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Class 66 locomotive sound


Pacific231G
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This is a very simple quiestion but can anyone explain the very distinctive ying ying ying sound that Class 66s (sheds) make especially when idling?

It's very clear in this clip.

https://www.youtube.com/watch?v=5LiRy_noywo

 

I've not heard any other diesel loco that makes this particular sound so Is it coming from some piece of auxiliary machinery or is it simply characteristic of the diesel engine employed? 

Edited by Pacific231G
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I believe it is the supercharger. I've never heard one in real life, but the GP60 sound chip I heard has a similar squeaking thing going on, which would make sense as the engines in eachv type are closely related.

Hi Zomboid

The explanation I found elsewhere is that, because it's a two stroke engine, the inlet air needs to be at a sufficiently positive pressure to purge the exhaust when both inlet and exhaust ports are open. At higher revs it's the turbo charger, driven by exhaust gases (AFAIK) that maintains that inlet pressure but at low revs it needs to be mechanically driven. It's that mechanical drive that makes the characteristic "ying, ying" sound at idle and low speeds.

 

I don't know how accurate that explanation is but it agrees with what I know about large two stroke diesels.

I did find this clip of a UP (ex Central Pacific) GP60 that had been parked with its engines running in winter for about five days.

https://www.youtube.com/watch?v=igW8QAlQgAg

 

According to Wiki "All 710 engines are two-stroke 45 degree V-engines. The 710, and the earlier 645 and 567, are the only two-stroke engines commonly used today in locomotives."

Edited by Pacific231G
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The supercharger is driven off the engine through a viscous coupling, which then disconnects it above a certain rpm as it then becomes an unnecessary load. By then the turbochargers are providing the charge air pressure driven off the exhaust gases.

The road going version was the Lancia Delta Integrale, same principle but a four stroke.

 

Dave

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