Why Are There Crushed Stones Alongside Railroad Tracks?

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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.

Amazon's Under-the-Radar Coupon Page Features Deals on Home Goods, Electronics, and Groceries

Stock Catalog, Flickr // CC BY 2.0
Stock Catalog, Flickr // CC BY 2.0

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

Now that Prime Day is over, and with Black Friday and Cyber Monday still a few weeks away, online deals may seem harder to come by. And while it can be a hassle to scour the internet for promo codes, buy-one-get-one deals, and flash sales, Amazon actually has an extensive coupon page you might not know about that features deals to look through every day.

As pointed out by People, the coupon page breaks deals down by categories, like electronics, home & kitchen, and groceries (the coupons even work with SNAP benefits). Since most of the deals revolve around the essentials, it's easy to stock up on items like Cottonelle toilet paper, Tide Pods, Cascade dishwasher detergent, and a 50 pack of surgical masks whenever you're running low.

But the low prices don't just stop at necessities. If you’re looking for the best deal on headphones, all you have to do is go to the electronics coupon page and it will bring up a deal on these COWIN E7 PRO noise-canceling headphones, which are now $80, thanks to a $10 coupon you could have missed.

Alternatively, if you are looking for deals on specific brands, you can search for their coupons from the page. So if you've had your eye on the Homall S-Racer gaming chair, you’ll find there's currently a coupon that saves you 5 percent, thanks to a simple search.

To discover all the deals you have been missing out on, head over to the Amazon Coupons page.

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Why Do We Have Daylight Saving Time?

Patrick Daxenbichler/iStock via Getty Images
Patrick Daxenbichler/iStock via Getty Images

As you drag your time-confused body out of bed at what seems like a shockingly late hour next week, you might find yourself wondering why on Earth we even have Daylight Saving Time.

Though Benjamin Franklin was mostly joking when he suggested it as a money-saving tactic in a satirical essay from 1784, others who later proposed the idea were totally serious. In 1895, entomologist George Vernon Hudson pitched it to the Royal Society in New Zealand as a way to prolong daylight for bug-hunting purposes, and William Willett spent the early 1900s lobbying British Parliament to adopt an 80-minute time jump in April; neither man was successful.

During World War I, however, the need to conserve energy—which, at the time, chiefly came from coal—increased, and Germany was the first to give Daylight Saving Time the green light in 1916. Britain and other European countries quickly followed suit, and the U.S. entered the game in 1918. The practice was dropped almost everywhere after the war, but it was widely resurrected just a few decades later during World War II.

After that war ended, the U.S. abandoned DST yet again—sort of. Without any official legislation, the country devolved into a jumble of conflicting practices. According to History.com, Iowa had 23 different pairs of start and end dates for DST in 1965, while other areas of the country didn’t observe DST at all.

In 1966, Congress put an end to the chaos by passing the Uniform Time Act, which specified that DST would begin at 2:00 a.m. on the last Sunday in April, and end at the same time on the last Sunday in October. (The Energy Policy Act of 2005 extended DST by shifting these dates to the second Sunday in March and the first Sunday in November.) It didn’t require that all states and territories actually observe DST, and some of them didn’t—Arizona and Hawaii still don’t.

Throughout its long, lurching history, the supposed merits of Daylight Saving Time have always been about cutting down on electricity usage and conserving energy in general. But, as Live Science reports, experts disagree on whether this actually works. Some studies suggest that while the extra daylight hour might decrease lighting-related electricity use, it also means people could be keeping their air conditioners running for long enough that it increases the overall usage of electricity.

If your extended night’s sleep seems to have left you with a little extra time on your hands, see how DST affects your part of the country here.

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