A lot of discussion has been about the largest, strongest, heaviest, most tractive effort… Etc
But I have never heard what Locomotive has the largest drivers.
I have always heard that driver size roughly converts to speed in MPH so I would expect this record holding locomotive to be a Fast Passenger engine.
I am mostly interested in American Locomotives but I would also like to hear about Locomotives from any location.
Thanks
Later Bill
84 in drivers on the Santa Fe and Milwaukee road Hudsons
Well, in the USA I would vote for the Dripps 6-2-0 built for the Camden and Amboy, a Crampton type locomotive. It had 96" drivers. This was relatively early in locomotive development, in the 1840’s. Crampton’s reasoning for the huge driver diameter was to reduce piston speed as opposed to producing an extreme high speed locomotive, although the Crampton’s in England were said to run as fast as 75 mph… that’s really rolling in the mid 1800’s.
Here are a couple of wikipedia links:
http://en.wikipedia.org/wiki/6-2-0
http://en.wikipedia.org/wiki/Crampton_locomotive
How about 86" drivers on P&R P5 camelback Atlantics built in 1907 for Camden to Atlantic City service?
Just musing here, but I often wonder where the limit might have been if steam had had a longer run. I guess the answer would not have been in more unsprung mass, which larger/heavier drivers would necessarily be, but a combination of such and bearings on drive mechanisms, etc. might have had steamers doing well in excess of 110 mph continuously.
I believe some of the Jubilee Class of CPR’s stable, the 4-4-4’s, had 82" drivers, and I thought I had read that one of those held the Canadian steam locomotive speed record somewhere near 110/112 mph…but I’m fuzzy on that.
-Crandell
As I recall in the late 1800s several classes of single-driving-axle engines in Great Britain had drivers over 8 feet-- I’ll check.
Excessively large drivers were not needed for speed with a modern steam design. The N&W J could hit 110 mph with 70" drivers, and the C&O J3a can run all day at 100 mph and hit over 120 mph with 72" drivers.
Because of very intelligent counterblancing and relatively lightwieght rods
Casserly’s pocket book on British steam says somebody built a 10-ft driver engine in 1838, but it didn’t last long. The Bristol and Exeter 4-2-4Ts of 1853 did last some years with their 9-ft drivers. (Which were flangeless, it says.)
One problem with tall drivers on British engines with inside cylinders: the bottom of the boiler has to clear the inside cranks.
Here is one of those Bristol & Exeter high steppers, Broad gauge to boot!
There was also a French engine, named L’Aigle, which was built in 1855 and had 9’ 4" diameter wheels. It was exhibited at the Paris Exhibition of 1855 and put into regular service. It was considered a failure and had a short operating life.
While not having the largest drivers, NYC&HR 999 was originally equipped with 86" drivers. The locomotive was later re-boilered and re-equipped with smaller drivers.
Class P-2 Atlantics of the Burlington & Missouri River RR had 84-1/4" dia. drivers.
PRR S1 had 84 inch drivers. There are unofficial reports of the famous K4 and T1 locos doing over a buck ten on the flats with 14 to 16 cars in tow. There are stories of round house foremen tossing the speed recorder charts in the firebox to cover some of the valuable engine men from losing their jobs.
Pete
Hi everyone,
the steamer with the largest drivers I know of is the east German DR 18 201. Their drivers have a d diameter of 90’'. The top speed is rated at 180 km/h (approx. 112 mph), as the loco develops relatively meagre 1600 kW only. The design is a 4-6-2 btw.
Gerd
in addition to the ATSF & milw. hudsons w/ 84" drivers, the C& NW had hudsons, and the milw’s streamline atlantics had 84" dia. also - as of the mid to late 1930’s. alas only one machine still exists in North America out of all these: ATSF hudson 3461 on display in wichita KS.