I understand that large steam locomotives, even the so called “balanced” ones, could really “pound” a track because of the up and down movement of the side rods and counterbalanced drivers. Track then was the segmented, bolt joint “clickety clack” rail.
Nowadays track is welded in long segments. It seems (might be a perception on my part) that it’s heavier, too. My primitive understanding is that diesel and electric locomotives still bring stresses to the track, but that it’s much different than a steam locomotive.
So, my question is this: Would today’s heavier, welded rail withstand the stresses of yesterday’s road freight steam engines better, or worse?
My notebook and pen are out awaiting the physics and mathematics answers.
CWR is also a lot easier on equipment in general, everytime a wheel would hit a joint it would produce wear and tear, resulting in more maintenance all around.
CWR also provides a much smoother ride to those few people who still partake in passenger rail service.
Riding in a locomotive or on a passenger train, outside of the clicking from jointed rail, one can’t appreciated the ride differences between jointed and welded rail.
Ride a caboose over territory that contains both and the differences are brought home in spades. Caboose trucks are sprung as stiffly as freight car trucks and the ride over jointed rail is jaring to say the least. Traversing segments of both welded and jointed rail, you pray that the next welded rail segment is quickly approaching.
Your “perception” of heavier rail is basically correct. Although steam pounded 155 lb (per yard) rail on PRR’s Horseshoe Curve, I don’t believe anyone else has ever used rail that heavy. On the other hand, 133 lb (or thereabouts) is much more common today than it was when steam was the dominant form of motive power.
Mudchicken would know more about this, but word is he is on the road. He had told me that I would be riding on jointed rail on in Kansas and Colorado on the Santa Fe “pasenger” route, now the route of the Southwest Chief.
Perhaps not as dramatic as the ride in a caboose, I can assure the the difference in the ride quality between jointed and welded rail in a SuperLiner is big.
N&W had about ten miles of a test application of 155 Lb. rail east and west of Webb, W. Va. on the Kenova District. Their normal standard at the time was 132 Lb.
The steam locomotive is going to pound the rail, whatever its length or weight. The heavier the rail, the better it will withstand the pounding.
The side of the engine that had the lead (the drivers being “quartered” - the piston on one side on dead center and the other side at mid-stroke - the piston on one side will therefore begin its stroke before the other, and is said to have the lead) will tend to pound the rail harder.
Most US engines had right-hand lead. Pennsy used mainly left-hand lead.
In the category of one is never too old to learn something new, your note about the lead side being harder on the rail falls there.
I am not very knowledgable about the details of steam locomotives, and it was only a few years ago that I learned about the drivers being quartered. I think I picked that up in a story about an N&W engine having lost the cylinder or rods on one side in a wreck and being run light to a shop for repairs. It was noted that if the engine was stopped with the piston dead at either end of the cylinder it would take a bit of a roll to get going again.
The problem with diesel locomotives is the “Unsprung Mass”. The normal US locomotive has traction motors which are described as “axle hung”, the motor being supported on bearings directly on the axle with the other end, the “nose” being carried on rubber bushings on the truck frame. The frame is carried on springs, but the axle of course sits directly on the rail, so at least half the motor mass is “unsprung”. This is an important cause of impact at rail joints, and for high speed locomotives particularly, reduced unsprung mass is important. The British Rail (now GNER) Class 91 electric locomotives intended to run at 140 mph, have body mounted motors driving through cardan shafts and right angle gear boxes.
If you check the engineering standards of some railroads, some used “suspended” rail joints where, as Mark H said, the rail joint was a break in the beam. That is, there were ties on both sides of the joint but not underneath it. (What they would do however was use tighter tie spacing.)
Other railroads would put a tie directly under the joint, although how the rail was fastened to it, assuming it was fastened, is not clear to me. Whether this had any practical effect I do not know but it would seem there should be some beneficial effect.
Having said all that, two weekends ago when the Soo Line 1003, a 2-8-2, was running photo excursions on the Wisconsin & Southern for the late Dave Goodheart, a welded rail snapped under the locomotive (fortunately not failing entirely until the historic wood Soo Line caboose had passed over it), cancelling the first planned runby of the day. The rail is welded but it has rolling dates in the 1920s. The right of way itself dates from 1856 and can get rather rough.
Dave Nelson
Thanks for the answers!
It seems that CWR came into use sometime in the 70’s- maybe the 80’s? If the improvement in ride and (I assume) maintainability costs were improved as significantly as everyone seems to say they were, how come railroads didn’t use CWR much earlier? Was there a change in welding technology or in metallurgy that enabled CWR?
I remember looking up railroads in our new 1957 Compton’s Encyclopedia as if it were yesterday and the photograph of CWR being installed. That was the first I’d ever heard of it, but, of course, I was only 9 years old. When did the long rail begin to be used? Somehwere I thought I read that in the days of steam, fairly light rail was used because it tended to move with the heavy drivers and didn’t get beaten up so badly. Did I misread that?
Jock Ellis
Like any other technology, CWR required more than just the welding development to become industry practice. Some of the other items included:
Development of long rail transport and delivery
Mechanization of rail laying as opposed to a track gang
Control of expansion joints
Inspection technologies that recheck the welds
Coupled with the long life of stick rail in most locations, developing these methods slowed CWR installation for many years.
There are some other considerations that may be of interest.
I think it may be valuable to separate the potential track damage from steam locomotives into several categories (mudchicken, when he reads this, may revise this to a better set):
Railhead damage
Rail deformation
Rail breakage through shock or defect propagation
Lining/surfacing defects caused by ‘knocking’ the rail in various planes
Lining/surfacing defects caused by pumping rail against the ties, and track against the ballast
Note that I’m leaving the joints out of this discussion. Comments so far are accurate on that subject, but I think the original question involved continuous track structure more than joint effects. One comment: it might be considered that the frequent shocks and high forces caused by steam locomotives might keep bolted joints a bit more free – helping, for example, eliminate sun-kink problems – than smoother operation with well-suspended diesel-electrics…
OT might have mentioned that N&W was one of the more advanced railroads in the country – I might argue in the world – with respect to steam-locomotive balancing theory and practice. The J-class 4-8-4s had an interesting method of eliminating many of the ‘problem’ areas of dynamic balancing.
One consideration that hasn’t been mentioned is that modern rail has a different metallurgical composition, and a different required method of ‘head hardening’. I believe that much of the theory and adoption behind current rail steels has presumed the absence of high shock loading (as would be generated by conventional large 2-cylinder steam locomotives with ‘normal’ cross- and overbalancing). I would expect to see aggravated problems with crack propagation in the martensitic railhead-surface layer, with gauge-corner cracking problems in general, and perhaps with catastrophic crack propagation on chilled sections of LWR under tension.
Having been a part of the locomotive crew on AWP 290 when in operation in the mid-1990’s I can say from personal experience that CWR gives a much better ride than jointed rail, especially at speeds over 30-40 mph.
However, that is not an indicator of the kind of wear that is occurring at rail level. The dynamic augment (the pounding that occurs to the rail) occurs with all steam locomotives with side rods and pistons varies based on cylinder bore diameter, steam pressure, side rod weight, and counterbalancing combined with the overall weight of the locomotive applied to the drivers. Some locomotives were easier on rail that others due to lighter reciprocating forces or better counterbalancing. Also, dynamic augment was largely something that occurred at different rates at different speeds, again varying from one locomotive to another. Heavier rail would naturally withstand the effects of dynamic augment better than lighter rail; CWR would not have the inherant weaknesses that jointed rail possess, no matter what the effects of dynamic augment.
One other area of wear that occurs to rail is in curves. In the days of steam the roadbed was super-elevated in the curves, that is the outside rail of the curve was elevated higher than the inside rail, much like the banked turns of a race track. While there is still some superelevation used today, it was greater in the days of steam on most US mainlines. The present track dynamics used for todays diesels would need to be changed to reduce wear in the curves if steam were still in wide use. This would be due to the longer continuous wheel base of steam as compared to diesel.
Essentially, there will be wear to the rail and to the wheels of all locomotives over time. CWR at the present standard of around 130 to 136 lbs would have improved wear over the jointed rail of equal or lesser weight. More modern steam would undoubtably have improved the overall nature of the characteristics of dynamic augment by using stronger and lighter ma
I think the location of the Jing Peng line in a high altitude desert area with a very high temperature range may be a major reason for the use of jointed rail. The risk of rail breakages in continuous rail in an isolated area may have been regarded as too high compared with the need to supply (still relatively cheap) labour to check the bolted joints.
Also, the “pounding” effect of the steam locomotives mainly used on this line is independent of rail joints, unlike the unsprung impacts of diesel locomotives which are directly caused by rail joints.
The Jing Peng was a privately financed railway, and their use of steam locomotives was related to the ready availability and low initial price of used steam locomotives compared to new diesels. Building the line with bolted rail in an area of relatively low labour costs may have resulted in lower up front costs to get the project under way.
Several of the writers mentioned experience on the N&W; today, the one railroad with experience of how steam behaves on welded rail would be UP. Does anyone who actually has worked for this road know what UP has found re how its “historic” engines treat their modern plant? I know UP was an early user of the 131-133 lb. rail in mainline applications and considered 2-10-2s and 4-8-4s to be “small” steam power. No doubt the UP has company data on the difference between 131-lb welded and 131-lb. bolted, and no doubt such a safety-conscious company would be well aware of the effect use of something as big as a challenger would have on track not laid with such locomotives in mind.
I’d have to go way back to my college days to be able to write the equations of motion for a reciprocating steam engine and calculate the forces. And, since Mr. Peabody is already using the only known “way back” machine, I’m stuck.
But, on the surface of it, I think you can pretty much balance the rotating mass, but the reciprocating side rod, et. al. is the real problem and most of the resultant force would longitudinal and could cause the locomotive to want to “waddle” or yaw more than any vertical “pounding”.
I guess you could configure a lever driven balancing mass the would move opposite to the driving rod to counter balance the forces, but the complexity would probably exceed the benefit.
Mark, you’re probably right about the ravages of time on a memory. Maybe you could help me with something else apropos to this post. Now working in magnetic and flourescent non destructive testing for GE, I have become interested in the history of the discipline. But the history seems to be almost nil. Has Trains or any train mag ever done stories on NDT? I know it started as a result of railroad needs but that is about all I can find out.
Jock Ellis
Don’t forget that today’s pounding of the rails is by equipment with wheel flatspots, and the criterion for most freight cars is not sufficient to eliminate the bang bang bang we sometimes hear while a freight passes by. If there is noise, there is also mechanical energy.