Track Fundamentals-- Staggered Joints vs. Laid Square
I have been thinking about how stick / jointed rail was always laid with staggered joints, at least into this post-1900-era leading into the current time of welded rail and joint elimination. The reason they staggered the joints always seemed to intuitively make sense to me, although I had not thought about it deeply.
Generally, I was thinking that offsetting the joints would create a lesser disruption to the carriage of wheels of the trucks since they would only encounter one joint at a time. Whereas, placing the joints side by side would have both wheels hitting the joints simultaneously, so it seems like the impact on each joint might be higher if both joints were side by side. Both wheels together would drop a larger portion of the entire carload into depressed joints if they were side by side.
However, I have noticed historical references to rails being laid with joints “square,” which is described as laying the rails with their joints side-by-side. So I assume that this might have been an early, intentional alternative to staggered joints. But why? What was the case for square-joint rail in track? And how common was it? Was it a near-universal practice during the earliest era? Or was it a more individualized preference from one road to another?
I wonder if there was a time when startup railroads had to decide whether to go with staggered or square joints; similar to the decision of which gage to build to during the gage wars.
Simple, Staggered joints because of the alternating pounding of locomotive rods, distribution of joint impact on trucks…check basic histories of railroads for complete and detailed reasons and experiments…
Laying track on tangent was done “square” because the flat car that carried the rails could be rolled right up to the point of laying the rail… if they were staggered, the flat car would have to stop short of the shortest end of the track and the workers would have to carry the stick an extra 20 ft or so, slowing things down considerably.
It might also have something to do with a dynamics issue called harmonic vibration which would magnify the effect of hitting both joints at the same time making for a rougher ride and potential track damage.
The linked book - Railway Track Engineering - is from India, and appears to reflect British practice (as opposed to US), where staggered joints were more common - less axle loads, for one reason.
Kinking in curves is a major reason there. On tangent track that might seem to be not true, but a heat (“sun”) kink will develop far faster in a track with opposite joints than staggered - the lateral stability/ Moment of Inertia at a rail joint is very low.
Impact on the ties at the joint is another reason. With parallel joints there’s a greater risk of 'center-binding" and breaking the ties, which is obviated with staggered joints - only 1 side at a time feels the impact.
It is obvious that staggered joints are standard in the U.S. now. I am just wondering if that was always the case. The fact that the reference cited is for Indian railways may or may not matter. Much of Indian practice is probably universal or more widespread than just used in India. The Indian reference cites wheel coning and rail canting identical to U.S. practice, for example. Is it current practice to lay rails square in India? Is it current practice in Britain?
The reason to wonder if square joints were once common in the U.S. is that the Indian reference explains the advantage of square joints over staggered joints. I never realized that there was an advantage to square. It seems like if the advantage exists in India, it would also exist in the U.S.
I had someone point out to me once that staggering the rails evenly led to potentially dangerous rock and roll conditions, but if they were staggered with the joints one third of a rail-length apart the harmonics might not lead to that.
The “rock and roll” harmonics from opposite-staggered joints which caused derailments were not very common until the 1970’s, when increasing car weights on poor track conditions (low joints, bad ties, pumping “mud ballast”, etc.) interacted to cause that result more frequently.
ConRail’s track specifications (maybe the 2nd issuance, circa 1980) specified that the joints be placed at a 1/3 point of the opposite rail. With welded rail becoming almost universal, that is moot in most tracks, and is now relevant mostly for industrial sidings/ sidetracks.
Another reason parallel or opposite joints may have been more acceptable in British practice - but not in the US - is that the British have always had a fairly tight and rigid system of fastening their rails to their ties (or “sleepers”), such as the ‘bulb’ rail, chairs and wedges, screw spikes, etc. (and even stone sleepers in the early days). In contrast, US practice is quite a bit ‘looser’ with the spaces between the spikes and the base of the rails (both horizontal and vertical) and the flat ties plate (when used - not often in the earlier days) allowing some movement under load. If both rails could move (outward) at the same location due to parallel joints, gauge widening that could develop to the extent of causing a derailment would be more frequent; but if one rail is continuous there, only the other rail is more susceptible to moving at that point.
When I was railfanning in Japan half a century ago, the rail joints were:
Squared.
Laid on two very closely spaced ties.
Connected by angle bars that were much more substantial than those I had seen on NYC a decade earlier.
Since labor was still fairly inexpensive at the time, even unimportant routes were maintained like the Norfolk & Western. I never saw mud ballast or badly-sunken joints anywhere - not even on dying, poverty-stricken narrow gauge tramways to nowhere.
It seems that there basically three different practices for positioning rail joints, each with its own advantages and disadvantages:
Staggered joints.
Joints laid square.
Joints slightly staggered.
This reference says that rails laid with joints square was more popular overseas. It says there were pros and cons to both staggered joints and square joints:
The staggered joint pattern has each joint lined up with the midpoint of the opposite rail. However, that alignment will drift as track rounds a curve because the distance traveled by the outside rail will be greater than the distance traveled by the inside rail.
How far out of a perfectly staggered pattern does the alignment need to get before it must be reset by cutting back one of the rails to re-match the pattern?
Do you mean that the joints can drift to within 6.5 feet of being aligned, but no closer than that? I suppose a lot of curve drift gets reversed by curves in the opposite direction.
A lot of the roads in Queensland Australia were square dew to the fact of rigid base 4 wheel rollingstock which would literally fall of the track (Most lines were built to very light axel loadings with little or no ballast at all)