Scots Guardsman

Just been watching some videos of Scots Guardsman on Youtube, and I wondered if the exhaust sound is different to other Royal Scots back in the day? Every revolution of the driving wheels, there's a deep sound which I can't identify... Is it a sharper exhaust beat, or is it big end knock? It almost sounds like "Gresley knock", apart from the distinctly different Stanier 3-cylinder music.

It's very evident in this excellent footage:


Richard.

 

Driver's side cylinder drain valve leaking steam perhaps.
It seems a little more off-beat in reverse but not unduly so.

 

Do you mean what could be a sort of squeak from 3:30 onwards?

 

There's a drain cock leak briefly on the departure from Llandudno Junction, but it soon stops. The exhaust beat itself seems very regular to me. But there is a very odd sound throughout the last (long) clip, most noticeable about 3½ minutes into the video. It sounds almost like a brief blip of the hooter once per revolution, though I hardly think it could be that.

 

The noise is very apparent from 3:30 onwards, but to me it sounds like either a louder exhaust beat, or some kind of knock, rather than a squeak. Definitely not the same sound as the leaking drain cock though.

Richard.

 

The (former East) German Pacific 18 201/02 0201 I recall as having a different sound in the exhaust twice per revolution of the wheels. I put this down to a resonance in the exhaust system.

 

I have always referred to it as a knock, it was more evident during its first ticket, 2009 onwards, it is the first time I have heard it during her return to service, it almost sounds like a klonk when a con rod has become easy on the crank pin..

 

That's just reminded me that it was making that sound when I saw it last year. I think it was when it was climbing at Shap Wells on 8th August 2020. As you say, it sounded like blips on the hooter at the time. I'd almost forgotten it. I've seen 46115 a few times since then but not heard that sound again until this clip.

 

A bit like a WD at speed?

 

Exactly..but only on one engine, but which one ?

 

A thought has just occurred to me... If the chimney has been lowered to fit the modern LG, could this have affected the exhaust sound slightly?
I think it is knock, but it's odd that it only occurs once every complete revolution of the drivers... I would have thought it would be apparent at each end of its stroke, ie. twice per revolution...

Richard.

 

I agree ref. twice per rev, a few variables at play here though, ovality of crank pin, bearing bush wear etc.

 

As I understand the term, a "knock" is literally that, typically a big end knocking against the crank pin because of excessive clearance. The sound from SG seems to me nothing like that.

 

I've seen and heard Scots thousands of times but never heard one make that sound .

could it be summat to do with air brake compressor?

 

I don't think so, as it is on one 'beat' of exhaust every revolution of the driving wheels. I would possibly think that a valve (or the settings) need attention. Air brake pumps pump with their own timing, not matching the revolutions of the driving wheels.

 

Never heard a LMS 3 cyl sound like that...hope it's not a bearing.

Dave

 

46115 isn’t air brake fitted.

 

Not that then !

 

Is it definitely from the loco? Is it possible there is some sort of vibration in the video microphone which is caused by a certain frequency in the incoming sound?

 

That wouldn't explain me hearing the same sound last summer, thinking that something must have been bumping the hooter connections as it passed.