Diesel Mechanical Multiple Unit performance

[matchmaker]

The 79xxx very soon had a modification made to enable multiple working with what became the Class 126. Incompatibility evidently lasted less than a year, maybe just months, because there are several reports of mixed 79xxx & 126 cars on Ayrshire workings in days before the entire 126 fleet had been delivered and even for some years after as strengthening vehicles in the summer for instance.

There was arguably no need for the 79xxx/126 to be compatible with the 120s, as they never came into contact really.

The only other Class in the area of 120 operations was the 105s based at Kittybrewester and those were Blue Square and frequently operated together with the 120s, even all the way to Inverness at times.


Both 79xxx and 126 were White Circle but the 79xxx system was based on the early Yellow Diamond system, the 126s on the later standard Blue Square system.

Initially the two batches thus had some control and wiring incompatibilities but these were soon resolved and the two batches were used in mixed formations very early on.

The 79xxx/126s also different couplings and gangways to the 120s - buckeyes and Pullman gangways on the former, screw couplings and scossors gangways on the latter.

 

[hexagon789]

The 79xxx/126s also different couplings and gangways to the 120s - buckeyes and Pullman gangways on the former, screw couplings and scossors gangways on the latter.

Indeed, and the normal buffing gear on the 79xxx/126s was lightweight and only designed for shunting; even if they were Blue Square, they wouldn't have been able to run with non-buckeye units.

I always viewed these design feature as reinforcing the 'Inter-City' or mainline principles of their design.

They were basically powered mainline stock.

 

[LickeyIncliner]

In the 1970s most Birmingham - Worcester - Malvern - Hereford local services travelled via Stourbridge, and Bromsgrove had a very limited service - so there weren't so many DMUs over the Lickey (as far as I remember, mostly some peak hours 'fast' Worcester trains). I'm sure I did travel up it on a DMU once or twice, but it's too long ago to remember how slow/fast it was.

IIRC, the weekday service at Bromsgrove for most of the 70s and 80s consisting of one morning train up and two evening trains back. The up train was a locomotive-hauled Gloucester-Sheffield service, usually a Peak, and the down trains were DMUs. On Saturdays there was an extra service each way around midday, both worked by DMUs. My recollection is that the DMU was painfully slow all the way up the bank, then very lively from Blackwell onwards. I don't recall many non-stop DMU workings through Bromsgrove in those days.

 

[AJM580]

From my own collection of logs dated 1981 to date, it always seemed to me that units with 2 power cars performed better. The BRCW 118s were good for 70 mph past Exminster and I had a 115 unit do 72 through Wymondham. Likewise the 3 car 101 sets allocated to Norwich were always quicker off the mark than the 2 car sets. The old Cravens sets used to shake themselves to bits at 55 mph, so can't imagine what 70 would be like.

 

[Magdalia]

The old Cravens sets used to shake themselves to bits at 55 mph, so can't imagine what 70 would be like.

A Cravens doing 70 mph down Hethersett Bank on the 30 foot jointed track was an experience!

 

[Zamracene749]

Caught an elderly Cravens unit years ago on a hot summer Leeds to Blackpool service. Left on time, full and standing. By New Pudsey we had lost about 5 minutes and I can still recall the smell of hot oil and diesel fumes, the poor thing was literally sweating blood! Then it had to contend with Copy Pit. Just before the summit, it was going so slow that all the passenger chattering died down, you could tell everybody was willing it over the top

 

[delt1c]

IIRC, the weekday service at Bromsgrove for most of the 70s and 80s consisting of one morning train up and two evening trains back. The up train was a locomotive-hauled Gloucester-Sheffield service, usually a Peak, and the down trains were DMUs. On Saturdays there was an extra service each way around midday, both worked by DMUs. My recollection is that the DMU was painfully slow all the way up the bank, then very lively from Blackwell onwards. I don't recall many non-stop DMU workings through Bromsgrove in those days.

Thge 3 car would be better as had 600 hp for 3 cars as apposed to a 2 car ( trailer twin ) which had only 300hp . Now a power twin was something else

 

[Pigeon]

IIRC, the weekday service at Bromsgrove for most of the 70s and 80s consisting of one morning train up and two evening trains back. The up train was a locomotive-hauled Gloucester-Sheffield service, usually a Peak, and the down trains were DMUs. On Saturdays there was an extra service each way around midday, both worked by DMUs. My recollection is that the DMU was painfully slow all the way up the bank, then very lively from Blackwell onwards. I don't recall many non-stop DMU workings through Bromsgrove in those days.

They would just about make it into second gear if they were in good nick, but it was pushing it a bit. As time went on it became more and more common for them to have to go all the way up in first.

The time taken for the gear change mechanism to get from first to second was a problem; they would often lose enough speed while the power was off during the change that second would now be too high a gear and they would have to drop back into first, and drivers trying to rush the change to get around this problem risked having it not go into gear at all and grind to a halt. More cautious drivers would not bother trying.

Probably more Worcester services didn't call at Bromsgrove than did, but having the run at the bank didn't help much; they would very rapidly lose speed and end up in first, same as the ones that did stop.

 

[Taunton]

For all that classic dmus were frequently pilloried, they did provide a substantial amount of service for more than a generation.

Some things seemed to be imposed by BR, and some left to the individual builders. Broadly anything beneath the underframe was standardised, power train, Blue Square controls etc, and the bodywork above was up to the designer. Some seem to have had Region input, such as interior colour schemes corresponding to their sponsoring region.

I wonder what it was about Cravens designs that got them such a poor reception. Their 100 single-engine but higher powered cars were indeed plagued with problems, but it must have been a BR idea to deviate from the symmetrical norm. The rest of what they did was mechanically standard, they built in steel instead of alloy, but they just seemed lacking in interior ambience.

 

[E27007]

I had a run on the S&C in the company of a retired Cravens Engineer, he told me Cravens export units were to a high standard, but BR only wanted a "cheap job", the proud Chief Engineer would look at the BR units with remorse "just look at what BR have done to my nice DMU's"

 

[Sir Felix Pole]

I remember the Cravens twin sets when they were based at Newton Heath for the North Manchester services. The extra power was useful on the hills, such as the Oldham Loop, but they seemed to symbolise the general decrepitude of the railway in the area at that time. The distinctive curved backed bus seats, the rattling Formica panels, the fume filled passenger saloons. Happy Days.

 

[Pigeon]

For all that classic dmus were frequently pilloried, they did provide a substantial amount of service for more than a generation.

Indeed, it is often said that their introduction on such-and-such a line resulted in a substantial increase in passenger numbers, so they can't have been all bad... I do sometimes wonder what they were like when they were brand new, before they had accumulated the plethora of minor faults and deficiencies none of which are very significant on their own but do clobber the experience badly when you have 30 years' worth of all the different varieties in one vehicle - chorus of squeaks and rattles, smelly heaters, daylight round the doors and so on. The rigidity of modern monocoque bodyshells, in contrast to the old wobbly frame construction, has done wonders for the ones we have these days.

And they did seem to suffer especially badly from the endemic failure of those times to ever clean anything - one thing the modern railway does get right is remembering to put things through the carriage washer and to change the covers on the seat cushions before you can't see what colour they are supposed to be. Particularly up north they used to get into an appalling state both inside and out, seats the same colour as the platforms and windows so opacified with mucky brown greasy brake dust that you couldn't see out. Trundling round industrial Lancashire/Yorkshire on a wet day in something resembling a skip was a pretty grim experience. I doubt we'd see anything like the number of passengers we do see nowadays if the modern ones were neglected as badly as the old ones used to be.

 

[Magdalia]

I wonder what it was about Cravens designs that got them such a poor reception. Their 100 single-engine but higher powered cars were indeed plagued with problems, but it must have been a BR idea to deviate from the symmetrical norm. The rest of what they did was mechanically standard, they built in steel instead of alloy, but they just seemed lacking in interior ambience.

The Cravens did not have a poor reception in East Anglia

The Cravens had better interior ambience than any other, with a hint of art deco in its elegance.

Having 2 windows instead of 3 at the front also gave them much clearer sightlines from the seats behind the driver.

But everything rattled: seats, windows, luggage racks, and especially the ashtrays in the smoking saloons.

 

[Revaulx]

It was all various classes of Derby in South Manchester, apart from a handful of Gloucesters and the very smartly turned out 3-car BRCWs (Class 104) on the Buxton line.

The North Manchester scene was a lot grimmer; the Cravens power twins stank of fumes, as did the powerful Calder Valley BRCWs (Class 110). The Blackpool 104s were really dingy compared to the Buxton ones.

The Trans Pennine express units were lovely and felt like proper trains, but they were underpowered from the start and had to be driven flat out up the hills; inevitably they were completely shot after little more than a decade.

 

[Springs Branch]

I remember the Cravens twin sets when they were based at Newton Heath for the North Manchester services. The extra power was useful on the hills, such as the Oldham Loop, but they seemed to symbolise the general decrepitude of the railway in the area at that time. The distinctive curved backed bus seats, the rattling Formica panels, the fume filled passenger saloons. Happy Days.

Speaking of Cravens units and the Oldham Loop, I wonder how the Power Twins fared on the notorious 1-in-27 Werneth Incline from Middleton Junction to Oldham?

The Oldham Loop went from steam to DMUs in 1958. The huge majority of services went via Failsworth, of course, but at dieselisation a couple of trains in the weekday peak still went to Oldham via Middleton Junction for a year or two until the Werneth line closed in 1963. I haven't read any accounts of fun and games in poor weather conditions and the like, but I imagine there might have been a few.

Apparently the last train up the incline on 5 Jan 1963 - a LCGB 'Werneth Incline Rail Tour' steam-hauled brake van special - slid to a halt in icy conditions and had to be rescued by a banking loco.