Guys,
Here’s somehting that has bothered me for a while, but I could not find an answer anywhere:
Why are the rail joints on jointed rail ( I mean the old 39-foot rails) usually not
parallel but offset? Is there a reason behind it or is it just that after the first curve, the joints were offset anyway ?
Thanks for some enlightening answers.
Martin
Martin,
There are, of course two views on this. It is usual in the USA for the joints to be offset, in Australia we called this “Staggered Joints”, and I think the other way was called “Square Joints”. Where I grew up, in Sydney, we had square joints, and in Melbourne, staggered joints were usual.
One possible reason for staggered joints would be to reduce the ground pressure and disturbance to ballast resulting from the impact forces of wheels on the rail joints, since these impacts would be spread over a larger area. This became a problem in areas of poor drainage, where in wet weather the “square joints” caused “pumping” as the earth beneath the ballast turned to mud and rose up through the ballast, causing a low point in both rails.
The dynamic effect on suspension of the different joint spacing was, of course different, with staggered joints resulting in a rolling effect, while square joints just gave a vertical jolt.
When in 1961, a standard gauge line through Victoria from Melbourne to Albury was nearing completion (5’3" gauge having been used previously in Victoria) truck designs were being considered for a new through passenger train. The two systems could not agree on a single design, since, the Victorians preferred a design that worked best on staggered joints (A US design) while NSW preferred a local design that worked better on square joints. Eventually, both designs were used, based on who paid for each car!
Peter
US railroads feel the dynamic loads are less with staggered joints.
Dave H.
I have seen evidence of pumping on both staggered and square joints (sometimes called snap track) – even on continueous ribbon rail if drainage is a problem. What I am trying to figure out is why I saw a rail joint with bolts in only one rail? MoW slipup perhaps?
dd
Harmonics caused by square joints creates surface defects that are absurd to deal with in the US. Being that the joint is the weakest part of the track structure, you do what you can to minimize the risk and maintain track speed. You may lay them square with panels, but you slide one rail to offset joints so that they get more than 16’ -6" apart… I’m sure Unihead, CSXEngr., LTDclear and the others can tell you about the phenomena about switches being hard to throw because the locomotive is stopped too close to the points. (Courtesy of square joints & unconsolidated ballast…the stockrail and the switch points get “bound up”)
Wear and tear would seem to be the main thing. However, if you stop and think
about it;with staggered joints,you get the “clickity-clack”. With squre joints,basicly
all you get is a “thud”[:)]
Thanks, guys, for bringing me “on top of matters”. Seems to me that here in Germany the “square joints” also need double ties at each joint, so this means more labor and more material.
American freight cars have trucks that are allowed to pivot freely in all three dimensions. Here in Europe, most freight cars used to be of the four-wheel kind for a long, long time and those would not tolerate the staggered joints too well, I presume.
MS
Mudchicken-
With the improvments (?) in track technology, is there still a “memory” problem with jointed rail that was replaced with welded? On the CNW, we had numerous locations that, even with ballasting and resurfacing, in a few months low spots would develop in the new welded rail where there was a low spot in the jointed rail.
Or was it simply that the CNW did it’s trackwork the same way it did it’s locomotive maintenance (C&NW–Cheap & Nothing Works)?