isolated cabs but apparently not .

 

The AC44C6M units have three dynamic brake fan/grid units while CW44-9s have only two of the same capacity. This won't help cab noise while in dynamic brakes.

Having watched Virtual Railfan, can anyone explain the "purple haze" colour seen in these grids at night? Looking at home toasters, they appear to be red/orange. Is a different resistor material involved?

Peter

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Posted by Overmod on Sunday, November 27, 2022 5:45 PM

The color of dynamic-brake grids will NEVER be in the blue-to-violet range, regardless of the resistive material.  Higher than that and you might start checking for soft X-rays...

The grid emissions are thermal (and infrared) ranging up through red and orange, but they will get no hotter (if you don't want them to start to sag and burn out).  Since the 'color' is the sum of all longer emitted wavelengths, you go from orange to yellow to white without seeing the color as 'green'.  Then you get violet-white at dramatically high temperatures.

I'd expect the grid elements will be made of a material like the Nichrome in toasters, or Calrod elements, which has internal resistance characteristics that make it 'resist' along its full length, rather than being hotter at the point current enters the element.

My guess is that the color response of the Virtual Railfan camera is showing some effect like bloom, perhaps by having false color for infrared radiation as in some Night Shot-style "zero lux" CCD designs.

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Posted by foamductor on Sunday, November 27, 2022 7:50 PM

In my time at the horsey railroad I was involved in various union pushed efforts to investigate/reduce the noise on the AC44C6M units. 

The AC44C6M are signficantly louder in the cab than the Dash 9 units they were made from. Additionally AC44CWM rebuilds like the CP 8000 units are bad as well. Much louder than the AC44s they were rebuilt from. 

The answer I was able to eventually figure out was that the orignal Dash 9/AC44 had a signficant amount of insulation in the cab walls and floor to deaden the sound from the prime mover, which on FDL equipped units is mounted directly to the frame. 

When the Evolution series units came out, GE isolated the prime mover/alternator from the locomotive frame. This move cut down on cab noise signficantly. 

At first the cab design was left alone, these early ES44 units are exceptionally quiet. However when the cab design was changed in the late 2000s GE changed the insulation design of the cab. Removing much of the underfloor insulation.(when the nose door switched sides) I'm asuming that GE deemed it unnessicary because the prime mover isolation did a fairly good job of reducing noise levels. 

Fast forward to roughly 2015-2016 GE starts doing the C6M/CWM rebuilds. In this program the units get new cabs and electrical cabinets of the latest ES44 design. These cabs do not have the insulation and sound deadening of the cabs that they replaced, and as such are MUCH louder. 

The early units are the worst. NS 4000-4001 are exceptionally bad. As the problem was recognized there were some changes made to quiet them down but they are still louder than what they were as Dash 9s and AC44s. 

As I have been removed from the frieght side of things for a bit I don't remeber the actual numbers for just how loud the rebuilds were, but it was slightly worse than the non-isolated cab EMD SD70M-2/ACe

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Posted by M636C on Monday, November 28, 2022 6:11 AM

My guess is that the color response of the Virtual Railfan camera is showing some effect like bloom, perhaps by having false color for infrared radiation as in some Night Shot-style "zero lux" CCD designs.

I seem to recall that standard digital SLR cameras had filters to inhibit false colour IR response and that modified versions were available for astronomical photography that, among other things, lack that filter...

I'd agree that the "purple haze" is some form of anomaly in the camera. I think it is only seen in one particular camera when viewing at night.

Peter

 
 

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