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Just scraping a living

PMV

The Frenso scraper showed that sometimes it only takes a simple solution to change the earth. PMV goes backtracking to know more about how it all started in 1883

Not to be confused with motor-graders, scrapers are the vast earthmoving machines that appear on the regions highway projects. These big machines appear broken backed as the giant tractor units tow the scraper blade and bowl along behind, moving thousands of tonnes of sand before the fine grading can begin.

Today, the road and rail projects require a high level of automation, with some machines boasting tractor units at both ends. As we all know there are several types of scrapers, some having elevating lifts to move the dirt, while others use auger screws or aprons and bowls.

Back in years past, scrapers were not so advanced. Mostly, they were just a variant on the original ‘bull dozer’, being a blade pulled instead of pushed, by animals.

These early blades, hammered into being by local blacksmiths, had a crucial shortcoming in that there was nowhere for the waste to go once it had been scraped, meaning teams of men with shovels and carts had to work alongside the scraper. This clearly wasn’t very efficient, and so it came down to a chap with an idea.

In 1883 James Porteous was a Scottish immigrant smithy living in Fresno, California. When he noticed how much double handling of material was involved during the construction of the canals and roads he thought of a better way of doing it. Instead of manually handling the dirt,, he wanted a machine that could not only scrape the soil, but discharge it at a certain depth. While experimenting with designs, he bought several patents from three other inventors living in the same part of California, being William Deidrick, Frank Dusy, and Abijah McCall.

Before long he had honed his invention, which he simply named the Fresno Scraper.

 It really wasn’t anything very complex as it was just blade to slice the top of the soil, along with a bowl, apron and ejector. In fact it sort of resembles an old-style push lawnmower, minus the rotary blade, but like the best simple breakthroughs, it more than quadrupled productivity.

Early machines slid over the ground and were predominantly pulled by beasts, later conveyances were larger, had wheels and were pulled by steam power.

Thousands were sold, and the device was instrumental in shaping the Panama Canal twenty years later. By the 1920s, when the Fresno was outmoded by newer designs from the likes of LeTorneau the majority of scrapers were pulled by tractors.

In 1991 the Fresno Scraper was designated as an International Historic Engineering Landmark by the American Society of Mechanical Engineers.

For his part Porteous could comfortably live off the income, with money spare to plough into other pet projects and inventions (in later years he was fond of telling his grandchildren how it was in fact he who invented the aeroplane, but of course, there is no evidence to believe it.) Today, the bent bit of metal from an ex-pat blacksmith is recognised as one of the most important civil engineering machines ever made. 

 

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