-=> Quoting Andrew Hamblyn to Gregory Procter <=-
 GP>  "hammer blow force" is spread over all the equalized springs, not just 
the
 AH> ummm... this only occurs at high speeds, well beyond what is
 AH> attainable here  in New Zealand, and the damage that is incoured by
 AH> this was very rarely seen  here.
Around 1969 I used to pace the "Limited" (The old Southerner) pulled by a 
Ja"
between Rolleston and Islington (just south of Chch) on my motorcycle. The
motorcycle was capable of 70+ mph and with me flat over the tank the train 
would
"walk away" from me almost every time! There are numerous stories of the 
Kb"s
on the Midland line averaging 100Mph on the long downhill runs. I've talked 
to a
number of older drivers to get some verification of 100 mph, and they all
thought it quite possible and not surprising. I also have a record (sound
recording) on which a Ja was running near Levin. There is an inspector and 
he
sound recordist on the footplate. The recorder is calling out the speed as 
he
speedometer increments upwards, 88...89.....90! Then there is a gruff 
ommand,
"that will be enough!"
According to various drivers, the "J"s became too uncomfortable in the cab by
90mph due to the rocking induced by the connecting rods, while the "K"s would 
go
to around 100.
Of course, the drivers might have been having me on, but I've had much the 
same
story from 3 or more on separate occassions. A friend who was the South 
sland
motive power development engineer suggested 90mph might be morereasonable.
      For those not familiar with NZR and the locomotives, we have 3'6" 
(1067mm)
      gauge and the "K" series are 4.8.4s with 4'6" drivers built in the 
930s
      while the "J' series are lighter weight 4.8.2s also with 4'6" drivers.
      The designs are very well balanced.
My point here is that we did have high speeds here in NZ, and in fact our 
locos
achieved much higher wheel revolution rates than almost anywhere else in the
world! 622 rpm. Mallard at 129mph = 549rpm. Those numbers are theoretical, no
allowance for slippage etc but they will give you the idea. The NZ locos have 
a
proportionately shorter strock, so the piston speed still falls well within 
the
accepted norms of the time (at 70mph)
      Greg.P.
  
... Catch the Blue Wave!
--- FMail 1.02
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