Ever since Mr. Bronze Age had the inspired thought that led to the wheel humans have been trying to think of new ways to get from point A to point B. Several thousand years after Mr. Bronze Age's inspired invention, in the 1770s to be rather inexact, British inventor Richard Lovell Edgeworth, created the ancestor of what would eventually become the continuous track method of locomotion. Don't recognize the term? You'll certainly know it when you see it in operation on many tractors or, where it's head-smackingly obvious, on every tank that's been on every battlefield since the British first used it in World War One.
But in 1868 the American inventor Jacob Morath had a truly inspired idea: a screw-propelled vehicle. Don’t recognize that term either? That's not surprising because, even though many people today will celebrate its virtues, it's not exactly a common sight.
The basic idea of a screw-propelled vehicle is simple enough: instead of wheels or tracks, you build a vehicle with a pair of, as Wikipedia puts it "auger-like cylinders fitted with a helical flange." To make that a bit easier to understand, think of a machine that literally crawls along the ground on a pair of giant screws. To turn you use the same method a tank does: one screw either gets locked in place while the other one doesn't or, to make a 360 turn, turn one screw one way and the other ... well, the other way.
In 1907, James and Ira Peavey, were quite literally driven to create a practical screw-propelled machine to help their lumbering in Maine. The machine proved very useful since the screw-propulsion could move whatever you wanted moved through snow and mud and all kinds of nasty conditions. You also didn't need to worry about anything getting caught in the tracks, like with a caterpillar, and since they had much fewer moving parts they were easier to maintain.
Quite a few screw machines were built afterwards, though they remained less than popular. But when World War Two loomed, the idea of a screw-propelled war machine intrigued the eccentric genius Geoffrey Pyke -- who you no doubt remember as the inventor of the iceberg aircraft carrier. Alas, Pyke's concept of a very small, very fast, attack machine got (ahem) shot down and his idea was eventually whittled down to the very-rarely known Weasel. Unfortunately, the Weasel was whittled down even more and the screw propulsion was dropped in favor of standard caterpillar tracks.
Another benefit screws have over caterpillars is the possibility of being amphibious. There's no reason, for instance, that the screws couldn't be hollow and so could also act as floats. During the Vietnam war, for example, Chrysler experimented with a screw-propelled machine. Unfortunately, their take on the technology didn't exactly wow the US military and the project was dropped.
The Soviets, in the meantime, had a machine specifically designed to go where no man ever wanted to go -- in their case to retrieve cosmonauts from remote landing sites: the poetically named ZIL-2906.
One of the most amazing uses of screw propulsion has to be Joseph Jean de Bakker's. In the 1960s the Dutch inventor created the Amphirol, a machine designed to take anyone pretty much anywhere. What made Joseph Jean de Bakker machine better than other versions of screwing yourself across the landscape was its performance. Not only could his Amphirol go across marshes and over other sticky situations but it was also amphibious. That wasn't the end of its wow factor, though, because the Amphirol could do all that and also crawl sideways. Try doing that with four wheels or with caterpillar tracks.
While still rare, the idea of screw-propulsion is still out there: the concept appearing in all kinds of civilian and military proposals. While watching one in action, though, William Cowper's quote comes immediately to mind: it "moves in a mysterious way."
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