Why top and tailed 66's?

[edcayton]

In my son's flat yesterday and saw what looked to me a fairly ordinary train of vans heading South through Stevenage at about 4 or half past. The thing is that the train was top and tailed. Now I know that various works trains need this, but is this an indication that we are moving towards what are, in effect, multiple unit freight trains? Seems to me to be a rather expensive use of loco's.

 

It occurs to me that if we are heading this way then why not have two lower powered (and presumably cheaper) loco's with the rear one remotely controlled from the front, which I believe is what happens in the USA.

 

Ed

[Torr Giffard LSWR 1951-71]

....avoids need to run round....can assist with traction power as necessary e.g. heavy HOBC consists....avoids need for propelling, driver always at leading end of train (safety considerations)....spare loco in case of failure.....locos can be stepped up on worksite so that one loco can bring the wagons of the adjacent train off the worksite in the opposite direction to that which they arrived if req. etc etc

 

Dave

[PaulRhB]

If it's a standard freight then it's likely that due to engineering it can't run round in a usual place or has to reverse somewhere where it can't run round due to a revised route. You'll see extra locos moving in convoy around the weekend to position locos for working the actual engineering trains or for top n tailing normal workings where required.

[PaulRhB]

It occurs to me that if we are heading this way then why not have two lower powered (and presumably cheaper) loco's with the rear one remotely controlled from the front, which I believe is what happens in the USA.

 

Ed

The US doesn't use lower powered locos they just add locos until enough power is available for that tonnage on that route. They use distributed power to allow longer trains on steep grades where drawbar a would snap or on curves where stacking all the power up front would drag wagons off sideways. The trains tend to be heavier anyway as there's more room in loops etc. The smallest US mainline diesels are comparable in power to the 66's and most six axle ones now are a lot more powerful in the 4000+ range.

[ELTEL]

If it's a standard freight then it's likely that due to engineering it can't run round in a usual place or has to reverse somewhere where it can't run round due to a revised route. You'll see extra locos moving in convoy around the weekend to position locos for working the actual engineering trains or for top n tailing normal workings where required.

Weekend before last while at Carlisle Station a rake of 7 yes 7 Freightliner class 66 heading north.

 

My understanding they would be on engineering duties over the weekend

 

As it was the DRS Kingmoor open weekend there many photographers present, so I am photographs and a explanation will appear in the railway press

 

Sometimes I understand they will tag a locomotive on the rear of a freight train for stock movement to save costs ( ie line charge sand driver )

 

Eltel

[PaulRhB]

Dead locos in transit are usually put behind the train loco rather than on the back. A big heavy lump at the back can put unnecessary strain on the couplings on a lighter train if it isn't needed there for operational reasons. It will drag out and bunch up the train and it's easier to drop the train off at a yard and then take the locos on to depot if they're all together.

[ELTEL]

Good point!

[black and decker boy]

Checking realtimettains, there was a Barrington to Wembley working through Stevenage at 1618. This would have been I imagine, bulk box wagons rather than vans and could be top & tail because the facility at Barrington is brand new and perhaps the run round isn't complete yet

 

http://www.realtimetrains.co.uk/train/R78257/2015/07/31/advanced

[black and decker boy]

From information received on Wnxx.com, it appears this was probably nothing untoward in that a loco had failed.

 

"Sighting on Anglia gen said 66155 on front and 66040 on back. Apparently 66040 failed" posted by Mark

[edcayton]

Thanks guys. Can't see the trains so well from son's flat now as the trees and hedge are getting too big.

 

Ed

[edcayton]

I didn't know there was any traffic from Barrington any more. Is the line from there to Foxton still open?

 

Ed

[black and decker boy]

I think it's the opposite of what you are thinking, the cement works has closed and they are now importing spoil waste into the old quarry workings. They are using the old connection to foxton and have laid new track & unloading point at Barrington suitable for mainline trains & locos.

[Godders]

The US doesn't use lower powered locos they just add locos until enough power is available for that tonnage on that route. They use distributed power to allow longer trains on steep grades where drawbar a would snap or on curves where stacking all the power up front would drag wagons off sideways. The trains tend to be heavier anyway as there's more room in loops etc. The smallest US mainline diesels are comparable in power to the 66's and most six axle ones now are a lot more powerful in the 4000+ range.

 

Hi Paul,

 

Are you sure this is true? Surely on full size railways, where the curves are relatively large, the sideways forces from the couplings are quite small compared to the weight of the vehicles involved.

The worse case would surely be the first vehicle following the locomotive and the best case the last vehicle. Thus the forces will decrease from first to last vehicle.

The first vehicle will have the full drawbar forces from the locomotive and the greatest trailing load from the rest of the train.

The addition of locomotives at the back of the train would worsen the situation unless the loco could be guaranteed to be pushing 100% of the time and that can't be true. The load must fluctuate between pushed and pulled.

 

Cheers

 

Godders

[br2975]

Are you sure this is true? Surely on full size railways, where the curves are relatively large, the sideways forces from the couplings are quite small compared to the weight of the vehicles involved.

The worse case would surely be the first vehicle following the locomotive and the best case the last vehicle. Thus the forces will decrease from first to last vehicle.

The first vehicle will have the full drawbar forces from the locomotive and the greatest trailing load from the rest of the train.

The addition of locomotives at the back of the train would worsen the situation unless the loco could be guaranteed to be pushing 100% of the time and that can't be true. The load must fluctuate between pushed and pulled.

It may be Wikipedia, but it's a reasonable explanation.

 

https://en.wikipedia.org/wiki/Distributed_power

 

Brian R

[PaulRhB]

Hi Paul,

 

Are you sure this is true? Surely on full size railways, where the curves are relatively large, the sideways forces from the couplings are quite small compared to the weight of the vehicles involved.

The worse case would surely be the first vehicle following the locomotive and the best case the last vehicle. Thus the forces will decrease from first to last vehicle.

The first vehicle will have the full drawbar forces from the locomotive and the greatest trailing load from the rest of the train.

The addition of locomotives at the back of the train would worsen the situation unless the loco could be guaranteed to be pushing 100% of the time and that can't be true. The load must fluctuate between pushed and pulled.

 

Cheers

 

Godders

Yes fraid so it's a well known problem although rarer these days.

Straight-lining or stringlining are the terms used

http://www.railpictures.net/viewphoto.php?id=329747&nseq=792

There are impressive videos of Tehachapi in the 80's with 16 3000hp locos split through a train if you search YouTube. It depends on the weight of a train and Railroads policy how they split the power, most prefer locos up front if possible on light intermodal trains, front and back for longer ones and medium weight trains but really heavy goods such as coal often means there is power inserted in the middle too. Putting the power into the middle is avoided where possible because it takes time to split and reform the train so only used where absolutely necessary but it is more efficient in track occupation and crew than two trains following each other.

Distributed power replaced manned banking and relying on the banking crew to judge it. It's not perfect and they still have 'stringlining' if something goes wrong. When a train is long enough to to crest several hills and dips plus curves it's quite an art to keep the train together and broken knuckle couplers are quite common even now in mountain districts. The locos cut into a train have to push a certain amount of wagons to prevent dragging them off the inside of corners but equally mustn't be push so hard they bunch up the slack to the locos ahead and push off the outside. Distributed power is quicker to deal with unexpected changes, if a loco fails, as manual control relied on radios to warn the helpers and often lost contact at the critical moment.

There are quite a few photos on sites such as Railpictures.net of accidents from this.

[Fat Controller]

I think it's the opposite of what you are thinking, the cement works has closed and they are now importing spoil waste into the old quarry workings. They are using the old connection to foxton and have laid new track & unloading point at Barrington suitable for mainline trains & locos.

Looking at the layoutof the mainline connections in Quail, it seems that two locos may have been used for operational convenience. If only one loco was used, then the train would have to run round in the plant, then, when loaded, set back on to the Down Cambridge, before changing direction and heading off via the crossover to the Up line. Presumably, if there was a loco at either end, then the movement from the sidings could be made more quickly than a setting-back move; I suspect there may be a speed limit for such moves, but don't know what it might be.

It seems very odd that a failed loco would be at the tail of the train; far more likely that the second loco was being towed Dead-In-Train after leading the manoeuvre from the yard.

How was this siding worked in earlier days? Did traffic go to and from Cambridge? 

[Rugd1022]

Doing it 'manually' is still a bit of a fine art, I was the 'tail end Charlie' on 6Y58 (all 3,300 tons of it) from Northampton to Rugby last night and between me and my colleague on the front loco, with the aid of our back to back radios we managed a nice smooth run off the slow line at Mill Lane Junction (25mph) out onto the Down Fast and up the bank as far as Bridge 69 near Watford Lodge Tunnel. It still seems strange watching everything receding away from you in the rear cab but route knowledge works backwards just as well as it does going forwards...!

 

[The Stationmaster]

Hi Paul,

 

Are you sure this is true? Surely on full size railways, where the curves are relatively large, the sideways forces from the couplings are quite small compared to the weight of the vehicles involved.

The worse case would surely be the first vehicle following the locomotive and the best case the last vehicle. Thus the forces will decrease from first to last vehicle.

The first vehicle will have the full drawbar forces from the locomotive and the greatest trailing load from the rest of the train.

The addition of locomotives at the back of the train would worsen the situation unless the loco could be guaranteed to be pushing 100% of the time and that can't be true. The load must fluctuate between pushed and pulled.

 

Cheers

 

Godders

There are lots of factors involved and Coupling Strength is just one of them.  But let's get the top & tailed 66s out of the way first - if it was booked working the rear loco would be ANR (Attached Not Required) so it would not be powering except where assistance in the rear was specifically authorised.  The only exception to that would be if the train loco had failed in which case if it was not easy to get an assistant loco on the front it would be permitted to be assisted rear as far as was necessary to clear the line or to a point where the assistant engine could be put on the front.  

 

It is nowadays quite common, as already explained above, to have locos running ANR on the rear of trains, especially freight and engineering trains, in order to avoid running round - but those locos are not running under power and they are usually not even manned.

 

Now to assistance (often referred to as 'banking').  There are, in British practice, two ways of doing it - you put the assistant engine on the front or the back.  Booked assistant rear is not really suitable on an undulating route but with a continuously braked train it is to a degree safer than with a loose coupled train.  The other element which is very important is Coupling Strength - this has gradually increased since, the late 1960s which has also made it much safer to have a loco attached ANR on the rear of a train or to assist from the rear and of course it has also increased the trailing load which can be run when a train is assisted front.

 

Knuckle couplings generally tend to have higher Coupling Strength figures than traditional shackles thus many of the wagons used in, for example, stone and iron ore working, have had 50 ton couplings fora  good many years and have allowed multiple numbers of loco on the front especially if outer wagons have specially strengthened shackles to minimise the risk of a breakaway.  This situation also affected the marshalling of the Mendip stone trains because once they went to a 5,000 tonne trailing load the leading part of the train had to have knuckle couplings while wagons with shackle couplings went on the rear although the conditions were - for obvious reasons - not so onerous on trains of empties.

 

So important factor No.1 is Coupling Strength.  Important factor No.2 is the ability of the traction to release the brakes through the train.  This becomes of crucial importance on an undulating route where part(s) of a long train can be going uphill while another part/parts can be going downhill.  The drag of slowly releasing brakes at the back of a long train can put even greater strain on couplings and dynamically the best answer is to put an assistant loco/locos within the train and not at the rear and thus spread the coupling strain - in fact it is, I believe, the main reason why mid-train helpers were introduced in the USA and it was very definitely the reason why the train was marshalled that way when we ran the 12,000 tonne train out of Merehead back in the early '90s.  Don't forget too that in the US they use end of train monitors to let the Driver Engineer know what the Brakepipe pressure is doing at the back of the train in order to avoid applying too much power at the front and in the middle while the brakes are not fully released at the rear.

 

In Britain we found on the Merehead trial that with a mid-train helper and the right marshalling we could go up to 12,000 tonnes trailing with no problems of couplings pulling anything out of line on curvature (including some fairly sharp curves) but then in reality it wasn't much different from running 5,000 tonnes trailing everyday with a single Class 59 on the front.  But - not entirely unexpectedly - we hit the brake release problem on undulating road and the train parted due to a broken coupling hook; but then that was one reason why it was a trial. 

[Talltim]

Some FREDs can also apply the brakes remotely, allowing the loss of brake pressure to spread from both ends of the train at once. (HSTs do this too)

[Fat Controller]

Some FREDs can also apply the brakes remotely, allowing the loss of brake pressure to spread from both ends of the train at once. (HSTs do this too)

How do they do this; I know HSTs do it electrically via the train-line, whilst EP-stock has been doing the same since the 1950s or earlier, but I've not seen any freight vehicles in the UK with any sort of electrical connection, barring those formed with MPVs.

[ElectroSoldier]

Freightliner do it because there is nowhere to run around. You drive in in one cab and out in the other.

 

Is it common...
Its common for a movement to have a tail if there is nowhere to run around yes, its not if there is a headshunt to run around in unless you need a bank.

Double heading motive power can be seen as common or not common depending on the working, our 86s usually double head, though they do work singles too, most of you guys can see it over the WCML, you will see a pair of 86s with both the pantographs up then they are both working, sometimes you see the rear loco with it down but thats rare and so as to get the loco to where it needs to be for its next working or because the trailing weight means you dont need a pair. Or it could mean the movement was booked for a single but a failure meant you had to use another loco to haul it with, maybe.

[Guest eddie reffin]

Also some routes will not permit double heading so additional locos would have to be placed elsewhere in the formation. Although in this case it's lower RA lines like we have up here in Scotland. I crossed a southbound ballast working during the last week which was 37610 then 10 AutoBallasters and 2 dead 66s on the back 66111 and a failed DRS one. All very bizarre!

[Pugsley]

How do they do this; I know HSTs do it electrically via the train-line, whilst EP-stock has been doing the same since the 1950s or earlier, but I've not seen any freight vehicles in the UK with any sort of electrical connection, barring those formed with MPVs.

In the US it's done with radio, but I'm not aware of anything like that in use in the UK.

[Talltim]

In the US it's done with radio, but I'm not aware of anything like that in use in the UK.

Sorry, yes I was talking about US ones

[jamie92208]

Sorry, yes I was talking about US ones

The USA are also experimenting with a form of EPB particularly on long container trains and also possibly for crude oil trains after the lastest set of derailments. The wagons are all wired and through wired to the loco so that all brakes release and apply at the same rate. Apparently on trials some years ago it made train handling a lot easier but it went on the back burner until recently. Obviously there are cost implications.

 

Jamie