A retired acquaintance, who used to be a manufacturer’s rep for Timken Products,
made the claim that superpower steam really was enabled by the use of the roller bearing. He points to the Big Boy as an example, and says a power plant of that
enormous weight would not be able to efficiently transfer power to the drivers if
it were not for the development of the roller bearing. As he is many years my senior, I thought it wise not to disagree. But other opinions would be welcome. Any comments?
Enhanced, maybe. Enabled, probably not.
Superpower came along before the roller bearing.
Very true. Burt Pennypacker implies in the latest issue of Classic Trains that the B&O 2-10-2 “Big Sixes” of the mid-1920’s were the among the first “Superpower” designs. They were operational long before roller bearings on locomotives became common place.
No doubt that roller bearings enhanced the performance of locomotives. One only has to look at the “roller bearing everything” B&O EM1 from 1945. Those locomotives were over 125’ long and close to 1.1 million lbs., yet they could be push around the yard by 3 men !
See this link for Timken’s 1930 all-roller-bearing ALCO 4-8-4
http://www.catskillarchive.com/rrextra/trbc1111.Html
or
http://www.timken.com/industries/rail/overview/overview3.asp
and finally this Trains article on super power:
http://www.trains.com/Content/Dynamic/Articles/000/000/005/301ndbru.asp
I had a guy the other day try to convince me that the trucks under one of UP’s passenger cars were friction bearings, even when it said “TIMKEN ROLLER BEARINGS” on the lid. He thought it was a plain bearing just because of the cover, lol! Some people.
Back in some cranny of my brain there is an old magazine article about Timken bearings and their effect on engine operations. It said the typical modern steam locomotive required about 6,000 pounds of tractive effort just to move itself. Roller bearings, however, reduced that number to something in the low hundreds allowing a substantial increase in power available at the drawbar. That 6,000 pound figure always seemed a little suspicious to me, but there is no doubt that the bearings made a substantial difference. The three women with a rope prove it. I do know that engineers reported a marked improvement in pulling power for roller bearing equipped locos versus friction bearing locos.
BTW “three women with a rope” sounds a little dangerous, don’t you think? It might be a good name for a rock band. Call Dave Barry.
Did someone say “Timken”?
There is a difference in rolling drag between roller bearings and properly lubed ‘friction’ bearings (which is something of a misnomer – if the things are properly maintained, friction isn’t quite the right word – but I won’t get into that here!). However, the difference isn’t all that large, and is quite variable (under certain conditions, in fact, a ‘friction’ bearing may actually have less – not more – drag, oddly enough).
However… there is a tremendous difference, as has been pointed out in a number of threads, in what might be called ‘starting’ drag, which is one of the major reasons for using roller bearings wherever possible. The other major reason is maintenance – note that I said above ‘properly lubed’. Ask any old-timer about the task of oiling around a friction bearing equipped engine… !
A better term is “plain” bearing rather that “friction” bearing. In a properly designed and maintained (and maintanence is very critical) plain bearing, the two surfaces don’t touch. They actually ride on a thin film or “wedge” of lubricant.
Roller bearings, while less maintenance entensive, are far more design critical. As you correctly stated, an improper roller bering can actually have the opposite effect on rolling friction.
A “plain” or “friction” bearing drawback is that after sitting still gravity has a tendacy to squeeze the “wedge” down to virtually nothing. They float on a sheet of oil while turning. The " wedge" exists on both sides of the axel tapering down to nothing after they have been sitting still. If hot when parked they would weld themselves to the bearing and break off small pieces when moved again. Part of the job was to inspect the axels looking for pits in the axels or groves and gouges in the bearings. [2c] As always ENJOY
The oublished friction values of roller bearings vs plain oil lubricated bearings is .0018 vs .08. This is enough to to reduce the 6000 lb drag force down to135 lbs. In addition, plain bearings are dependent on the oil being supplied under pressure for proper operation. (This is why your car engine will seize up if your oil pump fails.) This is an additional parasitic loss. Roller bearings, on the other hand, work best with only a drop of oil every 2-4hr. Flooded lubrication increases friction because the rolling elements are now churning through the lubricant instead of just rolling on it (sort of the difference between when a speed boat is running through the water vs when it is planing on top of the water) .
Leon’s friction values are for static, or starting friction. A good plain bearing, properly maintained, should have a friction value on the order of 0.004 to 0.005.
Properly maintained…
The Static Coeffficient of Friction is .10,. 08 is dynamic. This is from an EIT Ecam book, Sixth edition, table 9.2 on page 9.16. Potts “Design of Machine Elements” identifies the values as average. They are found on page 407 of the fifth edition.
Well, Leon, I won’t argue with an EIT book… when I got my license, 40 plus years ago now, we didn’t have the EIT, nor the book learnin’ that went with it. Probably just as well, or I’d never have bean able to move a plain bearing box car with a pry bar…
Another big issue with plain bearings was starting a train that’s been sitting around at 0 degrees F. The bearing lube is about the consistancy of molasses at that temp, and I believe some RR’s de-rated the tonage locos could pull in winter.
As far as Superpower, it’s interesting that Northern Pacific was an early user of roller bearings on all axles of their Northerns, but the 2-8-8-4 Yellowstone’s had plain bearings. UP’s first series Challengers also had plain bearings, although many were later rebuilt. Except for the 2 streamlined locos, a 4-6-2 and a 4-8-2 with Timken rods used for the Golden Gate Expo in 1939, UP never specified roller bearing rods on the Challengers, Big Boys, or Northerns built later. AFAIK, the Timken rods weren’t removed when the 2 locos were de-streamlined, but I’ve never run across an explanation for why they did what they did. Anyone?
B&O BM1 steamer that could be “pushed around the yard by 3 men”…?? Expand on that thought a bit {GP40-2}…Wouldn’t the friction in the steam cylinders be enough to prevent even a chance of starting all that dead weight by human power…???
Nope. The agility of the EM1 is well documented in B&O historical texts. In car terms they were “tricked out”, with Baldwin throwing every modern appliance they had on them. Besides the all roller bearing construction, they had lateral suspension dampers to ease the locomotive into curves at high speed, and their running gear was a totally new design from other big articulated locomotives, again to enhance high speed stability. EM1’s could, and often did run at full passenger speeds.
The EM1 was designed as a fast heavy frieght locomotive, not a high tonnage drag locomotive. It was designed to exceed the performance of a 4 unit EMD combo at the time (the B&O wanted EMDs, but the War Production Board said no), hence it’s diesel-electric like speed range. In my book, they were very similar to the N&W Class A, but with 2 extra drive axles.
From a mechanical engineering prospective, they were engineering masterpieces, and as others have long said, it is downright criminal not one of them was saved.
…It sure is a good looking engine and in my younger days I no doubt saw them in action. Home area is in B&O territory. {Pennsylvania}.
Wonder how they managed to get all the extra cost and engineering updates for the era, past the War Board at the time when everything was done bare bones just to get the job done.
If anyone doubts GP40-2’s statement about an EM-1 being able to move with the best of them, take a look at pg 197 in B&O Power by Sagle and Staufer. I know it’s been out of print for years, but if you can possibly find a copy to read, check the photo on this page. It’s 7620 on an express train, looks like somewhere in Ohio, and speed is right up there!! The last cars of the train are lost in the swirling dust , smoke and steam. Great photographic tribute to a great loco.
G’day, Y’all,
This was a great post; I learned a lot. When I was single and had descretionary income, my second Porsche 356 had a roller crank. It certainly would spool up faster than my first which had a plain bearing crank.
With all the extra cars a roller bearing equipped steam locomotive would pull, the railroad executives probably would have extended steam’s longevity by at least 24 hours.