Tale of the Lift

In her book, Built, Roma Agarwal tells the story of the elevator (lift). The problem since the age of Rome when gladiators “rose from the pits of the Colosseum up into the fighting arena on a moving platform” was the lack of safety: if the rope snapped, the platform fell and injured or killed people. Elisha Otis (yes, the same Otis name you see on lifts) came up with this ingenious solution.

 

He decided to use the “wagon spring”. Like any spring, it “springs” back into shape once the force is removed. But a wagon spring had one additional characteristic:

“When it has a force on it, the wagon spring is flat, but when it’s released, it curves.”

It was this change in shape that was the basis of Otis’ idea.

 

First, he replaced the “smooth guide rails (which kept the platform in position)… with toothed or ratcheted rails”. Then he created a structure to hold the lift, but with “feet sticking out at the base”. The rope was attached to the wagon spring which in turn was attached to this structure.

When the rope was intact, the wagon spring was flat, and the entire combo moved nicely between the rails. But if the rope snapped, the wagon spring changed shape and curved. The change in shape of the spring in turn causes the structure to tilt. And when it tilted, those sticking out feet would get stuck in the toothed rails. And so the lift would come to a halt.

 

Otis still had to demo his idea, and looked for a big stage. He found the 1853 World Fair in New York. He built the entire setup, loaded it with goods, stepped in and had it lifted to the maximum height.

“He called for the hoisting rope to be cut, and his assistant swung the axe.”

The crowd gasped, the platform lurched downwards, and just suddenly, it stopped. It had only fallen a few inches. Otis shouted to the crowd:

“All safe, gentlemen. All safe.”

 

Ever since, his company and name are synonymous with lifts world-over:

“Until he developed the safety elevator, the height of a building was restricted by how many stairs people were prepared to climb. The elevator smashed that barrier.”

The age of the skyscraper had arrived. The new constraint?

“We can’t make elevators that travel much further than 500 m because the steel cables to hoist them up and down become too heavy for the machinery to work efficiently."