[glatt]

Originally Posted by dar512

Well, the locks are older. So you'd expect less advanced technology.

Agreed. Sometimes, less advanced technology is better because it is simpler and more reliable.

This new boat wheel is elegant looking and is fascinating. The rotation of it seemed simple enough with the two tubs acting as counterweights, but I couldn't imagine how the gates worked. Usually a lock has the gates open against the uphill side of the water so water pressure will hold them shut when they close. These gates have space constraints. There is basically zero clearance between each gate of the tub as they are closed against the mating gates of the canals. There is no place for them to open. The only solution I could imagine is that the gates somehow lie flat on the bottom of the tub, and then rotate up into position. Then I couldn't imagine how they could seal, since there would be little water pressure against them.

So I looked it up. Turns out I was right that the gates are very complicated.

The original source of many of these innovative ideas was in fact work already carried out an proven by Bennett Associates, in other fields. The lock gate seals, for example, used a proven solution from the design of air lock doors from the tunnelling industry. The seals at each end of the gondolas and on the canal gates of the aqueduct and the basin below it are totally watertight. With traditional lock gates some degree of leakage can be tolerated. The gates themselves form an extremely tight seal and are held shut by the pressure of the water that they are holding back and are pre-loaded by a pre-loading ram powered by an accumulator.

To release the seal and open the doors necessitates a powerful hydraulic ram. A situation complicated by the fact that the gondolas themselves carry no power pack with which to power such a ram. The solution to this particular conundrum was provided by Bennett Associates' experience in sub-sea pipeline systems. The seals are in fact released by a method known as 'hot stab', the necessary hydraulic pressure being provided from an external self-aligning hydraulic link that automatically connects each time a gondola docks with the aqueduct or canal basin.

That sounds pretty complicated to me. Far from elegant.

Another article I found says that the system is computer controlled and requires input from over 600 sensors to run properly. This is sounding less and less elegant all the time.

With the boats loaded and the gondola end gates closed, a computer-controlled water-pumping system equalizes the water levels in the two gondolas to establish near perfect weight balance before the Wheel turns. Fairfield Control Systems, Nottinghamshire, developed the software for the computer system that monitors and controls all Wheel functions. Using I/O from more than 600 points, the system meets all safety standards. For instance, it will not allow the Wheel to rotate until the safety locks on all the gates are confirmed operational.

That last sentence reminds me of Washington D.C.'s aging Metrorail system. The subway trains have sensors in the doors. When the doors are open (or the sensor says the doors are open) the train will not move. Problem is that as the sensors age, simply leaning against the doors can cause the sensor to read that the door is open, and the train stops. If all the doors are closed, but a faulty sensors thinks a door is open, they have to offload a train and take it out of service.

I predict that this boat lift will be extremely expensive to maintain, and that it will cease to operate within 20 years or become a huge money pit as engineers try to keep it working. However, it will probably still be measured as a success, because it's true purpose it to be a tourist attraction, and it succeeds at that. It's a unique engineering marvel.