Driving DMUs with different top speeds

[Lewisham2221]

Apologies if this has been asked before, I have done a search but couldn't find anything...

When operating a train consisting of two or more DMUs with different top speeds (e.g 158+153), how does the driver remember to stick to the lower top speed when driving from the faster unit? Is there anything in the cab to facilitate this, or is it just a case of memory, or scribbling "75mph" on a bit of paper and sticking it somewhere in the cab to remind yourself?

 

[Ashley Hill]

or is it just a case of memory, or scribbling "75mph" on a bit of paper and sticking it somewhere in the cab to remind yourself?

Pretty much this.
Sometimes the guard would give the driver a gentle reminder too,especially if the speed was creeping over 75 mph.

 

[DarloRich]

surely you have to go at the speed of the slowest member.

I assume a simple aide memoire is required to remind the driver of that speed!

 

[Taunton]

Little different to the old days of making up trains from various types of stock which had different speeds - and the guard should advise the driver of the formation and thus the maximum speed as a result.

Look at the report into the Raynes Park big derailment from more than 50 years ago for what happens if this is not followed.

 

[43066]

Apologies if this has been asked before, I have done a search but couldn't find anything...

When operating a train consisting of two or more DMUs with different top speeds (e.g 158+153), how does the driver remember to stick to the lower top speed when driving from the faster unit? Is there anything in the cab to facilitate this, or is it just a case of memory, or scribbling "75mph" on a bit of paper and sticking it somewhere in the cab to remind yourself?

I haven’t actually done this, but it will be down to the driver: aide memoire, write on the diagram or whatever works for you.

The same as remembering train lengths, or remembering which speed for your stock in the case of differential speeds.

 

[Bletchleyite]

Pretty much this.
Sometimes the guard would give the driver a gentle reminder too,especially if the speed was creeping over 75 mph.

I've been on a 142 which, on the back of a 158, did go somewhat over 75 on the Hope Valley (I forget what it got up to now, it was ages ago). It was more than a little bouncy, shall we say. So I guess it happens occasionally, presumably resulting in conversations lacking in tea and biscuits when it does.

 

[ainsworth74]

I've been on a 142 which, on the back of a 158, did go somewhat over 75 on the Hope Valley (I forget what it got up to now, it was ages ago). It was more than a little bouncy, shall we say. So I guess it happens occasionally, presumably resulting in conversations lacking in tea and biscuits when it does.

I'm sure someone mentioned the time that a poor 153 got taken to 100mph whilst attached to a 170 once.

 

[Sly Old Fox]

153s aren’t known as caravans for nothing.

 

[craigybagel]

ERTMS fitted 158s have a handy feature where when you set up the system (which you have to do every time you change direction or formation) you can tell it if there are any 75mph vehicles in the formation, and if you drive much over 75mph it will sound a warning in the cab, and eventually apply the brakes

 

[RailWonderer]

ERTMS fitted 158s have a handy feature where when you set up the system (which you have to do every time you change direction or formation) you can tell it if there are any 75mph vehicles in the formation, and if you drive much over 75mph it will sound a warning in the cab, and eventually apply the brakes

Despite having a 90mph top speed I was always sure a 158 could be geared up to 100mph if needed. They ride solidly at 90 and the engines have just about enough power.

 

[tramdan]

Some of our drivers (when working 158+156 pairs) would stick a little bit of electrical tape onto the 158 speedo at the 75mph position as an aid memoir.

 

[craigybagel]

Despite having a 90mph top speed I was always sure a 158 could be geared up to 100mph if needed. They ride solidly at 90 and the engines have just about enough power.

A Cummins 158 maybe - with a Perkins 158 it can be a struggle to even hit 90 without gravity assistance

 

[norbitonflyer]

Similar problem with some 1st generation DMUs - some had automatic (hydraulic) transmissions but were supposedly compatible with those with mechnical transmissions - including having a gear shift lever to control the gears in a mechanical unit when beiong driven from the cab iof a hydraulic unit. Inevitably drivers occasionally had lapses and forgot to change gear, resulting in damage to the engine and transmission of the mechanical unit as it raced along at 50mph whilst still in 1st gear. Eventually the hydraulic units - which would later be classified 113 and 127) were given a different coupling code (red triangle instead of blue square) and, in the case of the 127s, confined to the St Pancras- Bedford line. Neverthless the trailer cars remained interchangeable with those of Class 115, and indeed when the 127s were withdrawn following electrification several of them found a new home at Marylebone.

 

[Wilts Wanderer]

Similar problem with some 1st generation DMUs - some had automatic (hydraulic) transmissions but were supposedly compatible with those with mechnical transmissions - including having a gear shift lever to control the gears in a mechanical unit when beiong driven from the cab iof a hydraulic unit. Inevitably drivers occasionally had lapses and forgot to change gear, resulting in damage to the engine and transmission of the mechanical unit as it raced along at 50mph whilst still in 1st gear. Eventually the hydraulic units - which would later be classified 113 and 127) were given a different coupling code (red triangle instead of blue square) and, in the case of the 127s, confined to the St Pancras- Bedford line. Neverthless the trailer cars remained interchangeable with those of Class 115, and indeed when the 127s were withdrawn following electrification several of them found a new home at Marylebone.

And at Tyseley. The intermediate trailers without toilets found their way into the Tyseley ‘Quad’ sets that worked (mainly) the Cross City line until about 1993.

 

[dk1]

It was something we used to pay little attention to. Most 150, 153, 156 classes will happily cruise along at 87mph on their own let alone with help from a 158 or 170. These days the darn OTMR has ruined all the fun of the fair.

 

[berwicksfinest]

I've been on a 142 which, on the back of a 158, did go somewhat over 75 on the Hope Valley (I forget what it got up to now, it was ages ago). It was more than a little bouncy, shall we say. So I guess it happens occasionally, presumably resulting in conversations lacking in tea and biscuits when it does.

I think I might know all about this !!!! That was one of Peterborough's finest

 

[61653 HTAFC]

I've heard of stories from guards having to buzz drivers of 158s to remind them they had a 75mph unit on the back. In particular one involving a 144 being dragged at 95mph in the days before OTMR.

Can't recall if it was debunked or not, but it's been mentioned on here in the past that units are tested at the maximum permitted speed +10%- as part of the certification process. Which would mean 158s tested at 99mph, and Pacers and 153s tested at 82.5mph.

 

[Doctor Fegg]

There were reports on uk.railway many years ago of 158s approaching 110mph in their very early days (can’t remember the exact speed).

 

[Wilts Wanderer]

It was something we used to pay little attention to. Most 150, 153, 156 classes will happily cruise along at 87mph on their own let alone with help from a 158 or 170. These days the darn OTMR has ruined all the fun of the fair.

The unit might have been happy, but the passengers most likely weren’t! Yaw dampers are fitted to 80mph+ stock for a good reason.

== Doublepost prevention - post automatically merged: 20 Jun 2023 ==

There were reports on uk.railway many years ago of 158s approaching 110mph in their very early days (can’t remember the exact speed).

Several overspeed incidents led to the engines being governed to shut power off at 93mph. When I was commuting through the Severn Tunnel for several years, it was clear which drivers were routinely hitting this limit between Patchway and Pilning on the falling 1:68 of the down line.

 

[william.martin]

If let's say a 150+158 traveled at (for example) 85MPH with the 158 leading would some kind of emergency overspeed system kick in on the 150?

 

[185]

Pacers used to wobble at 90 when stuck on the back of a 158. You'd get to the back of the 158 after doing tickets, blissfully unaware, open the cab door and swear extremely loudly whilst running to the cab to cab handset.

 

[Taunton]

Similar problem with some 1st generation DMUs - some had automatic (hydraulic) transmissions but were supposedly compatible with those with mechnical transmissions - including having a gear shift lever to control the gears in a mechanical unit when beiong driven from the cab iof a hydraulic unit. Inevitably drivers occasionally had lapses and forgot to change gear, resulting in damage to the engine and transmission of the mechanical unit as it raced along at 50mph whilst still in 1st gear. Eventually the hydraulic units - which would later be classified 113 and 127) were given a different coupling code (red triangle instead of blue square) and, in the case of the 127s, confined to the St Pancras- Bedford line. Neverthless the trailer cars remained interchangeable with those of Class 115, and indeed when the 127s were withdrawn following electrification several of them found a new home at Marylebone.

It was a silly design; quite late in dmu development Cravens were given a substantial order (their last) for 100 dmu cars, half with mechanical and half with automatic hydraulic transmission. For some reason the mechanicals were sent to St Pancras, where the bulk of the existing fleet was automatic hydraulic, and drivers were expected to always remember this odd gearshift was required. There were various issues of course, exacerbated by no safety freewheel device being incorporated for overspeeding, plus the transmission was adjacent to the fuel lines so when it overheated and broke up, it flailed the fuel lines. They were a rather flawed design overall, and although some of the newest dmu vehicles, were among the first to be retired and scrapped.

 

[dk1]

If let's say a 150+158 traveled at (for example) 85MPH with the 158 leading would some kind of emergency overspeed system kick in on the 150?

No, nothing like that is fitted to these units although if these days connected to real time fleet technical systems it would flag up as going beyond the maximum design speed.

 

[Horizon22]

I haven’t actually done this, but it will be down to the driver: aide memoire, write on the diagram or whatever works for you.

The same as remembering train lengths, or remembering which speed for your stock in the case of differential speeds.

Or when to speed up after the TSR/ESR dependent on coach lengths etc etc. All things drivers need to be professionally aware of in the cab!

 

[InkyScrolls]

A Cummins 158 maybe - with a Perkins 158 it can be a struggle to even hit 90 without gravity assistance

I have experienced the former at 96 mph, once, which rather surprised me.

 

[12LDA28C]

On Chiltern's units the driver was required to input the maximum speed of the formation into the ATP system when setting up the leading cab. Once this was done the maximum speed would be displayed on the speedo and the ATP would warn the driver if that was exceeded, applying the brake if they failed to react. Of course this would only work if the driver took care to observe the full length of their train prior to setting up the cab.

 

[D365]

On Chiltern's units the driver was required to input the maximum speed of the formation into the ATP system when setting up the leading cab. Once this was done the maximum speed would be displayed on the speedo and the ATP would warn the driver if that was exceeded, applying the brake if they failed to react. Of course this would only work if the driver took care to observe the full length of their train prior to setting up the cab.

ETCS is much the same, from my understanding.

 

[pokemonsuper9]

Of course this would only work if the driver took care to observe the full length of their train prior to setting up the cab.

Isn't that very simple to do by just looking at the train?

 

[D6130]

Most 150, 153, 156 classes will happily cruise along at 87mph on their own let alone with help from a 158 or 170.

Can't recall if it was debunked or not, but it's been mentioned on here in the past that units are tested at the maximum permitted speed +10%- as part of the certification process. Which would mean 158s tested at 99mph, and Pacers and 153s tested at 82.5mph.

Really? The maximum speed I ever managed to get out of a single 153 running on its own was 69 mph....and that was on a non-stop training run between York and Scarborough!

 

[pokemonsuper9]

Really? The maximum speed I ever managed to get out of a single 153 running on its own was 69 mph....and that was on a non-stop training run between York and Scarborough!

York to Scarborough seems to be on a very slight incline/decline, maybe they could achieve that speed with a steep decline to have gravity help?