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201 Class power output

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Been wondering for a while what the power-at-rail of a 201 Class is. I've looked in various ITG books and the most recent Platform 5 Irish Railways book but none give the power-at-rail for a River class.

 

Would anyone happen to know what it is? I've seen 2,970hp traction listed on Wikipedia but I assume this is simply what you can get out of the 3,200hp for moving the train and not the actual power-at-rail rating?

 

Thanks in advance, regards Ben.

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Posted (edited)

I don't know what it is myself but I do remember reading before that when the locos used HEP mode on the Enterprise, HEP took away around 900hp from traction to power the DD sets.

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Have a look at the Wikipedia page for the BR Class 66. It has detailed stats for tractive effort and since it is a similar model to the 201 it might give you a good indication.

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21 minutes ago, irishthump said:

Have a look at the Wikipedia page for the BR Class 66. It has detailed stats for tractive effort and since it is a similar model to the 201 it might give you a good indication.

Not really, the 66 is a very different beast. Lower top speed, different gearing ratio traction motors optimised for long, heavy freight drags. Not a mixed traffic loco like the 201. A 66 I think has around 3 times the tractive effort of the 201. The class 59 is related too but it's in another league again for tractive effort.

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45 minutes ago, Railer said:

Not really, the 66 is a very different beast. Lower top speed, different gearing ratio traction motors optimised for long, heavy freight drags. Not a mixed traffic loco like the 201. A 66 I think has around 3 times the tractive effort of the 201. The class 59 is related too but it's in another league again for tractive effort.

I stand corrected!

So is "power at rail" synonymous with tractive effort?

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Well this is weird, I replied to this a few hours ago, but the reply is gone, bizarre.

 

I shall try again.

10 hours ago, Railer said:

I don't know what it is myself but I do remember reading before that when the locos used HEP mode on the Enterprise, HEP took away around 900hp from traction to power the DD sets.

 

Sounds about right. I know a typical UK loco can provide about 475kW (nearly 640hp) for HEP.

 

8 hours ago, irishthump said:

Have a look at the Wikipedia page for the BR Class 66. It has detailed stats for tractive effort and since it is a similar model to the 201 it might give you a good indication.

 

Thank you, it seems they share D43 traction motors and a BR Class 66 is given a power-at-rail of 2,240kW (just over 3,000hp). Therefore I wonder if 2,970hp is actually the relevant figure for an IÉ 201 then, allowing for its slightly less powerful engine.

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I shouldn't get involved with discussions on Diseaseals, but as the Class 66 is a freight loco, every HP produced goes to pulling things - there's no provision for head end power?

If memory serves, it was the provision of HEP which was the downfall of the 201s on the Enterprise and resulted in many of the failures. I assume that the new generator van has improved matters?

You guys don't know how blessed you are with nice comfy trains, not the ghastly, rough riding (possibly dangerously so - they haven't got the "damping" right yet), hard-seated (Hungraian wooden seats were better in the 1970s) Jap Crap we are having foisted on us over here.

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Power at rail and maximum tractive effort (TE) are separate functions.

Tractive effort is about pulling power and was measured in lbs.  Horse power about how fast you can accelerate a train to the required line speed

The 2,790 hp power at rail for the 201 Class is the power available for traction after taking out the power absorbed by the auxiliaries (compressor, cooling fan, generator, traction motors and mechanical losses. Republic Loco quotes 80% efficiency for locos with AC traction 70% for older DC units

 TE for diesels and steam is calculated differently.

Diesel: 

The relationship between power and tractive effort was expressed by Hay (1978) as

{\displaystyle TE={\frac {375*P*e}{V}}}{\displaystyle TE={\frac {375*P*e}{V}}} [11]

where

  • TE is tractive effort, in pounds-force (lbf)
  • P is the power in horsepower (hp)
  • e is the efficiency, with a suggested value of 0.82 to account for losses between the motor and the rail, as well as power diverted to auxiliary systems such as lighting
  • V is the speed in miles per hour (mph)

Steam its a function of boiler pressure, wheel diameter and cylinder bore D and stroke! 

Tractive effort (TE) (or "tractive force") is in principal determined by boiler pressure, cylinder proportions, and size of driving wheels: 

TE = D² * S * const * p / d 

with D = cylinder diameter, S = piston stroke, p = boiler pressure, and d = driving wheel diameter. ("const" being a heuristic constant in the range 0.75 ... 0.85, depending on speed.) 


http://www.republiclocomotive.com/locomotive-power-calculations.html

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10 hours ago, Mayner said:

Power at rail and maximum tractive effort (TE) are separate functions.

Tractive effort is about pulling power and was measured in lbs.  Horse power about how fast you can accelerate a train to the required line speed

The 2,790 hp power at rail for the 201 Class is the power available for traction after taking out the power absorbed by the auxiliaries (compressor, cooling fan, generator, traction motors and mechanical losses. Republic Loco quotes 80% efficiency for locos with AC traction 70% for older DC units

 TE for diesels and steam is calculated differently.

Diesel: 

The relationship between power and tractive effort was expressed by Hay (1978) as

{\displaystyle TE={\frac {375*P*e}{V}}}{\displaystyle TE={\frac {375*P*e}{V}}} [11]

where

  • TE is tractive effort, in pounds-force (lbf)
  • P is the power in horsepower (hp)
  • e is the efficiency, with a suggested value of 0.82 to account for losses between the motor and the rail, as well as power diverted to auxiliary systems such as lighting
  • V is the speed in miles per hour (mph)

Steam its a function of boiler pressure, wheel diameter and cylinder bore D and stroke! 

Tractive effort (TE) (or "tractive force") is in principal determined by boiler pressure, cylinder proportions, and size of driving wheels: 

TE = D² * S * const * p / d 

with D = cylinder diameter, S = piston stroke, p = boiler pressure, and d = driving wheel diameter. ("const" being a heuristic constant in the range 0.75 ... 0.85, depending on speed.) 


http://www.republiclocomotive.com/locomotive-power-calculations.html

 

Thank you for the detailed reply, though it was only the power-at-rail rating I was looking for which I think must be the 2,970hp figure.

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Actually it appears I'm wrong. 

 

I must admit 2,970hp seemed quite high, it would appear that the figure is actually likely 1850kW (about 2,480hp).

Oh and wikipedia is wrong about BR Class 66s having 3,300hp rated engines.

They are in fact 3,200hp exactly the same as BR Class 67s and the IÉ 201 Class.

 

Nevertheless, despite answering my own question I do appreciate the above replies.

Thanks all.

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