Manchester Metrolink ride quality.

[jbg]

Is it me, or is the ride quality of the 5000 series (3001-upwards) getting beyond acceptable?

Not just the violent swaying on the Bury line, but the vomit inducing bouncing and juddering on the Rochdale line (amongst others). It's like being driven up a cobbled street at speed, with solid tyres.

The ride between Beckenham Junction and East Croydon last week was far more comfortable.

 

[gordonthemoron]

when was the track on the Bury line last renewed?

 

[jbg]

when was the track on the Bury line last renewed?

Not that long ago. 4 or 5 years at most I would guess.

Some of what was replaced was over 50 years old if I remember correctly.

 

[James268]

The swaying between Bury and Radcliffe was...violent! So much so that the first time I rode it I had genuine concern that we would de-rail.

Recently the ride quality has been okay. Nothing overly jarring. I believe the trams may have had some suspension modifications to combat this. Don't quote me on that though!

It does feel as if the speed limit has also been dropped by around 10mph (or drivers are going slower of their own accord) to increase the ride comfort, this is just based on feel when comparing journeys, it does feel like you're travelling slower than previously.

 

[WatcherZero]

Grinding rails every so often helps but its the fundamental issue with the highly conical wheels used by light rail to allow the tight curves and experienced on the Underground, DLR and other tram systems. They start to hunt and ride quality deteriorates quickly around 50mph because the wheels don't have as much surface contact with the rails they move side to side and hit the flanges more often. On a tram train you generally put on wheels closer to heavy rail which are larger and less conical though cant manage quite as tight curves.

 

[Peter Mugridge]

On a tram train you generally put on wheels closer to heavy rail which are larger and less conical though cant manage quite as tight curves.

That could be interesting given that Sheffield are planning to use their "traims" as part of the normal tram fleet pending the opening of the through services they were designed for; have the 399s been designed specially to cope with tighter curves than would be normal for this kind of vehicle? Or are the curves in Sheffield not as tight as on other systems?

 

[WatcherZero]

The ones that will operate the new track have different wheels to the rest of the tram fleet though they have the normal tram ones fitted at the moment while awaiting for the infrastructure.

 

[Peter Mugridge]

Ah, I see - that makes sense.

 

[edwin_m]

As I understand it the tram-trains are OK on 25m curves which are the minimum on Sheffield or Manchester. Something the proponents of tram-trains for Nottingham should watch out for, as there are tighter curves there (as well as requiring narrower vehicles).

 

[Ianno87]

Not that long ago. 4 or 5 years at most I would guess.

Some of what was replaced was over 50 years old if I remember correctly.

2007 was when the last of the old jointed track was replaced

 

[507 001]

Bombardier have been trying to improve the ride quality of the M5000s over the last three years. It has improved greatly to be fair, but is still an ongoing process.
They have wheel profile issues as mentioned further up thread. This initially manifested itself as a low frequency hunting motion, you could actually see the nose of a vehicle coming towards you deviating from the centre line by about 6 inches in each direction. A change in wheel profile, and a step change in the pace of the rail grinding programme largely eliminated this issue. Unfortunately the new wheel profile has resulted in a high frequency hunting motion (the vehicle feels like it is shaking and bouncing) in certain areas. This is currently being looked at, and has resulted in a temporary speed restriction between Dane Road and Old Trafford on the Altrincham line where it was worst.

Some vehicles (3024 and 3105 onwards) have a different Damper set up, this gives a much firmer ride largely eliminating most of the 'bouncyness' at speed at the expense of low speed ride comfort. It was originally intended to roll this new set up across the fleet as and when vehicles came up for overhaul (first ones will be due in a year or two) however there have been issues with the new set up and I'm not sure if this will still go ahead.

It is worth noting that when the K5000s were ordered for Köln, they were intended for 100kph running. It was quickly found that there were issues with high speed ride quality and they were demoted to lower speed routes and replaced with Refurbished Stadtbahn B sets which they were originally intended to replace. It should therefore be no surprise that the M5000 ride quality is.... lively.

As for the ride quality in Croydon being better, that could be down to the CR4000s being low floor (lower centre of gravity etc) or it could have something to do with their track being in better condition.

The T68s had air suspension, which largely eliminated many of the track defects, so it wasn't as important to keep the track in 100% tip top condition, the M5000s feel every single dip and kink in the track however.

So yes, it is an issue, and yes, it is being worked on. However it's a bit like unravelling a ball of string.

(For those that don't know, I'm a Metrolink Driver)

 

[northwichcat]

The new trams have to approach Altrincham platform at around 5mph to prevent them hitting the platform on approach. It's almost comical to see a tram leave Navigation Road when a Northern train is at the adjacent platform with the guard starting the process of closing the doors and yet the slower accelerating, guard controlled train can still be stopped at Altrincham with it's door opens before the tram which left Navi Road first!

By Metrolink's own omission the new trams have slowed down a Bury/Altrincham to Manchester journey by around 4 minutes and a Bury to Altrincham journey by around 8 minutes.

 

[WatcherZero]

Ive personally always blamed this issue on modern stock (including heavy rail) as arising out of the trend of mounting seating horizontally to the side walls to allow easier cleaning beneath seats. It transfers all the weight from the centre of the floors to the outside edge of the bogies as well as raising the centre of mass, that's naturally going to make for a more unstable vehicle.

 

[edwin_m]

Ive personally always blamed this issue on modern stock (including heavy rail) as arising out of the trend of mounting seating horizontally to the side walls to allow easier cleaning beneath seats. It transfers all the weight from the centre of the floors to the outside edge of the bogies as well as raising the centre of mass, that's naturally going to make for a more unstable vehicle.

Attaching the seats to the sidewalls instead of down to the floor wouldn't directly affect the weight distribution - the only effect is the raising of the CofG if it requires a heavier structure above the existing CofG. Since the CofG is typically somewhere around the top of the seats it may even lower it.

Metrolink trams have very little under the floor with most of the equipment on the roof, so along with the high floor the CofG is probably pretty high.

 

[Ianno87]

The new trams have to approach Altrincham platform at around 5mph to prevent them hitting the platform on approach. It's almost comical to see a tram leave Navigation Road when a Northern train is at the adjacent platform with the guard starting the process of closing the doors and yet the slower accelerating, guard controlled train can still be stopped at Altrincham with it's door opens before the tram which left Navi Road first!

By Metrolink's own omission the new trams have slowed down a Bury/Altrincham to Manchester journey by around 4 minutes and a Bury to Altrincham journey by around 8 minutes.

Presumably, some of that journey time extension is also down to conversion to line of sight signalling requiring lower speed limits around bends, through tunnels, etc?

 

[WatcherZero]

Bogies are mounted centrally on a pivot point to the carriage body to allow some rotation on cornering. If the weight of the carriage body is further from the centre fulcrum then force will be magnified by the distance from the centre point. Roof mounted equipment shouldn't really be an issue as the weight is generally balanced in the centreline and will be transmitted equally down both sides. However unequal passenger loading e.g a load of passengers sitting on one side would have their weight transmitted to the extreme edge outside the bogie frame. This would contrast with say traditional seating which transfers the weight down to the edge of the corridor near the centre of the carriage inside the bogies or standing passengers which again would focus weight in centre and may act to dampen osscilations. There are sometimes but not always secondary suspension or dampeners on the outside edge of the bogie but again the weight in this modern seating arrangement is outside that point.

https://www.hud.ac.uk/media/univers...ctober2012/in-pagestoryimage/10_IRR_main1.jpg

 

[northwichcat]

Presumably, some of that journey time extension is also down to conversion to line of sight signalling requiring lower speed limits around bends, through tunnels, etc?

No that was how much they added on before line of sight and the East Didsbury line was opened. When they first tried to use M5000s and T68s alongside each other, the T68s often caught up the M5000s when they were supposed to be 6 minutes behind them, so they reworked the times.

 

[rebmcr]

Some vehicles (3024 and 3105 onwards) have a different Damper set up, this gives a much firmer ride largely eliminating most of the 'bouncyness' at speed at the expense of low speed ride comfort. It was originally intended to roll this new set up across the fleet as and when vehicles came up for overhaul (first ones will be due in a year or two) however there have been issues with the new set up and I'm not sure if this will still go ahead.

I remember the old signs instructing drivers to switch T68s in and out of 'Street Running Mode' -- do the M5000s have a similar mode change, and if so, is it capable of altering the damping force? Hopefully Bombardier will see this if that's feasible!

 

[rebmcr]

Bogies are mounted centrally on a pivot point to the carriage body to allow some rotation on cornering. If the weight of the carriage body is further from the centre fulcrum then force will be magnified by the distance from the centre point. Roof mounted equipment shouldn't really be an issue as the weight is generally balanced in the centreline and will be transmitted equally down both sides. However unequal passenger loading e.g a load of passengers sitting on one side would have their weight transmitted to the extreme edge outside the bogie frame. This would contrast with say traditional seating which transfers the weight down to the edge of the corridor near the centre of the carriage inside the bogies or standing passengers which again would focus weight in centre and may act to dampen osscilations. There are sometimes but not always secondary suspension or dampeners on the outside edge of the bogie but again the weight in this modern seating arrangement is outside that point.

https://www.hud.ac.uk/media/univers...ctober2012/in-pagestoryimage/10_IRR_main1.jpg

The frame of the train body is, from the perspective of the bogie, a rigid structure. Its centre of mass will vary according to passenger load, but the method of transmitting that load to the mounting points is categorically irrelevant.

 

[Greybeard33]

No that was how much they added on before line of sight and the East Didsbury line was opened. When they first tried to use M5000s and T68s alongside each other, the T68s often caught up the M5000s when they were supposed to be 6 minutes behind them, so they reworked the times.

I believe that there has been a more recent relaxation of timings on the Altrincham line, even though (unlike the Bury line) it is straight enough not to need line of sight speed restrictions. I can remember that Altrincham to Old Trafford was 13 minutes only a couple of years ago. Now it is 15. The trams seem to be able to keep to the timings without exceeding 40mph.

 

[507 001]

I remember the old signs instructing drivers to switch T68s in and out of 'Street Running Mode' -- do the M5000s have a similar mode change, and if so, is it capable of altering the damping force? Hopefully Bombardier will see this if that's feasible!

That didn't do anything to the suspension set up. It just removed the 30mph limiter and switched from Street Whistle to Segregated Horn.

 

[edwin_m]

Some vehicles (3024 and 3105 onwards) have a different Damper set up, this gives a much firmer ride largely eliminating most of the 'bouncyness' at speed at the expense of low speed ride comfort. It was originally intended to roll this new set up across the fleet as and when vehicles came up for overhaul (first ones will be due in a year or two) however there have been issues with the new set up and I'm not sure if this will still go ahead.

This sounds like damping of bogie rotation.

Traditionally train bogies were free to swivel on curves, but in conjunction with wheel conicity this encourages lateral oscillation (hunting) which became a big issue in the 1960s as speeds increased. Part of the answer was to add dampers, often in the form of horizontal shock absorbers mounted on brackets between the bogie and the body on either side. These provide some resistance to bogie rotation, reducing the tendency for hunting. However on a tram they could also increase rail wear, noise and even derailment risks on tight curves, as the bogie is less able to align itself with the rails.

Active dampers might allow their resistance to be altered by a control circuit driven by a speed sensor, but I don't think even very sophisticated trains have progressed to that sort of technology yet.

 

[northwichcat]

That didn't do anything to the suspension set up. It just removed the 30mph limiter and switched from Street Whistle to Segregated Horn.

It also seems with both the old and new trams the street whistle is automatically sounded when the tram starts moving after becoming stationary. If not the drivers must suffer from RSI!

 

[northwichcat]

I believe that there has been a more recent relaxation of timings on the Altrincham line, even though (unlike the Bury line) it is straight enough not to need line of sight speed restrictions. I can remember that Altrincham to Old Trafford was 13 minutes only a couple of years ago. Now it is 15. The trams seem to be able to keep to the timings without exceeding 40mph.

I have a Metrolink route map which has Serco small print on the back which gives
Altrincham to Piccadilly - 26 minutes
Altrincham to Bury - 46 minutes

And another with Stagecoach small print on the back which gives
Altrincham to Piccadilly - 30 minutes
Altrincham to Bury - 54 minutes

Traveline currently shows
Altrincham to Piccadilly - 31 minutes
Altrincham to Bury - 55 minutes

 

[507 001]

This sounds like damping of bogie rotation.

Traditionally train bogies were free to swivel on curves, but in conjunction with wheel conicity this encourages lateral oscillation (hunting) which became a big issue in the 1960s as speeds increased. Part of the answer was to add dampers, often in the form of horizontal shock absorbers mounted on brackets between the bogie and the body on either side. These provide some resistance to bogie rotation, reducing the tendency for hunting. However on a tram they could also increase rail wear, noise and even derailment risks on tight curves, as the bogie is less able to align itself with the rails.

Active dampers might allow their resistance to be altered by a control circuit driven by a speed sensor, but I don't think even very sophisticated trains have progressed to that sort of technology yet.

Don't think so, it's just a stiffer conventional damper and spring set up than original.

It also seems with both the old and new trams the street whistle is automatically sounded when the tram starts moving after becoming stationary. If not the drivers must suffer from RSI!

Nope, it's not automatic.