Tag Archives: invention

Gravel, tar and steamrollers!

I tried, but couldn’t draw a tarmacadam picture half as wild as this one from an old French postcard of road-builders on le Champs-Élysées.

In Scotland, John Loudon McAdam designed roads made of layers of crushed stone, which are then steamrolled. Edgar Hooley improved McAdam’s process by covering the gravel with hot tar. The tar kept the gravel from forming wheel-ruts, and protected rubber tires from the sharp-edged stones. This whole shebang is called the tarmacadam (tarmac) process. Streets in Paris, France were the first to get paved this way. By the late 1800s the United States began paving tarmacadam roads. Driving a Model T would be less bumpy—and safer.



What’s the Difference Between Tarmac and Asphalt?



Here’s what a steam roller looked like—

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More cars, please

The Tin Lizzie

Henry Ford figured out how to produce gas-powered cars quickly and inexpensively.

First, he used standardized, interchangeable parts. The passenger door for one Model T automobile will fit on any other Model T. Same with the axles, wheel rims, door handles, pistons, cylinders, cup-holders, nuts, bolts—nothing on the car needed to be specially-made.

Second, Ford introduced a moving assembly line. Instead of his builders moving from car to car, cars moved from crew to crew, pulled by a chain down the line. Each crew had a specific task, like putting the doors on, attaching the wheels, installing the engine, or painting the body. That might get repetitive but—they could build a whole car in an hour and a half.

Can you imagine that? Cars were shooting out of that factory so quickly that Ford could charge a low price for them and still make a profit. The steam cars were expensive because they were more or less custom-made. So people bought gas-powered Model T Fords.



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Swimming upstream

By now I’m sure you’ve spotted the pattern: there’s a situation where people struggle to get from Point A to Point B, and some tinkerer comes along and says, “I bet I could make those people’s lives easier.” We saw how Watt’s steam engine turned a wheel to pump water out of a mine. Trevithick developed that idea into a steam locomotive to haul carts of coal. Stephenson improved the locomotive to move cars full of people along rails made of Bessemer steel.

In Great Britain and the United States, inventors worked on the problem of moving a vessel in water. Just like a locomotive, a steam engine would pump a piston to turn a wheel. This time the wheel had paddles and was mounted on either the stern or the sides of a boat.

John Fitch proposed a design with banks of oars, like an Indian war canoe.

John Fitch and James Rumsey designed steam-powered boats that operated on the Delaware River between Philadelphia and New Jersey. In Scotland, William Symington designed a boat for towing on the Forth and Clyde Canal. In 1801 his steamboat the Charlotte Dundas ran successfully upstream on the Carron River. The Mississippi is a big river with a powerful current. It would take a powerful engine to move a boat against it.


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Hot and steamy!

George Stephenson is another one of those tinkerers whose genius is improving an existing invention. Like Trevithick, he worked in a coal mine. Stephenson took the steam locomotive to its next level, making it more powerful.

The basic principle of a steam engine is: fire heats water in a boiler; the water turns to steam; the steam expands and creates pressure; the steam escapes into a cylinder to push a piston. The cylinder has 2 openings to let in steam so that the piston is pushed back and forth as steam fills one side and then the other. The piston is attached to a wheel, so the piston’s back-and-forth motion is changed into circular motion.

How to improve that? One way was to run copper pipes from the fire through the boiler so water gets hotter. Then you could mix the smoke from those pipes with the steam exhaust (from the cylinder) in a smoke box. The super-hot smoke and steam want to quickly escape up through a blast pipe (chimney). That in turn pulls more air into the firebox and makes the fire burn hotter. That means more steam, more pressure—so the piston moves faster with more power.

Stephenson designed the cylinders/pistons closer to horizontal, so they lost less energy. He also attached them directly to the driving wheels. Trevithick’s design had pistons that turned great gears that turned the driving wheels. It transferred energy from a piston to a gear to another gear, losing a little energy with each step. Remember how concerned Harrison was with friction between moving parts of a clock?



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The Age of Steam

Over-simplified drawing of a steam engine. The fire heats the water; water turns into steam, steam expands and enters the chamber; steam forces the piston into the other chamber; piston pushes the beam; beam turns the wheel. The wheel pushes the switch that shuts off first chamber so steam enters the second chamber; piston moves down.

As sailing ships were being designed bigger, speedier and lovelier—two or three tinkerers were fooling around with a way to get water out of coal mines.

Mines are dug to extract valuable minerals. Sometimes the digging will open up a spring and water flows in, flooding the mine. Horses or men worked pumps to empty the mines, but animals and people tire out easily. In 1698 Thomas Savery invented a steam pump to get water out of mines. His invention had limitations (it didn’t work if the mine were too deep) and it had an unhappy tendency to explode.

In 1712, Thomas Newcomen invented a steam engine that moved a heavy beam which worked a pump. It had limitations as well—his engine needed constantly to be fussed with to keep it cool or hot, which made it inefficient. In other words, it needed lots of energy to make it put out energy.

In 1765, James Watt made some big design changes to Newcomen’s engine which made it efficient. It had a piston which could work a pump by turning a wheel.

https://www.livescience.com/44186-who-invented-the-steam-engine.html Elizabeth Palermo
https://www.livescience.com/2612-steam-engine-changed-world.html Heather Whipps