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Silk Town-Thesmar Canal

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Re: Spoiler element included at the end Re: Silk Town-Thesma
Post by Keith_w   » Tue Aug 25, 2015 9:40 pm

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SWM wrote:
lyonheart wrote:Hi Gamarus,

Maybe not.

The Cascade Locks and Canal which I just clicked on were 90 feet high to deal with a 55 foot [17m] variation on the Columbia River, while the wiki Lock article reports that Portuguese locks on the Douro River have rises of 108 [33m] and 115 feet [35m], while the Irish have a couple of 100 feet [30.5m] locks on the Shannon.

Given another 300 years of improving technology in the Terran Federation, I suspect much higher rises are quite possible.

L

The problem is not in the construction--the problem is filling and emptying the locks. Large rises require modern pumping. Safehold-tech locks can't be that high.


Why would you need pumps? You need valves and pipes to allow water to flow from the upper level to the lower level in a controlled manner.
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Re: Spoiler element included at the end Re: Silk Town-Thesma
Post by n7axw   » Wed Aug 26, 2015 1:53 am

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Keith_w wrote:
Why would you need pumps? You need valves and pipes to allow water to flow from the upper level to the lower level in a controlled manner.


I think you are right. You would allow water from the upper plateau to flow into the lock until levels are equal. Then to lower the level in the lock, you would simply allow it to drain to the lower side. That presumes a steady supply of waterto the upper side, which provision might have to be made for with a canal. But with that qualification, it should work.

Don
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Re: Spoiler element included at the end Re: Silk Town-Thesma
Post by isaac_newton   » Wed Aug 26, 2015 2:49 am

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n7axw wrote:
Keith_w wrote:
Why would you need pumps? You need valves and pipes to allow water to flow from the upper level to the lower level in a controlled manner.


I think you are right. You would allow water from the upper plateau to flow into the lock until levels are equal. Then to lower the level in the lock, you would simply allow it to drain to the lower side. That presumes a steady supply of waterto the upper side, which provision might have to be made for with a canal. But with that qualification, it should work.

Don


And yet on the Great Canal Raid, they specifically mention blowing up the pumps, so they seem to be an integral part of at least some of the locks.
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Re: Spoiler element included at the end Re: Silk Town-Thesma
Post by Keith_w   » Wed Aug 26, 2015 6:54 am

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isaac_newton wrote:
Keith_w wrote:
Why would you need pumps? You need valves and pipes to allow water to flow from the upper level to the lower level in a controlled manner.



And yet on the Great Canal Raid, they specifically mention blowing up the pumps, so they seem to be an integral part of at least some of the locks.


They certainly did. I recall reading that some of the canals have external water supplied from a river to maintain the level in the canal. Perhaps that was what the pumps were for. But for raising and lowering vessels through the locks within a canal, you don't need pumps.
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Re: Spoiler element included at the end Re: Silk Town-Thesma
Post by PalmerSperry   » Wed Aug 26, 2015 7:39 am

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Keith_w wrote:Why would you need pumps? You need valves and pipes to allow water to flow from the upper level to the lower level in a controlled manner.


That works fine provided you have large enough water supply for the desired traffic rate, otherwise you'll need pumps to reclaim the water that would otherwise be lost. Said pumps don't necessarily have to be used to empty/fill the locks (given Safehold tech levels that would likely be too slow) but could be used to reclaim water from the lowers level of any run of locks and feed it into storage ponds higher up.

On canals built by the archangels I could imagine there being more "imaginative" water provision that likely couldn't be matched by the natives later on. e.g. Dam this river here, and divert the flow through this tunnel cut through the mountain and now we've got more than enough water!

As an aside, the impression I'm getting from the books is that generally the locks are just singletons, i.e. lower-level + lock chamber + higher-level, without there being any flights of locks or lock staircases? There's certainly references to parallel lock chambers for higher throughput, but I haven't seen anything suggesting sequential locks?
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Re: Spoiler element included at the end Re: Silk Town-Thesma
Post by Easternmystic   » Wed Aug 26, 2015 11:42 am

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Keith_w wrote:
Why would you need pumps? You need valves and pipes to allow water to flow from the upper level to the lower level in a controlled manner.


Pumps are often used to fill and empty tanks that act as counterweights to open and close lock gates.
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Re: Spoiler element included at the end Re: Silk Town-Thesma
Post by Keith_w   » Wed Aug 26, 2015 7:51 pm

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PalmerSperry wrote:
Keith_w wrote:Why would you need pumps? You need valves and pipes to allow water to flow from the upper level to the lower level in a controlled manner.


That works fine provided you have large enough water supply for the desired traffic rate, otherwise you'll need pumps to reclaim the water that would otherwise be lost. Said pumps don't necessarily have to be used to empty/fill the locks (given Safehold tech levels that would likely be too slow) but could be used to reclaim water from the lowers level of any run of locks and feed it into storage ponds higher up.

On canals built by the archangels I could imagine there being more "imaginative" water provision that likely couldn't be matched by the natives later on. e.g. Dam this river here, and divert the flow through this tunnel cut through the mountain and now we've got more than enough water!

As an aside, the impression I'm getting from the books is that generally the locks are just singletons, i.e. lower-level + lock chamber + higher-level, without there being any flights of locks or lock staircases? There's certainly references to parallel lock chambers for higher throughput, but I haven't seen anything suggesting sequential locks?


Why would you want to reclaim water from the lower level? If there isn't enough water at the top or bottom, the barges aren't going to float along the canal to or from the lock, and since the water is flowing down canal, it needs to be replenished with water from the up-canal side anyway.
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Re: Spoiler element included at the end Re: Silk Town-Thesma
Post by Keith_w   » Wed Aug 26, 2015 8:08 pm

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Easternmystic wrote:
Keith_w wrote:
Why would you need pumps? You need valves and pipes to allow water to flow from the upper level to the lower level in a controlled manner.


Pumps are often used to fill and empty tanks that act as counterweights to open and close lock gates.

At first that struck me as a good idea until I thought about why would you want to empty a counterweight except perhaps for winter so that the water doesn't freeze, but in that case wouldn't it make more sense to simply make your counterweight out of something that doesn't freeze? In any case, I can't see them using counterweight to balance the weight of the gates. I can see them using a long arm as a lever to open and close the gates. By the time you open the gate, the water levels should be equal so there will be no rush of water to fight against so you only have to move the weight of the gate and a long arm sideways from the gate should be sufficient. The long arm is called a balance beam. There is a really interesting article on Wikipedia about how locks work. https://en.wikipedia.org/wiki/Lock_(water_transport)#Gates
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Re: Spoiler element included at the end Re: Silk Town-Thesma
Post by isaac_newton   » Thu Aug 27, 2015 3:22 am

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Keith_w wrote:Why would you need pumps? You need valves and pipes to allow water to flow from the upper level to the lower level in a controlled manner

SNIP
The long arm is called a balance beam. There is a really interesting article on Wikipedia about how locks work. https://en.wikipedia.org/wiki/Lock_(water_transport)#Gates


Yup - that is interesting. Here is the relevant bit about water usage/pumping

The main problem caused by locks is that, each time a lock goes through one fill-empty cycle, a lockful of water (tens of thousands up to millions of litres) is released to the lower pound. In more simplistic terms, on a canal where only one boat will fit into a lock, a boat travelling from the summit pound to the lowest pound is accompanied on its journey by one 'personal' lockful of water. A boat going the other way also transfers a lockful of water from the summit pound to the lowest pound. To prevent the canal from running dry, some method must be used to ensure that the water supply at the canal summit is constantly replenished at the rate that the water is being drained downwards. This is, of course much more of a problem on an artificial canal crossing a watershed than on a river navigation.
...
Pumping
Where it is clear that natural supply will not be sufficient to replenish the summit level at the rate that water will be used (or to allow for unexpected periods of drought) the designer may plan for water to be back-pumped back up to the summit from lower down. Such remedies may of course be installed later, when poor planning becomes apparent, or when there is an unforeseeable increase in traffic or dearth of rain. On a smaller scale, some local pumping may be required at particular points (water is continually recycled through some locks on the Kennet and Avon canal).
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Re: Spoiler element included at the end Re: Silk Town-Thesma
Post by Easternmystic   » Thu Aug 27, 2015 6:12 am

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I'm sure that canal operators and builders everwhere are astounded that they have been doing it wrong for centuries!

The tank or tanks are normally empty and the lock gate is in the closed position. When the gate needs to be opened, water is allowed to flow into the tank which changes the weight as well as the weight distribution of the gate mechanism. the combination of the two forces the gate open. To close the gate, The water is pumped out of the tank.

Finally, canal gates are only opened when the water level on each side of a gate has been equalized. Equalizing the water levels, requires the use of valves and plumbing to raise or lower the water level in the lock before opening one of the gates. Trying to open a lock gate when the water levels sre unequal usually results in damage to the lock, tha lock gates and the vessel in the lock at the time. It's generally considered to be a bad thing to do.
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