Third rail maximum current

[hexagon789]

I wish someone could do an actual rail horsepower combination between a 12 car cig and a 12 car rep + 8tc. I believe the motor ratings given were 1 hour ratings - indeed looking at a output curve they produce more than their 1 hour rating during acceleration (peaking at about 40 mph) when in weak field and then output tails off rapidly to below the 1 hour rating especially at higher speeds above 70 mph.
But the balancing speed of a CIG set was in the low 80s on level track. I’ve seen a few logs where they struggled to reach that between Surbiton and Woking. Multiple formations were quicker. 12 car 4 rep + 8TC formations despite only having 200 hp extra on paper had lots of grunt; they could easily sustain and exceed 90 mph on level track and indeed climb the 1/252 to Worting jct at 80 mph compared with unmodified CIGs that could barely make that speed on level track !

The way UIC one-hour ratings were calculated was a 10% overrating on the continous figure taken on nominal operating voltage. So with the nominal voltage being 750V the actual continous output would be about 91% of the hour-rating and then taken in proportion to the available voltage. With the minimum 3rd being about 590V I think, the actual available power would be about 715hp in such cases.

 

[Richard Scott]

I wish someone could do an actual rail horsepower combination between a 12 car cig and a 12 car rep + 8tc. I believe the motor ratings given were 1 hour ratings - indeed looking at a output curve they produce more than their 1 hour rating during acceleration (peaking at about 40 mph) when in weak field and then output tails off rapidly to below the 1 hour rating especially at higher speeds above 70 mph.
But the balancing speed of a CIG set was in the low 80s on level track. I’ve seen a few logs where they struggled to reach that between Surbiton and Woking. Multiple formations were quicker. 12 car 4 rep + 8TC formations despite only having 200 hp extra on paper had lots of grunt; they could easily sustain and exceed 90 mph on level track and indeed climb the 1/252 to Worting jct at 80 mph compared with unmodified CIGs that could barely make that speed on level track !

Remember 73110 and 3-REP with 8-TC unit hitting 103mph between Southampton and Bournemouth. Stood by speedo in one of the TC cars and hit 100mph, that was as high as it went so resorted to stopwatches. Sure the platform 5 book showed a 73 could produce just over 3000hp for a short period (not sure I believe it though).

 

[WAO]

If you can find a copy, "Electric Trains in Britain", Cooper B K, Ian Allan, London, 1979 ISBN 0 7110 0972 4 has diagrams on pages 18, 19 (Ch 2) showing speed vs Amperes (Fig 3) and Motor Amps & speed vs time for suburban stock. Note that the suburban gear ratio (65/17) will be lower than the express ratio (61/19).

Moody's "Southern Electric 1909 - 1979" (p244/5) gives BR suburban stock balancing (level) speeds of 63mph and 72mph for express stock, probably at 675V.

Hope this helps.

WAO

 

[notadriver]

Remember 73110 and 3-REP with 8-TC unit hitting 103mph between Southampton and Bournemouth. Stood by speedo in one of the TC cars and hit 100mph, that was as high as it went so resorted to stopwatches. Sure the platform 5 book showed a 73 could produce just over 3000hp for a short period (not sure I believe it though).

What’s a 3REP please ? Does it have one or two motor coaches ?

 

[hexagon789]

If you can find a copy, "Electric Trains in Britain", Cooper B K, Ian Allan, London, 1979 ISBN 0 7110 0972 4 has diagrams on pages 18, 19 (Ch 2) showing speed vs Amperes (Fig 3) and Motor Amps & speed vs time for suburban stock. Note that the suburban gear ratio (65/17) will be lower than the express ratio (61/19).

Moody's "Southern Electric 1909 - 1979" (p244/5) gives BR suburban stock balancing (level) speeds of 63mph and 72mph for express stock, probably at 675V.

Hope this helps.

WAO

I seem to recall balancing speeds of 72mph for 3-car 205s and 88mph for a 4CIG without the extra stage of field weakening

 

[hexagon789]

What’s a 3REP please ? Does it have one or two motor coaches ?

I guess the lash-up formations of 4REPs which had one DMSO removed and replaced by a Class 73.

 

[hexagon789]

Remember 73110 and 3-REP with 8-TC unit hitting 103mph between Southampton and Bournemouth. Stood by speedo in one of the TC cars and hit 100mph, that was as high as it went so resorted to stopwatches. Sure the platform 5 book showed a 73 could produce just over 3000hp for a short period (not sure I believe it though).

The BR diagram books agree with Platform 5. What became the 73/0 have a max rail hp of 2450; the 73/1s 3150hp. Both are 1,420hp continous on 675V per motor:

 

[notadriver]

I seem to recall balancing speeds of 72mph for 3-car 205s and 88mph for a 4CIG without the extra stage of field weakening

I recall it being 69 mph for a class 201 (which has the same power to weight ratio as a 205?) but looking at logs between Herne Bay to Birchington which has a downhill stretch to aid acceleration followed by 4 miles I’d dead straight and level track and no slam door emu could reach the line speed of 90 mph. The CIGs were best reaching 85 but the CEPs were markedly slower strangely.

 

[hexagon789]

I recall it being 69 mph for a class 201 (which has the same power to weight ratio as a 205?) but looking at logs between Herne Bay to Birchington which has a downhill stretch to aid acceleration followed by 4 miles I’d dead straight and level track and no slam door emu could reach the line speed of 90 mph. The CIGs were best reaching 85 but the CEPs were markedly slower strangely.

Aren't 201s 500hp engines and 205s 600hp?

 

[AM9]

Aren't 201s 500hp engines and 205s 600hp?

Not quite according to wikipedia. The family of thumpers all have 4SRKT MKII prime movers. For the classes 202 & 203, they are charged to provide 500 shaft bhp and each drive two EE507s which are 250bhp each. The rest of the family, - classes 201, 204, 205, 206 & 207 have the $SRKT MKIIs charged to 600 sbhp,but still drive the same 2 x 250bhp EE507s. Given the ability of traction motors to have short term loads far greater than their continuous rating and the DC generator conversion losses, it is likely that all of the available shaft power of the 600bhp rated classes would be used at times to the benefit of performance at the rail.

 

[notadriver]

Aren't 201s 500hp engines and 205s 600hp?

Yes but I don’t think 100 hp (and engine hp at that) will make that much of a difference

 

[notadriver]

If you can find a copy, "Electric Trains in Britain", Cooper B K, Ian Allan, London, 1979 ISBN 0 7110 0972 4 has diagrams on pages 18, 19 (Ch 2) showing speed vs Amperes (Fig 3) and Motor Amps & speed vs time for suburban stock. Note that the suburban gear ratio (65/17) will be lower than the express ratio (61/19).

Moody's "Southern Electric 1909 - 1979" (p244/5) gives BR suburban stock balancing (level) speeds of 63mph and 72mph for express stock, probably at 675V.

Hope this helps.

WAO

Do you happen to know if the 4REPs has a different gear ratio to other express stock ?

 

[hexagon789]

Yes but I don’t think 100 hp (and engine hp at that) will make that much of a difference

Are the traction motors the same then? If so, why did they decide to fit uprated engines to some Thumpers?

(I did find my 72mph figure is for a different kind of Thumper.)

 

[hexagon789]

Not quite according to wikipedia. The family of thumpers all have 4SRKT MKII prime movers. For the classes 202 & 203, they are charged to provide 500 shaft bhp and each drive two EE507s which are 250bhp each. The rest of the family, - classes 201, 204, 205, 206 & 207 have the $SRKT MKIIs charged to 600 sbhp,but still drive the same 2 x 250bhp EE507s. Given the ability of traction motors to have short term loads far greater than their continuous rating and the DC generator conversion losses, it is likely that all of the available shaft power of the 600bhp rated classes would be used at times to the benefit of performance at the rail.

I suppose so, I can only find reference to the uprating to 600hp being for the 3-car sets anyway.

 

[WAO]

Do you happen to know if the 4REPs has a different gear ratio to other express stock ?

I believe they were the same as it was governed by wheel diameter and maximum safe armature speed. The ratio was common with the 73/1's with similar B6 motor bogies. Wonderful SR!

A complication was the gradual raising of the voltage from 660V to 750V, first with the Kent Coast electrification and completed in the suburban areas in the 1980's after the 4SUB units' withdrawal. Their compressors and Christmas tree lighting circuits couldn't cope! There is also evidence that the Voltage West of Branksome to Weymouth was raised to 850V to reduce costs. The trackside feed was also reduced from 33kV to 11kV, like LUL and Merseyrail!

WAO

 

[big all]

the average thumper would draw around 1100 amp without going "pop"
you could almost gtee at 11mph you would be in notch 7 unless a very steep gradient then you would wait an extra say 2 or 3mph
also worth mentioning all the heating 'compressors' lighting'cooling and battery charging come off the engines power .

 

[AM9]

I suppose so, I can only find reference to the uprating to 600hp being for the 3-car sets anyway.

It is really the only type of DMU where published power ratings can be directly co

 

[paul1609]

I recall it being 69 mph for a class 201 (which has the same power to weight ratio as a 205?) but looking at logs between Herne Bay to Birchington which has a downhill stretch to aid acceleration followed by 4 miles I’d dead straight and level track and no slam door emu could reach the line speed of 90 mph. The CIGs were best reaching 85 but the CEPs were markedly slower strangely.

I think the slammers power at the rail was very dependant on the line voltage present at a particular location. I'm reliably told that the typical 12 cars uphill speed was increased by 10 mph when the SEML channel tunnel electrification modifications were completed.

 

[hexagon789]

It is really the only type of DMU where published power ratings can be directly co

Directly compared?

To what sorry? Your post has been cut off.

 

[A0]

There is also evidence that the Voltage West of Branksome to Weymouth was raised to 850V to reduce costs.

Care to provide that evidence? Because that's not the evidence most have.

 

[WAO]

Care to provide that evidence? Because that's not the evidence most have.

"Until 1939 lines were electrified at 600V except for some in the inner suburban area. Lines in Kent south and east of Gillingham, Sevenoaks and Maidstone, that is those electrified by British Railways, have been at 750V since electrification. The Weymouth line West of Bournemouth is electrified at 850V. The Isle of Wight line is electrified at 630V while the Waterloo & City [now part of the London Underground] remained at 660V."

Southern Electric History and Infrastructure Part 4 - Re-Privatisation - Infrastructure, 2nd para line 13, SEG group.

The SEG group could be wrong - unlikely. That's why I only said there is evidence.

WAO

 

[AM9]

Directly compared?

To what sorry? Your post has been cut off.

Sorry, don't know what went wrong there. I'm on a mobile now so not easy to post. What I meant to say is that on DEMUs, knowing the shaft bhp gives the absolute maximum amount of power available, (less auxiliaries and hotel load) except where the motor bhp is significantly less than that. If say a DEMU has 600 hp at the engine shaft, connected through a generator to 2x250hp motors, then after allowing for generator inefficiency and aux. etc., The continuous power at the rail will Max out at around 500hp. With a DMU, including a hydraulic transmission type, the limited power band of the diesel engine will limit the rail power to a few bands of speeds depending on the engine speed. Even a torque converter doesn't broaden up the band(s) much and is very dependent on operating temperatures.

 

[A0]

"Until 1939 lines were electrified at 600V except for some in the inner suburban area. Lines in Kent south and east of Gillingham, Sevenoaks and Maidstone, that is those electrified by British Railways, have been at 750V since electrification. The Weymouth line West of Bournemouth is electrified at 850V. The Isle of Wight line is electrified at 630V while the Waterloo & City [now part of the London Underground] remained at 660V."

Southern Electric History and Infrastructure Part 4 - Re-Privatisation - Infrastructure, 2nd para line 13, SEG group.

The SEG group could be wrong - unlikely. That's why I only said there is evidence.

WAO

Well, NR's own documentation says Southampton to Weymouth is 750v DC throughout - search for Weymouth RUS and you get a downloadable link from the NR website.

More inclined to believe NR's RUS who actually run it than an enthusiasts group.

 

[WAO]

The SEG is a serious and respected group; we should value its statements, although like you, I would still seek original sourced technical manual information.

It may be that both assertions are true; Weymouth remains within 750V tolerance for both NR's PR and internal publications but the transformer tappings have been set marginally higher as the system is known to be of low capacity.

We shall see.

WAO

 

[Dr Hoo]

I guess the lash-up formations of 4REPs which had one DMSO removed and replaced by a Class 73.

Just spotted this. Apologies if it has already been replied to.

The Modern Railways article on the 'invention' of the 4-REPs specifically said that they were designed to swap out a defective motor coach with a Class 73. The original pared-down fleet (11 units?) was quite tightly diagrammed with up to 3-and-a-half Waterloo-Bournemouth rounders per day and the SR was worried about losing a set for an extended period after a mishap. Running with 11 rather than 12 passenger vehicles would not generally have caused many passenger problems.

 

[edwin_m]

Well, NR's own documentation says Southampton to Weymouth is 750v DC throughout - search for Weymouth RUS and you get a downloadable link from the NR website.

More inclined to believe NR's RUS who actually run it than an enthusiasts group.

It's possible it was set to 850V originally and adjusted downwards when regeneration came in a few years ago. Very little regeneration would be possible at 850V before the line hit the limit of around 900V.

 

[Richard Scott]

Just spotted this. Apologies if it has already been replied to.

The Modern Railways article on the 'invention' of the 4-REPs specifically said that they were designed to swap out a defective motor coach with a Class 73. The original pared-down fleet (11 units?) was quite tightly diagrammed with up to 3-and-a-half Waterloo-Bournemouth rounders per day and the SR was worried about losing a set for an extended period after a mishap. Running with 11 rather than 12 passenger vehicles would not generally have caused many passenger problems.

The run in question was during 1988 when 3-REPs were formed so one motor coach could be withdrawn and its traction equipment removed for use in the 442s. The 73 then substituted for the missing motor coach.

 

[hexagon789]

Just spotted this. Apologies if it has already been replied to.

The Modern Railways article on the 'invention' of the 4-REPs specifically said that they were designed to swap out a defective motor coach with a Class 73. The original pared-down fleet (11 units?) was quite tightly diagrammed with up to 3-and-a-half Waterloo-Bournemouth rounders per day and the SR was worried about losing a set for an extended period after a mishap. Running with 11 rather than 12 passenger vehicles would not generally have caused many passenger problems.

Yes as I understood the 4REP and Cl. 73 motors and motor bogies were fully interchangeable as was much of the control equipment.

Southern Region parts commonality at its finest

The original frequency was broadly bi-hourly, but to enable greater maintenance cover and a regular hourly interval service the extra 4REPs were built in the early 1970s.