AC Electric early cab Color

[MidlandRed]

Interesting.

 

These locos, when new, were quite stunning just in the plain electric blue with the extensive white trim, and red buffer beams - the stainless steel raised numerals and cast British Railways emblem set this off superbly also - so a bit of a design classic in my view - they were, for a few years, a very bright and modern vision in a sea of grey looking steam locos (and often diesels), and contrasted with the generally lined maroon coaches they appeared with.

 

For me, BR got the livery on these right - the stainless bands on your loco reminds me of the Bristol/ECW Railbuses, of which there were two. There was Design Panel involvement also. Lovely model again.

 

Many of us think the chromatic blue was actually rail blue, but as a result of the 'eggshell' matt type of finish used initially, the stock could look a different colour even though it wasn't!! Colour photo rendering also contributes, as does the extent of the yellow warning panel.

[rodent279]

On 16/11/2020 at 23:11, Evertrainz said:

 

Interesting. The AM10s, 24s/early 25s, and later 25s (the funny sounding ones?) all had Desilux. Here was the only horn clip I could find of a 310 on YouTube: https://youtu.be/2HvFftsi3kQ?t=485. I assume mounting location, air pressure, and how tightly the bell was screwed into the horn base all varied the sound alot even within a single class. You can tell D1015's squeaky horn from D1010's flatter horn sound. D821's horn sounds different from D832. 

 

The 86s had Westinghouse horns like fitted to Class 31s, but maybe they were swapped out later on? The Desilux had a reputation for being very loud whereas the Westinghouse were more quiet.

 

Someone kindly sent me photos and audio of a pair of Desilux horns from a roarer. Actually he said that one horn was from an 81, but the second horn was, after cleaning the grime off, marked with 85007. So I assume at least 85s and 81s were originally fitted with Desilux horns. Some 85s later were swapped out (?) with the Westinghouse horns fitted to 86s. If you remember did all the roarer horns sound more-or-less the same? 

 

AM10's, apart from being the best units BR ever built () had very distinctive horns, slightly off tone and short & sharp.

 

As regards power, the big limiting factor in power developed by traction motors is keeping them cool. If they get too hot, nasty things start happening to the insulation and the brush gear. If you can keep them cool, then they can run at a higher rating, as long as the maximum voltage of the insulation isn't exceeded. In fact the 1 hour rating can be exceeded, usually for no more than 15 minutes, so powers in excess of those quoted are at least theoretically possible.

Edited November 25, 2020 by rodent279

[rodent279]

On 17/11/2020 at 23:45, stovepipe said:

Perhaps you are being too harsh on yourself - the standards you have reached already surpass what many would be happy with I'm sure. But I can understand it, I have many proto routes that I haven't released because they aren't 'finished enough'. I guess the LMR South route by glen1974 might be the best bet for an early WCML route.

 

It sounds like it may be possible to do most of the characteristics of the loco in the API. I think it may be more interesting to model the neutral section behaviour before line voltage fluctuations - which would not vary greatly normally and the timetable would be cast to mitigate having too many trains in the section.

 

I found this little video of a mercury arc rectifier from a loco - you can see why a fire might have occured on a poor riding roarer, and why they were changed out for a semi-conductor! There were usually one per traction motor, but one AL design, I forget which, had two larger rectifiers powering two TMs each.

 

 

I think it was AL4's that had two Ignitrons. The difference that they had a single anode, the other types (Excitrons?) were multi-anode designs.

Or was it the other way round? :-)

[rodent279]

On 17/11/2020 at 11:24, Anadin Dogwalker said:

Re max power in electrics, its best to think of the throttle being different in diesels and electrics. In diesels it controls supply (ie revs from the engine block) and in electrics it controls demand from the OHLE/3rd rail which is at full power all the time - unless there are lots of trains drawing current at the same time, or the system has become relatively underpowered with age (I model the Milwaukee Road 3000v DC electrification in the Pacific Northwest of the US; it was designed in 1915  for 3000hp boxcab sets and barely coped with pairs 5100hp Little Joes of 1948 vintage). 

 

Horsepower converts to watts; 1000hp approx= 750 kilowatts. 1 watt= 1 amp x 1 volt. When the throttle is advanced on electrics of any type it's increasing the voltage available to the motors, in the case of 81-87 as typically 38 notches as taps off one side of the transformer or other (high on the 82,6,7, low the rest). The motors then draw enough current for their speed to match load conditions and balance when the back EMF voltage meets that supplied. The voltage supplied is fixed for each tap but the amps the motors draw in order to catch up (when accelerating) are not. The greater further and faster the throttle is advanced, the more catching up there is to do, the greater the current draw.  The ammeters on the electrics were colour shaded to make life easier for drivers not having to remember specific numbers that would vary between classes. Irrespective of the notch, the green band indicated what amperage could be maintained indefinitely without overheating (and the top of the green band and at  maximum volts= the continuous rating) . The yellow band was permitted to be used when accelerating, but did involve some overheating which could be tolerated for variable amounts of time- the greater the load the shorter the time. Hour ratings are commonly quoted but 5 and 10 minute ratings for even higher powers would exist, whether or not the numbers are available for reference. These would be in the red zone of the ammeter.

To create a maximum power situation, you'd need a maximum voltage and maximum amps; think of a heavy train or on a gradient with a clear road ahead and then notching up the power rapidly. The amps would build rapidly but peak power demand would occur if notch 38 (max voltage) is reached and maximum amps are being drawn. When the train speed balances and stops accelerating the amps should then settle back into the green zone. If the ammeter remains in the yellow zone, the driver ought to notch back unless there's a mitigating reason, eg making up for delays or cresting a gradient. So a full power scenario is a bit of a freak, while exceeding the continuous rating -ie use of the yellow ammeter band- would be a routine occurrence with gradients and during acceleration. As a very rough rule of thumb the the maximum output of the AC electics was about 50% above the continuous rating; 7800hp for the 87s rings a bell.

 

FWIW the horsepower curve of a class 71 peaks at something like 4000hp, against a continuous rating of only 2500hp, compared with a Deltic at 3300hp at the driveshaft. It' illustrated in OS Nocks Locos of the 20th century vol 3. So while the 83 has the least continuous horsepower of the AC electrics and less than a Deltic, it would easily thrash a Deltic in a drag race thanks to the extra power the 83 could draw. A 71 probably would too.  Not that that ever happened.

Cheers, Neill Horton

I think drivers were instructed not to have the ammeters in the red zone for more than 15 minutes in any 1 hour period-can any AC drivers confirm this?

[rodent279]

On 17/11/2020 at 11:24, Anadin Dogwalker said:

Re max power in electrics, its best to think of the throttle being different in diesels and electrics. In diesels it controls supply (ie revs from the engine block) and in electrics it controls demand from the OHLE/3rd rail which is at full power all the time - unless there are lots of trains drawing current at the same time, or the system has become relatively underpowered with age (I model the Milwaukee Road 3000v DC electrification in the Pacific Northwest of the US; it was designed in 1915  for 3000hp boxcab sets and barely coped with pairs 5100hp Little Joes of 1948 vintage). 

 

Horsepower converts to watts; 1000hp approx= 750 kilowatts. 1 watt= 1 amp x 1 volt. When the throttle is advanced on electrics of any type it's increasing the voltage available to the motors, in the case of 81-87 as typically 38 notches as taps off one side of the transformer or other (high on the 82,6,7, low the rest). The motors then draw enough current for their speed to match load conditions and balance when the back EMF voltage meets that supplied. The voltage supplied is fixed for each tap but the amps the motors draw in order to catch up (when accelerating) are not. The greater further and faster the throttle is advanced, the more catching up there is to do, the greater the current draw.  The ammeters on the electrics were colour shaded to make life easier for drivers not having to remember specific numbers that would vary between classes. Irrespective of the notch, the green band indicated what amperage could be maintained indefinitely without overheating (and the top of the green band and at  maximum volts= the continuous rating) . The yellow band was permitted to be used when accelerating, but did involve some overheating which could be tolerated for variable amounts of time- the greater the load the shorter the time. Hour ratings are commonly quoted but 5 and 10 minute ratings for even higher powers would exist, whether or not the numbers are available for reference. These would be in the red zone of the ammeter.

To create a maximum power situation, you'd need a maximum voltage and maximum amps; think of a heavy train or on a gradient with a clear road ahead and then notching up the power rapidly. The amps would build rapidly but peak power demand would occur if notch 38 (max voltage) is reached and maximum amps are being drawn. When the train speed balances and stops accelerating the amps should then settle back into the green zone. If the ammeter remains in the yellow zone, the driver ought to notch back unless there's a mitigating reason, eg making up for delays or cresting a gradient. So a full power scenario is a bit of a freak, while exceeding the continuous rating -ie use of the yellow ammeter band- would be a routine occurrence with gradients and during acceleration. As a very rough rule of thumb the the maximum output of the AC electics was about 50% above the continuous rating; 7800hp for the 87s rings a bell.

 

FWIW the horsepower curve of a class 71 peaks at something like 4000hp, against a continuous rating of only 2500hp, compared with a Deltic at 3300hp at the driveshaft. It' illustrated in OS Nocks Locos of the 20th century vol 3. So while the 83 has the least continuous horsepower of the AC electrics and less than a Deltic, it would easily thrash a Deltic in a drag race thanks to the extra power the 83 could draw. A 71 probably would too.  Not that that ever happened.

Cheers, Neill Horton

The way I look at it is that a motor also acts as a generator as it turns. When a voltage is applied to it, it starts to turn, and will try to continue accelerating until its back EMF (the internal voltage it is generating) very nearly equals the applied voltage. Of course, the mechanical load applied to it may mean that it can't reach its electrical balancing speed.

Edited November 25, 2020 by rodent279

[Evertrainz]

Interesting.

 

To try and get a realistic simulation - what causes the amps to slightly differ between TMs? is it just down to the railhead itself, or are there internal factors?

[rodent279]

I don't know. I would think mainly rail conditions, also weight transfer, and small differences in wheel diameter, and no two motors will be completely identical electrically.

Edit-I guess it's possible that small differences in wheel diameter and tyre profile might make it possible for one pair of wheels to "pick up" and start slipping before another. Once they start slipping, they'll carry on until either power is removed, anti-slip brakes are applied (if fitted), or rail conditions are restored to normal.

Edited November 26, 2020 by rodent279

[DY444]

21 hours ago, rodent279 said:

I think drivers were instructed not to have the ammeters in the red zone for more than 15 minutes in any 1 hour period-can any AC drivers confirm this?

 

The only thing I can find in the driver's manual is that if the ammeter remains in the red position for more than a few seconds then you should notch down.

 

AIUI providing you weren't exceeding the max allowed trailing load the only places really where you could get into the red zone and it stay there for any period of time was climbing Beattock (and maybe Shap although that's a shorter climb) in the down direction. 

Edited November 26, 2020 by DY444

[Evertrainz]

Anyone would happen to know how many tap notches were in the Class 83? ISTR that it was something like a dozen less than that of the 86, in one of the earlier electrics?

 

I have read very interesting factoids on this forum that certain loco sheds would tune up the governer and load regulator such that idle speeds sometimes could vary within a class. What might be an equivalent factor of controlled variation that might arise in simple/early AC electrics, if any? 

 

Render. Bodywork (that really should be bogiework) is nearing completion. Just some underframe pipework on the opposite side, vac bags/air hoses, and work on properly completing the pantos, and I should be able to paint up  .

[DY444]

7 hours ago, Evertrainz said:

Anyone would happen to know how many tap notches were in the Class 83? ISTR that it was something like a dozen less than that of the 86, in one of the earlier electrics?

 

Nope.  83 had 38 + 2 weak field the same as 81, 82, 84 and 85.  86 had 38.