Scotrail HST WSP fitment

[Railperf]

How is the program to fit WSP going? In the latest edition of Modern Railways, Ian Walmsley reports that an HST he was travelling on to Inverness came to a stand three time on the climb to Dromochter summit due to wheel slip - despite being fitted with a new westinghouse WSP system. It is reported the system was very dififcult to set up. And he noted these trains don't have sanders either - due to lineside vegetation being so close to the train and dropping leaves on to the line. The result a 91 minute delay! Apparently the low adhesion causes a 'seized' warning, which ended up limiting the train to 40mph!
That's disappointing news!!

 

[scotraildriver]

All power cars are now fitted. HSTs have never had sanders. You quite often get locked axle warnings when wheelspin happens, you normally just reset the WSP rack to clear it.

 

[Railperf]

All power cars are now fitted. HSTs have never had sanders. You quite often get locked axle warnings when wheelspin happens, you normally just reset the WSP rack to clear it.

Is the WSP improving performance or should sanders have been fitted?

 

[RiverDon]

The new WSP is good. In fact the maintenance staff are saying it is a little too good which is what is causing the locked axle indications, though they seem to be sorting this issue out now too.

I don't see them spending mega money to fit sanders to the HSTs now so late in these trains life but there is an ongoing program to fit improved sanders to the 158s and 170s which are a vast improvement on what they had previously.

 

[millemille]

The Knorr-Bremse WSP system doesn't control wheel spin/slip, only slide. The traction control electronics does this.

Walmsley is talking out of his hat.

 

[fgwrich]

On a side note, The BR / Westinghouse system on the trailers was always better than the Girling system. No wonder why some operators had tried to standardise their fleet with the former.

 

[scotraildriver]

Is the WSP improving performance or should sanders have been fitted?

It only improves braking performance and reduces wheel flats which it does well. It won't stop a train from slipping on an uphill gradient.

 

[hexagon789]

On a side note, The BR / Westinghouse system on the trailers was always better than the Girling system. No wonder why some operators had tried to standardise their fleet with the former.

As I understand it, the Girling system can only release brake pressure on a whole bogie, the BR MkIV system can do it per axle.

The Girling system also has only one WSP rack for each trailer, the BR MkIV has a rack for each axle.

The Girling system is essentially a simpler, less sophisticated design. The 312 EMUs and E&G Mk2Zs had the same system, with the same drawbacks.

 

[Railperf]

It only improves braking performance and reduces wheel flats which it does well. It won't stop a train from slipping on an uphill gradient.

How much an issue is wheel slip on acceleration compared to wheel slide on braking? 90 minute delay seems pretty bad. But how often does that happen?

 

[tumbledown]

How much an issue is wheel slip on acceleration compared to wheel slide on braking?

One will make you pass a signal at danger, potentially. But perhaps you meant something else.

 

[Railperf]

One will make you pass a signal at danger, potentially. But perhaps you meant something else.

Granted. So are we saying drivers have more faith in the braking system because drivers can now brake less cautiously than before - either to avoid passing a signal at danger and also importantly at station stops where less time can be lost?

Fixing the wheel slide issue does not improve wheel slip . How much is wheel slip an everyday issue? Would drivers prefer sanders if / when the power cars cannot get enough grip?

Are there particular locations where wheelslip under power is a common issue?

 

[tumbledown]

My physics intuition says that stopping wheelslip when decelerating is the same process as stopping it when accelerating - but the software probably treats them differently and wheel flats are only a decelerating problem.

 

[RiverDon]

Granted. So are we saying drivers have more faith in the braking system and this improves overall performance because drivers can brake less cautiously than before either to avoid a SpAd and also importantly at station stops where less time can be lost?
But fixing the wheel slide issue does not improve wheel slip . How much is wheel slip an everyday issue? Would drivers prefer sanders if / when the power cars cannot get enough grip?
Are there particular locations where wheelslip under power is a common issue?

Tbh wheelslip when accelerating isn't a huge issue with the HSTs. They do slip but the control gear deals with it and for big slips you just shut the power knob wait a few seconds and try again. You are taught how to brake and accelerate in poor adhesion conditions and just adapt your driving accordingly. They do carry sand in the luggage van in case you get stuck (stop the train and apply by hand) but I haven't heard of anyone actually using it

 

[Railperf]

Tbh wheelslip when accelerating isn't a huge issue with the HSTs. They do slip but the control gear deals with it and for big slips you just shut the power knob wait a few seconds and try again. You are taught how to brake and accelerate in poor adhesion conditions and just adapt your driving accordingly. They do carry sand in the luggage van in case you get stuck (stop the train and apply by hand) but I haven't heard of anyone actually using it

So the issue repoted by Ian Walmsley in Modern Railways was a rarity then? He says:

Three times we slipped to a stand then somehow managed to restart. ...the PA reports we have a seized wheelset...it evidently isn't becaus we are to do a rotation test - move the train a few yards back and see if it turns. It did, so we are allowed forward at 40mph.

He late claimed that the delay repay forms could have totalled appx £6000...

, probably a similar number for all the other delayed trains...you could buy a lot of chainswas with that

...to cut the vegetation back from the track to avoid the problem in the first place.

So do we need improved wheelslip protection in the form of sanders, or is Walmsley right ...the vegetation needs cutting back?

 

[RiverDon]

I have no idea who Ian Walmsley is but I take it he's a journalist rather than a driver? I can only tell you my experience of driving the things every day.

 

[Railperf]

I have no idea who Ian Walmsley is but I take it he's a journalist rather than a driver? I can only tell you my experience of driving the things every day.

He is a journalist with extensive rail experience. He was a regional railways depot engineer Cardiff Canton, transferring to Derby as maintenance and later projects engineer. Joined Porterbrook as New Trains and Development Engineer. Retired from Poterbrook in 2014.

 

[RiverDon]

Sounds like you rate his opinion then. I'll bow out here. All the best.

 

[Railperf]

Sounds like you rate his opinion then. I'll bow out here. All the best.

The magazine does, as they emply him to write regular columns. I'm only asking if his experience (as a passenger) is a common one? I never experienced any slipping as early as 2019 when they were first introduced, but there was a clear difference in how drivers seemed to approach braking compared to the 158/170's - lets say more cautious!

 

[scotraildriver]

I've never had a problem gaining traction with an HST. I suspect there may have been another issue on this occasion, perhaps one of the power cars wasn't powering properly or something. 2 power cars with only 4 or 5 coaches make light work of any gradients we have. Sanders would definitely help but there's no way Scotrail are going to go through all the development and fitting costs given the short time they have left. It's a very uncommon occurrence.

 

[Nym]

I've never had a problem gaining traction with an HST. I suspect there may have been another issue on this occasion, perhaps one of the power cars wasn't powering properly or something. 2 power cars with only 4 or 5 coaches make light work of any gradients we have. Sanders would definitely help but there's no way Scotrail are going to go through all the development and fitting costs given the short time they have left. It's a very uncommon occurrence.

Particularly with how long it would take to get a system tendered, designed and fitted.
Would do great for the scrappers...

 

[Railperf]

I've never had a problem gaining traction with an HST. I suspect there may have been another issue on this occasion, perhaps one of the power cars wasn't powering properly or something. 2 power cars with only 4 or 5 coaches make light work of any gradients we have. Sanders would definitely help but there's no way Scotrail are going to go through all the development and fitting costs given the short time they have left. It's a very uncommon occurrence.

Thanks for that. It sounded a strange incident, especially as the power cars only put out around 1770hp at the rail and the power delivery is supposedly limited under 30mph anyway.

== Doublepost prevention - post automatically merged: 30 Nov 2025 ==

Particularly with how long it would take to get a system tendered, designed and fitted.
Would do great for the scrappers...

Yes. It wouldn't ake sense to do it now - with possibly a 'new' (read replacement) fleet coming in the next 5 to 10 years. It took long enough for this latest version of WSP to be installed. I just wondered whether that should have been part of the design. but based on all the feedback so far, it doesn't sound lke it is a crucial ommission.
So are we seeing improved availability of sets due to reduced wheel flats? How is the fleet faring mechanically. And yes, we all know these are 50 year old trains now lol.

 

[millemille]

The original Invitation to Tender Notice that came out in late 2022 for the SRT class 43 WSP upgrade was actually for WSP AND sanders, but when it came to the crunch the business case for the sanders didn't work.

 

[43096]

The original Invitation to Tender Notice that came out in late 2022 for the SRT class 43 WSP upgrade was actually for WSP AND sanders, but when it came to the crunch the business case for the sanders didn't work.

Of course, what should have happened was to fit the upgrade when went through Brush before going to ScotRail. It was de-scoped for some reason - there’s a pretty simple payback on it in terms of extended bogie/wheelset life.

But then ScotRail have botched the entire HST project.

 

[Thepinkpig73]

The HSTs can struggle when taking power towards Druimuachdair, particularly if they’ve stopped at Blair Atholl or Newtonmore. I know of at least one occasion when an HST failed leaving Blair Atholl purely because of low adhesion.

 

[Railperf]

The HSTs can struggle when taking power towards Druimuachdair, particularly if they’ve stopped at Blair Atholl or Newtonmore. I know of at least one occasion when an HST failed leaving Blair Atholl purely because of low adhesion.

So mainly an issue on the Highland main line north of Blair Atholl then?

 

[Nym]

If sanding in traction is such a requirement, I'm mildly surprised that the Dual Variable Rate Sanders (DVRS) on the Turbostars didn't include an enhanced sanding in traction mode.

 

[Rockhopperr]

The HSTs can struggle when taking power towards Druimuachdair, particularly if they’ve stopped at Blair Atholl or Newtonmore. I know of at least one occasion when an HST failed leaving Blair Atholl purely because of low adhesion.

I very nearly ground to a halt in a HST this October near Dalnacardoch climbing to Drumochter. It wouldn’t even accept notch 1 of power. Lost speed from 60 all the way down to 15mph before conditions allowed traction to be regained. Happens every autumn.

 

[Railperf]

Is this vegetation issue? Or do the HST's need sanders? How do 158's and 170's perform under the same conditions?

 

[bahnause]

Is this vegetation issue? Or do the HST's need sanders? How do 158's and 170's perform under the same conditions?

Sand could help, of course. Depending on the situation, the vegetation does not even need to be nearby. An area where dirt can accumulate is sufficient.

Whether WSP improves traction transmission depends heavily on the specific type. In older types, as the word 'protection' suggests, it is purely a protective mechanism. Optimising power transmission requires computing power and a fast-responding traction control system. This is possible today with asynchronous or synchronous motors, but not so much with older vehicles that respond more slowly. This is particularly true if power/traction force can only be regulated in steps for the entire vehicle and not per axle or bogie. Maybe take a look at the Siemens XLoad Vectron that was heavily optimised for higher traction forces.