Class 47 Acceleration and Braking

[ComUtoR]

Well I didn't know that but judging by how much 465/9s wheelslip I don't think they have sanders either lmao

They have sanders.

 

[SolomonSouth]

They have sanders.

Really? I went on one today that slipped in dry conditions. Maybe the driver just didn't use it lmao

 

[ComUtoR]

Really?

Yes really

Maybe the driver just didn't use it lmao

Maybe they didn't want to

 

[Railperf]

Have to say I doubt you'd see any further action of this sort very often over the last decade+ or indeed going forward unless it's faulty measurement equipment or a driver's last ever shift (possibly if they feel naughty).

Driver pal of mine was warned in a friendly manner by his DM not to go mad on his last day at a TOC. Must be an emotional reaction to have a last 'blast'.

Goung back to the '47' has anyone confirmed at what speed the TSW2 version maxes out at?

 

[SolomonSouth]

Goung back to the '47' has anyone confirmed at what speed the TSW2 version maxes out at?

120mph. I know, ****ing ridiculous

 

[matchmaker]

Clocked one at 107 once, if want a serious speeder how about a 50 at 116?

I can quite believe it. I timed a pair of 50s on a Glasgow - Euston service (pre electrification north of Preston) at 108mph when we got a signal check.

 

[SolomonSouth]

I can quite believe it. I timed a pair of 50s on a Glasgow - Euston service (pre electrification north of Preston) at 108mph when we got a signal check.

Ok

 

[hexagon789]

47s? Unreliable? No they must be reliable or they wouldn't build 512 of them, BREL aren't dumb
Imagine the maintenance cost of 512 unreliable locos
Therefore they must be very reliable, they wouldn't even build loads of an unreliable design in the first place

Well, definitely shaky at first with the engine crankshaft overstresses. After derating they were better.

They have never been that reliable - they were permanently de-rated from 2750hp within a few years of being built.

Asides from the early issues I'm not sure they were that unreliable in middle life. Not only average, I think it just seemed more if them failed than other classes because there were so damn many of them!

Maybe compared to a 46 but a 45 could easily hold its own against a 47 due to its more sophisticated electrical systems. Five stages of field diversion in the 45 gave it the edge on acceleration and no point mentioning too much about weight as a 45/1 only 13 tons heavier than a 47/4 so pretty negligible.

45s would slightly outperform a 47 with an equal load on passenger runs. A 45 would probably win on acceleration with the additional field diverts maintaining higher motor current through the speed range but also a 47 unloads at 80, and 45 can sustain full output for a further 5mph.

Though for sheer speed a 47 would seem to be the more capable, even if not hugely.

Yep. Pretty quick machines back in the day and good for a ton if pushed too...

Very much, I think as with so many classes, they lost out on one point - my enough if them. The 47s were always going to win the standardisation war.

Oh ok. 45 and 47 accelerate the same in TSW2 so its feasible it could be the same IRL.

Does the class 55 overload amps easily or something?
Also I wonder how a 66 compares to a 47.

A 55 will fairly easily overload, you cannot pull that power handle right back too soon or you will very easily end up either overloading the traction motors or more likely spinning the wheels. The Deltics are quite light for their installed power. A Deltic will be outdone by a 47 at lower speeds, a Deltic wins on hauling heavier passenger trains at sustained speed not on acceleration. A Deltic can manage loads at 100mph that a 47 would struggle to maintain much beyond the low/mid 80s.

== Doublepost prevention - post automatically merged: 26 May 2021 ==

I can quite believe it. I timed a pair of 50s on a Glasgow - Euston service (pre electrification north of Preston) at 108mph when we got a signal check.

I've seen similar speeds for singles.

== Doublepost prevention - post automatically merged: 26 May 2021 ==

120mph. I know, ****ing ridiculous

Depends on the load, I have seen logs of 47s nearing the 120 mark.

== Doublepost prevention - post automatically merged: 26 May 2021 ==

The RPS archive has at least one Class 47 run clocked at 112mph over several miles

I've seen a log of a max 112.1mph round Cullompton curves(!) (110+ was sustained for at least 4 miles) and a log with a speed of 111.9 down Wellington bank.

 

[SolomonSouth]

A 55 will fairly easily overload, you cannot pull that power handle right back too soon or you will very easily end up either overloading the traction motors or more likely spinning the wheels. The Deltics are quite light for their installed power. A Deltic will be outdone by a 47 at lower speeds, a Deltic wins on hauling heavier passenger trains at sustained speed not on acceleration. A Deltic can manage loads at 100mph that a 47 would struggle to maintain much beyond the low/mid 80s.

Thanks for the info. I did realise they had good power-to-weight tbh

 

[47827]

Can well believe that on odd occasions 47s neared 120mph (not impossible). Let's not forget, up until the 1990s (and to a lesser extent just after that decade) a lot more could be got away with in the optimum conditions. Modest loads of several coaches, high speed at the top of a gradient than let it rip at full power on a safe downhill drop and you could hit 100+ the mid to late teens. Flying down Beattock is one such place where its rather too easy with a nutter of sorts in the driving chair, but of course the wear and tear to running gear, wheelsets, brakes and all other vital organs wouldn't be worth the excessive running if done enough to damage the loco in multiple ways.

Once had a rather wild run in the early 90s on an S&C drag with a DVT rake southbound down from Blea Moor to Settle Junction. Felt like we were going to derail at times but probably didn't touch 100mph as the state of the track at the time may have brought us off (on that route back then 80-90 probably felt like 120!!!), although who knows. We were a lot of minutes early into Blackburn though.

 

[Richard Scott]

Can well believe that on odd occasions 47s neared 120mph (not impossible). Let's not forget, up until the 1990s (and to a lesser extent just after that decade) a lot more could be got away with in the optimum conditions. Modest loads of several coaches, high speed at the top of a gradient than let it rip at full power on a safe downhill drop and you could hit 100+ the mid to late teens. Flying down Beattock is one such place where its rather too easy with a nutter of sorts in the driving chair, but of course the wear and tear to running gear, wheelsets, brakes and all other vital organs wouldn't be worth the excessive running if done enough to damage the loco in multiple ways.

Once had a rather wild run in the early 90s on an S&C drag with a DVT rake southbound down from Blea Moor to Settle Junction. Felt like we were going to derail at times but probably didn't touch 100mph as the state of the track at the time may have brought us off (on that route back then 80-90 probably felt like 120!!!), although who knows. We were a lot of minutes early into Blackburn though.

I must admit to being somewhat dubious about 120mph. 47s unload at low 80s mph so can't see there's a chance that with motors turning at speeds required the back emf will be substantial by then. I've never personally had one over 107mph, not saying they haven't, but think 120 is pure fantasy.

 

[47827]

I must admit to being somewhat dubious about 120mph. 47s unload at low 80s mph so can't see there's a chance that with motors turning at speeds required the back emf will be substantial by then. I've never personally had one over 107mph, not saying they haven't, but think 120 is pure fantasy.

Maybe/maybe not. Old fashioned point to point timing by the keen stopwatch holder aboard produced a few surprises in the past. I'm inclined to think it possible (maybe) purely based on flying down a steep enough gradient at a high enough speed from near the top at full power even if the loco starts cooling its efforts at higher speeds. My car is meant to perform similar to a 47 then start cutting off power at 104mph using limiter technology. But that model can hit the 100mph + mid to late teens easily on the downhill stretches if left to keep flying but will be back to about 105-107 at best on the flat. Of course it could only be tried driving in one of the few places on earth its legal such as a German motorway, operating only advisory speed limits is the only means of testing this out in suitable conditions. I have driven through Germany once but won't comment further on the trip.

 

[big all]

Maybe/maybe not. Old fashioned point to point timing by the keen stopwatch holder aboard produced a few surprises in the past. I'm inclined to think it possible (maybe) purely based on flying down a steep enough gradient at a high enough speed from near the top at full power even if the loco starts cooling its efforts at higher speeds. My car is meant to perform similar to a 47 then start cutting off power at 104mph using limiter technology. But that model can hit the 100mph + mid to late teens easily on the downhill stretches if left to keep flying but will be back to about 105-107 at best on the flat. Of course it could only be tried driving in one of the few places on earth its legal such as a German motorway, operating only advisory speed limits is the only means of testing this out in suitable conditions. I have driven through Germany once but won't comment further on the trip.

It is worth a mention that around the 70s or perhaps 80s counting the clicks on welded rail with a stopwatch could mislead as good condition 60ft rail would be "cropped" and made into long welded 600ft rails. Basically a 60ft rail would be "cropped " by removing the rolled rail ends plus the bit with the holes so perhaps 2ft each end or 4ft total, it may be more it may be less I don't know, but counting "clicks" at say 100mph could be between say 7.5% or 15% out depending on 1ft or 2ft cropping each end??

 

[Richard Scott]

Maybe/maybe not. Old fashioned point to point timing by the keen stopwatch holder aboard produced a few surprises in the past. I'm inclined to think it possible (maybe) purely based on flying down a steep enough gradient at a high enough speed from near the top at full power even if the loco starts cooling its efforts at higher speeds. My car is meant to perform similar to a 47 then start cutting off power at 104mph using limiter technology. But that model can hit the 100mph + mid to late teens easily on the downhill stretches if left to keep flying but will be back to about 105-107 at best on the flat. Of course it could only be tried driving in one of the few places on earth its legal such as a German motorway, operating only advisory speed limits is the only means of testing this out in suitable conditions. I have driven through Germany once but won't comment further on the trip.

The problem is full power on a 47 is only available until about 82mph. At this point the generator has reached magnetic saturation so as speed rises the back emf of the traction motors causes the generator to effectively unload. This will keep happening as speed rises hence why I doubt a 47 could get anywhere near 120mph. Afraid comparing a DC transmission locomotive with a car is not a decent comparison as a car behaves totally differently even if electric. You could drop it off a cliff, that may be the easiest way for a 47 to hit 120mph!

 

[ac6000cw]

A Deltic will be outdone by a 47 at lower speeds, a Deltic wins on hauling heavier passenger trains at sustained speed not on acceleration. A Deltic can manage loads at 100mph that a 47 would struggle to maintain much beyond the low/mid 80s.

Exactly - the Deltics were designed as primarily passenger locos, not compromised 'mixed-traffic' machines like most of BR's diesel fleet. As such they exchanged some low-speed tractive effort for power at high speeds (just as the HST design did). One comment on them that I've seen was along the lines of 'they were only BR diesels that you could watch the speedo needle visibly move all the way to 100 mph' (I suspect the fuel gauges probably moved almost as fast in the other direction, though )

 

[hexagon789]

Thanks for the info. I did realise they had good power-to-weight tbh

Could certainly shift once into speed. For a period they hauled the fastest timed locomotive-hauled service - King's Cross to Retford non-stop on the Hull Executive. Timed at 91.4mph start-to-stop from May 1979 and the 55s had no trouble keeping that very tight booking with the featherweight eight coach trains.

I must admit to being somewhat dubious about 120mph. 47s unload at low 80s mph so can't see there's a chance that with motors turning at speeds required the back emf will be substantial by then. I've never personally had one over 107mph, not saying they haven't, but think 120 is pure fantasy.

I have seen one and only one log with 117, that's the fastest 47 speed I've ever come across. The next best are some logs (two are in the RPS archives) with 111/112 and some sustained 110mph running.

The 47s do indeed unload at 80, after they were derated the performance drop was noticeable at 80+, not so much at lower speeds.

With the light 7-coach XC Mk2 sets they could certainly get well into the 100s but I think for anything over 110 you would need a good downhill stretch.

Exactly - the Deltics were designed as primarily passenger locos, not compromised 'mixed-traffic' machines like most of BR's diesel fleet. As such they exchanged some low-speed tractive effort for power at high speeds (just as the HST design did). One comment on them that I've seen was along the lines of 'they were only BR diesels that you could watch the speedo needle visibly move all the way to 100 mph' (I suspect the fuel gauges probably moved almost as fast in the other direction, though )

I understand practice was to fuel after each trip on Anglo-Scottish duties, though that was probably at least partly being safe (rather embarrassing if the Flying Scotsman ran out of fuel or similar mid-run!).

As to 'watching the speedo' - as noted above derated 47s unload at 80, Deltics don't even begin to unload at 100...

 

[ac6000cw]

Deltics don't even begin to unload at 100...

I've heard that too - so how fast has a Deltic been recorded on level track (no gravity assistance)?

(I'm thinking about the 'swansong' period after HSTs had taken over most ECML trains, and the Deltics were hauling the London-York 'semi-fasts' on 125 mph track).

 

[Cowley]

I've heard that too - so how fast has a Deltic been recorded on level track (no gravity assistance)?

(I'm thinking about the 'swansong' period after HSTs had taken over most ECML trains, and the Deltics were hauling the London-York 'semi-fasts' on 125 mph track).

I’ve definitely heard of one reaching 124 mph as that’s been discussed on here a few times. I can’t for the life of me remember which thread it was though.

 

[===gricer===]

Acceleration is rate of change of velocity so distance comes into the eqaution
when quoting 0-50 mph figures for example ...

 

[hexagon789]

I've heard that too - so how fast has a Deltic been recorded on level track (no gravity assistance)?

(I'm thinking about the 'swansong' period after HSTs had taken over most ECML trains, and the Deltics were hauling the London-York 'semi-fasts' on 125 mph track).

Obviously there is the 125mph down Stoke Bank, on the level I've seen a very good log with a max of 114/115 over a quarter mile, max 112.5 over a full mile and sustained 110mph running.

The working was 1A31 1652 Harrogate/1730 Leeds-KGX. Load 8. Departure was 11.5 late from Doncaster, the hard running meant arr. KGX was 0.5 early by the WTT.

I’ve definitely heard of one reaching 124 mph as that’s been discussed on here a few times. I can’t for the life of me remember which thread it was though.

Certainly 125 down Stoke, but I'm not sure about the level. The 117 from one log for a 47 was over a 1/4 mi and so subject to the usual discrepancy issues. I think the 112 is believable though. For a Deltic you would expect faster but it's a struggle to find substantially higher tbh unless the RPS has something 'good' hidden away

 

[SolomonSouth]

The problem is full power on a 47 is only available until about 82mph. At this point the generator has reached magnetic saturation so as speed rises the back emf of the traction motors causes the generator to effectively unload. This will keep happening as speed rises hence why I doubt a 47 could get anywhere near 120mph. Afraid comparing a DC transmission locomotive with a car is not a decent comparison as a car behaves totally differently even if electric. You could drop it off a cliff, that may be the easiest way for a 47 to hit 120mph!

Exactly.

47s unload at 80, Deltics don't even begin to unload at 100...

Does this mean 47s are power restricted above 80 and Deltic isn't power restricted at all? If a 47 was not power restricted would it go 120 just MAYBE?
People in this thread have said the 47 accelerates better than Deltic. There are no figures for either though. And I dare say Deltic would be way better above 60mph than a 47.
I doubt either could hold a candle to the 66. According to here: https://www.kentrail.org.uk/Class 66.htm it does 0-60 in 23 seconds.

 

[hexagon789]

Does this mean 47s are power restricted above 80 and Deltic isn't power restricted at all? If a 47 was not power restricted would it go 120 just MAYBE?
People in this thread have said the 47 accelerates better than Deltic. There are no figures for either though. And I dare say Deltic would be way better above 60mph than a 47.
I doubt either could hold a candle to the 66. According to here: https://www.kentrail.org.uk/Class 66.htm it does 0-60 in 23 seconds.

Not power restricted, simply the point where the main generator output tails off because the power is not longer sufficient to maintain the same acceleration at speed.

A 47 pre-derated would perform better, though mainly in terms of not being so sluggish over 80.

A 47 has lower gearing and can take full power from a stand which is why in the low-medium speed range it will perform better than a 55. At over 60 a Deltic will start to outperform a 47. Worth remembering that after the ETH mods a Deltic would start away on one engine until the handle was at least 1/4 open. That would affect initial acceleration as well.

That's light engine though. Light engine I think a Deltic would provide a good show

And 66s have lower gearing again still and modern traction electronics both of which will help in a 'drag race'.

 

[47827]

47s with light loads with everything fully functioning are fully capable of 8-10mph over permitted speed on the flat but it's a struggle to get over that. Reduction in output over 80mph isn't something I'm disputing but on a light train, especially where the train isn't too heavy or you have a pair in multi if you hit the top of a steep hill going quickly enough the surviving amount of power versus gravity can do wonders. Point to point timing, indeed even over longer stretches can be a reliable indicator of performance and better than a speedo that may or may not be functioning 100% and the needle on it can bounce a little. Regarding my car, it shuts off power completely, supposedly, in the unlikely event of ever hitting 104mph so a downhill stretch of decent gradient is useful should anyone want to top 110. A 47 may not kick out as much power after 80mph but unlike a 66 won't knock off it completely to protect itself unless you cause damage to the engine sufficient to cause the electrics to burn out or equipment to seize, for example. That's how a speed like 117mph downhill is probably not guaranteed to be fiction even if it's very difficult to achieve on most lines.

 

[SolomonSouth]

Not power restricted, simply the point where the main generator output tails off because the power is not longer sufficient to maintain the same acceleration at speed.

A 47 pre-derated would perform better, though mainly in terms of not being so sluggish over 80.

A 47 has lower gearing and can take full power from a stand which is why in the low-medium speed range it will perform better than a 55. At over 60 a Deltic will start to outperform a 47. Worth remembering that after the ETH mods a Deltic would start away on one engine until the handle was at least 1/4 open. That would affect initial acceleration as well.

That's light engine though. Light engine I think a Deltic would provide a good show

And 66s have lower gearing again still and modern traction electronics both of which will help in a 'drag race'.

Yeah

47s with light loads with everything fully functioning are fully capable of 8-10mph over permitted speed on the flat but it's a struggle to get over that. Reduction in output over 80mph isn't something I'm disputing but on a light train, especially where the train isn't too heavy or you have a pair in multi if you hit the top of a steep hill going quickly enough the surviving amount of power versus gravity can do wonders. Point to point timing, indeed even over longer stretches can be a reliable indicator of performance and better than a speedo that may or may not be functioning 100% and the needle on it can bounce a little. Regarding my car, it shuts off power completely, supposedly, in the unlikely event of ever hitting 104mph so a downhill stretch of decent gradient is useful should anyone want to top 110. A 47 may not kick out as much power after 80mph but unlike a 66 won't knock off it completely to protect itself unless you cause damage to the engine sufficient to cause the electrics to burn out or equipment to seize, for example. That's how a speed like 117mph downhill is probably not guaranteed to be fiction even if it's very difficult to achieve on most lines.

I guess.

 

[hexagon789]

47s with light loads with everything fully functioning are fully capable of 8-10mph over permitted speed on the flat but it's a struggle to get over that. Reduction in output over 80mph isn't something I'm disputing but on a light train, especially where the train isn't too heavy or you have a pair in multi if you hit the top of a steep hill going quickly enough the surviving amount of power versus gravity can do wonders. Point to point timing, indeed even over longer stretches can be a reliable indicator of performance and better than a speedo that may or may not be functioning 100% and the needle on it can bounce a little. Regarding my car, it shuts off power completely, supposedly, in the unlikely event of ever hitting 104mph so a downhill stretch of decent gradient is useful should anyone want to top 110. A 47 may not kick out as much power after 80mph but unlike a 66 won't knock off it completely to protect itself unless you cause damage to the engine sufficient to cause the electrics to burn out or equipment to seize, for example. That's how a speed like 117mph downhill is probably not guaranteed to be fiction even if it's very difficult to achieve on most lines.

Oh yes, as I said with the later-era short XC sets they were very capable of speeds, indeed some of the greatest sustained 100+ logs are with such workings.

I wish I could find the log with the 117mph. I have seen it somewhere about and linking to it might prove interesting for some comparisons.

 

[SolomonSouth]

Oh yes, as I said with the later-era short XC sets they were very capable of speeds, indeed some of the greatest sustained 100+ logs are with such workings.

I wish I could find the log with the 117mph. I have seen it somewhere about and linking to it might prove interesting for some comparisons.

A 47 went 117mph once? Poor engines man.... must've been practically cremated within mintues

 

[Railperf]

A 47 went 117mph once? Poor engines man.... must've been practically cremated within mintues

Why would it be cremated? The engine would be running at its design speed as would the alternator. If the loco was designed for 10% overspeed, then it should be able to handle 105mph with ease. It would probably take a fiat while on the flat to achieve and maintain that sort of speed, but down a decently long 1 in 100 grade a fair bit more than 105mph would have been possible. The biggest issue would have been the pounding given to the track by the loco, and the fact that this loco suspension was not designed for those sorts of speeds, so i would expect a lively ride. And of course the driver would have needed a lot of bottle and confidence to brake the loco and train from such excess speeds. Remembering that HST was designed to brake from 125mph in the same distance as a loco hauled train. It would have demanded a fair bit of nerve to drive at almost 20mph over the loco and track speed limits on three-aspect signalling!! I'm not sure even the most confident drivers would want to attempt that - even in those days. Different of course under test conditions where the signallers can keep other traffic out of the way and create a long enough clear road to attempt those sorts of speeds.

 

[47827]

A 47 went 117mph once? Poor engines man.... must've been practically cremated within mintues

The pair with 40 odd mins Carstairs to Carlisle under the belt and a very smokey arrival into Carlisle sure must have topped 110 for a good distance on the downhill off Beattock and a fair whack the rest of the time. Neither was terminally ill afterwards and both enjoyed further plentiful use with one still merrily running around now with 2 further owners since. There were no cooked generators or major part damage issues reported. Imagine if they started doing it daily it might be different.

 

[Railperf]

The pair with 40 odd mins Carstairs to Carlisle under the belt and a very smokey arrival into Carlisle sure must have topped 110 for a good distance on the downhill off Beattock and a fair whack the rest of the time. Neither was terminally ill afterwards and both enjoyed further plentiful use with one still merrily running around now with 2 further owners since. There were no cooked generators or major part damage issues reported. Imagine if they started doing it daily it might be different.

Interesting that 47827 is one of the loco's with a decent 112mph under its belt!!

 

[SolomonSouth]

Why would it be cremated? The engine would be running at its design speed as would the alternator. If the loco was designed for 10% overspeed, then it should be able to handle 105mph with ease. It would probably take a fiat while on the flat to achieve and maintain that sort of speed, but down a decently long 1 in 100 grade a fair bit more than 105mph would have been possible. The biggest issue would have been the pounding given to the track by the loco, and the fact that this loco suspension was not designed for those sorts of speeds, so i would expect a lively ride. And of course the driver would have needed a lot of bottle and confidence to brake the loco and train from such excess speeds. Remembering that HST was designed to brake from 125mph in the same distance as a loco hauled train. It would have demanded a fair bit of nerve to drive at almost 20mph over the loco and track speed limits on three-aspect signalling!! I'm not sure even the most confident drivers would want to attempt that - even in those days. Different of course under test conditions where the signallers can keep other traffic out of the way and create a long enough clear road to attempt those sorts of speeds.

The engines would be practically cremated because, my friend:
The top speed on level track is 95mph. 10% overspeed - 104.5 mph. Engines are probably screaming hot.
117mph is a 23.5% overspeed of course the engines won't handle it that's over double the "intended" overspeed the loco was meant to handle