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Class 378 Noise

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TH172341

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Apologies if this has been covered before but just something I hadn't really realised till recently.

Noticed upon initial acceleration (not always) and certainly when applying the brakes you can hear a clunking noise on the 378s (they've always done it seemingly - even in a video from 2010), after driving my new 378 addon with soundpack, and then watching some videos online of the 378s. I haven't ridden a 378 for a couple of years (that will change this weekend!) so never really picked up upon it.

Can anyone shed any light on this - I'm guessing it's to do with the motors/brakes?

Thanks!
 
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Bigfoot

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My guess is door locks engaging/releasing above their set speed around 3/5mph
 

James Wake

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You get that door locking sound as well on the class 350/444/450 Desiros, I'm sure the door locking is what the noise is, travelling on the 378s quite often.
 

TH172341

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Could be that - it's also kind of a creaking noise if that helps? Motors perhaps?
--- old post above --- --- new post below ---
Rode two 378s the other day - both excellent - sat in the DMSOs of both. Noticed on one the creak/clunk sound when brakes first applied and at low speed stopping. However on the other one there was nothing from what I could detect. Perhaps wearing down of a component?
 

MrPIC

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Could be the brakes? I don't know specifically about 378, but on 379's, when you first apply the brakes, a small amount of pressure is applied to the discs and then released as the regen brake takes hold, and then again under about 10mph the regen drops off and the discs take over the last bit.
 

TH172341

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Thanks - That sounds quite logical - would fit in with when the noise occurs and that it doesn't always happen (i.e perhaps starts to happen when the discs wear down).

Not my video (hope I am allowed to link to it - unsure of the rules) but you can hear the sound around 0:40 and 3:11 when the train is departing also also particularly 2:15 when coming below what would seem 10mph as you say. Would fit in with the idea of the disc brakes being released and applied.

https://www.youtube.com/watch?v=zX4EMxKdN9I
 

Skoodle

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Yes it would be the friction brakes. 378s have had a modification that keeps the parking brakes on until Door Interlock has been achieved. If you take power straight after gaining interlock, you're still fighting against 3 bar of brake pressure as it releases. As mentioned above when stopping, above 10mph the rheostatic brakes are used, with a tiny bit of friction, at 10mph it is blended in to friction only which is what you are noticing.
 

TH172341

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Excellent - that would make sense.

And then when the friction brakes start to wear a bit then they start to make a creak sound.

Thanks for the responses :)
 

MrPIC

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I think the creak sound is the brakes applying, regardless of wear and tear
 

notadriver

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Yes it would be the friction brakes. 378s have had a modification that keeps the parking brakes on until Door Interlock has been achieved. If you take power straight after gaining interlock, you're still fighting against 3 bar of brake pressure as it releases. As mentioned above when stopping, above 10mph the rheostatic brakes are used, with a tiny bit of friction, at 10mph it is blended in to friction only which is what you are noticing.

Interesting - is that because drivers have been rolling back ? Makes the trains even slower to get going though :(
 

TH172341

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Ahh right - strange why I couldn't here it on 378202 - in both I sat in the end cars, although in 201 it was the 001 DMSO (A) end and in 202, the DMSO (B) 102 end. Could be due to the air con or some are louder than others?

Are the disc brakes fitted to every bogie?
 

MrPIC

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Its the hill start feature used to prevent a train rolling back, at my TOC its what they like us to do every time we move away from a stand. Its because unlike older stock that has separate brake and power controllers so you can apply power while still having a holding brake, modern trains have it all combined in one controller so you physically can't apply brakes and power at the same time- unless you use the hillstart.
 

Skoodle

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Just as an aside, the Hill Start is different from what I mentioned above, we still have it, but it wasn't what I was referring to. If any door is open, the parking brakes are on (3.5 bar roughly).

Having another listen to the video, I don't think it is to do with the brakes, but is to do with the motion of the train as at some points you can hear the "creaking" whilst it is coasting, I'm guessing the primary suspension springs or air suspension bags maybe?
 
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