4464 Bittern to do 90mph on ECML - 29 June & 27 July 2013

Sorry, But I shot it at 25 fps. As you well know that plays havoc with a WW2 Mk3 H2S. And you did not account for the hidden message in "Autobahn"

 

You forgot the Flux Capacitor Air Pressure

 

Try this for an(other) alternative approach. A couple of well-spaced reference/ timing points are the signal gantry to the west of the station (just east of the Bath Road underbridge), and the station footbridge itself. Magnification of the Google Map aerial view of this section gives an intervening distance of 1650 feet, give or take, using the 200 foot scale provided.

My average of three attempts to time the point at which Bittern's exhaust strikes the underside of each structure gives me an average value of 11.9 seconds for the point-to-point time between the two.

This suggests that the 90 mph claimed in the video title is indeed correct. Or is this just too simplistic/ inaccurate??

Any views?

 

OK, my more serious take: any of the methods outlined will need to take into account the uncertainty in both distance and time. If you underestimate the distance and overestimate the time, you'll tend to get an answer for speed that is a bit low. If you overestimate the distance and underestimate the time, you'll tend to get an answer that is a bit high.

For the estimates based on train length, that should be pretty well known - a Mark 1 is a known length etc, so a train of loco+7 coaches passing a fixed point is a known length to probably less than 0.5%. However, that gives a very short time, and if you are hand-timing, I'd doubt you could get a repeatable accuracy of less than about 0.2s in, say, 4s. That gives an error of 5%. Adding the errors gives about 5-6% error, so you probably can't get within about 4-5mph using that method.

For the estimate based on distance between bridges, the greater time inherently reduces the timing error: say 0.2s again, but in 12 seconds, not 4, so a timing error of around 1.5%. However, scaling from Google will give a correspondingly greater error on distance (it would be easy to be out by about 50 feet just measuring from a computer screen, which is 3%). Again the error is of the order of 4-5%, or about 3.5-4.5mph.

So, my best guess is basically "fast +/- 3-5mph", where "fast" is whatever value you choose to put in

In other words, on the basis of that video evidence alone, I don't think you can claim 90mph; simply that it is very fast and probably around 90mph +/- 3-5mph.

Tom

 

The rest of us can't do this using YouTube, but if MrKnowWun goes back to his original footage on the timeline of his video editor, he can calculate the number of frames for the train to pass a fixed point, or to travel between two fixed points, and so get a measure of time accurate to 1 or 2 25ths of a second.

 

That would give a timing error of 4/25s. (It's four frames, not two, because the point when you start timing could be up to one frame in advance or one frame in the rear of the "true" moment when the train passes the reference point; and likewise there is a two frame error on the moment when the train passes the end point. The errors are cumulative, so a four frame error.

Given that, you really need two points that are as far apart as possible, to make the elapsed time as long as possible and therefore the 4/25s as small a percentage as possible. Based on the train length with a passing time of 4s (or 100 frames), four frames error still means 4%. Based on the bridges with a passing time of 12 seconds (or 300 frames), the error is reduced to 1.3%.

So even without allowing for any uncertainty in distance (presumably the distance between bridges is a known quantity to a high accuracy; just not by scaling from Google) you still aren't going to get down to less than about 1.5% error by studying YouTube footage, or very roughly the same figure in mph.

It's probably a bit of a triviality in this case. But if ever permission were given for 100mph running rather than 90mph, you can guarantee that the internet would go into meltdown with discussion!

Tom

 

Nnnoooooooooooooooooooooooooooooooo................... LOL

Some of these debates can go on a bit.

I was sitting in a German Plandampf steam hauled train less than ten years ago and was talking about the 1967 run with 34102, Lapford when we reached the, at the time, a hotly debated 100 mph near Fleet.

I said I thought it was at least 99 mph, but wasn't sure it was 100. From the back of the coach an aggrieved shout in English came back, "No, it was definitely 100 mph".

That was around 40 years after the event!

Subsequent to that I have examined my Brothers detailed log of the run, he took more notes than most back in those days, and from the 1/4 mile stop watch times and also from the individual mileposts times he took we did reach 100 mph.

So take care, this debate may have a loooooooooooooooooooooooooooooooooooong way to run!

 

Thanks for getting up at silly o' clock to film that, made a tingle run down mine spine! I think you must have been just about the only person lineside this morning....................................

Nice to see an A4 doing what she was designed to do - Fly!...................................................................................

Roll on July 7th.

 

As we all know Kraftwerk's "Autobahn" was recorded at an ambient temperature of 27C. Todays temperature at 05.55 at Taplow was of the order of 11.5C.

Did you take that into account Tom, it has a significant impact on the repetitive bass beats?

Furthermore the railings at Taplow, being on the GWR, are set up for 4 cylinder steam locomotives. Albeit sloppily as you point out. This will have a direct influence on your estimate when passed by a three cylinder steam locomotive.

 

Yes, I am really surprised that a: I was the only person at that location, and b: more videos have not appeared on the tube. (there is one other at time of writing)

 

Here is the other video:

She is really flying in the second clip.

 

I suppose there is no chance of someone being able to physically measure the distance is there?
Possibly using something like a Rangefinder between structures before the next run.
The problem then will be determining the exact moment of passing the structure.

 

I hear Southall Locomotive services have also been working on some coloured fuel logs to throw in the fire to boost the speed...................
The high speed runs are actually being used to get Jeremy Hosking's special DeLorean up to 88 MPH as he is going back in time to see the record set by Mallard.............

 

He can muck about with time as much as he likes, Palace will still be going back down again after 1 season in the premier weauge.

 

All this talk of Flux Capacitors et al, yet nobody's mentioned go faster stripes.................................................................. until now.................................... not that she needs them, heck she was quick!

 

Thanks for posting those clips...simply awesome!

 

Couple of lovely sequences there.

As to the speed. Well, leaving aside all the rather silly comments above, I can bring all my 53 year years of steam loco timing to then fore. I have made a very detailed assessment of all the facts. Run it all though a spreadsheet. Had it peer reviewed. Conducted a séance with C J Allen and O S Nock.

And can state, that in the second shot, 60009 is going like sh.t off a shovel.

 

Don't start me off on that one again!

To me, this year is for enjoying the chance of a steam loco in the UK being allowed off the leash. Slightly!

I won't be there. Will regret it later I am sure. But my work on my Owl book has to take preference over just about everything else at present and possibly for the next few years.

All I want to hear now is that the test went fine. That no significant problems emerged and that all is set for the public runs at 90mph.

And for the avoidance of all doubt, that is what I would like to hear, NOT what I have already heard, because I haven't.

 

Certainly agree there Brian although I think you mean 60019!

Must have been something to have been on the footplate this morning flying along like that, WOW!