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Weird Gillig sound


gilligfanboi

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I live in Orlando, home of Lynx, and have been wondering for quite a while about a certain sound some of our Gilligs make. I have only specifically noticed it from our 2013-2014 35-foot hybrids, which I think are BAE. Others may do it too.

You know the normal brief hissing sound of excess air being let out of the system? They do that. But they also make a sound of similar duration that, while similar to the hiss, has more of a tone to it for lack of a better word. It's sort of a high pitched noise that goes up in pitch as it progresses. It happens every so often, with no rhyme or reason. Kind of like the normal air hiss sound. I wish I had a recorded example.

Does anyone have any clue what I'm talking about?

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On 3/2/2017 at 8:53 PM, gilligfanboi said:

Does anyone have any clue what I'm talking about?

I know the sound your talking about since I hear it on many Gillig Low Floor Advantages. I have heard it on Allison-powered hybrids, as well as standard diesels. I assume it is the air brakes, though I don't know exactly why its just Gilligs that do it.

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On 3/6/2017 at 9:55 AM, WMATAC40LF said:

I know the sound your talking about since I hear it on many Gillig Low Floor Advantages. I have heard it on Allison-powered hybrids, as well as standard diesels. I assume it is the air brakes, though I don't know exactly why its just Gilligs that do it.

It's definitely not tied directly to braking. The sound is much more rare than every time the buses slow down. And it is definitely a sound distinctly and noticeably from the hiss of the release of air from the air system. I'm still struggling to describe it.

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2 hours ago, gilligfanboi said:

It's definitely not tied directly to braking. The sound is much more rare than every time the buses slow down. And it is definitely a sound distinctly and noticeably from the hiss of the release of air from the air system. I'm still struggling to describe it.

I hear it when the brakes are released and the bus drives off, not when they slow down. Is this the brakes being released? Could it be that this only happens after its been stopped for a while? 

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7 hours ago, WMATAC40LF said:

I hear it when the brakes are released and the bus drives off, not when they slow down. Is this the brakes being released? Could it be that this only happens after its been stopped for a while? 

No. It just happens randomly as the bus drives typically. Never seem to hear it when the bus slows, accelerates from a stop or idles. But it may happen during those times, too, and I just haven't noticed.

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  • 1 month later...
 

I live in Orlando, home of Lynx, and have been wondering for quite a while about a certain sound some of our Gilligs make. I have only specifically noticed it from our 2013-2014 35-foot hybrids, which I think are BAE. Others may do it too.

You know the normal brief hissing sound of excess air being let out of the system? They do that. But they also make a sound of similar duration that, while similar to the hiss, has more of a tone to it for lack of a better word. It's sort of a high pitched noise that goes up in pitch as it progresses. It happens every so often, with no rhyme or reason. Kind of like the normal air hiss sound. I wish I had a recorded example.

Does anyone have any clue what I'm talking about?

SamTrans' 2013 Gillig BRT Hybrids do this. It's just the way the air compressor cut off valve is set up (physically). To me it sounds like a fart or a sneeze. :P 

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15 hours ago, Detroit Diesel 6V92TA said:

SamTrans' 2013 Gillig BRT Hybrids do this. It's just the way the air compressor cut off valve is set up (physically). To me it sounds like a fart or a sneeze. :P 

That's not a bad description! Do those make the standard hiss sometimes as well? I feel like I hear ours do both.

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