Thanks James,
They were very fast and smooth runners, certainly capable of 70 MPH with the usual claims of even higher speeds.
Three retired Enginedriver's I worked with, live in my village, all of them worked J/J
A classes(and K
B) as Firemen in the 1960's in the South Island and later as Drivers in excursion service in the North Island: this subject came up in a discussion a few months ago after a few beers.
One claimed he was firing on an Express on the South Mine Line(South Is) and his ED had it right out, he thought easily doing 85 mph of above.
Second said to me quietly that anyone saying that speed was bsing, he doubted it for sure but added "in excess of 80 mph, certainly".
and the third said to me they were never in that much of a hurry on the North Main Line.....
However based on personal experience without witnesses, full out, down gradient on brand new heavy 50kg railed, concrete sleepered tangent track, you can attain high speed enough to chill your spine .......but that was running a light loco and Diesel