The most perfect locomotive -- N&W's J -- and Its TOP Speed of 128 mph!!!

[nw-mailing-list at nwhs.org]

Old saying: 'be careful what you ask for - you might get it'.  Let's  try to 
put the claims about steam locomotive speed accomplishments in proper  
perspective.
 
First; as to the LNER Pacific "Mallard".  The record, carefully  documented, 
was set on a 0.5 percent downgrade and the chart showed 125 mph was  sustained 
with only a momentary 'blip' at 126 mph.  Maybe someone bumped  the table ?  
Not usually mentioned is that the inside rod bearing was badly  damaged during 
the speed run, and the locomotive was taken off the train at the  next stop.
 
No other claim was as carefully documented.  A German Class O-5  'Hudson" 
achieved 124.5 mph on a level run in 1936.  With 90 1/2 inch  drivers, the O-5 
was probably capable of higher speed, but that nation's  government had other 
priorities at the time.
 
In addition to various claims for the N&W's Class J, others exist  for the 
NYC's # 999 (112.5 mph in 1893) and PRR's # 7002 (120 plus mph in  1905).  As 
these are not fully documented, 
and measurements were crude at best, they remain as 'maybe's'.
 
As to frequent claims that two cylinder locomotives with 'small' drivers  
(think the J's 70 inch) were not capable of speed; depends more on ample  
passageways for steam, careful design for exhaust velocity, and springing and  
balancing of the drivers.  
 
One last point: Sir Nigel Gresley was, IMHO, overrated.  I have read  
extensively on the subject; some British authors noted that his valve gear  designs 
were often modified behind his back by staff who copied from other  British 
designers.  And the conjugated valve gear used on the Mallard and  other 
locomotive classes had problems.  As bearings on the links wore, the  inside third 
cylinder assumed as much as one half of the total piston  thrust.  Great idea on 
paper; flawed in practice.
 
Anyway, Mallard does hold the DOCUMENTED steam locomotive speed  record.
 
Jerome Crosson   
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