Double heading of diesel & electric freight trains

[The Johnster]

The return empties might have been easier because you were coming downhill on the map...

[E3109]

For info, 2x86 are used on the Anglo-Scottish liners because they're able to beat Shap and Beattock at a velocity that diesels can only dream of, same with Skodas on the Russell jobs, albeit isolated TMs here and there.

 

Class 86/87 were arguably BR's best investment ever, a fact that their current owners seem to agree with, both in the UK and Bulgaria.

Pity the 87s had to go abroad for this to be realised, but hey!

From what I'm hearing lately, we can expect 86s to outlive all of us. G&W aren't daft, the company own them rather than lease them so I'd be very surprised if these venerable and capable old girls are binned anytime soon.

[45125]

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. 

 

Worked on many 40s, never seen any with brake blocks on the pony wheels........

[E3109]

EE actually proposed a superior bogie to the version preferred by BR, based on the mechanically similar 1200 class locos supplied to Rhodesia. BR declined the offer, maybe they should've taken it up although without checking I don't know if the pony wheels on the 1200s had brake blocks.

 

I used to attend engineering classes with a Springs Branch fitter who was happy to state that they used to rub grease into class 40 bogie fractures in order for them to pass exams.

[Rugd1022]

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.

 

You've just reminded me of a regular job we had with a pair of 25s when I was a secondman at Stonebridge Park Roy, we took a set of coal empties to Nuneaton at around 19.00hrs, ran round them there and put them in the old up side yard then went light engine back to London as fast as we could to get a pint in the BRSA Club at Willesden.

[Edwin_m]

Worked on many 40s, never seen any with brake blocks on the pony wheels........

Thanks for the info - we learn something every day.  So about 20 tonnes of the weight of the class 40 was of no use either for traction or for braking. 

Edited September 5, 2018 by Edwin_m

[Fat Controller]

Thanks for the info - we learn something every day.  So about 20 tonnes of the weight of the class 40 was of no use either for traction or for braking. 

It was there to hold the front end up..

[E3109]

Can somebody confirm that the cylindrical bomb-like appendages on the front of 40 and Peak bogies (and 10201 etc) were nothing but solid ballast weights?

I did see a post on another forum that suggested there were springs within, but I can't think why there would be.

Used to get up close and personal with 40s back in the day, but that's one aspect I never investigated.

Cheers!

[Zomboid]

Aren't they the pivot for the trailing wheels?

[Nearholmer]

I think they are sheet metal covers for the springs that load the inside (radial, or are they on a pony?) axleboxes of the carrying axle.

 

The bogie design is largely Bulleid/Ashford and you can see dents in these ones.

 

I’ve got a drawing of the bogie somewhere, but it’s currently packed away while I shift stuff around in the study.

Edited September 5, 2018 by Nearholmer

[Nearholmer]

Well, this is a really foggy extract from a model engineering drawing, and if it reflects the way the real bogie operates, I was wrong above ....... the ‘dustbins’ appear to cover the pivots, not loading springs, for the axleboxes. Possibly the pivot contains a roll-spring too, but my eyesight isn’t up to reading this properly.

 

If I find the proper drawing before anyone posts a definitive answer, I will add some solid facts.

Edited September 5, 2018 by Nearholmer

[Michael Edge]

If you find the drawings I would be very interested. The pony trucks have swing link pivots (inside the covers) to put the linkage outside the wheelbase. This is because the theoretical pony truck pivot position coincides with a traction motor. The same problem occurs in model 1-Co-Co-1s with gears in the way.

[Dagworth]

Lots of mention of the brake force of the train being the part that does the work, the bit I haven't seen mentioned yet is the speed restriction of light locos to 75mph due to lack of ability to stop!

 

Didn't stop one working I was on with a pair of light 37s heading from Ipswich to Bury St Edmunds passing Claydon at 110 mph!

 

Andi

Edited September 6, 2018 by Dagworth

[dvdlcs]

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.

 

 

The BP&GV was I believe built on a drained canal, which with various overbridges made for the very limited headroom.

 

I have a memory that the 03s were initially used because they were the only locos that BR (still) had with a sufficiently low axle loading for the line. The fact that you had to lash 3 together to move the train was possibly a secondary concern.

 

Wagons used were (at least) 16 tonners and 21 tonne hoppers, with the 03s being vacuum brake only locos, so possibly unfitted / partial fitted / vacuum fitted consists.

 

Later the 03s were replaced with 08s, also with cut-down cabs, not sure what changes to the infrastructure had been made to allow the larger locos to use the line. First 2 08s were vac only with the third being a dual braked example. Later on the rolling stock was changed over to HEA hoppers and the first two 08s were withdrawn and replaced with 2 air brake only examples.

 

There is probably a Wiki page somewhere with this information - and probably correct information - but this is what I can still remember from the 1980s, despite living far far away from the line.

[Mick Boyd]

If I remember correctly the pony wheels on the 1-C0 -C0-1s were mounted in a cannon box and has been correctly stated earlier the protuberances house the pivot.

 

Cheers, Mick.

[Nearholmer]

This is even further OT, but how does the geometry of the pivots work out to keep the axle radial to a curve? Or, is it one of those things where the angles are so small that it doesn’t matter?

[jim.snowdon]

This is even further OT, but how does the geometry of the pivots work out to keep the axle radial to a curve? Or, is it one of those things where the angles are so small that it doesn’t matter?

The angles aren't large, but are significant in terms of the wheel:rail interface and track spreading forces.

 

As to how the radial axles on the 1-Co-Co-1 family work, the answer lies in a pair of horizontal steering links between the bogie headstock and the radial axlebox. These links are not parallel, but arranged so that they converge behind the headstock. The resulting four-bar linkage causes the radial axlebox to describe an arc, centred on a virtual pivot somewhere under the bogie, probably in a place occupied by a traction motor. It's an ingenious solution that goes back to the Southern Railway, I think, to Ashford drawing office.

 

Jim

[Fat Controller]

The BP&GV was I believe built on a drained canal, which with various overbridges made for the very limited headroom.

 

I have a memory that the 03s were initially used because they were the only locos that BR (still) had with a sufficiently low axle loading for the line. The fact that you had to lash 3 together to move the train was possibly a secondary concern.

 

Wagons used were (at least) 16 tonners and 21 tonne hoppers, with the 03s being vacuum brake only locos, so possibly unfitted / partial fitted / vacuum fitted consists.

 

Later the 03s were replaced with 08s, also with cut-down cabs, not sure what changes to the infrastructure had been made to allow the larger locos to use the line. First 2 08s were vac only with the third being a dual braked example. Later on the rolling stock was changed over to HEA hoppers and the first two 08s were withdrawn and replaced with 2 air brake only examples.

 

There is probably a Wiki page somewhere with this information - and probably correct information - but this is what I can still remember from the 1980s, despite living far far away from the line.

I suspect one of the reasons the 03 were used was that they had mechanical transmission- 'Kymer's Canal' was prone to re-enacting its previous existence every 'rainy season'. The 03s weren't replaced until the chord from Coedbach to Kidwelly was reinstated in the 1980s; after this, mainline diesels could work as far as Coedbach, whilst the modified 08s could work as far as Cwm-mawr, at the head of the valley. A non-modified 08 was sent in error one day; it lasted as far as the bridge over the line just north of Coedbach, where it displaced a water main and converted itself to a rhombus-shape. I have fond memories of walking the line when preparing a paper on the line for my A-level Geography exam in 1973- its origin as a canal were still all-too-evident.

[Gibbo675]

Lots of mention of the brake force of the train being the part that does the work, the bit I haven't seen mentioned yet is the speed restriction of light locos to 75mph due to lack of ability to stop!

 

Didn't stop one working I was on with a pair of light 37s heading from Ipswich to Bury St Edmunds passing Claydon at 110 mph!

 

Andi

Hi Andi,

 

I've had experience of the lack of ability to stop light engine on steam locomotive positioning moves with just a support coach on tow.

 

We were once late departing Preston after detaching from a train to run home engine and one and so the driver (an unnamed Crewe man) decided to make up time by running at over 60 mph. This was fine along the WCML up to Euxton junction but there after we were under three aspect signalling through to Castleton via Bolton and Manchester, he spotted a yellow and applied the brake which was then made a hasty full application when he realised that the next one was red, we passed the signal post and avoided tripping the overlap by a matter of feet. He was fortunate that it was a dry day with a dry rail.

 

It is my guess was that he was thinking, "Fetch my bicycle clips !"

 

Gibbo.

[rob D2]

Am I right in thinking blue era 47s couldn’t be multied, and that came along with RFd ?

[russ p]

Am I right in thinking blue era 47s couldn’t be multied, and that came along with RFd ?

There were two Immingham 47/3s that had experimental TDM type multiple working and one 47/0 that had a blue star type of multiple working but for working with an experimental driving trailer for proposed push pull working.

The DRS ones initially had DRS's version of blue star and did work with 37s and 20s but wasn't 100% successful and they had the RFD green spot system fitted instead

[Michael Edge]

This is even further OT, but how does the geometry of the pivots work out to keep the axle radial to a curve? Or, is it one of those things where the angles are so small that it doesn’t matter?

That's why I would like to see the drawing, I've never found a good pony truck solution for these locos and I would be very interested to see the prototype geometry.

[Zomboid]

Just to keep waaaaaaay off topic, 45s actually had their multi equipment removed, fairly early I think. If I recall correctly it's because the couplers are on the bogies, so the tractive force of 1.5 locos would have been transmitted through the bogie pivot on the second loco, which wasn't really up to it for a train which actually needed 2 type 4s. Helpfully it provided space on the buffer beam for the ETS kit on the 45/1 conversions.

 

I assume the same goes for 44s and 46s.

[Nearholmer]

Jim

 

I'm still not totally sure I understand how the pivots steer the axle boxes - any chance of a sketch?

 

The bit that I really don't get is that, to achieve a radial action, the rods/bars would need to get shorter/longer ..... are there slots or something to give dead motion?

 

The drawing I have is a side elevation, so even when I find it, I now don't think it will help.

 

Kevin

[Michael Edge]

I did once see a drawing of this but can't remember where, there are two swing links, no slots or anything like that, the radial movement is produced by the angle and the length of the links. Swing link pony truck were used in other locomotives but with the links pivoted inside the wheelbase.