PRR K4 Top Speed

There are likely instances that PRR steam ran at speeds much higher than the official top speeds. Supposedly between 900-100 mph when double headed on the Fort Wayne Division where the 7002 hit its alleged record, but the reality is the normal top speed for the K4s's or the Atlantics would be 80 mph.  Typically top speed is a function of driver diameter.  Yes there are recorded instances of higher speeds but these were not sustained.  Likely the fastest of the PRR locomotives was the S1 with its 84" diameter drivers when it was actually running.  It regularly ran 100 mph and allegedly ran as fast as 134 mph but that is unofficial.  The A4 Mallard still holds the official record at 126 MPH.

For most steam, the top speed was about 1.1 times the driving wheel diameter, or 90 mph for the K-4s.  The E6's, with less reciprocating mass were a little faster, but that claim of 127 mph was a wild exaggeration.  I don't know about the S-1, but there are apocryphal tales of T-1s with their highly advanced valve gear eclipsing 130 mph, trying to make up time in flatland Ohio after a slippery start.  They had much, much more horsepower than the A4 Mallard, but there's no official proof.  I just read an account in Bill Withuhn's book of how difficult it was to measure the speed of a locomotive without special equipment, once you get above 100 mph.  That being said, I'm pretty sure that the duplex passenger locos were the fastest steam locos on the Pennsy.

Some late steam with disk drivers, lightweight roller-bearing rods, etc., had exceptional balancing and could exceed the rule of 1.1.  The N&W 'J' could reportedly run 110 mph with 70" drivers!

The J class Northerns are freaks of nature.   Amazing machines.

Maximum authorized speeds for different classes of locomotives were listed either in the employee timetable or in a special instruction.  There was some variance on where the information was posted.  Some railroads (Santa Fe) put this in the timetable.  Other railroads (and I think Pennsy was one) issued employees a book like the timetable, containing only System Special Instructions, thereby putting only the Division information in the timetable.  The reason for this is that the timetable would have to be re-issued more than once a year, to reflect schedule changes of regular trains, while the System Special Instructions only had certain pages amended throughout a year.  Printing costs were reduced by not reprinting everything with each new Division timetable.

If anyone on this Forum has a Pennsylvania Railroad publication from the late 1940s or early 1950s, listing the maximum authorized speed for locomotives, it would be interesting to know what was allowed some of Pennsy's more commonly modeled locomotives, such as 4-6-2, 4-4-2, 2-8-0, 2-8-2, 2-10-0, 4-8-2, the duplex steam engines, and EMD E7's.

Without doubt, on every railroad, the maximum authorized speeds were sometimes exceeded by individual Engineers.  The maximum authorized speed was the speed authorized by the Mechanical Department, mainly to optimize locomotive maintenance.  The maximum safe speed was another matter, and was normally quite a bit higher than the authorized speed, but at the price of increased wear and tear on the equipment, especially the crank pins, rods, and bearings.  And, at some speed beyond good sense on the part of the Engineer, every steam locomotive could kink rails.

On my home road, an Engineer with no common sense ran an ancient 2-8-0 (which was allowed 30 MPH) so fast that thirty miles of 90 MPH railroad was placed under a 20 MPH temporary speed restriction while hundreds of rails were replaced over a period of several days.

Regarding the speeds of PRR 460 and 7002, weren't those extrapolated from the time difference between reported signal tower passings? Not the most reliable, especially against an engine-based speedometer or modern radar gun.

I think the speeds as mentioned above were calculated from the time between towers.     Actually I think it is a fairly reliable way to calculate an average speed.     the distance between towers was accurate and well known.    If the operators  in the towers were paying close attention, they could record the time the loco passed the tower.    remember railroads had very strict standards for time and watches, so the operator watches should have been identical to within a few minutes a week.

It does give an average speed, however, not the maximum attained at any point.    

As a note on speeds, articles I have read state that PRR ordered the designers of the T1 to deliver a locomotive capable of pulling 10 steel (heavyweight) cars at 100 MPH.    From this I assume many locos were specified with speed according to load.   Unfortunately I have not seen this information for a K4.

I have to look for the book, but IIRC the PRR had speed recorders on their locomotives and upon arrival the recorder discs/tapes were sent to the locations supervisor where each engine's route was analyzed for speed, braking and other operationally collected data which directly affected the performance evaluation of the respective locomotive crew.

Keystone posted:

I have to look for the book, but IIRC the PRR had speed recorders on their locomotives and upon arrival the recorder discs/tapes were sent to the locations supervisor where each engine's route was analyzed for speed, braking and other operationally collected data which directly affected the performance evaluation of the respective locomotive crew.

Maybe on the early diesel units, but I don't recall seeing ANY speed recorders on their steam locomotives, especially the K4s locomotives.

I would concur with Ted above about the T1 possible being the fastest that PRR had if not  THE fastest anyone had. Trains Magazine had a short piece back in the 1970's (1973?) on a last run of one from Crestview OH to Ft Wayne. It was pulling a lengthy mail train that had 2 K4's when one of them went down. The engineer had to make up time so on the flat stretch coming into Ft Wayne, they may have hit well above 130 mph according to estimates that day. A great story and one that started my fascination with the amazing Duplex.

Slugger posted:

Regarding the speeds of PRR 460 and 7002, weren't those extrapolated from the time difference between reported signal tower passings? Not the most reliable, especially against an engine-based speedometer or modern radar gun.

Most steam locomotives did not have speed indicators.  The engine crew was expected to regulate speed based on elapsed time per mile, and the employee timetable and special instructions listed maximum authorized speeds in minutes and seconds, not miles per hour.  We were well into the diesel era when timetables began to list speed in miles per hour.

Once the Engineer had timed a few miles, he could tell the speed by listening to the exhaust.  It was a skill, not a science.

Beginning in the 1930's, some of the last and most modern steam locomotives began to be built with Valve Pilot and Speed indicator/Recorder devices from Chicago Pneumatic.  Barco and Chicago Pneumatic Speed Indicator/Recorder devices began to be applied to road diesels beginning in the 1930's.  Retrofitting of older steam locomotives was uncommon.

I have read somewhere in the late 1930's ARR conducted speed tests. PRR and the UP both participated . The UP mechanical engineers first went to the PRR to observe the K4 pulling a train. The best the K4 could muster was a little over 90 MPH.  Then the PRR mechanical engineers went to the UP. The PRR men said no way a 4 coupled locomotive could generate any speed (The UP used a early FEF1 4-8-4.) The PRR men were blown away. For the same tonnage, the 4-8-4 ran at 110 MPH!

Chuck Sartor posted:

I have read somewhere in the late 1930's ARR conducted speed tests. PRR and the UP both participated . The UP mechanical engineers first went to the PRR to observate the K4 pulling a train. The best the K4 could muster was a little over 90 MPH.  Then the PRR mechanical engineers went to the UP. The PRR men said no way a 4 coupled locomotive could generate any speed (The UP used a early FEF1 4-8-4.) The PRR men were blown away. For the same tonnage, the 4-8-4 ran at 110 MPH!

Just another example of the "not invented here" mindset of the PRR Mechanical Dept.. The same thing happened when the PRR "tested" an N&W J Class 4-8-4, and with its 72 inch diameter drive wheels, the PRR folks didn't believe it could ever exceed something like 75 MPH. Again, in the 1940s, the PRR folks were "blown away" by the 110 MPH performance of the big N&W locomotive with the "little drivers"!

                    Barco speed indicator- NYS&W F45 #6370, Maybrook, NY Jan. 87' 

PAUL ROMANO posted:

                    Barco speed indicator- NYS&W F45 #6370, Maybrook, NY Jan. 87' 

Nice, but this has nothing to do with the discussion about the speeds of PRR K4s steam locomotives, which did NOT have speed indicators, nor speed recorders.

70 inch drivers on  J class, not 72.

Standard Gauge posted:

70 inch drivers on  J class, not 72.

Thanks for the correction. I knew they were REALLY small for a 4-8-4. Thus truly mind boggling for those PRR Mechanical Dept. folks.

In the book, Set Up Running: The Life of a Pennsylvania Railroad Engineman, 1904-1949, the author tells the stories of his father who was an esteemed PRR Engineer out of the Williamsport division.  One of the train assignments he had in the book was a passenger consist that went south from Williamsport through Northumberland, and into Harrisburg. The story references that when the train was running behind the timetable, a K4 would run 110+ MPH on the final portion of the line in approach to Harrisburg to make up the time.  And, that when he was sometimes assigned the K2 or K3 clocomotive for the same run, that there simply wasn't the same power that the K4 had, and the lessor locomotives would top out in the 90-100mph range. 

And, another story describes how he ran light in a K4 to aid the rescue of a stranded express passenger train. Since he was on a time sensitive rescue run, running light, the stories reference was that his speed was well in excess of 100mph.

So, I would make the suggestion that not only could the K4 run at speeds well in excess of 100 mph, but also that they would do so in certain occasions in regular service. I would also suggest that the K4 was capable of speeds in excess of the 126 mph record, and probably ran that speed in service in unrecorded situations. Of course we never really know but in the case I believe in the power of the Pennsy.

I would take that book with a grain of salt. I have never heard of a K4 running in excess of 100 MPH. Maybe possibly at the Altoona test plant under controlled conditions.