Bumping and jerking HST

[marks87]

The thread title is obviously not unheard of but this is particularly bad.

I'm currently on an LNER HST that has been jerking about at least since I boarded 40 minutes ago. It's almost as if the rear power car is randomly pushing harder than the front is pulling.

Is that possible? Or could it be any number of things? Not exactly comfortable either way.

We are also late and in reverse formation.

 

[Mintona]

Could well be poor railhead conditions. The train I was on this morning was suffering with the same. A lot of leaves have come down in the stormy weather in the last 24 hours, and mixed with some rain and no railhead treatment trains yet it’s not an ideal situation.

 

[Kneedown]

Sounds a lot like wheelslip. When the leading power car encounters wheelslip, the load regulator reduces power to the main alternator windings to regain traction. This results in the rear power car, still at full power, lurching into the coaches and causing the effect you describe. More lurching occurs when the leading power car regains traction and pulls on the coaches.
It's a common occurance throughout leafall, and also any time of year if the rails are damp with drizzle following a dry spell.

 

[Journeyman]

The thread title is obviously not unheard of but this is particularly bad.

I'm currently on an LNER HST that has been jerking about at least since I boarded 40 minutes ago. It's almost as if the rear power car is randomly pushing harder than the front is pulling.

Is that possible? Or could it be any number of things? Not exactly comfortable either way.

We are also late and in reverse formation.

I had an absolutely terrible ride on an LNER HST last month, that was bouncing and jerking all over the place. It spilt about half a cup of coffee over the table, it was that bad. Added to that, the squeaking and rattling from the suspension and gangways was really annoying, and far worse than the at least constant and predictable sound from an underfloor engine.

They were great trains once, but it's time they were bean cans in my opinion.

 

[nat67]

Could there not also be a reason that as I have noticed when you start to move of from let's say Reading, the back power car pushes as little and the buckeye and corridor gangways push up hard together, wither that could be a slight lag between the controls of both power cars i'm not sure.

 

[eastwestdivide]

The last few runs I've had on LNER/VTEC HSTs, dating back to spring/summer, have seemed pretty bumpy. I suspect the maintenance isn't up to scratch somewhere.

 

[mrcheek]

This always seems to be more of a problem on the ECML. GWR HSTs were always a much smoother ride

 

[iantherev]

This always seems to be more of a problem on the ECML. GWR HSTs were always a much smoother ride

I think 'were' is the important word here. If anything it's more noticeable on the short set.

 

[DarloRich]

The last few runs I've had on LNER/VTEC HSTs, dating back to spring/summer, have seemed pretty bumpy. I suspect the maintenance isn't up to scratch somewhere.

the old maintenance run down prior to withdrawal trick?

 

[nat67]

the old maintenance run down prior to withdrawal trick?

And the BT10 bogies, if they are a bit run down and haven't been overhauled recently, plus the track on the ECML may not be brill I know that north of York its bumpy especially through Northallerton.

 

[Mag_seven]

plus the track on the ECML may not be brill I know that north of York its bumpy especially through Northallerton.

Similarly, the ride quality on an HST between Didcot and Swindon used to be awful - much better now though.

 

[marks87]

Thanks for all the replies.

Sounds a lot like wheelslip. When the leading power car encounters wheelslip, the load regulator reduces power to the main alternator windings to regain traction. This results in the rear power car, still at full power, lurching into the coaches and causing the effect you describe. More lurching occurs when the leading power car regains traction and pulls on the coaches.
It's a common occurance throughout leafall, and also any time of year if the rails are damp with drizzle following a dry spell.

That would make sense.

Presumably it's either not possible, or more undesirable, to reduce power to the rear power car at the same time to equalise things?

 

[thaitransit]

Try spending over 24 hours on these trains. Bouncing all over the place and constant squeaks and rattling throughout the trip. Its especially bad in Car A. Which means trying to get some sleep in the sleeping berths can be tough.

They need replacement ASAP preferably with modern diesel tilt train stock that will be squeak and rattle free!

 

[TractiveEffort]

Thanks for all the replies.



That would make sense.

Presumably it's either not possible, or more undesirable, to reduce power to the rear power car at the same time to equalise things?

The wheelslip detection system is individual to each power car and works by detecting a variance in traction motor voltage between motors.

 

[marks87]

The wheelslip detection system is individual to each power car and works by detecting a variance in traction motor voltage between motors.

Thanks.

I guess what I was thinking (and this is purely a lay person dumping their thoughts) is that if wheelslip is detected in either power car via their independent systems, the signal for the load regulator is sent to both.

 

[Kneedown]

Thanks for all the replies.



That would make sense.

Presumably it's either not possible, or more undesirable, to reduce power to the rear power car at the same time to equalise things?

It is preferable to maintain traction where possible. I usually reduce power by a notch or two when encountering wheelslip to reduce the harsh jolting, but you can't always eliminate it. Wheelslip is common to all traction, but the effect is felt more on an HST due to the buckeye couplings between coaches.

 

[GrimShady]

My understanding is the setup on Class 43 with the following Power Car was set to output slightly less power to reduce surging.

Maybe someone with more technical knowledge can comment.

 

[Rail Blues]

I'm sure they'll be some of the mk3 fan boys on soon to tell us that it is all in our heads and they've never travelled on a Mk3 that is anything less than magic carpet like.

 

[TractiveEffort]

My understanding is the setup on Class 43 with the following Power Car was set to output slightly less power to reduce surging.

Maybe someone with more technical knowledge can comment.

If the rear power car is on train supply, as is normal, the power will be very slightly reduced, but hardly noticeable. It can help to reduce power on the front power power car as that is the one that usually slips the most.

 

[scotraildriver]

HSTs are also not fitted with sanders so no way of reducing wheelslip/wheelslide with sand, unlike most other trains.

 

[GrimShady]

HSTs are also not fitted with sanders so no way of reducing wheelslip/wheelslide with sand, unlike most other trains.

Any particular reason why BR never designed them as such?

 

[GrimShady]

I'm sure they'll be some of the mk3 fan boys on soon to tell us that it is all in our heads and they've never travelled on a Mk3 that is anything less than magic carpet like.

I would count myself as one of them however I'm very much aware there's some pretty bad ones out there particularly with LNER. It tends to be over 100mph they have issues.

I do actually prefer MK4 on the ECML. MK4 can feel dodgy at times while being propelled at line speed on the curves north of Newcastle.

 

[Dren Ahmeti]

I do actually prefer MK4 on the ECML. MK4 can feel dodgy at times while being propelled at line speed on the curves north of Newcastle.

Try Didcot East Junction and the Avoiders on the MkIII’s at line speed!

 

[nat67]

Similarly, the ride quality on an HST between Didcot and Swindon used to be awful - much better now though.

I guess they have replaced some of the rail sections.

 

[rich-leeds]

There's an interesting discussion on Twitter on this topic. Suggestion is that GWR and VTEC /LNER have switched damper supplier which is leading to compromised ride quality.

Roger Ford (@Captain_Deltic) tweeted at 3:11 pm on Tue, Sep 04, 2018:
Same on ECML. Reputedly due to a combination of a cheaper supplier of dampers and running to end of life.
(https://twitter.com/Captain_Deltic/status/1036980104122060800?s=09)

 

[superkev]

There's an interesting discussion on Twitter on this topic. Suggestion is that GWR and VTEC /LNER have switched damper supplier which is leading to compromised ride quality.

Roger Ford (@Captain_Deltic) tweeted at 3:11 pm on Tue, Sep 04, 2018:
Same on ECML. Reputedly due to a combination of a cheaper supplier of dampers and running to end of life.
(https://twitter.com/Captain_Deltic/status/1036980104122060800?s=09)

I also read somewhere in line with the UK"s consultant culture rather than return to the original damper supplier east coast had appointed a consultant.
K

 

[43367]

There are quite a few LNER powercars running around with traction motors isolated at the moment, so this may have an effect on the ride quality, i.e. if the front powercar has 2 out of 4 motors isolated then the rear powercar is more powerful, and will cause the feeling of getting shoved from behind, a bit like when the class 91 is pushing a MK4 set towards London, however with the Mk4 this is cushioned by the device above the coupling, I forget the proper technical term maybe its a dampner or something.
With the HST's though there is nothing to cushion it when the rear power car is doing more work than the front which causes it to be more jerky and violent

 

[HaggisBotherer]

Added to that, the squeaking and rattling from the suspension and gangways was really annoying

One thing I will miss about the HSTs when they finally go is the cacophany of screeching in the gangway areas, especially as they lurch around the curves across Fife and Aberdeenshire. For me it's as characteristic as that odd screaming sound from the wheels when at speed on certain stretches of the ECML.

What causes that, incidentally?

 

[Journeyman]

One thing I will miss about the HSTs when they finally go is the cacophany of screeching in the gangway areas, especially as they lurch around the curves across Fife and Aberdeenshire. For me it's as characteristic as that odd screaming sound from the wheels when at speed on certain stretches of the ECML.

What causes that, incidentally?

This is what I find very hard to cope with on HSTs, it's a really grating sound that just irritates the hell out of me. I find underfloor engines much easier to stomach, given that modern trains have gangways that don't incessantly squeal and rattle.

 

[Rail Blues]

This is what I find very hard to cope with on HSTs, it's a really grating sound that just irritates the hell out of me. I find underfloor engines much easier to stomach, given that modern trains have gangways that don't incessantly squeal and rattle.

It is like nails down a chalkboard to me. I have often wondered why folk who complain about the noise of underfloor engines often find this one of the MK3's charming idiosyncrasies or similarly will get all excited about the hell fire thrash being generated by loco.