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Duchess Over Shap


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Morning all. Not sure if this of interest, but I was on the Cumbrian Mountain Express yesterday and just for the sake of experiment switched on the Sports Tracker app on my phone. I usually just use this for cycling, but I thought this was worth a punt.

 

So according to this far from scientific analysis, Duchess of Sutherland didn't drop below 50 mph on the climb, and touched 86 mph on the way down... (is this speed allowed???). This was with 10 coaches and a class 47 in tow.

 

Apologies for the quality of the pic, but it's the best I could cobble together with my limited techie skills.

post-993-0-94208700-1343553839_thumb.jpg

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Normally we'd remove something which could point to a breach of rules pending consideration but I think it's probably fairest to say that it isn't a recognised method of producing a record of time/distance and seems to raise inconsistencies (max speed in summary bar at top but the graph doesn't show anything appreciably above 75mph.), maybe it's accurate for the overall time distance but anything in between seems potentially a problem. The problem being that if something is put forward someone takes it as fact and those 'facts' could lead to someone's future being jeopardised if they were accurate.

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Normally we'd remove something which could point to a breach of rules pending consideration but I think it's probably fairest to say that it isn't a recognised method of producing a record of time/distance and seems to raise inconsistencies (max speed in summary bar at top but the graph doesn't show anything appreciably above 75mph.), maybe it's accurate for the overall time distance but anything in between seems potentially a problem. The problem being that if something is put forward someone takes it as fact and those 'facts' could lead to someone's future being jeopardised if they were accurate.

 

Quite agree Andy, looking at the graph of speed it seems to go up and down rapidly. Rapid accelleration and decelleration is not a feature of loaded steam trains. I'd say as an experiment in whether this technology is reliable for this application, the conclusion is no. Like you I hope that this does not cause questions to be asked about the crew.

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i sometimes use motionX gps to track my journeys, as pointed out these are a bit hit and miss at times.

 

i think the problem is when the gps is lost then restarts the device straightens the route between the 2 points, so if the line has been meandering for 2 miles between these points but as the crow flies its only 3/4 of a mile it will give an artificial reading

 

the screen grab below is a prime example

 

a244ca2d.jpg

 

trust me a 168 physically do that top speed, the ATP would warn me then stop me if i didn't react to it once the nuit reaches 103mph also there are 2 miles missing from the total mileage (moor st to marylebone)

 

still good fun though!!

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Yep there is a lot that does not add up - max speed in status bar says 91.8 mph, OP says 86 mph, orange line on graph just about touches 80mph grid line. OP says minimum of 50mph on the way up, but graph clearly dips below the 50mph grid line near the summit. Given all that inaccuracy, it is quite likely that the speed never exceeded the allowed 75mph on the way down.

 

However, graphs of that type do seem a bit spikey as the time interval along the bottom is quite compressed. Having driven a very underpowered van with the old fashioned card tachograph, I was quite suprised at how spikey the trace was even on the motorway with virtually nil acceleration.

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Wrong on both counts! It was the breach of the rules by the driver by driving too fast which was the concern, as publication could cause trouble for him. And the discussion seems pretty light hearted to me so far, especially big jims post.

 

Just shows how different people can interpret things! :)

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I'm afraid that many of the GPS tracking apps for phones and tablets are really not very good. Mostly, they've been written by people with a very limited understanding of the way GPS works and its possible error sources and make little or no attempt to deal with these issues. Single instantanious measurements are simply not reliable, so measurements need to be smoothed in some way or 'rogue' measurements need to be isolated and ignored.

 

Clearly, the two apps shown above display instantaneous measurements which can be wildly innacurate. The 91.8mph and Jim's 114.6 are most likely just single, highly innacurate, readings typical of those that occur quite frequently. Similarly, the orange trace in the OP is very spikey, as has already been noted. This is a perfectly normal outcome of just plotting the raw readings without any smoothing. To anyone who is used to examining long-term GPS readings there is no evidence there of a speed above about 75mph, if that. Indeed, it should also be fairly clear that a Duchess with a reasonable load is quite incapable of producing the acceleration and deceleration implied by those spikes.

 

The problem is compounded by several other factors. The inside of a largely metal box is not the best working environment for any GPS receiver, so 'rogue' readings are very common. The receiver chip in most phones/tablets is good for a navigational quality receiver but they are, of necessity, linked to a very poor antenna, one that must fit within the confines of the device case. Consequently, they struggle to achieve a reasonable signal in competition with the other electrical and radio components of the device.

 

As Jim said, it's all good fun, but just don't expect accuracy and ignore all those little spikes.

 

Nick

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Blimey, sorry I bothered now. Didn't realise I was I breach of rules and thought it might generate a bit of light-hearted discussion.

 

Won't do it again.

 

Problem was you seemed to be presenting the data as accurate when the measuring system is anything but.

 

Better off using a stopwatch and 1/4 mile posts, IMHO. Probably get a more accurate reading!

Used to do this between Coventry & Birmingham in the late 60s/Early 70s with the electric loco hauled services. (the journey was boring when you do it every day - need a distraction!)

Surprising how consistent the speed was between different journeys. Line speed was 100mph and it was rare to go much over it.

 

Keith

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Problem was you seemed to be presenting the data as accurate when the measuring system is anything but.

 

Better off using a stopwatch and 1/4 mile posts, IMHO. Probably get a more accurate reading!

Used to do this between Coventry & Birmingham in the late 60s/Early 70s with the electric loco hauled services. (the journey was boring when you do it every day - need a distraction!)

Surprising how consistent the speed was between different journeys. Line speed was 100mph and it was rare to go much over it.

 

Keith

 

Maybe the City of Truro had one of these!

 

:devil:

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The one I used clocked me at 29.8 mph going up a quite a steep hill.

 

Nothing strange with that until I say that I was walking and had blisters on one foot.

 

I now only use these things as a rough guide!!

 

Alistair

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Oddly, on another private 'forum' this was used as the basis of a lighthearted discussion on the relative merits with the same train load over shap of Duchesses, A4's, the Duke, Castles, 08 Shunters, Austin Maxi's, Honda 50 stepthrough's, Battle Space Turbo Cars etc. The limitations of the measuring technology were understood but not part of it. Incidentally we reckoned about a day for the Maxi, but with the limited braking power associated with drum brakes, a much quicker time on the way down. Which makes one wonder how fast a runaway would be going down Shap? Ignoring trap points etc...

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The one I used clocked me at 29.8 mph going up a quite a steep hill.

 

Nothing strange with that until I say that I was walking and had blisters on one foot.

 

I now only use these things as a rough guide!!

 

Alistair

 

I seem to recall seeing on "That's Life!" many years back when the police started using "speed gun" type devices and several people had complained about being caught when they weren't, they featured one clip showing Buckingham Palace as doing 8mph.

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as an aside to the original post and being as a few people have liked my previous post here is a track i recorded the other morning on the "silver train" from moor st to london as a comparison to the speeds shown on the previous screen grab which was also on the same run

 

7f21dcc4.jpg

 

as you can see the distance is the same, however the max speed is ever so slightly less and the average speed is different but there is a time difference of just under 3 minutes!!

 

however i thought you may find the next few screen grabs interesting, they show the speeds and gradients on the line between moor st and marylebone which i will break down for you

 

each blue bar is a 1 minute mark

 

a3aea9c1.jpg

00:00 - start of the journey, plat 3, moor st

00:03 - accellerating towards tyseley, dropping slightly

00:04 - 20 mph TSR tyseley north jn

00:08 - 85mph between olton and solihull

00:10 - 2 min station stop at solihull

00:11 - accellerating towards dorridge

00:13 - passing dorridge

00:14 - 100mph just past dorridge, gently dropping towards hatton

00:18 - 85mph line speed through hatton and the start of hatton bank

00:19 - 90 just beyond hatton (normally i leave it coast down here but i needed to make up a min or so)

00:20 - station stop at warwick parkway for just over a minute

00:23 - accellerating towards leamington spa (70mph max for lhcs)

00:26 - 40mph through leamington spa centre road

 

70fce18b.jpg

00:27 - accellerating away from leamington spa, as you can see its quite a climb towards banbury, not severe but enough to take it out of the train, takes almost 4 mins to get to the 95mph linespeed just before bishops itchington

00:33 - 75 at bishops itchington

00:34 - end of 75 and accellerating towards banbury, climbing again

00:36 - 90mph linespeed towards banbury

00:37 - dropping from "big tots" crossing towards banbury (and its not tots btw!)

00:40 - 75mph through banbury

00:42 - 90mph dropping towards aynho 

00:43 - aynho jn, climbing towards ardley tunnel

now this is where the speed anomolies start to appear

00:46 - ardley tunnel, gps signal lost for a few miles in the tunnel and cutting that follows

 

c8dd10d9.jpg

00:46 - ardley tunnel

00:47 - out of the tunnel the signal returns

00:48 - signal is lost again near where the m40 passes over the line

00:49 - and comes back in with a false reading of about 105mph at 00:50

00:50 - 100mph through bicester north

00:52 - blackthorn bridge

00:55 -  brill tunnel another area where the gps is lost which gave the false reading of 114mph as can be seen by the spike in the speeds

00:57 - ashndon jn, climbing towards haddenham

01:00 the one hour mark at ilmer between haddenham and risborough, i have a marker point here and  at this point i was 1:42 seconds up on the time i know i need to pass it to be on time

01:01 - 90 down to 85 through the centre road at risborough, you can see the climb up saunderton bank starting, again it takes a while to get to line speed up here

01:03 - saunderton station

01:04 - 100 mph dropping towards west wycombe

01:06 - 85 through west wycombe

01:07 - 60 through high wycombe

01:08 - accellerating and climbing away from wycombe

01:10 - another false reading passing through whitehouse tunnel

 

b33fc6c2.jpg

01:13 upto line speed just after beaconsfield, 

01:15 dropping from just before gerrards cross, slight blip at 01:16 through gerrards cross tunnel

01:20 dropping through wembley station

01:21 85mph at wembley depot

01:22 70 across neasden jn

01:23 began to catch the 172 in front of me around here so despite the line speed being 50 i kept the speed to 35 

01:27 into the tunnels and the gps signal is lost again for 2 mins 

01:30 gps signal returns just as i enter the station and come to a stop 

 

hope thats of some interest to you all

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