I'm currently sat on an IET having shortly left Paddington and enjoying what I can safely say is the most anxiety raising railway journey I've ever had. The train at times is shaking so hard it feels like its going to come apart, even the vestibule doors were having trouble staying closed. It seems the driver is aware of the problem as the train, after reaching linespeed at Ealing, has dared got anywhere near since. It almost seems like the bodyshell isn't attached to the bogie properly so running over points at high speed makes the whole thing shake. What's going on with these trains??
Not to impune your point, and while not had the pleasure of riding these new trains, going back to before they started , and before I was too ill to work , I had a career in IT technical, it took me far and wide, I had a project, based at little Rissington , and the nearest station was Kingham ( prer redoubling ), I mentioned this because rather than drive and pay the congestion charge or stress of parking , etc etc .
I took the train, I always found that even a HSzt in first class , could be quite ' lively ', I recall feeling a little unnerved, heading toward Kingham from Paddington on a HST set , and it was really noticeably ' lurching ', squealing and squeaking over a lot of track between the start at Paddington, and seemed to carry on for a fair few miles , it wasn't as bad sat in the centre of the coach.
I usually paid then then £10 premium to sit in first class, as it was often much quieter and calming.
But this only magnified , the sounds of what was probably a lot heavier train set , over , clearly rough track , point work and perhaps like some roads, places where the sub base , ( foundations) beneath the ballast had sunk slightly, perhaps allowing the track to drop and be enough it was perceivable from inside the train.
Mostly it was a HST , despite the mad dash on arrival at Kingham to find a door near the platform ( back then the platform was too short for a full length HST).
But it wasn't just the HST, I must be among the few that liked the Adalante class 180 , ( I used them on Hull trains to go home to my then Yorkshire home after my working week ), anyway .
That class of train, although some may disagree, and in first class and second was very smooth ( that said I'm not anywhere near as knowledge as you guys on trains and railways but am very interested).
Anyway the ride again to and from Paddington , got very lively , if anything the 180 did smooth out some parts the HST's , ' lurched over ', ( perhaps a more modern and better sprung and dampened bogie ?) , anyway those units did seem to sway , perhaps more than the HST , it wasn't easy to do a direct comparison, as during the outbound mornings it would be a HST for capacity , the 180's seemed to run later or as a stopper , like the Hull trains , on longer straight track sections , on the Great Western line , it was fine, but again , from Paddington, you could feel a lot of sideways movement , and the squeaks the interior fit and finish , I forgot to add , about the HST that the vestibule door not staying shut on the IET is not unique, it occured each time I was on a HST over rough track.
Sharp bends and sometimes points .
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My final comparison, would be the time, my business partner and I had taken a very nice smooth ride in the morning on a HST, on our return trip we'd finished early , but the station was rammed, after an earlier incident, we accidentally got directed to the wrong train , and thus were disgusted by it being a class 465 or 466 turbo ,now if you want hard, jumpy , noisy and worrying , that would be it .
Luckily we got off at reading and changed to the correct train.
I must say it was quite haur raising and i remember the poor ticket person , saying when I asked why it was swaying around so much , he said to me that it's down to the age and sheer amount of trains that over time had worn out the track for several miles from the buffers at Paddington.
Now I don't know if when it was electrified , if that track was ever rectified, but it's no surprise, given how busy that line can be.
Also the HST's I recall as a kid in the mid 80's, going south to visit relatives in Wales, just how bumpy and wild the ride could be , it was when they were installing the over head line masts, and track works were happening , the bit between Sheffield and Derby seemed worse , not to mention, most HST's I've ever been on when braking hard , smelt very strongly of burnt rubber.
Sorry for the long reply but I wanted to share my experience of that line , and while I cannot comment on the IET , one thing I would say is, if the Bogies where designed in Japan ( as the AT300)IET like it's class 395 sibling ) are based on the Japanese ' A' train , indeed you see their one is very similar, but the thing is , they have a huge amount of very high speed and quality lines, which have to be smooth .
So I do wonder if it's down to the Bogies not being cushioned enough , or being ' sprung ' enough , a bit like a hard sports saloon suspension, is there no way these trains can have the Bogies modified for greater comfort ?.
If you read in magazines or the books on the HST's so many of the issues spoken of today about the IET/Azuma were levelled at the then new HST sets .
Finally you don't hear of people saying this of the TPE 80X train sets ?.