Why is the DLR so wobbly?
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- Опубліковано 9 тра 2024
- A tale of ups and downs.
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The notification came through for this whilst I was wobbling on the DLR, just coming out of bank
Good timing! ⏱️
Jago Knows...
The best section of the DLR feels like your taking off on a plane
😁
Lots of horrible shimmey on the Metro in Sydney a while ago, which translated to violent forwards and backwards shaking on the inwards facing pax, the only seats on these Indian imports running on Spanish track in places over the second iteration of a viaduct built by an Italian company (the first collapsed) and controlled by computers overseen by a Chinese company. Labor states build real trains in single deck format, and track is made 100 km south in Port Kembla, the the union hating right wing reactionaries calling themselves Liberals wanted to to destroy as many Aussie jobs as possible, with driverless and guardless imports. Thankfully for heavy rail Labor is back in in NSW,, and will build double deckers here again. Meanwhile despite Victoria building teams they went with Crack And Faulty for light rail, and they formed massive tears in the wheel wells, which were blamed on tight curves, however heavy freight rail was blamed for this. It took a while to transfer T2 / T3 rolling stock over as this is all (segregated) street running with no use of train track, as on L1.
You should have titled the video _Good Wheel Hunting_ .
Brilliant word play top notch!😊
D’oh! Yes I should.
@@JagoHazzardThat's quite a climb in the footage at the end.
Was it worth a mention that light rail is inclined to wobble on an incline?
Probably not.
@@VictorianDad what is worse , going up, or coming down ?
*groan*
Hunting Oscillation (or lack thereof) is what causes heavy rail trains to derail at low speeds. The slight taper on the wheels is designed to keep the train stable at high speeds, but at low speeds, especially where there might be “side wear” on the track (that is the inner edge of the head of the rail is no longer vertical and has started to wear off at an angle, most common on points or curves) the wheel taper will begin to climb the rail, and if nothing knocks it back down it will climb over the head of the rail and hey presto, the train is now a bus. That is why when you hear of most derailments, it has been trains in depots or carrying out empty shunting moves at stations. It’s not a happy coincidence that there were no passengers, it’s the slow movement associated with these manoeuvres that contributed with it.
Trains travelling at speed (anything over 10mph) don’t derail without outside influence because there’s always enough lateral movement for the Hunting Oscillations to right themselves.
Conical wheel profile → better self-correcting at tight curves
But also
Conical wheel profile → worse over-correcting on straight runs
The Washington, DC Metro chose less-conical wheel profiles than usual to minimize hunting oscillations, at the cost of more squealing around curves. The adjustment for that with otherwise standard hardware is the reason why its gauge is a bizarre quarter-inch narrower than standard: 4 feet 8 1/4 inches.
could you not have variable wheels ?
@@MattMcIrvin The ¼" was added to allow wheels though suitable for 4' 8" to turn correctly, rather than bind. Looks like they just undid that fix.
@@highpath4776Aren't most on solid axles, unless on variable gauge systems?
Thank you Jago; I’ve experienced the DLR wobbles and wondered why and what’s the reason for, but you’ve explained it perfectly! Wobble on…
0:34 Finally, we’re in the Hazzardous Lair
😂
The flanges are not what keeps the train on the rails, except in extreme conditions. The conical profile means that if on wheel is higher up the rail than the other it will have a larger circumference and travel faster. This will steer the train back to the centre of the track.
The physics of hunting oscillation is quite interesting. And when a train is passing a platform at speed, it really matters that it's taken into account. Not that this will happen on the DLR, which stops at every station.
Main line rolling stock goes to great lengths to suppress hunting, especially on high-speed services. I believe it involves dampers that are a bit like car shock-absorbers and minimising the "unsprung weight", but I'd be interested to learn more from an expert. They probably do things with the permanent way as well.
@@neilturner3658 The most knowledgeable expert is (or was) Dr Alan Wickens. He was employed in the 1960s to investigate the issue. It became the most important & least well known aspect of the APT project.
Very interesting Jago, I always wondered why trains and rolling stock didn't have a form of differential. As in Ackermann's principle of steering. You are my differential to a curve. Thank you.
@@jadeboswell-rz2ly They don't need one, because the taper does it for them. The wheel on the outside of the curve rides up, and because of the taper now has a bigger circumference in contact with the rails than the one on the inside of the curve, which has moved down. That means that the wheel on the outside of the curve travels further for each turn of the wheels, which is exactly what you need to go round a bend
@@norbitonflyer5625 Even more so, if they did have a differential, the self-steering effect wouldn't work!
Notably, trains designed for dedicated high-speed lines (think Shinkansen, TGV) have less-tapered wheels to reduce the heroics needed in the suspension. Presumably the Mini-Shinkansen uses a more normal taper to run on the former conventional routes, resulting in a lower maximum speed on the dedicated section of the route.
There's a story about oscillation from closer to me, also. The Chicago North Shore & Milwaukee was an electric interurban railway that connected Chicago to Milwaukee, running through the area known as the North Shore (yes, sometimes a railway's name actually indicates where it went). They were known for high-speed service, with expresses covering the 80 miles between Chicago and Milwaukee in 90 minutes. They also operated on the Chicago Elevated structure (organized by that shifty Yerkes fellow) operating above the streets, and so had to negotiate curves as tight as 90-foot radius. After some issues with instability and vibration, they were curious how the wheels were behaving on the track, so they mounted a headlight and a motion-picture camera beneath a car and ran it at high speed. What they saw was extremely frightening, and they worked with a few other railways to develop a new wheel profile that was more stable at high speed.
Incidentally, a few of their cars came into the possession of the Illinois Railway Museum when the North Shore shut down in 1963, and I'm going to work as a trainman on some tomorrow.
We went to IRM years ago, it was great!
@@SteamCrane Definitely a fun place to work, and to visit. After all, we're not paid to be there.
@@SteamCrane We're ramping up operations for the year. Yesterday we test-fired the Shay, and today it will begin revenue service.
Sounds interesting. What was the wheel profile?
There's an interesting story there about the ground conical wheel profiles of railway rolling stock.
Essentially, no train has any differential gears, as road motor vehicles have, that is due to the the different circumferential lengths of the inner and outer curved rails, and the fact that rolling stock has fixed axle sets - due to points and switches - the inner and outer wheels would have a tendency to rotate at different speeds. The way the early rail engineers overcame this problem was to grind a tapering conical profile into the wheels so that the effective circumference of the outer wheel increases, effecting an apparent decrease in its rate of rotation.
The physicist Richard Feynman cited this as one of the hidden triumphs and treasures of engineering.
Spot On! 👍
For those wondering this is actually what keeps a mainline train on the track most of the time. The outer wheel effectively gaining speed through larger contact circumference steers the train into the curve. The flanges are only needed for safety and tighter corners. The screeching noise made by trains crossing between lines for example is the sound of flanges doing their thing
Follow up, has there ever been a train/rolling stock with differentials?
@@oliverbooth2872 Very good explanation, but I thought I'd seen elsewhere that the screeching is not necessarily the flanges even then, but the wheels slipping a bit on the rail to "catch up" their opposite number.
@@Batters56 Yes, there are road-rail double-use maintenance vehicles that do not have tapered wheels but instead use a differential.
2:59 Well, IKEA does sell light rails. I'll get me coat.
Some trams like the Variobahns in Croyden actually have near cylindrical wheels. They have independent motors on each side, and with the computer they effectively tank steer around the corners. It also means they don't need the axle though the middle so they can be low floor throughout.
Yet paradoxically, the Variobahn is worse in very tight curves than a traditional bogey with axles. We had Variobahn (then called Variotram) trams in Helsinki, but they worked so badly on Helsinki's old network with lots of steep curves that their manufacturer Adtranz (later Bombardier, who bought Adtranz*) had to do constant costly repairs to them at their expense. They were nicknamed "vauriotram", which translates to a "damage tram". Eventually they were retired only after 20 years of use.
They work perfectly fine on modern light rail tracks with curves no less than 25 m radius, though.
*) During the acquisition the EU made an antitrust ruling that Adtranz's tram manufacturing must go to Stadler, but Bombardier was still liable of all the prior tram purchase agreements.
In a sense, the tank comparison is spot on. :)
BART trains also originally had cylindrical wheels, which gave them a distinctive shriek going around curves.
@@synchronos1and now they’re Alstom 💀
@@synchronos1 They are so bad that my city decided on refurbishing the 90s stock and keep them running while getting rid of the newer Variobahnen.
Nice to see the model railway having a brief outing.
Way back in the mid 80s I was travelling on a Class 101 DMU east of Hunts Cross, and the hunting was so severe people's shopping bags were getting thrown about like leaves. 101s weren't especially prone to that in my memory, so I can only assume there was a wheel or bogie fault. Crew weren't interested, presumably they were used to it.
British Rail staff weren't really interested in anything. Many of their successors aren't either.
Thanks, I've never noticed or thought about the wobble when travelling on the DLR and now I'm going to think of nothing else.
One of the best experiences of my trip to the UK was sitting "in the captains seat" at the front left of the DLR. Great view!
This actually explains why all the light rail trains in Edmonton tend to wobble, and also why the new Valley Line trams seem to be wobblier than the bigger light rail trains on the Capital and Metro lines, since the trams traverse much tighter radius curves.
Same with SkyTrain in Vancouver.
Partially - the other contributing factor for the Valley Line relative to the others is that it uses low-floor vehicles, which require most of the electrical and HVAC components to be roof-mounted, making them top-heavy. It's the same thing with other low-floor light rail and tram systems to varying degrees.
Interesting, I noticed the Edmonton Valleyline wobbling coming out of Millwoods and thought the track layers must have been drunk!
Sounds like the "shoogling" of the original Glasgow Subway trains.
Ooh, DLR stuff, excellent.
2:59 I had no idea the DLR's wheels are produced in Sweden.
I thought they were bigger than that too.
IKEA?
Designed in Sweden, produced in some land with cheaper labour.
As I could decipher, "Made in Portugal".
@@simonneep8413 For IKEA products sold in my country (Singapore), many of them are made in Suzhou, China by the way
Hunting oscillation is a great term. Thank you for the explanation.
Riding the DLR brought back memories of travelling on Romanian railways 😭
Essentially, the hunting oscillation is caused by each bogie travelling in a wavy line on top of the straight track.One way to stop this is to have damping on the rotation of the bogie in relation to the body, wich will discourage this and damp it down to travelling staight.
It is, but also increases complexity, maintenance & therefore cost. It really depends on how useful it is to go faster.
Perhaps adopting Jacobs bogies can also increase train rigidity & reduce hunting
This was wheely good
I've found many unusual parts of Bank station where I've had to throw up because of the DLRs wobble - and thanks to the lovely staff who knew what was happening and let me into those parts.
Sometimes you really do need to re-invent the wheel
Years ago on South West Trains a passenger was concerned about the speed. I explained we could go much faster but it would be too uncomfortable for the passengers.
Well how about that?
We were in London last week, we took the DLR for the first time and both of us remarked on how it seemed to excessively rock back and forth. I actually assumed Jago would have a video about it and here it is, just as we made it home. Excellent service I have to say!
0:34 jago has a science corner
I loved this scientifically wobbly tale from the tu... Oh wait the DLR. Nicely done Jago, keep it up
2:59 so does everyone have at least one of these bowls?
Excellent video, answers the question I ask myself as I spill my coffee between Shadwell and Limehouse.😊
What Jago means is that the cone angle on the DLR wheels is larger than on heavy and fast rail systems. This is related to the curve radius which can be negotiated. (Tight curves require more cone angle)
That sounds painful! 😂😂😂
I did have, but I broke them, they are a useless size. I do have some nice ex BR On Train Catering Bowls though with wide lips to catch the soup slops
Excellent video episode, thanks! Well my grandfather used to call that “wobble” the Shim Sham Shimmy. Apparently it’s highly appreciated in Philadelphia subway trains and beautiful women! A thing of beauty & a joy to behold in both cases.
Fun fact - early motor cars didn't always have dampers, and if they did, they were friction dampers rather than the conventional oil and piston damper we have today. This meant that on the early, rutted roads it was possible for a cars axles to meet their natural frequency of oscillating up and down leading to the bounce getting progressively greater and greater until the car would literally jump in the air and throw itself over the nearest hedge 😂
Good Morning Jago. Enjoyed you adding a few shots of your model trains to illustrate the point. You really "went to town" on this one. CHEERS!
I think this slightly misses the point of variable circumference.
In order for a train to go around a corner, the outer wheel needs to physically go further than the inner wheel. The reason why the wheels are conical is so that when this happens, the outer wheel is pushed onto the fatter end, causing the wheel to effectively become bigger, and the inner wheel becomes smaller. Since they are spinning at the same speed, the bigger wheel will travel further with each revolution so the outer side of the train goes slightly faster than the inner.
When the train comes out of the curve, the outer wheel is still bigger than the inner, so it steers the train towards the inner side of the track. This causes the inner wheel to be pushed up, and move further than the outer wheel, so the train is steered back towards the outer side. This is what causes the oscillation, not just gravity.
I remember there was a demonstration of this at the National Railway Museum when I was young. It was clear that gravity was unnecessary to see the effect because it worked just with an axle and wheels light enough to not hurt a child.
Increasing the cant of the tracks can reduce the need for this variable circumference of wheels
Last time I went on the DLR it was to a beer festival at the Docklands Arena. I got my bag caught in the bus-like folding doors of the tiny train.
They got rid of those in 1994
@@stuartparks8094 The Docklands Arena is long gone too!
The normal streetcar radius curve in the US,was/is approximately 50 feet,and that limited the length,and width requirements! One of tightest curves on Chicago's elevateds,is on the LOOP,downtown,whch had a fatal derailment,in the 1970's,and that also happened in Brooklyn, and Manhattan on the old elevateds! That was because of speeding,and overhunting on the trucks[bogies],so there can be consequences to that degree! Thank you,Jago,your technical prowess is showing up,and well presented! Thank you 😇 😊!
Here in Ottawa the line 1 LRT is having lubricators installed because some of the curves are so sharp they probably contributed to wheels falling off.
A complex subject very nicely summed up. Really. I mean that. I've spent ages looking at tram rails on curves trying to figure them out where it looked like the tram must be running on the wheel flanges as the rail head was so low.
The tyre profile will effectively alter the gearing on a corner as both wheels will be different diameters on different track radii and I assume will self compensate which is very simple, extremely neat, fascinating and thoroughly confusing, because, to my mind, the angle of the tyre profile doesn't seem much so there's a lot more to it, especially as the rails are canted and would imply a whole host of tyre profile ranges for different track gauges.
I've no idea if I'm on the right tracks but it must be something along these lines.
It's like going in a sudden leap in logic from a wooden wheel to a spoked and tensioned wheel while evolving wheel dynamics and the spoke formula over a cup of coffee at breakfast.
So there's a hell of a lot I just don't get, never quite have, and this video helps without giving me uncomfortable flashbacks to maths III at college.
Every day is a School day with Jago - I didn't know about this Jago - Thanks for sharing 😊🚂🚂🚂
I ask myself this every time I'm on these trains, thank you Jago 🙏
Thank you, Jago, for bringing model trains into the story!
love the wobbly bois. probably my favourite mode of transport in london
Note the check rail at 1:45. This is another measure to stop the wheels straying too far towards the outside of the bend - the flanges of the wheels on the inside of the bend bear against the check rail.
I always felt that this channel needed more crockery.
Useful explanation. Thanks.
I have been using the DLR ever since it first opened and for myself the most wobbly section is between
Shadwell and Bank.
Jagotastic TALE FROM THE DLR, Sir Jago!! ….and you are the *”Equilibrium to my Wobbly UA-cam”.*
Vancouver's skytrain uses steerable boogies. Which means the two wheel axles on the boogie can independently turn, allowing tighter turns. This allows the trains to use more conventional wheels which permit higher speed without hunting ossalation becoming a problem. It also avoid the squealing sound that trains get when taking tight turns.
That is really spooky, I was just talking to someone about this only yesterday and we were discussing about the issues and wheel profiles of Manchester Metrolink and the huntiing issues. We also discussed how at one time some experiments were done with what was called "Worn Wheel Profile" which was relatively successful until gauge widening on curves became the norm, which rendered it ineffective.
And this explains the real difference between Light and Heavy rail. Thank you.
An amusing consequence of their operating environments: Light rail vehicles are often heavier (at least for their size and capacity) than heavy rail vehicles (there's a whole bunch of factors that can cause this to not apply, mind you). This is pretty much entirely down to the specific types of accidents they can get into: light rail needs to be a lot more solid to protect it's passengers if it's going slowly and gets rammed in the side by a semi than heavy rail needs to be when going at high speed and hit in a similar manner, not to mention the light rail is far more likely to encounter such issues due to street running being exceptionally common while heavy rail only does so in exceptional (and usually far more controlled) circumstances.
Makes the names seem rather confusing at first glance.
One of the best and clearest explanations of a physical phenomenon I've ever heard - well done !
One of my favourite videos of yours, Jago
Interesting and comprehensive explanation, Jago... thanks!
I used the DLR on Tuesday evening (May 7th 2024) and I did notice the wobbling it was quite bad from Bank to Canary Wharf; more specifically it was on the section from Shadwell to Limehouse
Love it! I have learned something this sunny Saturday afternoon,
It's good to see your model railway again! You should come to the Model Railway Club near King's Cross on a Thursday one day and make a video about that.
If I ever got married, "you are the equilibrium to my wobbly wheels" would be in the vows.
As informative as ever. I always learn something new.
Thankyou, Jago. Appreciate the information.
I imagine the distance from the front of the train to the bogie pivot point also has something to do witht he sway. The further from the front of the train the greater the left-right sway of the front seats. Tight curves also give "Flange sqeal" as at St Pancras Thamesling, despite flange greasing equipment.
Good clear explanation. And not longer than it needed to be. Thanks!
Properly fascinating. Great vid!
As always, most informative and entertaining.
Amazing, I’m in my late 60s and still learning about the technical aspects of railways. Thanks Mr Wobbly Wheels ! I love the DLR.
Thank you. Well explained and as always in a very entertaining way.
a wibbly wobbly wonder
Very interesting and informative one of your best
As a West Londoner, the DLR seems to alien to a Hammersmith and City user.
The entire tube network seems alien to those of us who live in the country!
@@AtheistOrphana lot of Londoners don't leave their patch. I'm from our if London but visit when I can and suspect I've seen more different parts of London than most Londoners
What a _very_ interesting episode. Thank you for this … ‘most informative’ 😊
I remember my first time on the DLR as a kid, I thought the train was going to derail coming out of Tower Gateway. Went on it a few times recently and have come to the conclusion that its just the way it is. This video just the explanation I need. Jago up to the minute aa always 😎
Absolutely fascinating.
Hello Jago, that was a wheelie good explanation of why wobbly wailway trains wobble on the DLR wailway tracks. That’s all folks. I’ll close the door on the way out.
Great as ever 😊
Jago
"Why don't they just" suggestion: Wider wheels. In the middle of the wheels and further to the outside the profile is gently conical like on a regular train, so it can go straight properly. On the inside towards the flange it gradually gets steeper all the way to tram steepness, so it can go around curves. Maybe that is already what they have and it doesn't work as well as I imagine? Or maybe wider wheels cause more problems? They would be heavier and slower to accelerate at least.
They would also mess up regular switches (that would be an expensive fix). And you would probably not be able to run in a street, but I don't think the DLR does. And level crossings would probably be bad for the road vehicles, but those are probably rare for an automated system like this. MAYBE on a separate system like I imagine the DLR to be, something like this could work?
The LNER made some suburban rolling stock by taking old 4 & 6 wheel coaches and putting them on articulating bogies, three between two.
Tyneside electrics correct
A good explanation of it. Practical Engineering did a whole video on this.
I'd say the hunting is most visible when in the tunnels under the Thames, particularly Woolwich Arsenal. And if you're at the front or rear of the train, where the hunting isn't dampened by the next vehicle along.
Thanks!
The return of Jago’s Trains!
Congrats on the new place with room for the hobby.
It all adds to the Rollercoaster feel
Great video, I'd often wondered about the wobbliness on that faster section too!
Great video jago, very interesting,i now know more about the DLR 👌😀👍
IIRC the Heathrow Express Class 332s had to be periodically rotated (the whole unit, rather than the wheelsets) due to one-sided wear from going to and fro in an arc
Great explanation, I’ll look out for it next time
Skytrain in Vancouver has this "feature" to it aswell!
Especially with the oldest trains, with their old (and pretty busted) suspension.
Constructed in the same vain as the DLR, too, using old Interurban alignments
I knew the trains wobbled, but had no idea why. Thanks! 😁
Remind me never to travel on the DLR. I suffer from Vertigo and have balance issues as a result. Buses also cause me much aggravation.
if you have vertigo a long distance train is better, neartogo walk,
Thanks for answering.
"I've gone all wibbly wobbly!"
(Lee Evans)
I had never heard of "hunting oscillation" before, but it makes sense. I learn something new from every one of your videos.🙂
You get this "going faster than ideal" type hunting on the T&W Metro, too, where the green line joins the National Rail network on the way to Sunderland. It always seemed odd to me that when it moved onto a section which had smoother curves then it should hunt more, but I'd not thought about the speed.
And on the relatively fast and straight bit from Bank Foot to Callerton. I always wondered why it did that so it's great to hear an explanation.
After a ride on the DLR a trip on the peter pan dragon rollercoaster at Southend is a doddle
On Metrolink, the issue was also identified as being partly due to the articulation both on the T68 (which were basically trains with skirts) and the newer M5000 fleet too not helping matters. I suspect this also plays a part on the DLR. It also led to some rail damage during the transition between T68 and M5000 with a number of speed retrictions on straight sections of line, particularly on the Altrincham line.
What a nice short and direct to the point explanation.
So refreshing to focus on the technical issues and not immediately move to establishing political blame.
Funny how I find this video a day after riding the DLR and noticing how wobbly it is
Hunting Oscilation you say.
What happens if you catch one of these Oscilations? How big are thery?
Do you have to release it back into the wild? Can they be kept as pets?
Are they suitable to feed a hard up family?
They aren't particularly aggressive in the wild, but they're very quick so you have to be careful. They range in size from that of a small cat to that of a baby elephant. They must be released back into the wild as they're essential for the ecosystem. You can't keep them as a pet since they quickly become aggressive if kept in captivity, and they aren't edible so you can't eat them.
@@wta1518 Finally, I have found an Oscilation expert.
I have so many questions.
What is their favourite food?
Do they live in groups or are they solitary?
The former Docklands of London seems to be their preferred habitat. Where else can they be found?
Is there more than one species? Like Indian/African elephants or Grey/Red squirrels
What is the collective noun for a group of Oscilations? A Shake, Quiver, Frequency, Reverberation, Wave or Vibration?
Are they an endangered species?
Is an Oscilation's home called a Jago? Or was I being wound up
@@mikehiggins4079
They generally eat iron and alloys containing iron such as steel.
They typically live in groups of at least 10.
They can be found in most cities in the world, due to the abundance of iron in those areas.
They're the only species.
The collective noun is wibble-wobble.
They aren't endangered, but they could be if we continue hunting them.
Yes, they're home is indeed called a Jago.
As many gems in the comments as in the video itself as usual. LOVE this channel!
@@wta1518 Thank you for sharing your abundance of knowledge on the subject.
One last question.
The same source that told me an Oscilation lives in a Jago also said a male Oscilation is called a Yerkes.
Is he correct, and what is a female called?
Maybe we have found a worthy topic for a Jago Hazzard video. Unseen Life of the DLR & Underground!
Super interesting! Was also trying to match each DLR shot to where it was as quickly as possible. Think I got em all!
I liked the picture of Millwall wall.
...if only it was in timber, built by Edward Woodwood 😆
The Manchester Metrolink suffers quite badly with hunting now that the T68 LRVs have been replaced by the M5000s, the T68s were a much more robust vehicle and were around 49 tonnes so had a very smooth ride, the M5000s that replaced them are 10 tonnes lighter and on the former heavy rail sections (like the former Bury Electric line) they are notoriously bad - even after they've reprofiled the track. Also that section of track by Bury South signal box is quite a challenge for drivers, it has a very low speed limit (for obvious reasons) but the weight of the train coming down the "ski-jump" will begin to push quite hard, there is also a slight dip meaning if you are just a bit off touch with the brakes then the whole lot grinds to an embarrassing halt (still it's better than the alternative!).
Excellent! Were you an engineer? One curve solution you missed was the oiled pad. Shipley Station had them. They were a felt pad and a container with oil, that oiled the inside of the wheel flanges. They worked, but somebody had to refill the container; nobody does that now. Bradford-Keighley trains at Shipley now go very slowly, and still screech like a 200 ton train hard rubbing up a rail, with no oil on its flange.
Thanks. Cool and informative.
And thank you!
Every time the train wobbling between Custom House and Prince Regent give me a vibe that a footbridge between West end of PR and East end of CH favourable