The Schwebebahn has a big problem!

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London has noisy tube trains and sections of underground line that are just too damn noisy for passengers – not forgetting the residents who live above the lines. One would think the Schwebebahn wouldn’t be like this at all – its trains hovering through the city of Wuppertal silently, swiftly and surely. But it is making a big noise. And its causing problems all around because the Generation 15 train sets are a brand new fleet of highly advanced trains – and it means no-one is quite sure how exactly to tackle the problem!

Although the Generation 15 trains are designed for faster running (as well as automated operation) the issue is there’s a decree in force that the famous monorail must run its trains slower. This is because of the accident which happened just over a year and half ago – and which I wrote about on my blog at that time. The picture below shows the November 2018 problem in question – power conductor rails that suddenly fell off the line’s superstructure for no apparent reason.

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The fallen power rail 18th November 2018. This normally sits on the underside of the main structure. Source: Twitter.

Prior to that incident, the Generation 15 trains could run at their full 60kmh. Then Schwebebahn services were halted for the best part of a year whilst major repairs were undertaken to the infrastructure along the entire line in an attempt to prevent such an incident recurring. Services were given the go ahead to recommence full services less than a year ago, but with the 2018 accident still fresh in the authorities’ minds and many questions still to be resolved, a decree was given that the new trains could only run at 40kmh, not the 60kmh they are capable of.

How does that make the trains/the line much more noisy? Well its the unique single rail system the line uses. It means specially designed double flanged wheels have to be used. Under normal circumstances the wheels are more or less riding on the edges of the rail itself, which means there’s minimal contact between both wheel and rail.

Its a similar sort of physics to how normal railways work, but in terms of the Schwebebahn its a bit more complex because of the single wheel/rail interface. On normal railways its essentially the least friction between wheel and rail that’s important, and this is true also for the Schwebebahn. But because of the way the line is built (the trains are underneath the rails rather than on top) the wheels need to have a semi curved profile rather than the tapering profile found on normal train wheels.

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A view of the Generation 15’s bogies. The curved profile of the wheel itself is evident. The trains’ new type of suspension arrangement can too be seen. Source: Wikipedia

The problem arises because the trains are going slower than the speeds they were designed for (40kmh instead of 60kmh) which means the wheels are practically running squarely with the flat top of the rail – this has the action of wearing the semi curved profile of the wheel away quite quickly – and that makes for a very noisy railway.

What it means is the wear is in the wrong part of the wheel thus its semi circular profile is becoming flattened. The somewhat minor pendulum swing of the trains themselves allows the wheels to utilise that semi circular profile effectively and that is how this should work in fact. But currently the slower speeds means the wheels are having to work much more like a normal train wheel/rail interface throughout the 8 miles/13km of monorail route. And the Generation 15’s wheels have completely the wrong profile for that.

The problem here is Wuppertaler Stadwerke want to see the line eventually have a much more frequent service when the full capabilities of the new designs come into force (this includes automated operation.) It means the new trains need to have a somewhat different wheel profile compared to the older ones in order to meet those new requirements. It would be too expensive to change the wheelsets of all the trains to the older Generation 72 type profile and then change them all back when the new design was required once again.

In fact that couldn’t be done not without a lot of design change! Which means its not even an option, thus the Schwebebahn’s stuck with having to make the best it can of the ongoing situation.

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The new Generation 15 trains have been evaluated in every way possible both in terms of computer simulation, and in real world terms using some of the latest technologies. Yet the current problems are something that was not envisaged – and currently there isn’t absolute certainty on how best to go about it.

There’s yet another problem to this whole matter! The wheels have to be specially made – they are not off the shelf stuff. What it means is there are not enough wheels to go round and it means practically half the Schwebebahn’s fleet is out of service. As a result the service frequency has been reduced from every three minutes to every four and half minutes. Its not too bad currently because of the ongoing coronavirus lockdowns, but as things return to normal it may well present a problem. Wuppertaler Stadwerke have said normal frequencies on the line will hopefully be regained by the end of the summer.

The fact the wheels run in the way they currently do due to the enforced speed restrictions also damages the track. It means the track gets serrated, in other words it gets bumpy, it has those nasty imperfections which sorts of makes the train shudder, and in the process the wheels get flats – it too means the riding quality isn’t good – its been said the trains are making a very loud rumbling noise as they move along the tracks. Observers say the the trains act like ‘chatter boxes.’

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Generation 15 train on the Schwebebahn’s above road section (the Kasierstrasse) near Bruch. Source: Twitter

The noise in question is very annoying to the many residents who live close to the line as well as the passengers who use the trains. A campaign group was set up to highlight the sufferance the residents of Wuppertal have to tolerate in terms of this noise problem coming from the Schwebebahn. The campaign largely relates to the section of Schwebebahn between Zoo Stadion and Vohwinkel – along which trains regularly run just metres from residents’ bedroom windows.

One resident who lives by the line between Sonnborn and Hammerstein told the media he and his wife had known the Schwebebahn for years and it had never been that noisy. But it has been very different in recent months. ‘We can’t close our eyes before the last train at 11 p.m. and in the morning at five we fall out of bed due to the noise.’

There’s one other problem in regard to the situation. The older trains ran somewhat slower – they rarely got any faster then 40kmh and didn’t present the same problems – but then the bogie system on the Generation 72 trains and older was very different. On the Generation 15 trains its a completely new design. The question now being asked is whether the current problems are just related to the design of the wheels. Or is there some other factor at play? Is it the whole new design of bogie that is at fault? Running at 40kmh shouldn’t present such problems but it has.

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The older Generation 72 wheels had a somewhat less curved profile. Source: Westdeutsche Zeitung

It could be any number of things – the new bogie suspension, the soft monoblock tyres, the weight to wheel ratio, the design of the entire bogie system (including the automated braking which is done by way of sensors etc.) It could be that the new suspension system by way of its being separate from the wheel bearing itself is causing problems. The dampening mechanism is actually located between the drive gear and the wheels of the Generation 15 sets rather than on the bearings/axles of the older trains.

The wheels themselves were designed to last for 80,000km. Currently they are lasting somewhere around 60,000km which is about 75% of their normal serviceable period. Its said each wheel costs 4,200 euros each. There’s quite a cost in this in terms of both the wheels and the rails with at least 80 wheels needing replacement (that’s ten train sets.) Under normal circumstances there’s usually one or two trains in the depot for such tasks, and not normally such a large number of trains out of service with a shortage of wheels to boot.

There is ongoing debate as to who is going to stump up the costs of putting this problem right. Is it the operating company? Is it the manufacturers themselves (under the terms of their warranty) who make the wheels? Maybe even the Regional Government who issued the order that the trains run no faster than 40kmh? There’s clearly a lot of legal complexity to be had, and it seems so far no-one has an answer to these questions.

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In this view of some even older Schwebebahn wheelsets, the profile is more flat. Source: Die-Schwebebahn

Quite a large number of sections of rail too will have to be replaced and this is additional cost involved on top of the wheels themselves. Again that is up for debate as to who will be responsible for the costs of this work.

What is sobering in the midst of all this is the the Generation 72 trains could run for 200,000km between major wheel changes. The Generation 15’s trains will have a maximum of only 80,000km under normal service which means there is going to have to be a better maintenance regime in place. So far I do not know if this is being done, however the current problems clearly exacerbate that.

Wuppertaler Standwerk has a page which advises of the problems it is facing in regards to the train wheelsets (in German only): WSW machen die Schwebebahn wieder leiser.

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Wuppertaler Stadwerke’s official announcement on the problems it faces with the Generation 15 wheels.

Generation 72 = 1972 stock.

Generation 15 = 2015 stock.

The main feature image is of one of the Generation 15 trains sporting a ‘facemask’ during the 2020 coronavirus pandemic/lockdown – and was sourced from Wuppertaler Stadtwerke’s Facebook page.

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