5 ms·

That kind of cranes is very reliable, but in the real world they are used maybe 10% of their capacity [1]. In a normal building site they either do very few cy

by jaclaz 8y ago

That kind of cranes is very reliable, but in the real world they are used maybe 10% of their capacity [1]. In a normal building site they either do very few cycles per hour (at heavy loads) or a decent number of cycles per hour at a tiny fraction of their load capacity. Even when you use them intensively (with concrete buckets) to lift/pour concrete, that happens for a relatively short time (a few hours) each day. A typical cycle is 5-10 minutes and you don't actually have 12 or 6 of them per hour, each hour in a normal 8 hour shift and - with some exceptions you normally have 1 shift per day, 5/7 (it is rare that a site working with cranes operates 24/7). Besides, in a building site you don't work when it rains, and you cannot work with cranes if there is a not-so-strong wind blowing (for safety reasons). [1] no reference, you will need to trust my word for it, coming from some 30+ years experience in building sites

saulrh 8y ago
No need for a reference; now that you mention it it's obvious that the duty cycle will be totally different. In fact, I'd bet that cycle time is the limiting factor - the graphic [1] shows about 100 cylindrers per layer, 18 layers already stacked, and the system looks to be around 60% loaded, so total count could be around 3k cylinders to move for a full load. Six arms, then each is doing 1000 cycles a day. Assume 4 hours down a day, 20 hours up, 50 cycles an hour, a bit less than a cycle a minute. Yikes. I did notice that the cylinders were around twice the quoted capacities for tower cranes I was finding. It also sounds like they're building a much more expensive crane; that many cylinders, at 35 metric tons per and $90 for a yard of concrete, is upwards of $5m, and the article says that the concrete "could" be the most expensive part. Aaaaand random googling is giving me price tags for tower cranes that can't possibly be right - <$300k?! So the quoted system might be using a crane that's ten times the cost of a "normal" tower crane? I can... sort of seeing that buy a six-armed crane with twice the lift capacity but permanent construction, no need for a counterweight assembly, and better continuous performance. But now I feel like these numbers are lining up too well and I have to have done something wrong. 1. https://cms.qz.com/wp-content/uploads/2018/08/energy-vault-landscape_colorcorrected.jpeg https://cms.qz.com/wp-content/uploads/2018/08/energy-vault-l... 2. http://www.wolframalpha.com/input/?i=3000+*+($90+%2F+cubic+yard)+*+(35+metric+tons+%2F+(2400+kg+per+cubic+meter) http://www.wolframalpha.com/input/?i=3000+*+($90+%2F+cubic+y...)
- jaclaz 8y ago
  >I did notice that the cylinders were around twice the quoted capacities for tower cranes I was finding. A "normal" (very large) tower crane rarely exceeds 12 tons, BUT, more than that, usually these use not "single" cable, i.e. a largish crane is usually 6 tons max, but can lift up to 12 tons doubling the cable/rope (which implies halving the lifting speed). Moreover, cranes are rated/designed (loosely) on their reach, they are intended - within limits - to cover a whole building site, so arms of 20-30-40-50-60 meters. An electric tower crane (a "normal" one) is well below US$ 300 K, I seem to remember we paid for a very large one, 80/100 meters tall, 50/60 meters arm, 6/12 tons at arm point around 250,000 Euro a few years ago (but costs have not increased much as it is a stale market AFAIK). The "key factor" is the "overturning" moment at the base (that implies a much sturdier tower and heavier coounterweights), and the single tower design is aimed to have a "light", "transportable" and "easily assemblable/disassemblable unit" the actual lattice is subject to very heavy tensile cycles as it is extremely flexible. It would make much more sense (to me at least) to have a specially designed crane with an as short as possible arm, traveling on a track (which is also a setup commonly used in building sites) or a portal crane, like the ones used in quarries or pre-fabrication sites 35 tons are a lot of weight. Besides (reinforced) concrete is at the most 2.3 tons per cubic meter, so it is not very efficient as a weight/counterweight, though possibly it is among the lower cost per kg material. On the other hand rebar concrete is an excellent material for the actual tower, so in a fixed place it makes much more sense to build a (say) 100 m tall pier/pylon than using a "light" lattice /truss structure for the tower.
  - extralego 8y ago
    Thanks for sharing. This is helpful info. If a tower crane did not need to be transported, how much would the design change? I’m guessing not much, but curious. I was imagining there would be no counterweight but just opposing loads, then I realized that might be a safety hazard. But, I really don’t know about these things. I just love the elegance of this solution and immediately obsessed. I think it just ruined my productivity for the day.
    - blattimwind 8y ago

by jaclaz 8y ago

saulrh 8y ago

No need for a reference; now that you mention it it's obvious that the duty cycle will be totally different. In fact, I'd bet that cycle time is the limiting factor - the graphic [1] shows about 100 cylindrers per layer, 18 layers already stacked, and the system looks to be around 60% loaded, so total count could be around 3k cylinders to move for a full load. Six arms, then each is doing 1000 cycles a day. Assume 4 hours down a day, 20 hours up, 50 cycles an hour, a bit less than a cycle a minute. Yikes. I did notice that the cylinders were around twice the quoted capacities for tower cranes I was finding. It also sounds like they're building a much more expensive crane; that many cylinders, at 35 metric tons per and $90 for a yard of concrete, is upwards of $5m, and the article says that the concrete "could" be the most expensive part. Aaaaand random googling is giving me price tags for tower cranes that can't possibly be right - <$300k?! So the quoted system might be using a crane that's ten times the cost of a "normal" tower crane? I can... sort of seeing that buy a six-armed crane with twice the lift capacity but permanent construction, no need for a counterweight assembly, and better continuous performance. But now I feel like these numbers are lining up too well and I have to have done something wrong. 1. https://cms.qz.com/wp-content/uploads/2018/08/energy-vault-landscape_colorcorrected.jpeg https://cms.qz.com/wp-content/uploads/2018/08/energy-vault-l... 2. http://www.wolframalpha.com/input/?i=3000+*+($90+%2F+cubic+yard)+*+(35+metric+tons+%2F+(2400+kg+per+cubic+meter) http://www.wolframalpha.com/input/?i=3000+*+($90+%2F+cubic+y...)

jaclaz 8y ago
>I did notice that the cylinders were around twice the quoted capacities for tower cranes I was finding. A "normal" (very large) tower crane rarely exceeds 12 tons, BUT, more than that, usually these use not "single" cable, i.e. a largish crane is usually 6 tons max, but can lift up to 12 tons doubling the cable/rope (which implies halving the lifting speed). Moreover, cranes are rated/designed (loosely) on their reach, they are intended - within limits - to cover a whole building site, so arms of 20-30-40-50-60 meters. An electric tower crane (a "normal" one) is well below US$ 300 K, I seem to remember we paid for a very large one, 80/100 meters tall, 50/60 meters arm, 6/12 tons at arm point around 250,000 Euro a few years ago (but costs have not increased much as it is a stale market AFAIK). The "key factor" is the "overturning" moment at the base (that implies a much sturdier tower and heavier coounterweights), and the single tower design is aimed to have a "light", "transportable" and "easily assemblable/disassemblable unit" the actual lattice is subject to very heavy tensile cycles as it is extremely flexible. It would make much more sense (to me at least) to have a specially designed crane with an as short as possible arm, traveling on a track (which is also a setup commonly used in building sites) or a portal crane, like the ones used in quarries or pre-fabrication sites 35 tons are a lot of weight. Besides (reinforced) concrete is at the most 2.3 tons per cubic meter, so it is not very efficient as a weight/counterweight, though possibly it is among the lower cost per kg material. On the other hand rebar concrete is an excellent material for the actual tower, so in a fixed place it makes much more sense to build a (say) 100 m tall pier/pylon than using a "light" lattice /truss structure for the tower.
- extralego 8y ago
  Thanks for sharing. This is helpful info. If a tower crane did not need to be transported, how much would the design change? I’m guessing not much, but curious. I was imagining there would be no counterweight but just opposing loads, then I realized that might be a safety hazard. But, I really don’t know about these things. I just love the elegance of this solution and immediately obsessed. I think it just ruined my productivity for the day.
  - blattimwind 8y ago