Towing capabilities of first-generation DMUs

[frankmoh]

https://www.railforums.co.uk/threads/unusual-multiple-unit-couplings.293468/ based on this thread

Several of the consists in this thread have first generation DMUs towing trailer cars or even 'dead' motor coaches. What were the towing capabilities of these trains? How many trailers and motor coaches could be in one consist?

It would be interesting to know how a 117 stacked up against a 101, or even worse, the Bubble Car!

 

[DM352]

The 117/101/121 I think had 2x150hp per power car so should be the same and back in the day a 3 car could tow a parcels coach I believe.

In terms of limit, only example I have is those 4 car tyseley units where an engine on the 115 end failed on the cross city and it was just very slow losing time.Without going off topic I never understood why they did the tyseley 4 car with 116 115 power cars as it was already underpowered.

On a 108 power trailer once at Meadowhall I did notice one gearbox not engage only in first gear causing the engine to high rev and not drive hence a slow start but it picked up in subsequent gears.

 

[Taunton]

Two types of dmu car, lightweight (short, aluminium body) and heavyweight (long, steel body). Some lightweights by independent manufacturers were not so "light". Twin engines 150hp as standard, but various heavyweights had 230hp ones. And different initial formations and combinations of power cars and trailers. So all together you really need to know the power-to-weight ratio of any set first. Then there were the characteristics of the route, whether flat or hilly.

or even worse, the Bubble Car!

In fact the Western Region 150hp single cars were somewhat used specifically for haulage. The Plymouth to Saltash shuttle used twin sets of such power cars, which towed on several trips a couple of 6-wheeled milk tankers from the Saltash creamery, decidedly heavy when full. The similar parcels cars had 230hp engines, and hauled vans as standard.

The most extreme of this was the Northern Ireland Railway, which had even more powerful 275hp engines in their power cars. These were treated as loose formations, making up sets of these with trailers and standard coaches for each diagram, but they even used two power cars together to haul the remaining nightly freight train from Belfast to Londonderry and back, it just being accepted they were slow (and extremely noisy) on gradients. The transmissions later became unreliable, it was said this arduous duty had really overstressed them.

 

[Acathater]

the Western region 3-car cross country units classes 119/120 were occasionally used to tow single non-corridor coaches on busy summer weekends to Weymouth and other holiday spots. Performance was slow...

 

[hexagon789]

https://www.railforums.co.uk/threads/unusual-multiple-unit-couplings.293468/ based on this thread

Several of the consists in this thread have first generation DMUs towing trailer cars or even 'dead' motor coaches. What were the towing capabilities of these trains? How many trailers and motor coaches could be in one consist?

It would be interesting to know how a 117 stacked up against a 101, or even worse, the Bubble Car!

Perhaps not quite what you've asked, as I assume you meant more ordinary passenger DMUs, but one of the specifically designed parcels DMUs, the Class 128 Gloucester cars with 230bhp engines were quoted as:

Payload - 10 tons
Trailing load - 64 tons

The latter figure would be broadly equivalent to two loaded Mk1 BGs for example.

I believe normal trailing loads for ordinary DMUs were effectively equivalent to a one coach load, but figures varied depending on the ratio of engines and trailers within the DMU set.

 

[eastwestdivide]

If you google dmu tail loads, there are a lot of useful-looking hits

 

[Magdalia]

https://www.railforums.co.uk/threads/unusual-multiple-unit-couplings.293468/ based on this thread

Several of the consists in this thread have first generation DMUs towing trailer cars or even 'dead' motor coaches. What were the towing capabilities of these trains? How many trailers and motor coaches could be in one consist?

It would be interesting to know how a 117 stacked up against a 101, or even worse, the Bubble Car!

For blue square diesel mechanical DMUs the maximum number of power cars was usually six.

For haulage capability the key factor is power to weight ratio, and this depends on the number of trailer cars not the number of motor cars.

In East Anglia 2 car power car + trailer car sets hauled single van trailing loads until well into the 1970s, especially at this time of year to cope with heavy pre-Christmas mail traffic.

the Western region 3-car cross country units classes 119/120 were occasionally used to tow single non-corridor coaches on busy summer weekends to Weymouth and other holiday spots. Performance was slow...

I had the misfortune to make many journeys between East Anglia and the West Midlands in Swindon cross country units (class 120). Progress would be laborious, even though they weren't towing anything, I dread to think what they would have been like with a trailing load.

 

[norbitonflyer]

Several of the consists in this thread have first generation DMUs towing trailer cars or even 'dead' motor coaches. What were the towing capabilities of these trains? How many trailers and motor coaches could be in one consist?

It would be interesting to know how a 117 stacked up against a 101, or even worse, the Bubble Car!

Other than the extra cab, bubble cars (single units) were mecehanically identical to other power cars so actually had a better power to weight ratio than any unit that included a trailer. Add8ing a tail load would still give it tyhe same performance as a standard twin or quad unit.

In order of power/weight, allowing for the 238hp Albion engines in Classes 114 and 115 being about 50% more powerful than the standard BUT/AEC/Leyland 150hp examples
The Rolls Royce units (classes 110, 111) had 180 hp engines

Power twins, triples and quads had two power cars. Single units (obviously) and twins (unless stated to be power twins) had one. All power cars had two engines

300hp/carriage - Single unit or power twin
240hp/ carriage - RR engined 3-car (Calder valley units)
238hp/ carriage - Albion engined units (2- or 4-car)
200hp/unit - 3-car unit
180hp/carriage - Rolls Royce twin
160hp/carriage - Albion twin with tail load
150 hp / carriage - Twin unit, quad unit, single or triple unit with tail load
100 hp/carriage - twin unit with tail load


I well remember 114s operating with tail loads on the Lincoln-Grantham route. We often used to use that route, either to visit my grandma in London, or when Dad escorted her to Grantham to catch her train on her way back from visiting us. (she was perfectly capable of doing it herself - she was only in her sixties, and would still travel alone in her eighties (via Newark then of course, which she hated) - but it was a treat for us kids)

 

[sh24]

IIRC the Western had driving trailers specifically for use with the Bubble cars.

I can remember the Class 128 DMU’s sometimes having a swinger/tail load.

 

[Western 52]

the Western region 3-car cross country units classes 119/120 were occasionally used to tow single non-corridor coaches on busy summer weekends to Weymouth and other holiday spots. Performance was slow...

In their early days a few 119s had an extra coach inserted, a wired Hawksworth I think. I'm not sure how long this lasted.

 

[norbitonflyer]

In their early days a few 119s had an extra coach inserted, a wired Hawksworth I think. I'm not sure how long this lasted.

They were insread of a purpose built trailer

 

[WesternLancer]

I seem to recall seeing pictures of the original GWR streamlined railcars towing things. Am I correct?

 

[StephenHunter]

IIRC the Western had driving trailers specifically for use with the Bubble cars.

I can remember the Class 128 DMU’s sometimes having a swinger/tail load.

The EOR has a Class 121 driving trailer that is being used with the 117 driving motor.

 

[Taunton]

I seem to recall seeing pictures of the original GWR streamlined railcars towing things. Am I correct?

Yes, the first ones built did not, in fact they had no drawgear or even buffers, which made life challenging when broken down. The second batch did have these, and towed typically a van when required, there being no parcels etc accommodation in the railcar. It did mean it had to run round the van and shunt it as required itself at the terminus.

 

[coppercapped]

Yes, the first ones built did not, in fact they had no drawgear or even buffers, which made life challenging when broken down. The second batch did have these, and towed typically a van when required, there being no parcels etc accommodation in the railcar. It did mean it had to run round the van and shunt it as required itself at the terminus.

If I remember correctly from my train watching days at Reading General one of the later GWR twin sets was lengthened by including a Hawksworth corridor coach. It ran (some of?) the Reading - Newbury locals. This was before I went to Uni in 1962 so it must have been late 1950s, early 1960s.

 

[WesternLancer]

Yes, the first ones built did not, in fact they had no drawgear or even buffers, which made life challenging when broken down. The second batch did have these, and towed typically a van when required, there being no parcels etc accommodation in the railcar. It did mean it had to run round the van and shunt it as required itself at the terminus.

Thanks. Also I’d forgotten about the ones that were buffer free.

 

[Gloster]

I seem to recall seeing pictures of the original GWR streamlined railcars towing things. Am I correct?

The first seventeen, including the first parcels car, could not haul anything, but the later ones could. No 18 was designed with buffing gear and couplings, and was sent to the Lambourn branch, where it could haul up to two coaches or, more importantly on that line, several horseboxes. The design of this vehicle was a major step forward in the development of the DMU in Britain.

 

[norbitonflyer]

For blue square diesel mechanical DMUs the maximum number of power cars was usually six.

Did this ever happen? unless it was a very unusual formation (3x power twin?), it would need at least nine cars (3x3), and I don't recall ever seeing that. 2x4car or 4x2 car would only have four power cars.

I did once ride a train with five power cars - a DPU leading a pair of Class 117s - but never six as far as I can recall. The Trans Pennine units had four power cars, as did the 126s when in 6-car formation, but I don't think they ever operated in multiple, either within class or with anything else.

 

[Western 52]

Did this ever happen? unless it was a very unusual formation (3x power twin?), it would need at least nine cars (3x3), and I don't recall ever seeing that. 2x4car or 4x2 car would only have four power cars.

I did once ride a train with five power cars - a DPU leading a pair of Class 117s - but never six as far as I can recall. The Trans Pennine units had four power cars, as did the 126s when in 6-car formation, but I don't think they ever operated in multiple, either within class or with anything else.

I can remember some 9 car sets running. For example in the hot summer of 1976 we had 3 x class 116 on some Rhymney to Barry Island services. It was essential to make sure you were in the right set coming home as most stations didn't have long enough platforms.

 

[MarlowDonkey]

I can remember some 9 car sets running.

In the aftermath of the December 1973 Ealing derailment, there were some 9 car lashups which took the long way round via the Greenford branch on the New North Main Line to reach Paddington. These would have been 117 trlples.

In nornal times 7 car formations were used frequently. These would have been 2* 117 plus the unpowered trailer that could also run with a 121. You never saw these divided and running as a four car unit. Perhaps four powercars and three trailers was enough, but two power cars and two trailers didn't have enough power. Until the advent of HSTs, the seven car formations would rattle their way down the Mains non-stop at 70mph to Paddington from Burnham, Slough or Maidenhead at peak hours.

 

[Richard Scott]

In terms of limit, only example I have is those 4 car tyseley units where an engine on the 115 end failed on the cross city and it was just very slow losing time.Without going off topic I never understood why they did the tyseley 4 car with 116 115 power cars as it was already underpowered.

They needed 4 car units but not enough 115 power cars hence the mix. Extra power of one 115 car allowed extra coach to be inserted. Only a little off topic as the extra coach wasn't a trailing load?!!!

 

[Taunton]

Did this ever happen? unless it was a very unusual formation (3x power twin?), it would need at least nine cars (3x3), and I don't recall ever seeing that. 2x4car or 4x2 car would only have four power cars.

I did once ride a train with five power cars - a DPU leading a pair of Class 117s - but never six as far as I can recall. The Trans Pennine units had four power cars, as did the 126s when in 6-car formation, but I don't think they ever operated in multiple, either within class or with anything else.

Sure. I recall the shuttle service to the first motor show in 1978 held at the NEC, which had huge attendance. Outward from New Street to International was an 8-car 304 emu, which was unusual in itself to see them in multiple. Return was a 9-car dmu formation of Tyseley suburban 116s. All worked fine.

Liverpool had many Derby Lightweight power twins, and in summer sent an 8-car excursion formation of them to Blackpool each day, care being taken to mix in power-trailer sets as well so as not to exceed the 6 power car maximum, which I had read was down to voltage drop on the control circuits through the cars. I never quite got why the voltage drop was more going through a power car than through a trailer. Long dmu formations were common in early days, but died out - when the North Wales line was dieselised around 1965, taking over from steam services, 6-car formations of power trailer sets from various manufacturers were normal, and 8-car on the busiest services, all done with units surplus from elsewhere as building them had ceased by this time.

 

[hexagon789]

Did this ever happen? unless it was a very unusual formation (3x power twin?), it would need at least nine cars (3x3), and I don't recall ever seeing that. 2x4car or 4x2 car would only have four power cars.

I did once ride a train with five power cars - a DPU leading a pair of Class 117s - but never six as far as I can recall. The Trans Pennine units had four power cars, as did the 126s when in 6-car formation, but I don't think they ever operated in multiple, either within class or with anything else.

The 79xxx were formed as 9-car sets on certain workings during their brief stint on the WR.

The idea was to run 3s or 6s, then add an extra 3 if necessary.

The middle set had a gangwayed driving motor at each end, sandwiching one of the buffet cars - so through access was preserved regardless of full train length.

 

[furnessvale]

Slightly off topic but I can attest to the banking capability of BRCW dmus, having witnessed a 3 x 3 set of such units, complete with passengers, banking a stalled steam hauled freight out of the old platform one at Preston.

Presumably having decided to route the passenger into platform one after the departure of the freight, its stalling was no anticipated and the route ahead was blocked for the passenger.

It caused quite a stir in Ladywell House amongst the assembled management watching, and I do not know to this day the legality of the movement!

 

[Merle Haggard]

My recollection is hazy, but I think I can remember that the cabs had rows of (purple) lights which when lit confirmed engines running, coolant temperature and oil pressure o.k., one row for each power car, and I think only 6; would that not be a limit on the number of power cars?
I also remember 'LW' (stencilled in white) suddenly appearing on the ends of the 'lightweight' dmus in the later 1960s (i.e., after they had been in service for some time). I remembering hearing/reading at the time that this was to experience of frame distortion, although I can't remember whether this was the result of hauling training loads, or being formed in loco hauled e.c.s. to and from works. Sectional/regional appendices of the day had instructions, I think, particularly about the latter.

 

[6Gman]

My recollection is hazy, but I think I can remember that the cabs had rows of (purple) lights which when lit confirmed engines running, coolant temperature and oil pressure o.k., one row for each power car, and I think only 6; would that not be a limit on the number of power cars?

That is my clear recollection too.

I also seem to think there were sometimes 12-car lash-ups of 6 x 2-car motor/trailer units used on the North Wales coast in the 60s/early 70s.

 

[Grumpy]

I have a copy of a booklet issued in 1957 by the Western Region . This is titled "Multiple Unit Diesel Trains" and "For the information of Operating Department Staff".
It states that Inter-City trains must not convey tail traffic and the booked formation must not be varied.
Regular tail traffic must only be attached to other MU's where authorised and shown in train-working notices. Additional vehicles must not be conveyed unless specifically authorised by the District Operating Superintendent or Traffic Superintendent. The total trailing tonnage must not exceed the total weight of the power cars.
The booklet also states that in terms of loading each of the following is equivalent to one MU trailer-
One bogie van
One long-wheel-base, four or six wheel van
One milk tank
Two short-wheel-base four wheel vehicles.

 

[Magdalia]

Did this ever happen? unless it was a very unusual formation (3x power twin?), it would need at least nine cars (3x3), and I don't recall ever seeing that. 2x4car or 4x2 car would only have four power cars.

On Friday evenings in summer 1987 the 2035 Birmingham-Cambridge was booked for a 12 car DMU off Tyseley comprising 3*4 car sets.

 

[Taunton]

I seem to recall seeing pictures of the original GWR streamlined railcars towing things. Am I correct?

These were not what might be described as multiple units, as they were I believe mechanically single units whose controls only worked on the car. This was until the last ones were built, cars 35 to 38, which were two twin units, only one cab on each car, with the engines etc of the second car controlled from the first, with a system not far removed from what we now know as Yellow Diamond. However, I don't believe they had any control connections at the driving cab end, only at the inner end. A standard GWR carriage was then adapted to have through control wires, and inserted to give a 3-car unit. They did have vacuum brake connections on the outer end to attach vans. I'm still not sure how they heated trailing passenger carriages.

These cars were particularly unfortunate, and three out of the four were destroyed by (separate) fires in the early 1950s. Car 33 was then adapted to join the one remaining one. By 1962 I used to see it still in service, arriving at Bristol TM mid-afternoon, I believe from Weymouth.

 

[MadMac]

My recollection is hazy, but I think I can remember that the cabs had rows of (purple) lights which when lit confirmed engines running, coolant temperature and oil pressure o.k., one row for each power car, and I think only 6; would that not be a limit on the number of power cars?
I also remember 'LW' (stencilled in white) suddenly appearing on the ends of the 'lightweight' dmus in the later 1960s (i.e., after they had been in service for some time). I remembering hearing/reading at the time that this was to experience of frame distortion, although I can't remember whether this was the result of hauling training loads, or being formed in loco hauled e.c.s. to and from works. Sectional/regional appendices of the day had instructions, I think, particularly about the latter.

That’s correct, but there is a “twist” to that.

When the last of the 101 “power twins” were being transferred from Glasgow to Manchester (mid-2000 IIRC) there were a tot of 16 cars. The decision was to transfer them in two batches of eight - the first one was run “self powered” with eight power cars. I had some discussion with the owner of the Railcar site - his understanding was that someone had done some calculations and determined that there would be sufficient voltage on the control circuits to operate the rear cars, this being the main concern. That train apparently was put into Beattock Summit loop with the fire bells going off. The second batch the following week was hauled by two Class 37s.