Mk3 loco-hauled - why only 110mph?

[Guest stuartp]

and I'm guessing the AC EMUs with EP brakes

 

The 'lap' position between the Westinghouse and EP brakes on Class 308s was the cause of a couple of minor collisions when they were introduced on Leeds NW services, the RRNE drivers being more used to the 3-step brake on 14x/15x units. The usual scenario was somebody coasting gently to a stand in a terminal platform then moving the brake to 'Lap' thinking it was step 3. By the time you realised your mistake you'd already hit the buffers/stationary unit.

 

Once we'd solved that problem there was just the spontaneous combustion issue to deal with...

[Guest Phil]

The 'lap' position between the Westinghouse and EP brakes on Class 308s was the cause of a couple of minor collisions when they were introduced on Leeds NW services, the RRNE drivers being more used to the 3-step brake on 14x/15x units. The usual scenario was somebody coasting gently to a stand in a terminal platform then moving the brake to 'Lap' thinking it was step 3. By the time you realised your mistake you'd already hit the buffers/stationary unit.

 

Once we'd solved that problem there was just the spontaneous combustion issue to deal with...

 

 

 

Ahhh you see ................ Down in the West Midlands, we were already used to driving AM4s and AM10s with Westinghouse brakes. So when we got those handful of 308s while you were still putting your knitting up, we coped with them. As you say though, they were rather explodable.

 

Funny really, not too many images of them at work in the West Midlands before we packed them off to Yorkshire. Probably because they spent most of their time at Soho or Tyseley, instead of Four Oaks and Longbridge !!!!

 

Also - funny how things run in cycles - I believe you now have 321410 and a "Christmas tree" up there. I believe HSBC are leasing em to LM, who are subleasing em to WYPTE, who are having Northern operate them, to release a diesel for Workington shuttles.

[Ken.W]

I've just come upon this thread by chance, but if I can add some comments;

 

There seemed to be some confusion by the HST being described as having an EP brake. It's not. The brakes on an HST are a conventional two-pipe Automatic Air Brake, the same as other air-braked stock, and you can couple a loco on the front and it'll behave as any other auto air brake.

The difference is in the control of the Air Brake Pipe pressure, which is done by brake control units (E70s) on both power cars, these being controlled electrically by the driver's brake handle. Both E70s apply the brake but only the leading one releases it (in case of faults with the electrics). This give a more rapid application necessary for 125mph running on conventional 4-aspect signaling.

The difference in application time may not seem much, but remember the train's still doing 125 during this time. When doing the HST training, with a training special, we tried a full emergency brake application stopping from 125. The next run we tried again at the same location but with one E70 isolated, the train went a quarter mile further!

 

The 91s and Mk4s do use basically the same system, with a brake control unit on the 91 and DVT. As was said, unlike the Mk3's wheel mounted disc brakes, the Mk4s have ventilated axle mounted discs, but they do also have an extra disc, there's three disc brakes on each axle.

 

Regarding 140mph running with Mk4s, yes it was intended to use flashing greens as a fifth aspect to allow this. Flashing green would allow 140 running, then a steady green would mean reduce to 125 with the next signal possibly being double yellow.

The section of ECML fitted with flashing green aspects was Stoke Bank, the Up and Down Fasts between Peterborough and Stoke Summit. Although it was used for test running when the sets were being introduced, due to concerns over signal sighting at that speed it was decided in-cab signaling would be required for any increase over 125, and the system was never used for trains in service, service speed having always been limited to 125. It is still operational, and yes does give a useful advance warning at times  of yellows ahead when descending the bank.

 

Something that's not been mentioned, if an HST or 91/Mk4's running with the rear E70/DW3 isolated, it's limited to 110mph.

 

On the speed of the 67s, they're limited to 100 on EC thunderbird duties too, not that they'd manage much more with a full Mk4 set anyway. The heavy axle loading's an issue with them, and there's several underbridges between Berwick and Edinburgh where they're restricted to 60 crossing them.

[Fat Controller]

If the rear E70/DW3 is isolated, is it only the maximum speed that is reduced, or are proportionate reductions imposed at lower speeds?

[jim.snowdon]

6 hours ago, Ken.W said:

There seemed to be some confusion by the HST being described as having an EP brake. It's not. The brakes on an HST are a conventional two-pipe Automatic Air Brake, the same as other air-braked stock, and you can couple a loco on the front and it'll behave as any other auto air brake.

Given the need to minimise the brake build up delay, fitting a true EP brake as an overlay on the automatic air brake, as per the SR emus would seem an obvious option. It wasn't done, so presumably there were considered to be good reasons for adopting the double-ended air brake system that they did.

 

Jim

[roythebus]

An interesting topic. Having learnt how to use the Westinghouse brake as a guard with London Transport in 1970 I claim to know a bit about them, having used them in daily service when I became a driver at Waterloo.

 

With the Westinghouse, they taught us that you get 3 applications then run out of auxiliary air to operate the brakes, so they took a deal of skill to work. Tales from the old boys at Waterloo were that it was possible with a 12 car Nelson to break the couplings between the last 2 units due to the differing speeds of brake application as you went down the train. I only drove 4 and 8 car SUBs and the Waterloo & City, all Westinghouse and never had a problem.

 

Earlier in my career on bR I was a 2nd man at Rugby from late 1974. the class 81-86 were very rough riding at anything over 85 and at 100 it was almost impossible to leave a cup of tea on the desk without it spilling. That's why they modified the suspension on the 86s and the 87s had the side springs from new. At that time we still had vacuum braked sets, and one night I was with a driver doing the "midnight" (0012) Euston-Wolves. approaching Coventry we were going  a bit fast, 110 IIRC and I reminded the driver we had to stop at Cov. He replied "yes I know", dropped the vac to zero and we stopped bang on the mark. 

 

I moved to KX and worked everything out of there except the HSTs, they were being introduced as I got promotion to driver on the Southern.

[The Stationmaster]

19 minutes ago, roythebus said:

An interesting topic. Having learnt how to use the Westinghouse brake as a guard with London Transport in 1970 I claim to know a bit about them, having used them in daily service when I became a driver at Waterloo.

 

With the Westinghouse, they taught us that you get 3 applications then run out of auxiliary air to operate the brakes, so they took a deal of skill to work. Tales from the old boys at Waterloo were that it was possible with a 12 car Nelson to break the couplings between the last 2 units due to the differing speeds of brake application as you went down the train. I only drove 4 and 8 car SUBs and the Waterloo & City, all Westinghouse and never had a problem.

 

Earlier in my career on bR I was a 2nd man at Rugby from late 1974. the class 81-86 were very rough riding at anything over 85 and at 100 it was almost impossible to leave a cup of tea on the desk without it spilling. That's why they modified the suspension on the 86s and the 87s had the side springs from new. At that time we still had vacuum braked sets, and one night I was with a driver doing the "midnight" (0012) Euston-Wolves. approaching Coventry we were going  a bit fast, 110 IIRC and I reminded the driver we had to stop at Cov. He replied "yes I know", dropped the vac to zero and we stopped bang on the mark. 

 

I moved to KX and worked everything out of there except the HSTs, they were being introduced as I got promotion to driver on the Southern.

Roy I hope he stopped at Coventry on a rising brake   It was incidentally easy enough to just make a single application on a vacuum braked passenger train but you needed to know exactly where to put the brake in (and you didn't need to dump the lot).

[russ p]

On the GA intercity sets its policy for the DW3 to be isolated on the DVT when trailing,  the DW3 on the 90 is not isolated though when that is on the rear. 

Seems a bit odd to me as braking performance is different depending on where the train is driven from

[Ken.W]

4 hours ago, Fat Controller said:

If the rear E70/DW3 is isolated, is it only the maximum speed that is reduced, or are proportionate reductions imposed at lower speeds?

 

It's only the maximum speed that's reduced, below 110 it's operating as any other air-braked train

 

On the 91/Mk4s it's done automatically. A micro-switch on the isolating handle restricts the Auto Speed Limiter to a maximum of 110

[Ken.W]

1 hour ago, russ p said:

On the GA intercity sets its policy for the DW3 to be isolated on the DVT when trailing,  the DW3 on the 90 is not isolated though when that is on the rear. 

Seems a bit odd to me as braking performance is different depending on where the train is driven from

 

Interesting. Could it be with the extra speed allowed not being needed the DVTs isolated when trailing to prevent delays caused by TDM faults causing it to dump the brake?

When it's the loco trailing though, would it's E70 being isolated prevent the loco taking traction power?

[Fat Controller]

1 hour ago, Ken.W said:

 

It's only the maximum speed that's reduced, below 110 it's operating as any other air-braked train

 

On the 91/Mk4s it's done automatically. A micro-switch on the isolating handle restricts the Auto Speed Limiter to a maximum of 110

Thanks, Ken. With our trains, which are EP-fitted, any problem with the EP means reducing max speed from 140 kph to 100. Any other speed restrictions have to be taken at half the speed indicated on the TVM.  On a busy day, such a train is a real PITA.

[russ p]

Apparently it was something to do with dragging brakes .

Trying to think now if the loco is trailing and the E70 is isolated if you can get power as the air train pipe governor is made on the DVT.

On a 66 you can get power if the locos are in multiple if its isolated but even though its referred to as an E70 isolating cock it's got nothing to do with one as it's a PBL system. 

 

[roythebus]

On 10/11/2019 at 11:06, The Stationmaster said:

Roy I hope he stopped at Coventry on a rising brake   It was incidentally easy enough to just make a single application on a vacuum braked passenger train but you needed to know exactly where to put the brake in (and you didn't need to dump the lot).

Of course.   I think his name was Fred Green, ex Northampton man. Used to run a grocer shop in his spare time. Another old 'un at KX Sifd Stubbs, running into Stevenage on the down, approaching the last signal before the platform doing the ton, I reminded him we stop her..yes I know, put the air brake in and stopped on the mark! with a rising brake too. Lucky in both cases it was a dry rail.

 

[daveyb]

Mention of the EOTD on North American lines, they don't do much with brakes as you can run without them in some circumstances. They are used to say when a point has been passed e.g. when out of a loop or past a crossing. They are slowly doing away with fixed treadles for radio activation.

 

The big thing is the Distributed Power Units (DPU) or mid train helpers, and the trailing locos. They control the brakes and refill the system over a long train, but use radio signals rather than TDM or other electronic connection or just air.

[The Stationmaster]

3 hours ago, daveyb said:

Mention of the EOTD on North American lines, they don't do much with brakes as you can run without them in some circumstances. They are used to say when a point has been passed e.g. when out of a loop or past a crossing. They are slowly doing away with fixed treadles for radio activation.

 

The big thing is the Distributed Power Units (DPU) or mid train helpers, and the trailing locos. They control the brakes and refill the system over a long train, but use radio signals rather than TDM or other electronic connection or just air.

A big advantage of EOTDs is that they give you a flow meter indication for the brake system from the rear of the train so the Driver will know that the brakes are released or releasing back there.  This was why I asked EMD if they could get hold of one for use on the 12,000 ton Yeoman trial train because we were concerned about the rate of release at the rear of the train on an undulating road.  

 

Alas EMD were a bit less than helpful and we hit exactly the problem the EOTD would have avoided which resulted in a breakaway (at the midtrain helper - which suffered a broken coupling hook) because the brakes at the rear had not fully released when the leading loco put power on for the next stretch of rising gradient.

[daveyb]

I suppose that would depend on the position of the DPU, and it seems to be a bit random (I'm told the ideal place is a few spaces forward of the wagon at the draw bar capacity of the head end locos). Broken couplers are fairly common on this side of the Atlantic, too. 

 

If the length of the train requires a tail helper, then you get all the read-out that loco can provide, and a compressor, and a release valve.

[The Evil Bus Driver]

On 11/11/2009 at 20:50, Fat Controller said:

It's not directly to do with the wiring, but because of the system of brake actuation (not sure if it's a variant/development of electro-pneumatic braking), which applies and releases the brakes within an entire HST set at once, rather than the lag one gets between the application of the brakes to individual vehicles. On the basis that 'The ability to stop gives the right to speed' this means that HSTs are allowed a higher maximum top speed, as they can stop more quickly.

Do you remember the burning smell when an HST had its brakes applied? It was pretty horrible.

[Mark Saunders]

What has not been mentioned is on Mk lll hauled stock the air brake is only vented on the locomotive at the front while on an HST it is vented from both ends front and rear at the same time allowing a quicker application! 

 

On both systems a brake can only be created (air pressure made) by the driver at the front.

 

Mark Saunders

[Fat Controller]

1 hour ago, The Evil Bus Driver said:

Do you remember the burning smell when an HST had its brakes applied? It was pretty horrible.

More 'fishy' than burning, IIRC

[The Evil Bus Driver]

2 minutes ago, Fat Controller said:

More 'fishy' than burning, IIRC

Pretty horrid whatever it was

[Erixtar1992]

Little random bit to add, but HST’s run at 5.1 bar instead of 5 bar when in running (brakes released)

cant remember the exact reason, was told years ago now but im sure it was also to do with increasing the speed the brakes apply.

[45125]

3 hours ago, Erixtar1992 said:

Little random bit to add, but HST’s run at 5.1 bar instead of 5 bar when in running (brakes released)

cant remember the exact reason, was told years ago now but im sure it was also to do with increasing the speed the brakes apply.

The overcharge was removed from the E70/DW2, due to the unreliability of the way it is set up. So the brake pipe pressure was set u to give a fixed overcharge of 5.1 bar.

 

[Ken.W]

3 hours ago, 45125 said:

The overcharge was removed from the E70/DW2, due to the unreliability of the way it is set up. So the brake pipe pressure was set u to give a fixed overcharge of 5.1 bar.

 

 

Yeah that was the reason given, but didn't make sense as it doesn't serve the purpose the overcharge was for, or overcome the problem of not having one.

[royaloak]

10 hours ago, Erixtar1992 said:

Little random bit to add, but HST’s run at 5.1 bar instead of 5 bar when in running (brakes released)

cant remember the exact reason, was told years ago now but im sure it was also to do with increasing the speed the brakes apply.

I had one showing 5.4 the other week, I did query it but was told the gauge was over-reading and it was good to go. 

[Pete the Elaner]

All the focus so far has been on HSTs being able to apply/release braking more quickly.

MK3As do have C3 - 125 mph labelled on their data panels.

 

Mk3As were originally mainly deployed on the WCML, where it was deemed too twisty to go any quicker without sacrificing passenger comfort.

Surely if braking was the only obstacle, they could have designed something to ensure the brakes applied/released more quickly, such as introducing DVTs earlier & having these also control braking?

With 110mph being a restriction for curvature reasons, loco-activated braking was probably sufficient & anything further would be considered a waste.