Power output - R711 Relaunch to Bendigo tour

 
  1553 Locomotive Fireman



 
For those interested in the performance/power output of the four operating R class locomotives, I have calculated the following Rail Horsepower (RHP) figures for R711's recent re-launch tour to Bendigo and made some comparisons to the other three R's over the same climbs. The results are as follows, the columns represent the date, loco, load (including loco), speed held/attained at top of bank, the rail horsepower that equates to, and (when noted) the cut-off used;-
 
SUNBURY BANK
Dec 1984        R761   522 tons   16mph  1070 rhp
Jul   1985        R707   526 tons   21mph  1597 rhp
Sep 1985        R766    440 tons   19mph  1180 rhp
Oct 1986        R761    403 tons   26mph  1580 rhp
Oct 2012        R711    530 tons   24 mph 1763 rhp
 
 
 
MACEDON BANK
Dec 1984   R761   522t   29mph   2046rhp  -cut-off 15”
July 1985   R707   526t   25mph   1750rhp                12”
Sep 1985   R766   415t   34mph   1990rhp               
Oct 1986   R761   403t   41mph   2216rhp                18”
       1999    R711   518t   29mph   1953rhp                21”
Oct 2012   R711   530t    17mph   1177rhp
 
 
 
 

ELPHINSTONE TUNNEL


Nov 85   R766   518t   32mph   2205rhp


Mar 86   R761   545t   20mph   1500rhp


Apr 89    R761   540t   27mph   2030rhp


Oct 86    R761   403t   39mph   2263rhp   15”  (D.Colin Holl)


1999       R711   518t   27mph   1943rhp


2002 R761,707 877t   28mph    1770rhp


2012      R711    530t   22mph   1598rhp

One can draw their own conclusions from the above figures but there is no reason not to conclude that any of the R's are capable of readily achieving their VR rated 1800 HP and, given a good crew and pushed a little, can achieve around the 2200 RHP when required.  It is of interest that Sunbury Bank does not normally provide a great power output despite line speed being able to be regained between  Sunbury Station and the foot of the grade.  The climb to Elphinstone Tunnel (10kms) on the Up often produces a good performance and has the added advantages that long climbs produce, a test of the loco's steaming ability and stabilised speed.  It should also be remembered that a locos optimum power output is produced between 150-200 RPM (ie. between 33 - 43 MPH for an R class) therefore, if the load is heavy that speed range can never be achieved at the top of a long 1/50 climb. This is evident in the figures taken at Elphinstone Tunnel with R761 hauling gross load of 545 ton in March 1986 and 7 months later with 403 tons (this load was made up specifically for HP calculations and included the Dynamometer Car) where at the top of the climb almost double the speed (39mph) was achieved.

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  NSWGR 3827 Deputy Commissioner

Location: South of the Border


 
For those interested in the performance/power output of the four operating R class locomotives, I have calculated the following Rail Horsepower (RHP) figures for R711's recent re-launch tour to Bendigo and made some comparisons to the other three R's over the same climbs. The results are as follows, the columns represent the date, loco, load (including loco), speed held/attained at top of bank, the rail horsepower that equates to, and (when noted) the cut-off used;-

SUNBURY BANK
Dec 1984 R761 522 tons 16mph 1070 rhp
Jul 1985 R707 526 tons 21mph 1597 rhp
Sep 1985 R766 440 tons 19mph 1180 rhp
Oct 1986 R761 403 tons 26mph 1580 rhp
Oct 2012 R711 530 tons 24 mph 1763 rhp
 
 
 
MACEDON BANK
Dec 1984 R761 522t 29mph 2046rhp -cut-off 15”
July 1985 R707 526t 25mph 1750rhp 12”
Sep 1985 R766 415t 34mph 1990rhp
Oct 1986 R761 403t 41mph 2216rhp 18”
1999 R711 518t 29mph 1953rhp 21”
Oct 2012 R711 530t 17mph 1177rhp
 
 
 
 

ELPHINSTONE TUNNEL


Nov 85 R766 518t 32mph 2205rhp


Mar 86 R761 545t 20mph 1500rhp


Apr 89 R761 540t 27mph 2030rhp


Oct 86 R761 403t 39mph 2263rhp 15” (D.Colin Holl)


1999 R711 518t 27mph 1943rhp


2002 R761,707 877t 28mph 1770rhp


2012 R711 530t 22mph 1598rhp

One can draw their own conclusions from the above figures but there is no reason not to conclude that any of the R's are capable of readily achieving their VR rated 1800 HP and, given a good crew and pushed a little, can achieve around the 2200 RHP when required. It is of interest that Sunbury Bank does not normally provide a great power output despite line speed being able to be regained between Sunbury Station and the foot of the grade. The climb to Elphinstone Tunnel (10kms) on the Up often produces a good performance and has the added advantages that long climbs produce, a test of the loco's steaming ability and stabilised speed. It should also be remembered that a locos optimum power output is produced between 150-200 RPM (ie. between 33 - 43 MPH for an R class) therefore, if the load is heavy that speed range can never be achieved at the top of a long 1/50 climb. This is evident in the figures taken at Elphinstone Tunnel with R761 hauling gross load of 545 ton in March 1986 and 7 months later with 403 tons (this load was made up specifically for HP calculations and included the Dynamometer Car) where at the top of the climb almost double the speed (39mph) was achieved.

"1553"


Just a Few Questions and a Correction:

Are the HP figures you quote peak or sustained power?
What is the Max Load for a R Class on 1 in 50, I Can't remeber off the top of my head by from memory is about 400 Tons Yes?
R711's run in October 2012 was with a load of Only 310 Tons, Not 530!


  Valvegear Oliver Bullied, CME

Location: Norda Fittazroy
I hope twoodroffe is reading this. I would be very interested in his comments.
  YM-Mundrabilla Minister for Railways

Location: Mundrabilla but I'd rather be in Narvik


 
For those interested in the performance/power output of the four operating R class locomotives, I have calculated the following Rail Horsepower (RHP) figures for R711's recent re-launch tour to Bendigo and made some comparisons to the other three R's over the same climbs. The results are as follows, the columns represent the date, loco, load (including loco), speed held/attained at top of bank, the rail horsepower that equates to, and (when noted) the cut-off used;-

SUNBURY BANK
Dec 1984 R761 522 tons 16mph 1070 rhp
Jul 1985 R707 526 tons 21mph 1597 rhp
Sep 1985 R766 440 tons 19mph 1180 rhp
Oct 1986 R761 403 tons 26mph 1580 rhp
Oct 2012 R711 530 tons 24 mph 1763 rhp
 
 
 
MACEDON BANK
Dec 1984 R761 522t 29mph 2046rhp -cut-off 15”
July 1985 R707 526t 25mph 1750rhp 12”
Sep 1985 R766 415t 34mph 1990rhp
Oct 1986 R761 403t 41mph 2216rhp 18”
1999 R711 518t 29mph 1953rhp 21”
Oct 2012 R711 530t 17mph 1177rhp
 
 
 
 

ELPHINSTONE TUNNEL


Nov 85 R766 518t 32mph 2205rhp


Mar 86 R761 545t 20mph 1500rhp


Apr 89 R761 540t 27mph 2030rhp


Oct 86 R761 403t 39mph 2263rhp 15” (D.Colin Holl)


1999 R711 518t 27mph 1943rhp


2002 R761,707 877t 28mph 1770rhp


2012 R711 530t 22mph 1598rhp

One can draw their own conclusions from the above figures but there is no reason not to conclude that any of the R's are capable of readily achieving their VR rated 1800 HP and, given a good crew and pushed a little, can achieve around the 2200 RHP when required. It is of interest that Sunbury Bank does not normally provide a great power output despite line speed being able to be regained between Sunbury Station and the foot of the grade. The climb to Elphinstone Tunnel (10kms) on the Up often produces a good performance and has the added advantages that long climbs produce, a test of the loco's steaming ability and stabilised speed. It should also be remembered that a locos optimum power output is produced between 150-200 RPM (ie. between 33 - 43 MPH for an R class) therefore, if the load is heavy that speed range can never be achieved at the top of a long 1/50 climb. This is evident in the figures taken at Elphinstone Tunnel with R761 hauling gross load of 545 ton in March 1986 and 7 months later with 403 tons (this load was made up specifically for HP calculations and included the Dynamometer Car) where at the top of the climb almost double the speed (39mph) was achieved.

"1553"


Just a Few Questions and a Correction:

Are the HP figures you quote peak or sustained power?
What is the Max Load for a R Class on 1 in 50, I Can't remeber off the top of my head by from memory is about 400 Tons Yes?
R711's run in October 2012 was with a load of Only 310 Tons, Not 530!

"NSWGR 3827"


IIRC the full goods load for an R up Glenroy was 405 tonnes - 20 tonnes greater than an A2.
  duttonbay Minister for Railways

IIRC the full goods load for an R up Glenroy was 405 tonnes - 20 tonnes greater than an A2.
"YM-Mundrabilla"


My 1963 (Metropolitan) WTT shows R class allowed 400 tons (not tonnes) Melb Yard-Broadmeadows via Essendon (with no intermediate loads specified) compared to 385 for an A2.
  YM-Mundrabilla Minister for Railways

Location: Mundrabilla but I'd rather be in Narvik
IIRC the full goods load for an R up Glenroy was 405 tonnes - 20 tonnes greater than an A2.
"YM-Mundrabilla"


My 1963 (Metropolitan) WTT shows R class allowed 400 tons (not tonnes) Melb Yard-Broadmeadows via Essendon (with no intermediate loads specified) compared to 385 for an A2.
"duttonbay"


400 tons fair enough (that equates to 406 tonnes). I hadn't considered tons v tonnes.

Either way 'she'll be right' - we'll make it provided we don't tell the driver.....
  1553 Locomotive Fireman

In reply to 3827, peak power or sustained power? -bit of a grey area really, peak means after it reached a given speed on a steady climb, for some reason it then started to drop again, this is normally due to momentum having not fully run out or the boiler could not keep up with that rate of steaming. Sustained power is harder to measure hence British Rail performed these tests with the engines mounted on rollers with given amounts of built- in reistance. Sustained power could ideally be measured on a climb like Ingliston where the engine is required to perform continuously at a given rate for a considerable period.
The climb to Elphinstone Tunnel is probably sufficient to term the power sustained as speed on the final 2 miles of 1/50 (after 2 miles of 1/59) was held steady and not dropping.   The climb of Macedon I would not call sustained, in fact I had to take into account several major wheel slips at the top of the grade. It actually almost limped over the top -down to 11mph from memory!
The official VR load for an R on a 1/50 was 400 tons, this has some safety margin. If it could maintain and deliver all of its 210PSI pressure, it would be capable of hauling 460 tons. If the grades were all less than 2 miles in length and the running speed of the line permitted, it could  haul even more than the 460t - run on momentum.
Re the load R711 was hauling, you have stated as 310t but you must add the weight of the engine , passengers, generator equipment etc as these are RAIL horsepower figures. This is a measurement of power developed at the railhead for hauling the WHOLE of the train which includes locomotive. Other horsepowers sometimes quoted are drawbar or cylinder horsepower.  The carriage weights I obtained from the carriage underframes on the day but if you have it officially as 310t from a better source I would be happy to use your figure - the 30t say variation would only alter the rhp figures marginally, but worth noting.
  Carnot Minister for Railways

The comparison between R711's 1999 and 2012 climbs up Elphinstone are interesting.  Perhaps a good indication of the difference between a double lempor and standard exhaust setup?

Another factor could be variations in rolling resistance due to bearings, rail/wheel profile, brake dragging etc.

Incidentally, I read somewhere that one of the R-class runs to Bendigo in the mid-1980s came in under 2 hrs.  Any truth to that?
  1553 Locomotive Fireman

The comparison between R711's 1999 and 2012 climbs up Elphinstone are interesting. Perhaps a good indication of the difference between a double lempor and standard exhaust setup?

Another factor could be variations in rolling resistance due to bearings, rail/wheel profile, brake dragging etc.

Incidentally, I read somewhere that one of the R-class runs to Bendigo in the mid-1980s came in under 2 hrs. Any truth to that?
"Carnot"



Funny you mention that run, it is in fact the one showing with the highest rhp recorded at Elphinstone Tunnel. A friend of mine, Colin Holl, was driving (although retired, he had special permission for this run) and it was in fact part of the Dynamometer Car trials. Colin did set out to do the run in under 2 hours and was furious when he was held at Nth Melb as there were no platforms available. I have a letter that he wrote to me afterwards about the run. I can recall one of his comments was that 761 was running better than a lot of the R's when they were new.

I am not sure of the exact running time now, but remember the run was definately under two hours before being held at Nth Melb.
  1553 Locomotive Fireman

The comparison between R711's 1999 and 2012 climbs up Elphinstone are interesting. Perhaps a good indication of the difference between a double lempor and standard exhaust setup?

Another factor could be variations in rolling resistance due to bearings, rail/wheel profile, brake dragging etc.

Incidentally, I read somewhere that one of the R-class runs to Bendigo in the mid-1980s came in under 2 hrs. Any truth to that?
"Carnot"



Funny you mention that run, it is in fact the one showing with the highest rhp recorded at Elphinstone Tunnel. A friend of mine, Colin Holl, was driving (although retired, he had special permission for this run) and it was in fact part of the Dynamometer Car trials. Colin did set out to do the run in under 2 hours and was furious when he was held at Nth Melb as there were no platforms available. I have a letter that he wrote to me afterwards about the run. I can recall one of his comments was that 761 was running better than a lot of the R's when they were new.

I am not sure of the exact running time now, but remember the run was definately under two hours before being held at Nth Melb.
"1553"


Footnote  ;Some say there was no platform available, but conspiracy theories suggest VLine didn't want the embarrassment of a silly old steam train outperforming their diesels. Who knows.......?
Interesting comparison though with the latest trip. On the new "improved" Bendigo line, it took around 5 hours to do what we nearly did in 2 hours, 26 years earlier.
 
  LowndesJ515 #TeamRog

Location: Not in Victoria
Out of interest, how did you get the speeds?
  Carnot Minister for Railways


Interesting comparison though with the latest trip. On the new "improved" Bendigo line, it took around 5 hours to do what we nearly did in 2 hours, 26 years earlier.
"1553"


Perhaps one day someone could organize a special early hours run with the track cleared and TPWS turned off...Shocked

Even if it was run at 2:30am I'd buy a ticket and be on board....
  1553 Locomotive Fireman

In reply to Lownes;  I recorded all the main climbs using a professional sound recorder (I have been producing cassettes/CD's since the early 1980's) I can then later at my leisure sit down with my stop watch and time the number of revolutions per minute by counting every fourth exhaust beat (if a train is travelling slow enough you can count them individually). The RPM is multiplied by the wheel diameter and divided by 336 to give your speed in MPH.  On the Dynamometer runs my manual HP calculations were accurate to within 95% of what the dyno car was recording, which even surprised me!
  G41 Chief Commissioner

Location: Footplate of any K class
In reply to Lownes; I recorded all the main climbs using a professional sound recorder (I have been producing cassettes/CD's since the early 1980's) I can then later at my leisure sit down with my stop watch and time the number of revolutions per minute by counting every fourth exhaust beat (if a train is travelling slow enough you can count them individually). The RPM is multiplied by the wheel diameter and divided by 336 to give your speed in MPH. On the Dynamometer runs my manual HP calculations were accurate to within 95% of what the dyno car was recording, which even surprised me!
"1553"

You need to get a girlfriend lol.

In all serious though, this is amazing work as to how you get the numbers. Well done and keep it up.


  NSWGR 3827 Deputy Commissioner

Location: South of the Border
In reply to 3827, peak power or sustained power? -bit of a grey area really, peak means after it reached a given speed on a steady climb, for some reason it then started to drop again, this is normally due to momentum having not fully run out or the boiler could not keep up with that rate of steaming. Sustained power is harder to measure hence British Rail performed these tests with the engines mounted on rollers with given amounts of built- in reistance. Sustained power could ideally be measured on a climb like Ingliston where the engine is required to perform continuously at a given rate for a considerable period.
The climb to Elphinstone Tunnel is probably sufficient to term the power sustained as speed on the final 2 miles of 1/50 (after 2 miles of 1/59) was held steady and not dropping. The climb of Macedon I would not call sustained, in fact I had to take into account several major wheel slips at the top of the grade. It actually almost limped over the top -down to 11mph from memory!
The official VR load for an R on a 1/50 was 400 tons, this has some safety margin. If it could maintain and deliver all of its 210PSI pressure, it would be capable of hauling 460 tons. If the grades were all less than 2 miles in length and the running speed of the line permitted, it could haul even more than the 460t - run on momentum.
Re the load R711 was hauling, you have stated as 310t but you must add the weight of the engine , passengers, generator equipment etc as these are RAIL horsepower figures. This is a measurement of power developed at the railhead for hauling the WHOLE of the train which includes locomotive. Other horsepowers sometimes quoted are drawbar or cylinder horsepower. The carriage weights I obtained from the carriage underframes on the day but if you have it officially as 310t from a better source I would be happy to use your figure - the 30t say variation would only alter the rhp figures marginally, but worth noting.
"1553"


The reason I ask Sustained of peak Power is because if speed and Boiler Water and/or Steam was falling when the highest Hp figure was recorded the figure can be only be considered peak Output not sustained, continuous output (or sustained HP) can only be acuratly measuered/calculated with constant speed, Boiler Pressure and Water level.  BR also used the testing plant so they could test against Conastant evaporation to eliminate momentary peaks in output which could not be sustained for very long.

You say you got the Car weights on the day off the Underframes, then I am struggling to understand how you arrived at a different weight than I did.  K Cars being 40T each, and the S Cars being 50T.
  duttonbay Minister for Railways

In reply to Lownes; I recorded all the main climbs using a professional sound recorder (I have been producing cassettes/CD's since the early 1980's) I can then later at my leisure sit down with my stop watch and time the number of revolutions per minute by counting every fourth exhaust beat (if a train is travelling slow enough you can count them individually). The RPM is multiplied by the wheel diameter and divided by 336 to give your speed in MPH. On the Dynamometer runs my manual HP calculations were accurate to within 95% of what the dyno car was recording, which even surprised me!
"1553"

Assuming newly tyred wheels, or worn wheels? Smile
  LowndesJ515 #TeamRog

Location: Not in Victoria
In reply to Lownes; I recorded all the main climbs using a professional sound recorder (I have been producing cassettes/CD's since the early 1980's) I can then later at my leisure sit down with my stop watch and time the number of revolutions per minute by counting every fourth exhaust beat (if a train is travelling slow enough you can count them individually). The RPM is multiplied by the wheel diameter and divided by 336 to give your speed in MPH. On the Dynamometer runs my manual HP calculations were accurate to within 95% of what the dyno car was recording, which even surprised me!
"1553"

You need to get a girlfriend lol.

In all serious though, this is amazing work as to how you get the numbers. Well done and keep it up.

"G41"


That's Hardcore!! lol

But yes, I agree with G41, its pretty amazing on how you get all the figures together.
  1553 Locomotive Fireman

In reply to Lownes; I recorded all the main climbs using a professional sound recorder (I have been producing cassettes/CD's since the early 1980's) I can then later at my leisure sit down with my stop watch and time the number of revolutions per minute by counting every fourth exhaust beat (if a train is travelling slow enough you can count them individually). The RPM is multiplied by the wheel diameter and divided by 336 to give your speed in MPH. On the Dynamometer runs my manual HP calculations were accurate to within 95% of what the dyno car was recording, which even surprised me!
"1553"

Assuming newly tyred wheels, or worn wheels? Smile
"duttonbay"

I am using 73" diam, so it allows for a little bit of wear. It would be interesting to measure the wheels of each of the R class individually. Does anyone know how much wear is exceptable before needing re-tyring?
  t_woodroffe Assistant Commissioner

Referring to Drg 5912 Stock Size Tyres page 2A R Class driving (and leading and trailing!) wheel tyre diameter new is 72 15/16". The diameter at the condemning groove is 69 5/16".

TW
  1553 Locomotive Fireman

Referring to Drg 5912 Stock Size Tyres page 2A R Class driving (and leading and trailing!) wheel tyre diameter new is 72 15/16". The diameter at the condemning groove is 69 5/16".

TW
"t_woodroffe"

Thanks for that information, going on those figures, probably using 72" diam would be reasonable. Good one to ask Warren Hall about!
  62440 Chief Commissioner

In my struggling memory bank, I went to Bendigo by R761 in 1985 and on the return journey we stalled in the tunnel, presumably Elphinstone, and had to back out pretty sharpish. Definitely 1985 and R761.
  1553 Locomotive Fireman

In reply to 3827, peak power or sustained power? -bit of a grey area really, peak means after it reached a given speed on a steady climb, for some reason it then started to drop again, this is normally due to momentum having not fully run out or the boiler could not keep up with that rate of steaming. Sustained power is harder to measure hence British Rail performed these tests with the engines mounted on rollers with given amounts of built- in reistance. Sustained power could ideally be measured on a climb like Ingliston where the engine is required to perform continuously at a given rate for a considerable period.
The climb to Elphinstone Tunnel is probably sufficient to term the power sustained as speed on the final 2 miles of 1/50 (after 2 miles of 1/59) was held steady and not dropping. The climb of Macedon I would not call sustained, in fact I had to take into account several major wheel slips at the top of the grade. It actually almost limped over the top -down to 11mph from memory!
The official VR load for an R on a 1/50 was 400 tons, this has some safety margin. If it could maintain and deliver all of its 210PSI pressure, it would be capable of hauling 460 tons. If the grades were all less than 2 miles in length and the running speed of the line permitted, it could haul even more than the 460t - run on momentum.
Re the load R711 was hauling, you have stated as 310t but you must add the weight of the engine , passengers, generator equipment etc as these are RAIL horsepower figures. This is a measurement of power developed at the railhead for hauling the WHOLE of the train which includes locomotive. Other horsepowers sometimes quoted are drawbar or cylinder horsepower. The carriage weights I obtained from the carriage underframes on the day but if you have it officially as 310t from a better source I would be happy to use your figure - the 30t say variation would only alter the rhp figures marginally, but worth noting.
"1553"


The reason I ask Sustained of peak Power is because if speed and Boiler Water and/or Steam was falling when the highest Hp figure was recorded the figure can be only be considered peak Output not sustained, continuous output (or sustained HP) can only be acuratly measuered/calculated with constant speed, Boiler Pressure and Water level. BR also used the testing plant so they could test against Conastant evaporation to eliminate momentary peaks in output which could not be sustained for very long.

You say you got the Car weights on the day off the Underframes, then I am struggling to understand how you arrived at a different weight than I did. K Cars being 40T each, and the S Cars being 50T.
"NSWGR 3827"


I have had a look at my notes re the carriage weights. I wrote down the train consist but used figures from the tech drawings of each individual carriage to obtain their weights,as the underframe weights appear to be very rounded off. I was using 42 tons per K car Tare Weight as 600BK and 500BK both weighed 41.5 ton after re-build in 1997. This is tare weight so, as I mentioned above, passengers, equipment, luggage etc need to be added.  The specs for Buffet Car also shows as 52ton Tare weight rather than 50.
  G41 Chief Commissioner

Location: Footplate of any K class
Referring to Drg 5912 Stock Size Tyres page 2A R Class driving (and leading and trailing!) wheel tyre diameter new is 72 15/16". The diameter at the condemning groove is 69 5/16".

TW
"t_woodroffe"

Thanks for that information, going on those figures, probably using 72" diam would be reasonable. Good one to ask Warren Hall about!
"1553"


I can tell you that R707's driving wheels are definatly aproaching the condemning groove. I will get the exact messurement next time im at Newport for you. It is one of the reason's why we are going through so many engine brake blocks. Plans are in place to get R707 re-tyred this year.
  1553 Locomotive Fireman


Interesting comparison though with the latest trip. On the new "improved" Bendigo line, it took around 5 hours to do what we nearly did in 2 hours, 26 years earlier.
"1553"


Perhaps one day someone could organize a special early hours run with the track cleared and TPWS turned off...Shocked

Even if it was run at 2:30am I'd buy a ticket and be on board....
"Carnot"


Yes, I would too.   I go on trips just to hear how an engine performs.  Unfortunately, we are a minority and in reality there would probably be less than 50 people interested in such a trip.  I'm guessing, but I believe more than 3/4 of all rail enthusiasts are just interested in obtaining a good photo - not that there is anything wrong with that!.  Hence, when the RTM run nearly all their trips with a d.e. assisting from the rear, although I understand their reasons, it is very frustrating to some of us.  The trips are aimed at the general public, not enthusiasts, and as long as there is a bit of steam around and they can hear the whistle, they couldn't care less if a diesel is doing all the work from behind.
  Gwiwer Rt Hon Gentleman and Ghost of Oliver Bulleid

Location: Loitering in darkest Somewhere
Wheels with tyres newly-fitted and at maximum thickness will give different speed readings than those worn to the point of scrappage using the technique described.  The speeds differing by perhaps 1mph.  The difference in speeds will affect the apparent horsepower indicated as well.

Your admitted margin of error (± 5% of dynamometer car recordings) does not invalidate the work presented but bear in mind that 5% of, for example, 24mph as quoted for the 2012 run might mean the actual speed was anywhere between 22.8 and 25.2 mph which leads to entirely different calculations for horsepower.

Looked at another way the world steam speed record of 126mph with a ± 5% margin of error produces a range from 119.7 to 132.3mph  

With many technical articles offering power calculations in equivalent drawbar horsepower (edhp) rather than railhead and not having the formula to hand to convert is it possible to offer figures in that format as well from the original calculations?

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