Pennsy K4 vs. NYC Hudson?

There have been numerous discussions over the years.

Scroll down here: https://ogrforum.ogaugerr.com/...yString=k4+vs+hudson

The PRR K4 had superior tractive effort at 44,460 lbf. 

Where NYC Hudson had a tractive effort at 41,860 lbf.

It should be noted that other railroads had Hudsons with higher tractive effort than the PRR  K4.

TM Terry posted:

The PRR K4 had superior tractive effort at 44,460 lbf. 

Where NYC Hudson had a tractive effort at 41,860 lbf.

Is that number with or without the booster?

It should be noted that other railroads had Hudsons with higher tractive effort than the PRR  K4.

This thread reminds me of my Dad. He was enrolled at Penn State (1933-1937) with his major being Railroad Engineering. One field trip was to the Altoona Pennsy complex where his class watched a K4 on the [indoor] locomotive dynamometer steaming at full load making 60mph standing still. Dad said it was quite a spectacle. He had to switch to Industrial Engineering because Penn State dropped the Railroad major while he was attending.

Better at what?

Apples and oranges.   Two different entire beast design and built for two different territories.  One for flat level running and one for the hills/mountains of Pennsylvania, Ohio

Hot Water, educate me about “booster” for steam locomotives.

Is it as simple as higher boiler pressure and/or degrees of superheat?

A booster was a set (or maybe one) cyclinder on the trailing truck that drove that axle.   As far as I know, it was only usable for starting and slow speeds, but greatly increased the ability to start a train.    On steam engines, the horsepower increases as the speed does to a point, so once the train was started and moving say 20 MPH, the booster could be cut out and the engine could still pull the train.

A number of more modern steamers had boosters.

I'm not Hot Water, but I will note that the "booster" is an auxiliary steam engine, usually geared to an axle of the trailing truck, sometimes to a tender truck.  It was fed steam from starting through a few miles/hour to provide extra "boost" in tractive effort to get heavy trains going.  After the train got rolling, it was cut out, both because it was no longer necessary and because it became a liability at speed.

TM Terry posted:

Hot Water, educate me about “booster” for steam locomotives.

Is it as simple as higher boiler pressure and/or degrees of superheat?

No, it has nothing to do with increasing boiler pressure. The Franklin Railway Supply trailing truck "Booster", was essentially a steam driven, twin piston engine mounted on the trailing truck, which utilized steam pressure from the locomotive's main throttle. It drove a pinion gear, which when engaged, drove a large diameter bull gear, mounted to one of the trailing truck axles. Depending on the various locomotives that boosters were used on, it provided an additional 12,000 to 14,000 pounds of staring tractive effort. The booster was usually disengaged at about 20 to 25 MPH. Most of the NYC Hudsons were equipped with trailing truck, Franklin Railway Supply boosters.

If you have access to a 1941 0r 1944 Simons - Boardman Locomotive Cyclopedia, there is a wealth of information in it about boosters.

I don't know all the details of these engines (it is why I love these forums, make up for a lot of missed years of knowing these things!), but I agree with others, it depends on what you mean by better engine.  They both were built primarily as a passenger locomotive from what I know but could haul freight, so they were equally versatile, they had tractive effort within range of each other (and as others have pointed out, the Hudson's were designed for relatively level track, the K4 for mountains, so the extra tractive effort wasn't needed on the Hudson). Given they both ran for a number of years and basically were outmoded with the introduction of Diesels, it sounds like they did the job they were supposed to.

There are some factors that might make one engine better than the other, depending on us:

1)How often did the engine require maintenance (outside of mandated repairs by law), for example, how often did bearings fail? How often did they leak/crack, how often did the valve gear need replacing/repairing? (and not being a detailed expert on the workings of a steam engine, these are just off the top thoughts). There were some great looking and performing engines that died an early death, including some of the proposed replacements for the K4 from what I read, because of reliability issues and maintenance can be 

2)How long could they travel without refueling and/or taking on water? Again, even that might not mean much, because I would expect the K4 taking on more grades than a Hudson typically would burn more fuel/water. 

3)Weight could be a factor (and here I would assume the engines weighed roughly the same amount), if I was considering an engine for a particular route, and there were limiting bridge capacity on the route, could be one of them would be too heavy (and again, purely hypothetical).

I think from what I read it would be either of them, both of them seemed to have done the job and then some, if either of them was an inferior engine it would have ended up like the S2 turbine.

superwarp1 posted:

Apples and oranges.   Two different entire beast design and built for two different territories.  One for flat level running and one for the hills/mountains of Pennsylvania, Ohio

In a broad sense, that being both locomotive types had two cylinders and six drivers with 79" diameters, and similar boiler pressures (210 psi for the K4s and 225 psi for the J-1), they really are NOT "apples and oranges". The PRR K-4s is an older design, while the NYC J-1 being from 1927 era, was newer, the real difference developed later as the NYC kept improving and improving and improving their Hudson designs. The PRR with their practice of "standardization", never really forced the continued improvement of the K4s, with higher boiler pressures, feedwater heating systems, roller bearings on all axles, and of course the trailing truck booster.

The first NYC 4-6-4 #5200, with 225 psi boiler pressure had 53,260 lbs tractive effort with booster.

The NYC J-1 classes, with 225 psi boiler pressure, had 55,100 lbs tractive effort with booster.

The NYC J-3 classes, with 275 psi boiler pressure (later reduced to 265 psi), had 55,000 lbs tractive effort with booster, but also a serious increase in horsepower and high speed performance & efficiency.

You can visit a bunch of K4s. You can not visit a Hudson...they were all scrapped.

Joe Hohmann posted:

You can visit a bunch of K4s. You can not visit a Hudson...they were all scrapped.

What does THAT have to do with this technical discussion?

The Hudson was a more modern design.  The first NYC Hudsons were built in 1927.  The K4s came on the scene during WWI and the very last ones were built in 1928.  At least at first, the K4s were hand-fired, which might have limited their sustained horsepower.  NYC continued to improve its Hudsons into the 1940s.  That being said, the K4's specs were pretty similar to other heavy Pacifics, and RRs kept building and using those to the end of steam in North America.

At one point the Pennsy built a K5 "super Pacific" with the massive boiler also used on the Decapods.  This would have been more than a match for the J-1e, maybe even the equal of a J-3a.  The Pennsy didn't develop it further, because once the eastern electrification was complete, they had enough surplus K4s that they would just doublehead them on heavy trains.  Not sure about top speed, but the added tractive effort of a 2nd loco should have enabled the Broadway to out-accelerate the Century departing Englewood for Chicago!

Question for Hot Water and other steam gurus... I wonder how well the steam evaporation characteristics of the K4's Belpaire boiler compared to the (theoretically) larger grate area allowed by the Hudson's 4-wheel trailing truck?  Tractive Effort is mostly about adhesive weight.  But at the end of the day, a steam loco's power comes from its ability to boil water.  Some locos are described as "free steaming."  I wonder which was better in this important regard...

Hot Water mentioned that PRR standardized their locomotives, and particularly the K4. The maintenance inventory ($) would much less than the NYC maintenance inventory for their Hudsons. Thus all other considerations taken as equal, the PRR K4 would have lower operating expenses. Consistently the maintenance service time should be less with the PRR K4, thus more revenue time. 

TM Terry posted:

Hot Water mentioned that PRR standardized their locomotives, and particularly the K4. The maintenance inventory ($) would much less than the NYC maintenance inventory for their Hudsons.

Sorry but THAT is an "apples and oranges" comparison. Just the roller bearings on all axles of the NYC Hudsons alone would have been a HUGE maintenance cost saving, i.e. no grease cakes and the constant manpower attention to those grease cakes.

Thus all other considerations taken as equal, the PRR K4 would have lower operating expenses.

You are making an uneducated assumption, again.

Consistently the maintenance service time should be less with the PRR K4, thus more revenue time. 

Once again, another uneducated assumption.

Ted S posted:

Question for Hot Water and other steam gurus... I wonder how well the steam evaporation characteristics of the K4's Belpaire boiler compared to the (theoretically) larger grate area allowed by the Hudson's 4-wheel trailing truck?  Tractive Effort is mostly about adhesive weight.  

What makes you think the shape of the firebox has anything to do with steaming ability? 

Tractive Effort is certainly NOT mostly about adhesive weight. The formula for Tractive Effort has no variable whatsoever for "adhesive weight."

Folks asking these questions concerning these two engines should really consult "Riding the Limited's Locomotives," by Col. Howard G. Hill. He concludes the text by writing the following:

"When I rode in the cabs of the locomotives hauling THE BROADWAY LIMITED 12 days earlier, the K4s Pacifics produced 929,190 gross ton-miles, or 51,110 gross ton-miles per train-hour. Thus the work done by the Hudsons was 40.0% greater than that done by the Pacifics, and they produced 52.0% more gross ton-miles per train-hour over their entire run that then Pacifics produced. The best performance by the 5302, 85,925 gross ton-miles per train-hour, was 34.2% better than the best performance by the K4s Pacific No. 5439, which was 64,024 gross ton-miles per train-hour. The approximate total weight of the locomotives and train of THE BROADWAY LIMITED varies from 900 tons to 1200 tons. It is obvious that the Hudsons had to produce greater power output over the entire run than was the case with the Pacifics. The Hudsons were reported to have developed 4,075 horsepower at 66 miles per hour. All things considered, each of those two classes of locomotives produced outstanding performance in its respective sphere of operation."

There are locomotive spec sheets for each engine in the Appendix.

One Hudson was of insufficient tractive effort or horsepower output to handle a passenger train on the PRR's mountainous route. Hence Two K4s doubleheaded was the standard power for Pennsy name passenger trains. IRRC Pennsy engineering studied  larger 8-coupled power (4-8-2 and 4-8-4) as an answer to ever heavier trains but didn't like what those engines did to the track. So the T1 Duplex 4-4-4-4 was developed and was to be passenger Super Power for a generation......except the work of those pesky guys from Cleveland (EMC) doomed all steam power and the PRR was scrapping T1s while still taking delivery of the final engines in the order.

The biggest advantage the Hudson had, with the 4 wheel trailing truck, was more grate area (82 vs. 70 ft/sq) plus a larger combustion chamber on the Hudson which provided much more steam for the same fuel amount used..  I believe the number was 40% more efficient for the Hudson.

Hot Water posted:

Joe Hohmann posted:

You can visit a bunch of K4s. You can not visit a Hudson...they were all scrapped.

What does THAT have to do with this technical discussion?

Because it's better to be able to look at one in the flesh vs not being able to. And who said this HAD to be technical? Design aesthetics plays a role, especially for the streamlined versions.

It should be enough to say the J1 was developed more than 10 years after the K4 was developed and by gosh, that being the case when it comes to technology advances over time, the Hudson should have been a LOT more capable of a locomotive than the K4 ever was. The Hudson should have run rings around any K4 anywhere.   You guys mention driver diameter but ignore cylinder bore and stroke which in addition to that grate area and a bunch of other design details are what really defines how differently the two loco's will operate.

The K4 wasn't even originally designed as a superheated steamer.  No power reverse and no power stoker among other things. It was designed well before the advent of roller  bearings....It was made in great quantity, what 424 or 425 K4's compared to 301 NYC Hudson's.

They were both fabulous loco's, In my opinion the fact that the K4 became  and remained the King of the PRR rails from basically 1914 to the last day in 1957 is more than enough testament to it's greatness.  Better, it depends on your definition,  Each railroad had their own ideas about what the formula of a locomotive should be and pretty clearly, even though they were distinctively different, they both worked and worked well.

At the end of they day, to me this is just another Ford versus Chevy argument really.