I was out at Salinas this evening to meet our Railforum friend Jonathon and his dad as they passed through Salinas. (They're very nice folks, by the way. They'd make good next door neighbors.)

While I was waiting, the nightly freight train was hitched to the locomotives, then as per the routine I have witnessed several times now, it pulls up on the second track and stops with the last car in front of the UP offices in the station, where an end of train device is attached.

As I watched the train rolling slowly past, I noticed the track under the wheels was bending downwards at one joint every time a truck passed over it. Between trucks the track flexed back up. I would say it was bending down a good three or four inches each time. I saw some flexing at other joints, but not nearly as much as at this one. The ties at that joint looked kind of rotten.

Since this was just a siding, it doesn't take full speed trains, but it looked kind of freaky. Is this normal, or is the track falling apart?

------------------
Sing to the tune of Humoresque:
Passengers will please refrain,
From flushing toilets while the train,
Is standing in the station,
I love you.

Yes, the flexing at rail joints is a normal function. This is especially pronounced in side tracks or branch lines main tracks where welded rail is not economically justified, where speeds are slower by operating rules and where maintenance is less than the high speed main lines which are usually the topic of conversation here.

The one joint you observed appears from your description to be a candidate for maintenance
and given its location near the depot and offices will probably be taken care of soon.

I am not very knowledgeable about the technical aspects of trains. My main interest is advocacy, and what technical knowledge I have was mostly picked up en route to researching something else. But that's not to say I'm not curious about these things, its just a lower priority.

There is a lot more to track than meets the eye. I would suspect that if someone were trying to develop the concept at the current time it would never happen. Actually most of what we have now developed very gradually over a large number of years as individual problems presented themselves and fixes were developed. The basic track structure is a wonderful method of taking a very large load applied to a very small area and spreading it to a very wide area as a very small load to each unit of area.

Just some basics, this time.

A standard freight car today usually is limited to 286,000 pounds on four axles. This works out to 35,750 pounds per wheel. Usually loads are quoted as tons per axle, so this is usually called a 36 ton axle load. The stiffness of the rail spreads this over more than one tie. Since joint bars are much less stiff than rail, even when the bolts are tight, and they do not stay that way, jointed rail results in the ties near the joint carrying an excessive share of the load. The tie then distributes the load to the ballast. Since a wood tie is flexible, this spread is not uniform. The applied load under the rail is higher than in the center of track. That is why when the tamper comes along and packs the rocks of the ballast under the tie it is only done relatively close to the rails. Normally on heavy duty freight carrying lines wood ties will be spaced at 19.5 to 21 inches, which results in a mile of track having between 3000 and 3250 ties. The rock of the ballast then spreads the load to the underlying soil. Usually in new tracks the minimum depth of ballast under the bottom of the tie is about 12 to 15 inches. Under this will be a layer of subballast, which is essentially the same as a crushed rock road base or gravel road material. The depth of this should be developed based on soil conditions, but should be no less than 12 inches. Instead of subballast, a layer of asphalt base course of about 8 inch thickness can be used. This is IMHO a better choice because it is impervious and helps both stabilize the moisture content of the soil and prevent movement of fine particles in the soil into the ballast. By the time you get to the bottom of this the load on the soil will be under 20 pounds per square inch, in other words, less than automobile tire pressure. The soil underneath needs to be graded to a good cross slope for drainage and in cut areas have ditches adjacent tot eh track about 2 feet deep and sloped to drain water away from the track. As one of my professors used to say, the three most important thing in any roadway design are drainage, drainage, and drainage.

You can get away with a lot less than this type of cross section if you only want to run one heavy train occasionally move a few cars regularly at low speeds. This little tidbit has been a major source of surprises to the managements, and even to people who ought to have known better.