Ride Quality Queries

[SamJMathis]

Hi all,

Apologies if this has been answered before, but I have some questions about the seemingly poor ride quality of the Hitachi 80X’s:

First, does anyone know for sure what is the actual mechanism which causes them to jolt and shake at higher speeds? Is it predominantly hunting or some other problem?

Secondly, what aspect(s) of the train design causes this to happen? Wheel size? Train weight? Crappy bogies?

Thirdly, how theoretically difficult would it be to fix the problem?

Thanks

 

[mike57]

I have certainly noticed this on multiple occasions on the ECML. To me it feels like 'hunting', an un(under)damped oscillation. On a couple of occasions it has reached concerning levels, not as in 'going to leave the tracks' but certainly bad enough that a move to another carriage was warranted. Not every carriage seems to suffer to the same degree.

 

[Haywain]

I’m sure that I read somewhere, a couple of years ago, that part of the reason for the poor ride quality was that it was specified (contractually) as being optimised at 140mph and this gives a poorer ride quality at lower speeds. I think it was in Modern Railways but I do wonder if I picked it up somewhere else.

 

[FrontSideBus]

I’m sure that I read somewhere, a couple of years ago, that part of the reason for the poor ride quality was that it was specified (contractually) as being optimised at 140mph and this gives a poorer ride quality at lower speeds. I think it was in Modern Railways but I do wonder if I picked it up somewhere else.

Regarding the speed, I was recently on a 395 and when that thing got up past 130mph the whole carriage was rocking side to side quite alarmingly! It felt like the whole bogie was oscillating and not by a small amount and was quite alarming personally. You can't blame the track either as the line speed there is 190!

I've never experienced that before on Mk4's which are also designed for 140mph running. Nor on 390's which were also designed for 140?

 

[hexagon789]

Regarding the speed, I was recently on a 395 and when that thing got up past 130mph the whole carriage was rocking side to side quite alarmingly! It felt like the whole bogie was oscillating and not by a small amount and was quite alarming personally. You can't blame the track either as the line speed there is 190!

I've never experienced that before on Mk4's which are also designed for 140mph running. Nor on 390's which were also designed for 140?

Ironically, I felt the Azuma I took between Edinburgh and Newcastle (and return) last month rode significantly better than the IC225 I took between Edinburgh and York in 2019.

Permitted speeds between Edinburgh and Newcastle were raised by increasing the permitted cant deficiency above the normal level, so cornering is generally more lively than south of Newcastle but the Azuma took it very well in my opinion, the Mk4 by contrast was doing some "thru'penny bit" cornering.

I will say I rode in a vehicle with the standard heavyweight "motor bogies", not in one of the vehicles with the lightweight trailer bogies which I understand have a poorer ride.

 

[Haywain]

I've never experienced that before on Mk4's which are also designed for 140mph running. Nor on 390's which were also designed for 140?

There would be a difference between being designed for 140 mph running and suspension being optimised for it. That’s my limited understanding anyway.

 

[FrontSideBus]

There would be a difference between being designed for 140 mph running and suspension being optimised for it. That’s my limited understanding anyway.

I'm not sure how much in common there is between a Javelin and an Azuma aside from their visual similarities but I experienced this "motorbike tank slapper" when it was actually doing it's design speed of 140mph!

 

[Clarence Yard]

There are two main causes of poor ride on an 80x.

The first is the anti-roll bar bushes getting worn and they need changing out. The second is that the wheelsets are getting near tyre turning (approx every 200k) or need turning. In each case the train crew should report the vehicles concerned for rough riding and Hitachi will deal with it.

 

[SamJMathis]

There are two main causes of poor ride on an 80x.

The first is the anti-roll bar bushes getting worn and they need changing out. The second is that the wheelsets are getting near tyre turning (approx every 200k) or need turning. In each case the train crew should report the vehicles concerned for rough riding and Hitachi will deal with it.

I see. So provided there is regular maintenance, they ought to ride smoothly?

There’s no known design issue?

 

[Travellin’man]

I see. So provided there is regular maintenance, they ought to ride smoothly?

There’s no known design issue?

They have always ridden roughly even from new. For an "Inter city" type train they are appalling. With the probable exception of units built by Caf they are the worst in the country. The ride quality was hopelessly under specified when ordered. Older trains ride much better. Progress is backwards.

 

[SamJMathis]

They have always ridden roughly even from new. For an "Inter city" type train they are appalling. With the probable exception of units built by Caf they are the worst in the country. The ride quality was hopelessly under specified when ordered. Older trains ride much better. Progress is backwards.

This is what I thought. What puzzles me is the near-universal understanding that this is a problem, but lack of effort to sort it or even figure out what’s causing it.

Its the same thing with the standard class seats - why is it acceptable to provide metal bars to sit on and not at least put out a statement acknowledging the issue?

 

[occone]

I'm sure it's perfectly safe, but I've had one genuinely scary ride on a GWR 80X where a few people were looking around trying to see what was going on. Someone even spoke to the conductor, and then shortly after we slowed down.

Probably the only time I've felt genuinely unsafe on the network (excluding behaviour of other people!)

 

[mike57]

What puzzles me is the near-universal understanding that this is a problem,

It part of a more general problem, "The modelling says this is how it should behave, your perception of the vibration is wrong". I have been in Engineerring 52 years (not rail related), and over the years I have been told that something 'can't' happen. I have then witnessed what 'can't' happen happen on numerous occasions, sometimes with pretty serious results. Unfortunately real world testing seems to be replaced by modelling on more and more stuff, but usually the model is software driven, and the old software engineers formula Rubbish in = Rubbish out always applies.

 

[SamJMathis]

It part of a more general problem, "The modelling says this is how it should behave, your perception of the vibration is wrong". I have been in Engineerring 52 years (not rail related), and over the years I have been told that something 'can't' happen. I have then witnessed what 'can't' happen happen on numerous occasions, sometimes with pretty serious results. Unfortunately real world testing seems to be replaced by modelling on more and more stuff, but usually the model is software driven, and the old software engineers formula Rubbish in = Rubbish out always applies.

Completely agree. I also work in engineering and I notice a general reluctance to get away from your desk and go and look at the problem you’re trying to solve. There’s a money aspect too I’m sure