When my Father passed away in February, I (being the only railfan in the family) naturally inheritted all his rail books, magazines and railroadiana. I was reading a MUCH less than recent edition of Trains Magazine dated 1982 or 83 where it featured this "black beauty" on the cover and her return to service running out of Birmingham I think but I know it was Alabama.
Anyway, there was a passage in the article that refered to her speed..."an engine so powerful that her drivers can spin at 9 revolutions per second..."

I always knew that she was among if not THE most powerful 4-8-4 in the country and sincerely do NOT doubt the engineering skills of The Roanoke Shops in building such a fantastic machine, but could the author be right? Is (was and hopefully will be in the future) she capable of generating THAT much power? Can she spin her drivers at 9 revolutions per second!?
What would that amount to in MPH? How much fuel (coal and water) is she eating at that rate!? That's a BIG horse to make that much energy!

Steve,

I don't know the answer to your question, but I will note that the original J's were built with 275 psi boiler pressure which resulted in a tractive effort of around 73,000 pounds. Later the boiler pressure was raised to 300 lbs resulting in an increased tractive effort of 80,000 lbs, making the J's the most powerful 4-8-4's ever built. Number 602 was equipped with a booster in the 40s, but that didn't last long and I think was dropped when the boiler pressure was increased. The 611-613 of May, June and July 1950 were built new with 300 pounds boiler pressure and the higher tractive effort rating.

As much of a fan of the 611 as I am, one thing I have noticed from watching videos and have heard other discussions about was the fact that the J's had a factor of adhesion under 4.0, which was on the low-side. As a result the J's tended to be very slippery locomotives, which can be seen in videos of the 611 in excursion service as well as vintage videos of J's in regular service on the N&W. I am curious if the low factor of adhesion had anything to do with 611's stalling near the top of the now closed (since December 2001) Saluda grade with 5 passenger cars on October 25, 1992 on the first steam excursion run on the line in 20 years since 4501 took four cars up in June 1972.

As far as the speed goes, I read that the 610 reached a speed of 110 mph with a 15 car passenger train when the Pennsylvania Railroad borrowed the locomotive for tests near Crestline, Ohio in the mid 1940's. Maybe someone else here can answer the question of how much coal and water the J's would consume per hour. The 9 revolutions per second quote does sound right as I recall hearing the J's driving wheels could turn at a reported 540 rpm, which doing the math 9 times per second times 60 (seconds in a minute) equals 540.

My math might be wrong so bear with me....

The J's drivers are 70 inches tall so, that comes to 219 inches around. There are 63360 inches in a mile so, to cover a mile the J's drivers have to turn 289 times. At 60 mph that roughly 4.8 revolutions per second. 110mph is almost double 60mph so, that's 9 revolutions per second.

Here is a nice pacing video where you can try to count the revolutions per second.

http://www.youtube.com/watch?v=v6lWBp2APrQ

Going back to my math lessons here. I'm glad they finally came in handy.

(Diameter x Pi = Circumfrance) 70 inches x π = about 220 inches
/ 12 inches to a foot = 18.3 feet
x 9 revolutions a second = 164.9 feet per second
x 60 seconds a minute = 9896 feet per minute
x 60 minutes an hour = 593761 feet an hour
/ 5280 feet to a mile = 112.45 miles per hour

That sounds about right to what records say the J's could do. To say the least, impressive

Thank goodness Mr. Eau Claire was paying attention in math class! That's quite impressive.

I concur with the above figure. The usual number is 8.8 revs/sec at 110 mph, to 9 at 112 is correct.

The PRR tests of N&W Class J 610 was covered in the N&WHS magazine, The Arrow, in two issues, April-June 2008 (Vol.24, #2) and Oct-De3c 2009 (Vol.25, #4), as well as PRRT&HS magazine, The Keystone, Vol.41, #4 and Vol.42, #2. N&WHS does not sell individual back issues, only full year groups, but PRRT&HS does sell singles. See their website. 610 made maximum speeds of 109 mph (12/8/44, train 28, 13 cars), 110 mph (12/7/44, train 71, 15 cars) and 111 mph (12/8/44, train 57, 11 cars). These were regularly scheduled PRR passenger trains, not special consists.

During tests on Christiansburg hill, #604 developed 5,028 DBHP at 41 mph while evaporating 99,942 lbs of water per hour (this is total evaporation, not equivalent evaporation) and 13,068 lbs coal/hr. Although this was the highest figure achieved during the tests, they were not "maximum" figures in the usual sense of the word. The tests were constant speed tests at a nominal 40 mph in order to determine economies of raising the boiler pressure from 275 psi to 300 psi. As a result, the cutoff readings for the 300 psi runs were numerically lower than those at 275 psi. The locomotive was "hooked up" higher and less steam and coal were used. A full-flog maximum figure for the J is unknown. N&W didn't care about it.

The REALLY amazing thing about that 9 revolutions per second figure is that the piston, piston rod, crosshead, and main rod on each side of the locomotive, which combined weigh at least several hundred pounds (despite the fact they were made of the lightest, strongest alloys available), were being accelerated from a complete stop to about 50 MPH twice every revolution, or 18 times per second. Imagine bringing ~1000 lbs from 0 MPH to 50 MPH and back to 0 MPH in the space of 32 inches (the stroke) and then doing that 18 times per second. The forces involved were no doubt pretty astronomical.