Flying Scotsman

That's because it's filmed in slow motion, SLOPRO is a slow motion app.

Dave B

 

Thank God for that! Frightened me to death ! Fell for it hook line and sinker, what a T*T !!!

 

I thought the same when I first watched the clip, then I googled SLOPRO and realised why it sounded wrong.

Dave B

 

I thought there seemed something off about the video.

She sounds great in the other videos I've seen.

 

I think the poster of the clip was referring to the apparent loud beat among the rest of the beats.

 

At 40 mph, FS will produce an exhaust beat every 60 milliseconds. Against that background I think your hearing would detect an error of 10 millisec.

 

Here's a screenshot of the sound wave from the Shap Wells Langho video on the previous page:



This is from 47.28 seconds to 51.07 seconds. Looks pretty even but one beat of each six-beat group is definitely accented, & it looks like the fourth beat is accented too, but to a lesser degree.

So further to andalfi1's query, what causes this accentuation?

Pete S.

 

Interesting analysis! Nice to see facts!
I also found it interesting that in photos and videos, with the matt finish on the paintwork, it seems to be possible to see the water level in the tender!

 

Congratulations! Some measurements entering the discussion. Since it looks like every sixth beat it is only one side of
one of the valve/piston combinations. Imho it is the consequence of cold valve setting while we see/hear a hot engine.
If I take a second look at 00:48:25 that third beat is slightly smaller, so it looks like a difference between front and back.
Kind regards
Jos Koopmans

 

That's caused by condensation on the tank. I've seen it many times during winter in the shed at Didcot - almost a frosted appearance from the bottom of the tank & clear above the waterline.

P.

 

Most locomotives in the UK, but not all, do not have tail rods on the pistons. This means the volume of the cylinder is different on each side of the piston. Thus, even if the valve settings are perfect, there is a fundamental difference in the amount of steam admitted and thus exhausted on the forward and reverse strokes. Any locomotive without tail rods will thus have one strong beat and on slightly weaker one for each cylinder. There are lots of other things that come into play, as well. Steam chest pressure is not necessarily constant, especially if you are running on a throttled regulator. A two cylinder loco will always produce four beats per revolution thus: strong, strong, light, light. Add to this the fact that the exhaust passages are never totally empty of steam at anything like speed and the exhausting steam from one cylinder will have some slight interaction with that from the other cylinder. There is a well known phenomenon with Garratt locos where the exhausts from the two engines become syncopated at speed so, although there are four cylinders rotating independently, you only get four exhaust beats.
There's been a quite interesting diuscussion going on whilst I've been away . Hopefully, the above will be a positive contribution to it.

 

Deleted

 

For me, this video below which I have just found on YT sums up what all the work and effort from Ian Riley and the NRM has been for. There are not many trains or locomotives that can raise cheers from the adoring crowd like those in the video:

 

Think the word SLO on the clip may have been a bit of a clue.

 

Thanks to all at Trackside in crappy weather for the shots. Even if one of the cameras did slow up in protest

 

No idea, I have had a similar comment aimed at me by a photographer when I was talking to a footplate crew at a gala a couple of years back. Was met with a similarly terse response
.
Manners cost nothing and all that.....

Chris

 

Some locomotives are designed with valve gear that allows for a slightly longer cut-off on the rod side of the piston in order to try to account for the loss in piston area and cylinder volume. Another little something to dial into the equation.

Scotsman's exhaust beats are well spaced, this impressed me while the engine was on the ELR. The cause of the strong sixth beat is what I am wondering about. We have no idea how well the locomotive performs, that is to say we have no numbers to confirm impressions. Ian describes the locomotive as being brilliant on Thursday's test. It sounds rather distinctive and if no unevenness of effort is causing concern then the phenomenon remains interesting. The calculated allowances for cold setting taking into account thermal expansion have not always proved to give the best cylinder performance - Ian Gaylor found this out with the Bure Valley ZBs.

Maybe Sheff and his group will get the chance to indicate the machine one day but if it is performing well enough this is just a dream exercise.

 

I assume that was a typo, as the section shown starts at 00:47:28. Which beat did you mean?

Apropos the absence of tail rods: if the piston rod diameter is something like one tenth of the piston diameter, it reduces the effective area that side of the piston, and therefore the volume of steam, by something like 1%, which would certainly not be audible. Other factors are surely more significant.