Talk:Caisson lock
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[edit] More detail please
What an amazing piece of engineering. One thing that is not clear from the article is how water is retained in the cistern. Clearly the caisson decends to the bottom of the cistern. I assume that there is a door at the bottom of cistern to match the door in the caisson. Is this true? How does the caisson seal against the cistern to prevent water escaping? 203.23.210.116 22:25, 10 October 2006 (UTC)
[edit] Diagram
Is the diagram right? AFAIK the caisson couldn't be lifted above the water level, because of the weight of the ballast. Instead, the chamber wall was built higher than the water level in the top pound, and filled right up. There was an opening, normally closed by a guillotine-style door to keep the water in, into the top pound. Only when the caisson was in place tightly against the frame of the outer door, and a little air pumped into the space between them to equalize the pressures, was the door wound up to admit the descending boat. The same thing happened at the bottom: the increased water pressure improved the seal between the caisson and the door frame but the doors were forced solidly closed until air was pumped between them (at a higher pressure, of course). The pump was in the caisson and operated by the boat crew. Does any of this make sense? I can't draw, otherwise I'd try to fix it ––Moonraker88
Well the one existing diagram is a little unclear but looking at it again It appears you are right. I'll fix the diagram.Geni 11:03, 13 October 2006 (UTC)
- Added the above information, but disregarding the stuff about air pressure: Equalisation was achieved just by opening and closing taps/faucets. ––Moonraker88 15:24, 13 October 2006 (UTC)
- I've managed a tweak on Geni's caisson lock diagram to show the full-height cistern, as suggested. I've also simplified the labelling. May I upload it and try it in the article (full attribution to the original source, licensing as before, of course)? If it doesn't work I'll take it out Moonraker88 11:22, 28 October 2006 (UTC)
[edit] Caisson/cistern
I had to check on this as I was confused as well (see edit history). Originally "caisson" meant a water-tight box and "cistern" was a underground water storage chamber (not in the loft, as now). To our minds today this seems strange, but only because of the modern engineering use of "caisson" to mean a vertical, water-tight tower used underwater for excavations, concrete-pouring etc. It's the vertical, water-tight tower bit which would cause anyone a bit of doubt! Moonraker88 19:11, 13 October 2006 (UTC)
- The names make more sense if you think of this as an underwater boat lift.Geni 01:27, 14 October 2006 (UTC)
