Why Are There Crushed Stones Alongside Railroad Tracks?

iStock
iStock


Why are there crushed stones alongside rail tracks?David S. Rose:This is a good question with an interesting answer. The crushed stones are what is known as ballast. Their purpose is to hold the wooden cross ties in place, which in turn hold the rails in place.Think about the engineering challenge faced by running miles of narrow ribbons of steel track on top of the ground: they are subject to heat expansion and contraction, ground movement and vibration, precipitation buildup from rough weather, and weed and plant growth from underneath. Now keep in mind that while 99 percent of the time they are just sitting there unburdened, the remaining one percent of the time they are subject to moving loads as heavy as one million pounds (the weight of a Union Pacific Big Boy locomotive and its tender).

Put all this together, and you have yourself a really, really interesting problem that was first solved nearly 200 years ago, and hasn't been significantly improved since.

The answer is to start with the bare ground, and then build up a foundation to raise the track high enough so it won't get flooded. On top of the foundation, you deposit a load of crushed stone (the ballast). On top of the stone, you lay down (perpendicular to the direction of the track) a line of wooden beams on 19.5 inch centers, 8.5 feet long, 9 inches wide and 7 inches thick, weighing about 200 pounds ... 3249 of them per mile. You then continue to dump crushed stone all around the beams. The sharp edges of the stone make it difficult for them to slide over each other (in the way that smooth, round pebbles would), thus effectively locking them in place.



The beams are made of hardwood (usually oak or hickory), and impregnated with creosote for weather protection. In the U.S. we call them "cross ties" (or, colloquially, just "railroad ties"); in the UK they are known as "sleepers"; European Portuguese, "travessas"; Brazilian Portuguese, "dormentes"; Russian, шпала (read "shpala"); French "traverses." While 93 percent of ties in the U.S. are still made of wood, heavily trafficked modern rail lines are increasingly trying alternatives, including composite plastic, steel, and concrete.

Next, you bring in hot-rolled steel rails, historically 39' long in the U.S. (because they were carried to the site in 40' gondola cars), but increasingly now 78', and lay them on top of the ties, end to end. They used to be joined by bolting on an extra piece of steel (called a "fishplate") across the side of the joint, but today are usually continuously welded end-to-end.

It would seem that you could just nail them or bolt them down to the ties, but that won't work. The non-trivial movement caused by heat expansion and contraction along the length of the rail would cause it to break or buckle if any of it were fixed in place. So instead, the rails are attached to the sleepers by clips or anchors, which hold them down but allow them to move longitudinally as they expand or contract.

So there you have it: a centuries-old process that is extremely effective at facilitating the movement of people and material over thousands of miles ... even though nothing is permanently attached to the ground with a fixed connection!

The ballast distributes the load of the ties (which, in turn, bear the load of the train on the track, held by clips) across the foundation, allows for ground movement, thermal expansion and weight variance, allows rain and snow to drain through the track, and inhibit the growth of weeds and vegetation that would quickly take over the track.

This post originally appeared on Quora. Click here to view.

Wayfair’s Fourth of July Clearance Sale Takes Up to 60 Percent Off Grills and Outdoor Furniture

Wayfair/Weber
Wayfair/Weber

This Fourth of July, Wayfair is making sure you can turn your backyard into an oasis while keeping your bank account intact with a clearance sale that features savings of up to 60 percent on essentials like chairs, hammocks, games, and grills. Take a look at some of the highlights below.

Outdoor Furniture

Brisbane bench from Wayfair
Brisbane/Wayfair

- Jericho 9-Foot Market Umbrella $92 (Save 15 percent)
- Woodstock Patio Chairs (Set of Two) $310 (Save 54 percent)
- Brisbane Wooden Storage Bench $243 (Save 62 percent)
- Kordell Nine-Piece Rattan Sectional Seating Group with Cushions $1800 (Save 27 percent)
- Nelsonville 12-Piece Multiple Chairs Seating Group $1860 (Save 56 percent)
- Collingswood Three-Piece Seating Group with Cushions $410 (Save 33 percent)

Grills and Accessories

Dyna-Glo electric smoker.
Dyna-Glo/Wayfair

- Spirit® II E-310 Gas Grill $479 (Save 17 percent)
- Portable Three-Burner Propane Gas Grill $104 (Save 20 percent)
- Digital Bluetooth Electric Smoker $224 (Save 25 percent)
- Cuisinart Grilling Tool Set $38 (Save 5 percent)

Outdoor games

American flag cornhole game.
GoSports

- American Flag Cornhole Board $57 (Save 19 percent)
- Giant Four in a Row Game $30 (Save 6 percent)
- Giant Jenga Game $119 (Save 30 percent)

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The Reason Your Dog Follows You Everywhere

Crew, Unsplash
Crew, Unsplash

Depending on your mood, a dog that follows you everywhere can be annoying or adorable. The behavior is also confusing if you're not an expert on pet behavior. So what is it about the canine companions in our lives that makes them stick by our sides at all times?

Most experts agree on a few different reasons why some dogs are clingy around their owners. One is their pack mentality. Dogs may have been domesticated thousands of years ago, but they still consider themselves to be part of a group like their wild ancestors. When there are no other dogs around, their human family becomes their pack. According to Reader's Digest, this genetic instinct is also what motivates dogs to watch you closely and seek out your physical touch.

The second reason for the behavior has to do with the bond between you and your pet. As veterinarian Dr. Rachel Barrack told the American Kennel Club, puppies as old as 6 months can imprint on their human owners like they would their own mothers. Even older dogs will bond with the humans in their lives who show them care and affection. In these cases, a dog will shadow its owner because it sees them as an object of trust and security.

The last possible explanation for why your dog follows you has more to do with your treatment of them than their natural instincts. A popular training tactic is positive reinforcement—i.e. rewarding a dog with treats, pets, and praise when they perform positive behaviors. The point is to help your dog associate good behaviors with rewards, but after a while, they may start to associate your presence with rewards as well. That means if your dog is following you, they may be looking for treats or attention.

A clingy dog may be annoying, but it usually isn't a sign of a larger problem. If anything, it means your dog sees you in a positive light. So enjoy the extra companionship, and don't be afraid to close the door behind when you need some alone time.