Friday, March 18, 2011

Cheap Transportion: Aerial Ropeways

From Low-tech magazine:

Aerial ropeways: automatic cargo transport for a bargain

Adam wybe 1 These days, we use them almost exclusively to transport skiers and snowboarders up snow slopes, but before the 1940s, aerial ropeways were a common means of cargo transport, not only in mountainous regions but also on flat terrain, with large-scale systems already built during the Middle Ages.

Cargo tramways can be fully or partly powered by gravity, and some deliver excess power that can be utilized to generate electricity or to drive cranes or machinery in nearby factories. Some innovative systems have been constructed in recent years.
Ropeway in Gdansk/Danzig, 1644
A cargo ropeway offers the possibility of powering a neighbouring factory - solely by gravity.
Source 5 crossing a riverBefore we start, it is important to note that aerial ropeways (also known as aerial tramways or cableways) can be divided in two groups: monocable and bicable mechanisms. In a monocable system, one endless rope serves to both support and move the carriers in transit. In a bicable (or tricable) system, separate ropes sustain these functions: one or two static support ropes, the "carrying ropes" or "track cables", and one or two light travelling "haul ropes".
Ancient and medieval ropeways were of both variety, while modern ropeways (from the 1850s onwards) were initially exclusively monocable systems. Later, bicable systems took over almost completely. At the end of the 19th century, both ropeway methods were also applied to canal transportation (see the article on trolley canal boats), with monocable systems used for cable trains.

Bicable mechanisms are much better suited if the track spans larger distances and/or has steeper grades. If only one endless rope would be used on a track which includes a long span or a steep grade, it would become necessary to make the entire double length of the moving rope strong enough for the special strain that appears on that spot. Increasing the size of the rope affects the dimensions of the supports, sheaves and other fixtures throughout the line, adding to the costs. In a bicable system, the stationary carrying cable can be locally graduated to the strains it has to bear.

Ropeways in ancient times
Source 5 source elevator world october 1967 Ropeways have been used for more than 2,000 years, transporting both passengers and goods. The first sign of their use comes from the rugged Asiatic countries of China, India and Japan, where it is speculated that they may have been in operation since 250 BC. Men used rope to cross ravines, rivers and river-gorges, initially transferring themselves, hand over hand, with the body suspended by a crude harness. The harness eased the load and allowed a rest as the loop was slid along the rope track.

Source 5 source elevator world october 1967 2 Source 5 another japanese woodcutThe next application was to pull oneself back and forth in a basket or cradle, usually with a few belongings in tow. This was made possible by means of thinner cords fixed to the front and the back of the basket, or by gravity in case the arrival point was at a lower height than the starting point. The empty sling or basket was then drawn back to its original position by a smaller cord attached to the back as before.
Animal powered ropewaysSometimes, the rope was threaded through a hollow piece of bamboo before being attached, so that the person could slide down the rope without burning their hands.

All that was needed to build a ropeway was a rope, knots to tie the rope to a rock or tree or anchor on both sides, and a bow and arrow to shoot the rope across. After the invention of the crossbow by the Chinese, heavier cables could be shot over longer distances. Sometimes the rope was supported on simple wooden trestles....MUCH, MUCH MORE