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# Dynamic Counterweights for Elevators

Counterweights are selected based on the cargo weight.
 (+7) [vote for, against]

This may be baked... But I haven't found it yet.

An elevator uses a counterweight to move passengers up and down. This weight is usually 40% of the max load. When an elevator is 40% full, then the motor only has to overcome frictional forces. Any other occasion is a chance for optimization, though.

My proposal is for a dynamic counterweight system where the elevator registers the load and selects its counterweights accordingly. This would make the motor more efficient. Counterweights would be interspersed throught the shaft, with a mechanism for attaching to the chain based on input from the elevators ouput data. Hopefully, random processes would keep each interval of the shaft equipped with a sufficient number of counterweights.

 — daseva, May 16 2005

Patent WO2004039716 http://v3.espacenet...DX=WO2004039716&F=0
An autobalancing roping and drive arrangement for elevators which continuously balances the weight of an elevator cab and the weight of a counterweight [xaviergisz, May 17 2005]

I think this needs some maths and/or modelling.At the moment, I'm sitting on the fence:

Downside argument: my gut feeling is that you're going to wind up having to restore the counterweights to their original positions at some point, and the energy you save on the one hand, you will waste by having to re-juggle your counterweights. Unless you have hundreds of weights to ride the averages over the day.

Upside argument: what this is leading to, fundamentally, is a system for averaging the load over several journeys. Since everyone who goes up must eventually come down, any such time-averaging should help (net passenger load lifted over 24hrs=zero). So, this could lead somewhere.

Extrapolation from the above: maybe it makes more sense to use water as the variable counterweight. It's easier to add and remove, and a large water-tank in the roof could act as a buffer.
 — Basepair, May 16 2005

 Water is a nice element to this idea. Its sooo.... continuous... Then again, the floors are discrete, the load is discrete... not that quantifiability has anything to do with the soundness of an idea.

 I believe my idea (especially with water) deviates from the patent sufficiently.

 [BasePair], I'd be a fool not to hang around the fence, especially on my own ideas. But, you're reading my mind, and that scares me.

[Pa've], I think the 40% number should be a clue that gains can be achieved. Its shows compromise in design, and compromise is always cutting yourself short.
 — daseva, May 17 2005

rather than the additional counterweights being added from the elevator shaft, could you instead slide weights across from the elevator onto the counterweight cable (and then back again when needed)? The counterweight cable would have hooks at regular spacing to hold the counterweights...
 — xaviergisz, May 17 2005

 Unless all the occupants are jumping out of windows, they must be returning to the ground floor.

 Use regenerative braking to recover the excess power used to lift them in the first place.

Using variable counterweights is too halfbaked...
 — Ling, May 17 2005

 The trouble with using counterweights that you pick up and drop is that lift use in office blocks is quite 'tidal': lots of people going up in the morning, lots of people coming down in the evening.

 In a 10-storey building with a limit of 100 people per floor you'd need at least 65 tonnes of counterweight to fill the building with people. That's about 8 cubic metres of metal.

If you're willing to live with that weight spread about the building and a limit to how many people you can bring into the building then I think you've got a goer.
 — st3f, May 17 2005

 //too halfbaked.//

 [Ling], I'll take it as a compliment!

[st3f], That is mostly true. At some point in the day, you will have a maximum amount of PE in the people, and it will have to have come from the counterweights. Considering the "tidal" aspects of the office, this weight will be large, but are you sure that number is too large?
 — daseva, May 17 2005

Are the counterweights distributed amongst the floors? In other words, does each shaft have a cache of counterweights on each floor?
 — justaguy, May 17 2005

 Because the total delta P.E. over the course of a day is zero, this cache issue should not be a problem. But, I do see how all the weights collect somewhere and can't be used for the desired lift.

The water idea would require two buckets, one of them counterweighting the load. The other one will be the buffer. the buffer dumps into the counter until it matches the load. When the load is coming back down, the counter pours the water back into the buffer thereby retrieving the P.E. of the raised load.
 — daseva, May 17 2005

//But, you're reading my mind, and that scares me.// I knew you'd say that.
 — Basepair, May 17 2005

If water is to be used, rainwater could be collected at the roof for this purpose.
 — JakePatterson, Aug 07 2008

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