Class 309 EMU v Class 47 on 8 coaches

[Justin Smith]

I was musing on the performance differential between a Class 309 EMU and a class 47 hauling 8 coaches.

The class 47's rail horse power would be about 80% of it's rated power (i.e. 2064 hp) and total train weight about 400 tons : 5.2hp/ton
Interestingly O S Nock would probably have described 8 coaches on a class 47 as a ""feather weight" load !

The class 309 (for an 8 car set) rail power would be 2240 hp and the weight about 340 tons : 6.6 hp/ton
But I assume the quoted 2240hp power is continuous ? A class 86 it's continuous power rating is about 4000hp, but it is capable of putting out much more for shorter periods, up to 6000hp. What would the class 309s maximum power rating be ? And for how long ?

In the real world how much faster over say Liverpool St to Norwich, would the Class 309 be ?

 

[Bevan Price]

Cannot answer fully, but would expect the Class 309 to be slightly faster.
For eample, from Railway Performance Society "Historical Fastest Times", fastest recorded times from Chelmsford to Colchester:
Class 309 (8 coach) 16m 15s
Class 47 (Loco +7) 17m 18s

 

[Acathater]

Surely with these examples the main cause of difference is the better acceleration of the electric set with better torque, not simply the power rating

 

[Helvellyn]

I know the OP wants to compare an 8-car Class 309 (2 units) with a Class 47 + 8 coaches, but it shouldn't be forgotten that when the 309s were introduced (as AM9s) there were also 2-car units to boost peak capacity, and performance. So a 10-car unit had 3360hp (not sure of the total weight).

 

[Snow1964]

In their early years the peak hour trains were formed as 10car, with the addition of a 2car with same power as the 4car units. The theory was the more powerful configuration could offset longer dwell times on busy services.

Later on, some of the 2car sets were lengthened by adding former hauled coaches.

 

[45Fox]

Surely with these examples the main cause of difference is the better acceleration of the electric set with better torque, not simply the power rating

I would agree with this.
Comparing an EMU with a diesel loco hauled rake isn't really a like-for-like comparison, the acceleration of the electric unit would be far better.
I've driven both over the years.

 

[Sun Chariot]

Cecil Allen (November 1971). "Steam, diesel and electric exploits". Railway World. Vol. 32, no. 378. Shepperton: Ian Allan. p. 470
"....From 1971 it was found that additional capacity was required for the evening peak and the 17.40 departure from Liverpool Street station was increased to 12 coaches by the addition of a second 2-car unit; bringing the power output up to 4,512 hp from a train of 521 long tons (529 t) tare."

Sadly I was too young to enjoy that; all the 309s were 4-car units by the time my teen self was riding them.

 

[norbitonflyer]

The 2-car, and former 2-car units were always recognisable because of the pantograph over one of the cabs.

 

[Sun Chariot]

The 2-car, and former 2-car units were always recognisable because of the pantograph over one of the cabs.

And I always preferred riding in those longer saloons. A bit quieter with no door between 4th + 5th bays

 

[Helvellyn]

And I always preferred riding in those longer saloons. A bit quieter with no door between 4th + 5th bays

Probably was even nicer when they were DBMSKs if you could get one of the six compartments to yourself off-peak.

 

[nw1]

As an aside did the 2-car 309s see any off-peak use? Or were they solely used in the peak?

 

[Snow1964]

As an aside did the 2-car 309s see any off-peak use? Or were they solely used in the peak?

Not in normal service, although possibly there were rare workings.

Until about 1982 they operated as 8 cars dividing / joining at Thorpe-le-Soken with one portion for Clacton and other for Walton on the Naze. It was only peak trains that were strengthened.

As built was 8 2car (units 601-608), 8 4car with griddle car (611-618) and 7 4car no catering (units 621-627)

 

[Justin Smith]

Does anyone know the peak power that class 309s could pull out of the wires, or is it not like with locos (which have two ratings peak and continuous) ?

== Doublepost prevention - post automatically merged: 24 Feb 2026 ==

Cannot answer fully, but would expect the Class 309 to be slightly faster.
For eample, from Railway Performance Society "Historical Fastest Times", fastest recorded times from Chelmsford to Colchester:
Class 309 (8 coach) 16m 15s
Class 47 (Loco +7) 17m 18s

A class 47 on 7 : O S Nock would be having kittens......
I wonder what he'd have thought about a 4 coach HST !

 

[Harpo]

The 2-car, and former 2-car units were always recognisable because of the pantograph over one of the cabs.

The 2 car sets & former 2 car sets all seemed to be orientated with the pan at the country end. I seem to recollect that Clactons weren’t permitted at Colchester Town?? That would have turned them of course. They did, though, appear mid-formation.

 

[Taunton]

As both Cecil J Allen and O S Nock have been mentioned above, it was one of them that timed a 309 in the early electric years to accelerate eastwards from Chelmsford, getting up to 100 mph in just 4 minutes from the start, something I doubt a Class 47 could do.

As an aside did the 2-car 309s see any off-peak use? Or were they solely used in the peak?

As I somewhat recall it, the original plan was all 10-car sets from London, 4-car with Buffet to Clacton, 4-car standard to Walton, and the 2-car detached at Colchester to do all stations to Clacton.

 

[Sad Sprinter]

What about against an 86? I remember an interesting thread a few years ago that posed the question what if the original LMR electrification used 309s instead of loco hauled stock.

 

[Justin Smith]

What about against an 86? I remember an interesting thread a few years ago that posed the question what if the original LMR electrification used 309s instead of loco hauled stock.

Sounds very interesting.....

 

[AM9]

What about against an 86? I remember an interesting thread a few years ago that posed the question what if the original LMR electrification used 309s instead of loco hauled stock.

The 309s were originally intended for the ECML on services London to York. The electrification never happened though, (in the '60s, - it eventually did in the '80s), by which tome other (faster) electric options were available. A 309 set was also used for testing high speed running on the WCML but it only reached just over 100mph. I would suggest that the DC traction setup was tuned to the GEML route infrastructure.
Those tests, (around Chadderton) also had LMR class 81-85 electric locos which could be formed into higher hp/tonne consists, - clearly inadequate in passenger capacity terms, but it provided useful data for the upcoming APT design.

== Doublepost prevention - post automatically merged: 24 Feb 2026 ==

Cecil Allen (November 1971). "Steam, diesel and electric exploits". Railway World. Vol. 32, no. 378. Shepperton: Ian Allan. p. 470
"....From 1971 it was found that additional capacity was required for the evening peak and the 17.40 departure from Liverpool Street station was increased to 12 coaches by the addition of a second 2-car unit; bringing the power output up to 4,512 hp from a train of 521 long tons (529 t) tare."

Sadly I was too young to enjoy that; all the 309s were 4-car units by the time my teen self was riding them.

I was commuting on the GEML in the early '70s and clearly remember the 17:40 steaming through Shenfield just before my train, the 18:10 slow to Colchester arrived. I don't recall the absolute need for an extra 100 seats, I was told that the down paths ex LST, between 17:00 and 18:00 were so tight around the 17:40 that the timetable could be kept by increasing the power to weight ratio on that train. It certainly left anything on that line standing up Brentwood Bank and up to Mountnessing, where the 6.25KV changed to 25KV eastwards.
Of course, all things were relative, and 30 years later, a class 350 consist could easily match the 309's best performances, possibly except for comfort.

 

[Justin Smith]

Of course, all things were relative, and 30 years later, a class 350 consist could easily match the 309's best performances, possibly except for comfort.

Quite.....

== Doublepost prevention - post automatically merged: 25 Feb 2026 ==

The 309s were originally intended for the ECML on services London to York.

I feel more calculations coming on.....

Standard Class 309 EMU = 6.6 hp/ton
10 car Class 309 EMU = 7.7 hp/ton

(both at continuous rating, maximum - for a short period - would be higher ? )

Class 40 + 11 = 3.1 hp/ton
Class 40 + 8 = 3.9 hp/ton

Class 47 + 11 = 4.1 hp/ton
Class 47 + 8 = 5.2 hp/ton

Deltic + 11 = 5.4 hp/ton
Deltic + 8 = 6.9 hp/ton

HST (8 coach) = 8.6 hp/ton

(all the diesel electric locos at 80% rail power)

 

[jfollows]

What about against an 86? I remember an interesting thread a few years ago that posed the question what if the original LMR electrification used 309s instead of loco hauled stock.

My commute home used to be 86+5 mark 1 coaches, the power/weight ratio was pretty good. I once noticed 21 minutes Piccadilly-Macclesfield (booked time) despite a 20 mph slack between Bramhall and Poynton.

From memory, when mark 2 coaches were used there had to be more than 5 of them.

 

[Sad Sprinter]

My commute home used to be 86+5 mark 1 coaches, the power/weight ratio was pretty good. I once noticed 21 minutes Piccadilly-Macclesfield (booked time) despite a 20 mph slack between Bramhall and Poynton.

From memory, when mark 2 coaches were used there had to be more than 5 of them.

Why only 5? Was it a cross country service?

 

[jfollows]

Why only 5? Was it a cross country service?

16:23 Manchester-Coventry, yes. In the 1970s there was one service Manchester-Birmingham (and beyond) every 2 hours, previous service was 14:23 to somewhere like Plymouth, following service was 18:28 to Birmingham. Different times!

There were similar consists on the Manchester-Cardiff services, which changed locomotives at Crewe, although from memory these were more often 81-85.

 

[Taunton]

There is an early 1960s colour painting (by Cuneo?) which shows "Grantham electrified", with ECML services in the hands of a Class 81 (blue) and a Class 309 (maroon).

 

[AM9]

There is an early 1960s colour painting (by Cuneo?) which shows "Grantham electrified", with ECML services in the hands of a Class 81 (blue) and a Class 309 (maroon).

Now that would be interesting to see. I've looked at a list of pictures that purported to all of his published works but couldn't find anything like that.

 

[SteveB000]

I’m travelling at present but I recall the GEC WT401motors had a peak to continuous rating factor of around 1.8 so an 8 car unit would be about 1128 *2 * 1.8 = 4061hp in the range 20-35 mph or close to double the rail hp of a class 47

 

[Richard Scott]

I’m travelling at present but I recall the GEC WT401motors had a peak to continuous rating factor of around 1.8 so an 8 car unit would be about 1128 *2 * 1.8 = 4061hp in the range 20-35 mph or close to double the rail hp of a class 47

Be more than double if the 47 was required to provide ETH.

 

[Harpo]

The Clactons’ achilles heel was cooling. Adding more stops on the GE’s fast sections made them less reliable and their final NSE use was not what suited them best.

I seem to recall that their power controller was quirky too? Didn’t it have to go back to ‘off’ before using a lower power setting??

 

[SteveB000]

Most of the 1st generation ac units required the controller to return to off before using a lower setting. It was a function of the tap changer

 

[davidhg]

The mention of Manchester to Macclesfield makes me wonder how the 309s performed when transferred North late in their career?