Double heading of diesel & electric freight trains

[PM47079]

Where do they double head?

I have commuted on the southern section of the WCML for 16 years & have never seen double headed 90s.

They do the Russell traffic which is I believe daventry mossend. Three pairs are involved. Someone may need to correct the destination as I may not be 100%

[keefer]

The Ravenscraig iron ore PTA tipplers were triple-headed 37s to get up past Holytown.

Sometimes a cl.26 was used as the 3rd loco.

Initially the (coal) trains were banked by the third loco but after derailments, the third loco was added to the front.

[Edwin_m]

Thank you to all that have replied already.

 

Will someone correct me if I’m wrong on my physics here:

 

Tractive effort is the ability to physically put down power to get things moving, but once moving it’s more about the power (drawbar horsepower?) up front as to how quick that load moves. Thus an 08 with high tractive effort but a low horsepower of 350hp can move heavy loads, but not that quickly?

 

One would assume that tractive effort is a formula of power at rail (geared as required) and weight of the loco, through however many driven axles?

 

Brake force then is not so important on modern fully fitted trains, but more so on older unfitted trains? I’m thinking of an example of trying to stop Mrs Foden’s full shopping trolley at ASDA after she’s been paid. Mrs Foden is a much smaller class 20 and would find it harder to stop the unfitted trolley than the ‘ahem’ larger class 40 Mr Foden, who could stop a heavier trolley sooner.

 

But if the trolley had its own brakes like the luggage ones at the airport, the brake force is in the trolley, so becomes less of a consideration, only then the ability to get the trolley moving?

 

As a side note, what’s the difference in real terms between starting or peak tractive effort, and continuous?

 

In physics terms tractive effort is a force not a power.  It's usually expressed as a weight, as if a cable was hung over the coupling hook and round a giant pulley to lift that weight out of a well. 

 

The starting tractive effort is the weight on the motored wheels multiplied by the achievable coefficient of friction between the wheels and the rails.  More modern designs of locomotive have various tricks to increase the coefficient of friction so they can "pull harder" than an older loco of the same weight.  And the poor old Class 40 suffers by having some of its weight on unmotored axles so it doesn't contribute to tractive effort (though as those axles are braked it does contribute to brake force). 

 

Physics again, work equals force times distance.  Power is the rate of doing work over time, and speed is the rate of travelling distance over time, so power equals force times speed.  As a loco accelerates while maintaining the same (starting) tractive effort, the amount of power needed increases until it hits the maximum power available.  Above that speed tractive effort falls.  For reasons to do with how an electric motor works it actually falls even more, especially with DC motors, and resistance also increases with speed so there comes a "balancing speed" where the tractive effort matches the resistance and the train can go no faster except, as the saying goes, downhill with the wind behind it (an ascending gradient has a similar effect to increasing resistance). 

 

A more powerful locomotive may have no more tractive effort, so can only get the same weight of train moving, but once moving it is less limited by maximum power so can pull the load faster.  The power of a diesel is limited by the power the engine can provide, less the various losses.  However the limiting factor on the power of an electric locomotive is how hot the equipment gets, so it has a "peak" power exceeding the "continuous" power for a short period.  This doesn't affect tractive effort when starting, because that it limited by weight and friction, but it makes a difference at higher speeds and is one reason why an electric of the same power will reach its maximum speed in much less time than a diesel.  I've never heard "continuous" or "peak" applied to tractive effort, possibly because both values would be speed-dependent so wouldn't be that useful to quote. 

Edited September 3, 2018 by Edwin_m

[keefer]

Al Krug's website has lots of info on power, T.E. etc (particularly regarding US operations)

 

http://hm.evilgeniustech.com/alkrug.vcn.com/rrfacts/rrfacts.htm

 

(Hosted by someone as the site itself is offline)

[Downendian]

Some 1970s recollections of routine double headers in the Bristol area

Pairs of 25s and less frequently class 31s on trains of fertiliser from Avonmouth in VVVs (presumably required for the Lickey incline) heading North.

Pairs of 37s on Tytherington stone trains of PGAs (in the period between the Westerns and class 56s which operated singly, 1977-79)

Pairs of 47s (sometimes a class 46 and 47) on South Wales MGR coal trains to Didcot

Class 37 banking the Danygraig-Stratford freightliner as far as Stoke Gifford, with either a 47, 46 or 52 taking the train forward. To assist the climb from the Severn tunnel from STJ.

Pairs of LMR 25s on Adex summer Saturdays to the South West

Pairs of Bath road 25s on the PW trains needed for the 1975/6 HST GWML upgrade.

And of course often any type 4 loco assisting a failed class 50 in that era.

Neil

Edited September 3, 2018 by Downendian

[APOLLO]

They do the Russell traffic which is I believe daventry mossend. Three pairs are involved. Someone may need to correct the destination as I may not be 100%

 

Yes most days a couple of electric double headers pass my house north of Wigan. They go at one hell of a lick northbound up the 1 in 105 of Boars head bank and are quite noticeable sound wise.

 

Brit15

[DY444]

90s draw too much current to work as a pair on the GEML. That's why they are paired up on the WCML as the overhead lines are beefed up a bit more.

 

Whilst the current limit on the WCML is higher a pair of class 90s still draw too much current to operate without restriction.  The restriction being that one locomotive has to have a traction motor isolated so a pair of 90s on the WCML run with only 7 traction motors in operation. 

Edited September 4, 2018 by DY444

[The Stationmaster]

Not true. With a class 66 the stopping force is in the train, as the loco brakes are not very good. We used to work the Dee Marsh steel trains with a mix of traction. sometimes a pair of heavyweight 37's or 56's would substitute for a single 60, simple because the load for a single 60, or later 66, was far in excess of a single 37/7 or 56, so two would be required. Even then the load would be kept the same as a 60, although in theory a pair of 56's could haul more, to keep withing the max weight limit of the train. A train would always be dictated by the stopping force available, be it an unfitted, partially fitted or fully fitted train. The first thing I would check on the drivers slip was the brake force. If i had a brake force of at least one third the train weight, I was confident I could stop it at any speed. in the case of the Burngollow tanks, when they ran empty, the brake force was almost the same as the train weight. They used to be dangerous trains to work, as put too much brake on, and they'd put you through the drivers window. With unfitted and partially fitted trains, an extra loco on the front would give you the luxury of more brake force, but then the powers that be might up the load of the train, so you where back in the same position as if you had a single loco.

 

Paul J.

 

Exactly the so - the additional Brake Force you get from adding a second loco is chickenfeed compared to the Brake Force within the train; as with most trains it is the the train which provides the major part of the brake power and not the traction unit on the front.  

 

Don't forget we were working 5,000 ton stone trains out of the Mendips with a single Class 59 a long time ago and when we did the 5,000 ton test out of Whatley Quarry we only had the second loco in case the train engine was overpowered pulling up round Clink Road Jcn - as it worked out the single loco coped but the super-creep cut in to keep the train moving and prevent the loco from slipping.  And those trains were timed to run, back then, in 60 mph timings which they could easily achieve east of Reading and on the falling gradients west of there - and they would not have been timed that fast if they couldn't stop!

 

We moved to pairs of 37s on the Mendip stone trains purely to be able to increase the train load compared with a single Class 56 but we paid a penalty in reduced speed over the steepest sections of rising gradient.  Similarly when the 59s arrived we got a major lift in the trailing tonnage we could handle but, as with the paired 37s, we paid a penalty in loss of speed.  Exactly the same happened with the (West wales -) Theale tanks were we used pairs of 37s to increase the load but we had complaints from Drivers about poor performance climbing out of the bottom of the Severn Tunnel and when I put a Traction Inspector on to investigate it was clear that speeds out of the dip in the Tunnel were down to walking pace although the train was actually only losing a couple of minutes because the timings took account of the load.  Once the 60s were available we got much better performance.

[Rugd1022]

They do the Russell traffic which is I believe daventry mossend. Three pairs are involved. Someone may need to correct the destination as I may not be 100%

 

It's the Coatbridge - DIRFT - Coatbridge circuit, it usually arrives at Daventry at 06.50 with a Crewe man (or woman) who stays with the locos in the north end shunt neck while the wagons are stripped and reloaded in the Russells terminal, they then take the loaded train back north at 12.18.

[Foden]

Thank you for all the replies so far, it’s made a lot more sense of things.

 

Exactly the so - the additional Brake Force you get from adding a second loco is chickenfeed compared to the Brake Force within the train; as with most trains it is the the train which provides the major part of the brake power and not the traction unit on the front.

 

Don't forget we were working 5,000 ton stone trains out of the Mendips with a single Class 59 a long time ago and when we did the 5,000 ton test out of Whatley Quarry we only had the second loco in case the train engine was overpowered pulling up round Clink Road Jcn - as it worked out the single loco coped but the super-creep cut in to keep the train moving and prevent the loco from slipping. And those trains were timed to run, back then, in 60 mph timings which they could easily achieve east of Reading and on the falling gradients west of there - and they would not have been timed that fast if they couldn't stop!

 

We moved to pairs of 37s on the Mendip stone trains purely to be able to increase the train load compared with a single Class 56 but we paid a penalty in reduced speed over the steepest sections of rising gradient. Similarly when the 59s arrived we got a major lift in the trailing tonnage we could handle but, as with the paired 37s, we paid a penalty in loss of speed. Exactly the same happened with the (West wales -) Theale tanks were we used pairs of 37s to increase the load but we had complaints from Drivers about poor performance climbing out of the bottom of the Severn Tunnel and when I put a Traction Inspector on to investigate it was clear that speeds out of the dip in the Tunnel were down to walking pace although the train was actually only losing a couple of minutes because the timings took account of the load. Once the 60s were available we got much better performance.

What a fascinating read! Thank you for sharing these anecdotes.

 

However, one would have thought that 2x 37 would easily outpower a single 56, how much extra tonnage were the pair of 37s moving?

[Foden]

Out of interest, is there readily available literature out there which outlines what each class of TOPS loco is restricted to operate in tonnage?

Don’t suppose anyone has access to the above info they wouldn’t mind sharing, or linking to?

[Pete the Elaner]

Thank you for all the replies so far, it’s made a lot more sense of things.

 

 

What a fascinating read! Thank you for sharing these anecdotes.

 

However, one would have thought that 2x 37 would easily outpower a single 56, how much extra tonnage were the pair of 37s moving?

I remember reading once that you get less than twice the performance when double heading.

[jonny777]

I seem to remember from the 1970s, a double headed class 47 coal train working past Willesden (using that phrase in a relaxed sense) on the lines from Brent to Acton Wells Junction. I only used to see it occasionally when trainspotting or from passing trains on the WCML, but I have no idea where it was heading or if the second loco was attached part way through the journey to assist on gradients across London. 

 

Double headed 47s were a rare sight (apart from failures) in those days, and so any occurrence stuck in my mind. 

[Dungrange]

Out of interest, is there readily available literature out there which outlines what each class of TOPS loco is restricted to operate in tonnage?

 

I could be wrong, but I'm sure that varies by route depending on gradients etc, so I doubt you'll find a comprehensive list.

[Fat Controller]

I seem to remember from the 1970s, a double headed class 47 coal train working past Willesden (using that phrase in a relaxed sense) on the lines from Brent to Acton Wells Junction. I only used to see it occasionally when trainspotting or from passing trains on the WCML, but I have no idea where it was heading or if the second loco was attached part way through the journey to assist on gradients across London. 

 

Double headed 47s were a rare sight (apart from failures) in those days, and so any occurrence stuck in my mind. 

Coal for Northfleet cement works; sometimes 2 x Brush 4, sometimes Peak in tandem with a Brush 4.

[jonny777]

Wow, thanks. That has answered a question I have had in my head for 45 years.

[Rivercider]

Thank you for all the replies so far, it’s made a lot more sense of things.

 

 

What a fascinating read! Thank you for sharing these anecdotes.

 

However, one would have thought that 2x 37 would easily outpower a single 56, how much extra tonnage were the pair of 37s moving?

For comparison the 1993 Freight Train Loads book shows the following loads.

 

Milford Haven - Theale (via Felin Fran) maximum loads including loco(s)

2 x 37 = 2010 tonnes (clear run reqd 199m to 194m)

56 = 1576 tonnes 

 

Merehead - Acton via B&H (bogie vehicles)

2 x 37 = 2760 tonnes

56 = 2680 tonnes (clear run reqd 72mp to 70mp) 

 

cheers

[Gwiwer]

While on the subject of multiple heading of freights let us not forget the triple and quadruple-heading which occurred on the Burry Port & Gwendraeth Valley route.  Not with main line types but with class 03 shunters.  Those with the cut-down cabs for working on this very tight loading-gauge line.

 

I never did know whether those trains were multiple-headed for tractive effort, brake force or a combination of both, nor whether all or part of the train was not fitted with an automatic brake.  Coal trains in the Welsh valleys were not always fully braked as I recall which led to one or two runaways over the years.

[Swindon 123]

I have just found the notes I made on my MP12 course, regarding assisted loads for diesel locos. They make interesting reading. These notes were made back in 1984, when we were still training on making your own train lists, without the aid of TOPS. The rules regarding company block load trains were slightly different, and with the introduction of the class 59, 60 and 66, some of the requirements were amended.

 

 

With regards to doudle heading, and triple heading with 03's on the BPGV, it was all down to the HP required to get the train up there. Multi working on 03's had already been proven on the ER when it was mooted, and cutting down an 03 was easier than an 08, plus BR had lots of them around with not a lot to do. The one thing I was told to remember with unfitted trains,  is that it was always at the drivers discretion to pin down brakes if he was doubtful about descending a train down an incline. Most didn't as it took time to pin them down and take them back up again, hence the occasional mistakes.

 

Paul J.

[Downendian]

Coal for Northfleet cement works; sometimes 2 x Brush 4, sometimes Peak in tandem with a Brush 4.

  

Some 1970s recollections of routine double headers in the Bristol area

Pairs of 47s (sometimes a class 46 and 47) on South Wales MGR coal trains to Didcot

 

Neil

Hi Brian, I'm wondering now if this was the same working passing through Bristol. I distinctly remember it being MGR hoppers. Do you know what wagon types were used?

Neil

[Fat Controller]

   Hi Brian, I'm wondering now if this was the same working passing through Bristol. I distinctly remember it being MGR hoppers. Do you know what wagon types were used?

Neil

The one seen in North London would have originated in the Nottingham or Derbyshire coalfield, and worked to Kent; the second loco was added at Cricklewood, to give better acceleration on the very busy South-Eastern Division lines.

If the trains you saw had a Brush Type 4 as a train engine, with another diesel coupled in front, it would probably have been a South Wales- Didcot working, with the pilot loco dropping off at Stoke Gifford.

There was another working of MGR hoppers through Bristol in the early 1970s- the fly-ash trains from Aberthaw to various places along the route of the M5. These were worked by pairs of Class 37.

[SED Freightman]

A quick look in the WTT commencing 06/05/1974 shows the following double headed MGR services between Brent (Cricklewood) and Northfleet, all of which have a maximum load of 2059 Tons :-

 

6O85 0832 (SO) Boughton Jn to Northfleet - booked 1 x 45 + 1 x 47

6O98 1436 (TThFO) Boughton Jn to Northfleet - booked 2 x 47

6O85 1036 (SX) Welbeck to Northfleet - booked 1 x 45 + 1 x 47

6O33 1718 (SX) Welbeck to Northfleet - booked 1 x 45 + 1 x 47

6O59 2350 (SX) Welbeck to Northfleet - booked 1 x 45 + 1 x 47

 

As mentioned by the Fat Controller, a slow speed fitted 47 was added to the trains at Cricklewood, not only did this help to keep the train moving on the Southern but the slow speed fitted loco was used to haul the train around the discharge circuit at Northfleet.

 

Another factor to consider when attaching a second loco to move more tonnage is the coupling strength of vehicles within the train.  I believe that this is one of the reasons for locos being distributed along high tonnage American freight trains where positioning all the locos at the front would simply result in the coupling being wrenched out of the leading wagon.

[Mark Forrest]

They do the Russell traffic which is I believe daventry mossend. Three pairs are involved. Someone may need to correct the destination as I may not be 100%

There were a pair of 90s on this working when I saw it this evening:

http://www.realtimetrains.co.uk/train/H41982/2018/09/04/advanced

[Fat Controller]

A quick look in the WTT commencing 06/05/1974 shows the following double headed MGR services between Brent (Cricklewood) and Northfleet, all of which have a maximum load of 2059 Tons :-

 

6O85 0832 (SO) Boughton Jn to Northfleet - booked 1 x 45 + 1 x 47

6O98 1436 (TThFO) Boughton Jn to Northfleet - booked 2 x 47

6O85 1036 (SX) Welbeck to Northfleet - booked 1 x 45 + 1 x 47

6O33 1718 (SX) Welbeck to Northfleet - booked 1 x 45 + 1 x 47

6O59 2350 (SX) Welbeck to Northfleet - booked 1 x 45 + 1 x 47

 

As mentioned by the Fat Controller, a slow speed fitted 47 was added to the trains at Cricklewood, not only did this help to keep the train moving on the Southern but the slow speed fitted loco was used to haul the train around the discharge circuit at Northfleet.

 

Another factor to consider when attaching a second loco to move more tonnage is the coupling strength of vehicles within the train.  I believe that this is one of the reasons for locos being distributed along high tonnage American freight trains where positioning all the locos at the front would simply result in the coupling being wrenched out of the leading wagon.

Indeed; the maximum load for a single 92 through the Channel Tunnel is about 1300t. A pair is allowed a little over 1600t, not the 2600t you might expect.

[roythebus]

In my short time at Rugby as a 2nd man in 1974 the only regular double header we worked was a pair of 25s on the Bletchley Brickliner from rugby to Crewe. I don't know where it went to after Crewe as we didn't work it past there. It was always a struggle for the pair of 25s, though the return empties was a lot easier for some reason.

 

Remember too that the 47s were not fitted for multiple working so would always require another driver if they were to be of any use power-wise. The 50s were designed to be used double headed from new to increase the speed of trains over Shap before the WCML was electrified north of Crewe.