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Fastest Accelerating MUs in the UK

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dk1

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The old Class 309 Clacton express electrics were pretty astounding on the same tracks 60 years ago, especially in their original 10-car format. I seem to recall Cecil J Allen finding them starting from Chelmsford up to 100mph in less than 3 minutes.
They certainly where good units for their day.
 
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AM9

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I've yet to record any decent acceleration for S8 stock. Seems okay up to 30mph, but in common with most 3rd rail units, the acceleration above that is feeble compared with anything on the 25kV AC system.


The reports I've read of 309's and similarly regarding 321's is that they struggled to reach 100mph on level track.
Renatus Class 321's are much improved acceleration wise, but the braking performance is said to be less smooth and consistent than the standard 321 setup.
As you might expect from my username, I was (still am) an enthusiast of the 309s but am aware that no MKI EMUs stand direct comparison with even MKIII types as the power to weight ratios were much more modest in the '60s. The 321s had ratios of 7.7kW/tonne whereas the 309/2&3 class did their thing on just 4.9kW/tonne. They were also the only MKI EMUs geared for 100mph.* That is unless the REP 'tractor' units were counted, (12.5kW/tonne) because they never ran in passenger service without some deadweight 'TCs in tow. That would be like comparing the 309/1 2-car units in isolation (although they did often run alone between Thorpe le Soken and Walton-on-the-Naze), but that stretch of track was no speed-test strip. Their 8.4kW/tonne - would however have made them pretty snappy up to speed on the GEML.
* The 432s were geared for 90mph although there are many, (maybe apochryphal) reports -some on RUK, of wild speeds in excess of 100mph being logged. A 309 consist did actually acheive 109mph on some high speed test runs with frontal streamlining over a fast section of the WCML near Cheddington but their genuine 100mph gearing with less than 5kW/tonne and their 0.9mph/sec/sec rate was never going to make them rapid accelerators.

Interestingly, when the class 312s were introduced, their 90mph maximum speed was questioned, but it was explained that their faster acceleration (1.1mph/sec/sec) enabled them to slot into the faster ICs running both on the GEML, ECML and parts and the West Midlands LMR network, (much like the class 700's 100mph maximum is mitigated by their acceleration on the MML fasts).
 

DustyBin

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As you might expect from my username, I was (still am) an enthusiast of the 309s but am aware that no MKI EMUs stand direct comparison with even MKIII types as the power to weight ratios were much more modest in the '60s. The 321s had ratios of 7.7kW/tonne whereas the 309/2&3 class did their thing on just 4.9kW/tonne. They were also the only MKI EMUs geared for 100mph.* That is unless the REP 'tractor' units were counted, (12.5kW/tonne) because they never ran in passenger service without some deadweight 'TCs in tow. That would be like comparing the 309/1 2-car units in isolation (although they did often run alone between Thorpe le Soken and Walton-on-the-Naze), but that stretch of track was no speed-test strip. Their 8.4kW/tonne - would however have made them pretty snappy up to speed on the GEML.
* The 432s were geared for 90mph although there are many, (maybe apochryphal) reports -some on RUK, of wild speeds in excess of 100mph being logged. A 309 consist did actually acheive 109mph on some high speed test runs with frontal streamlining over a fast section of the WCML near Cheddington but their genuine 100mph gearing with less than 5kW/tonne and their 0.9mph/sec/sec rate was never going to make them rapid accelerators.

Interestingly, when the class 312s were introduced, their 90mph maximum speed was questioned, but it was explained that their faster acceleration (1.1mph/sec/sec) enabled them to slot into the faster ICs running both on the GEML, ECML and parts and the West Midlands LMR network, (much like the class 700's 100mph maximum is mitigated by their acceleration on the MML fasts).

Things have definitely moved on as you say, and the more powerful MK1 (and 2) based units were hamstrung in terms of acceleration by their higher gearing. The 309’s are a perfect example.

The 4-REPs were the exception to this but were an anomaly really and didn’t run in service without at least a 4-TC in tow
(there may have been the odd exception which would have been fun!). I always think of them as the Southern’s equivalent of a Deltic!

In terms of older units, has anybody mentioned the 487s? Only 380hp per motor coach but they ran singly or in pairs with no trailers, were light and geared for 35mph. They must have shifted from a standing start!
 
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Railperf

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For diesel, and I have said it before, a 185 will out-accelerate pretty much everything. Even a voyager, especially when second gear kicks in. Even tho the drive train is the same the 185 will outperform a 180 on acceleration and despite its much heavier weight. The lower top end speed of the 185 is what initially gives it the edge but it is also where the adelante and voyager both eventually catch up and overtake.

However since this post has been revived I would be tempted to think a 185 may have met its match in the 68/mk5 combo. 900hp per axle And ac traction more than outweighs the extra weight and is more powerful than an 802 on diesel. Them things seem to take off like a demented bat out on Man Vicc and storm up !Miles Platting
Again my fastest recorded figures for both classes say 222's have the edge over a 185. But neither in a 755/4 league.
 

TheEdge

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you must be getting bored with warp factor 5 by now :p . A news article also suggests delays caused by leaf fall were much lower this year too.

Absolutely not, I'm yet to get bored of whacking a /3 full open on the GEML and pretending I'm Picard on the Enterprise!

Their leaf fall performance this year has been brilliant. Last year they were a little hit and miss but a year of tweaking has had an impact. In my experience they are much more liable to spin and slide that the old stock initially but as soon as the WSP detects either they get it dealt with rapidly totally negating their slippy nature.
 

8J

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Again my fastest recorded figures for both classes say 222's have the edge over a 185. But neither in a 755/4 league.

You can compare 220/221/222s and 755s and 80x units together as they're Diesel Electric Multiple Units(diesel engines power the generator which in turns powers traction motors and auxiliaries). Sprinters, 180s and 185s are Diesel Mechanical Multiple Units which puts the power down in a different way and hence why you see a noticeable change in the rate of acceleration on a 185 in second gear.
 

Railperf

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You can compare 220/221/222s and 755s and 80x units together as they're Diesel Electric Multiple Units(diesel engines power the generator which in turns powers traction motors and auxiliaries). Sprinters, 180s and 185s are Diesel Mechanical Multiple Units which puts the power down in a different way and hence why you see a noticeable change in the rate of acceleration on a 185 in second gear.
To be honest..the difference between electric traction on the 22x and hydraulic transmission on the 18x series with the same engines and similar body weights adds to the interest as to how they perform so similarly on the road - despite 22x being detuned by 50hp per engine!!
 

Railperf

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378s definitely have better acceleration compared to 377s and 700s. They do have more traction motors per motor vehicle than a 377. Many times I've started moving at same time as one in platform next to me at Norwood Junction, them never passing me until I'm halfway in the platform at Anerley. 378s also do have a massive difference between running on DC and AC.
DC performance is always poor in comparison to 25kV AC. Mainly due to power supply limitations.
 

notadriver

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For diesel, and I have said it before, a 185 will out-accelerate pretty much everything. Even a voyager, especially when second gear kicks in. Even tho the drive train is the same the 185 will outperform a 180 on acceleration and despite its much heavier weight. The lower top end speed of the 185 is what initially gives it the edge but it is also where the adelante and voyager both eventually catch up and overtake.

However since this post has been revived I would be tempted to think a 185 may have met its match in the 68/mk5 combo. 900hp per axle And ac traction more than outweighs the extra weight and is more powerful than an 802 on diesel. Them things seem to take off like a demented bat out on Man Vicc and storm up !Miles Platting
I agree - a 185 seems to be more willing than a Voyager or 180. Yet I’m certain 222s are superior performers. I think the 68/mk5 combo are superior to the 185 especially at the higher speed ranges.
 

37057

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To be honest..the difference between electric traction on the 22x and hydraulic transmission on the 18x series with the same engines and similar body weights adds to the interest as to how they perform so similarly on the road - despite 22x being detuned by 50hp per engine!!

I suppose if you factor in the amount of fuel in the tanks and the number of people on board at the time of each measurement then things may differ slightly.

Lets say 1 tonne per 15 seated passengers and 0.8kg per litre of fuel.

If my crude calculations represent any sort of accuracy then a fully seated Class 185 (standees and luggage excluded) with tanks full of fuel comes in at roughly 17.5 tonnes heavier than one that is ECS running on fumes!

A Class 220 seems to balance out with a similar figure due to extra passengers but less fuel capacity.
 

Railperf

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I agree - a 185 seems to be more willing than a Voyager or 180. Yet I’m certain 222s are superior performers. I think the 68/mk5 combo are superior to the 185 especially at the higher speed ranges.
Aporox what percentage of 185s v 180 and 22x run with a full set of engines?
Am I right guessing 185's are most reliable?
Class 180s on both GC and HT were worst - almost a guarantee one if not 2 engines out!
 

AM9

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I suppose if you factor in the amount of fuel in the tanks and the number of people on board at the time of each measurement then things may differ slightly.

Lets say 1 tonne per 15 seated passengers and 0.8kg per litre of fuel.

If my crude calculations represent any sort of accuracy then a fully seated Class 185 (standees and luggage excluded) with tanks full of fuel comes in at roughly 17.5 tonnes heavier than one that is ECS running on fumes!

A Class 220 seems to balance out with a similar figure due to extra passengers but less fuel capacity.
Ignoring fuel and passenger load, a class 220 has a power curve that extends 25% faster than the class 185s, - and their power to weight ratio is 13% higher than their derated state than the TPE units, so the consistency of their power curve doesn't come with the disadvantage of the additional weight of the generators and controls.
 

londonmidland

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Departing York on a 222 at the same time as a HT 802, the 802 was left behind way before Colton Jn. In its defence, it was running on diesel.

Conditions were raining.
 

Railperf

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802's are slow on diesel.. Not worth a mention compared to the 222,s. Better than 153 156 158s and 170 though
 
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notadriver

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Departing York on a 222 at the same time as a HT 802, the 802 was left behind way before Colton Jn. In its defence, it was running on diesel.

Conditions were raining.
Not a really a good comparison. A 68 and mk5 would have been interesting.
 

py_megapixel

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802's are slow on diesel.. Not worth a mention compared to the 222,s. Better than 153 256 158s and 170 though
256? (I assume you meant to write 156).

Worth nothing by the way that a lot of the lesser accelerating stuff, particularly the more modern stock which doesn't seem to have been built for ride quality (*COUGHcivityCOUGH*) has a real jolt and feeling of force when it first starts off, which makes the acceleration feel a lot faster than it is...
 

20atthemagnet

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So with regards to what we’ve seen so far is there anything that can pip a 755/3 on juice? 27 seconds to 60 is ludicrous. 710 31 seconds, I assume a 345 would be just behind them, having a trailer in the middle does them no favours. Anything else?
 

AverageTD

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So with regards to what we’ve seen so far is there anything that can pip a 755/3 on juice? 27 seconds to 60 is ludicrous. 710 31 seconds, I assume a 345 would be just behind them, having a trailer in the middle does them no favours. Anything else?
Not in service yet but when the 777 comes in I reckon that'll give the 755/3 a run for its money.
 

Energy

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Not in service yet but when the 777 comes in I reckon that'll give the 755/3 a run for its money.
The 777s are designed more for acceleration. They, and the T&W units, will likely be incredibly fast judging by the 755s.
 

AverageTD

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One thing I didn't think of are the Stadler Citylink tram-trains. Although they probably wont win any awards for 0-60, their 0-40 time must be pretty impressive.
 

Dave1987

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Thing is about the 755/3 is the acceleration does not peter out as drag increases due to speed. As we know drag squares with speed but the acceleration of a 755/3 on the wires just doesn’t seem to die out all the way to 100mph. They just keep accelerating with seemingly little impedance all the way to 100mph
 

dk1

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The 777s are designed more for acceleration. They, and the T&W units, will likely be incredibly fast judging by the 755s.
The 755 will soon pass it even if it does accelerate any faster as it will crawl along at 75mph.
 
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