Tuesday, 27 January 2015

BBC or Daily Mash?

"Elevators travelling distances of more than 500m [1,640 ft] were not feasible as the weight of the [steel] ropes themselves become so large that more ropes were needed to carry the ropes themselves."

Answer here.

10 comments:

Lola said...

Sorry, smart arse me knew it was 'true'.
It was the invention of the elevator that made skyscrapers possible. Up until then the practical limit for buildings was about 5 floors (from memory).

Rich Tee said...

I knew the answer too.

It is elevator shafts that limit the height of buildings. The taller a building, the more lifts are required so the shafts take up ever more space and eventually it becomes uneconomic to build.

Mark Wadsworth said...

L, RT, yes, we knew that, what I meant was the bit about needing ropes to lift the heavy ropes. Which had me in fits of giggles.

Jim said...

like the rocket problem, you add more weight to the rocket, so you need more fuel to lift the weight, but now you added more fuel weight, so you need more fuel to lift the fuel that lifts the weight, but now you added more fuel, so you need more fuel that lifts the fuel that lifts the fuel that lifts the weight, but now you added more fuel...............................................

Mark Wadsworth said...

J, exactly, although the rocket problem is a straight circular calculation and thus probably solvable.

Jim said...

Its solvable in that you end up with a max payload, it gets to the point where its far cheaper to launch 2 rockets rather than a massive huge one.

Mark Wadsworth said...

J, aha yes, I was thinking about that today and guessed that there is an upper optimum limit.

Hence and why they built the ISS in sections.

Jim said...

"Bingo" - which brings us back to why the "space elevator" is such a promising idea, but then the weight of the cable - damn.

Mark Wadsworth said...

J, why bother? J Kittinger and F Baumgartner got there and back with nothing but a helium balloon and a parachute.

And a space suit, obviously.

Bayard said...

This isn't as stupid as it sounds. If you have two ropes hanging next to each other, both of the maximum length that the the strength of the rope can support its weight at the top and you take the bottom half off one and join it to the other one, half way down, the combined ropes can then support the weight of the missing half rope at any point along their length.

Jim, the cable for a space elevator would be made from monofilament or some other strong substance, not steel rope.