Flying Scotsman

Interesting to see the sound traces. Checked back with the video and the trace starts just as the loco becomes really audible. I also noted that as it disappears past the camera, the accentuated beat seems to reduce greatly.

Odd.

 

Nope, doppler effect would alter the tone of the entire sound, not the comparative volume of the beats. Or maybe I misunderstand you.

 

It's been realised for a long, long time that two cylinder steam engines without tail rods have two strokes per revolution that are more powerful and this is noticeable in the exhaust, both visually and audibly.
With regards to my earlier comment regarding the exhaust of one cylinder interacting with that of the other at higher speeds, this is also something that has been known about, especially where passageways are restricted. Indicator diagrams can show slight increase in back pressure in the cylinder at the point where the opposite cylinder opens to exhaust.
It would be a very interesting exercise to indicate a steam loco today and even though I'd like to use my Dobbie Mcinnes for the job, using modern technology is a fairly easy thing to do and much more sensible.

 

Curiously I changed it to 47:25 but it should be 48:25, left of the first large peak.
Kind regards
Jos Koopmans

 

Well on its way to York now

 

As for the missing tail rod argument, I checked the drawings folder of Phillipson. Plate 1 shows the A3 with what appears to be a dished piston. Plate 12 shows the dished piston itself, "combined Pistonhead and Rod, LNER, Gresley, designed for the Type A3 Pacific".
Since a dished piston corrects volume effects of a rod I do not think that the different volumes of the cylinder halves produce a valid
argument for exhaust beats in this case.
Conflicting exhaust flows from different cylinders produce a peak in the bottom line of an indicator diagram which should be flat.
This can be countered by a flow divider as shown by Goss, erronously called Kordina by the Lempor People.
Kind regards
Jos Koopmans

 

No offence but some people seem to have a lot off time on their hands. A serious question, what the hell does it matter and who cares?

 

That's a bit harsh. There is clearly an interest among those who value such topics and want to either express or gather knowledge.

 

Can I ask a possibly very stupid question...!

When she was retired from BR service in 1964, 60103 had a standard set of cylinder drain pipes with two pipes only. Her current set up has three drain pipes. This appears to be the same as the A4 Pacifics.

Is there any specific advantage to this setup? And why has it (or was it previously?) been applied to Scotsman?

 

Apology to all... I misled you with the previous waveform - it was from the Langho clip, not Shap Wells.

Most likely caused by the camera's microphone overloading as it went past. This causes 'clipping' (aka distortion) which has the effect of compressing the waveform by cutting off the top of the loud bits. Also, it sounded a bit blowy at Shap Wells & that masks quite a lot of what's going on.

Here's some more waveforms...

1. Langho in its entirety:



A = the photter's er... 'request'
W = the whistle
D = the diesel as it passes.

2. Shap Wells complete:



It's clear where the camera mic overloaded.

3: Shap Wells before clipping sets in:



In this one it's hard to pick out the beats. Pretty certain that's down to the low-frequency rumble of the wind masking them. The Langho clip is much better in that respect.

P.

 

Oh gawd, do I gave to add frequency analsys to the clips I put up on here now?

 

I don't have much to add other than

1. Scotsman looks and sounds amazing..

2. Has anyone noticed that the stronger 6th beat is almost identical to the stronger 6th beat on all the preserved A4s, particularly 07 and 19. I suspect it's the noise correctly set up conjugated gear makes maybe ?

 

Oh yes. With the frequencies separated so we can hear the tick of the mechanical lubricator hehehe

 

Could try a wavelet analysis to fully understand the frequency and amplitude content in an idealised time scale!

 

Is the dished element not there to create a clearance volume to aid efficiency? On the other side this as you have said would be negated to some extent by the rod. However, some clever set up with the timing could balance these conflicting elements out to a degree. I do agree however, we are talking again about small numbers, that would produce near inaudible differences in beat volume.

I did notice this on No.7. I have been toying with the idea that its about either two exhaust events closest together, or furthest apart that might produce it.

A good progressive response there...

 

8.45pm 6/2/16. The crowded platforms at Carnforth station earlier in the day are now virtually empty and there are just a few well wishers out to see Scotsman passing through en-route to York for repaint. I spoke with someone who'd just got off the Holyhead train, hauled by 46100 earlier in the day, and they were saying what a good trip that had been as well. Echoing an already similar comment on this forum, 6/2/16 was a great day for mainline steam!

 

What *does* matter about mid 20thC technology lingering on in essentially pointless nostalgia? If the historical engineering challenges interest you then its perfectly reasonable to be interested in even very fine points of detail. If it doesn't interest you feel free to ignore it. Personally I find the detail of the engineering much more interesting than establishing which rivet a transfer should be aligned against or exactly what livery might or might not be "authentic".

 

If I remember rightly, the extra pair of pipes are the front and rear drains' of the inside cylinder. Originally they drained under the front end of the loco, which in turn over a period of time could lead to problem with the lubrication of the front bogie. Not forgetting condensation and corrotion. Granted you still have those possible probems, but with the 'pipes being on the outside of the loco there's more space for the steam to escape and disperse quicker.