Increase efficiency in the cargo ship industry without a propellor

[256bits]

Unless the canal is actually a submerged concrete road, an underwater tractor will just trash everything, not only in the vicinity, but downstream for a long ways. Even if you're warped enough to think that's a decent tradeoff, it will also stop working after a couple trips, when the tractor starts bottoming out in the ruts.

What about a submerged rail ? Or, overhead, like a trolley bus.

Right. Churn up the river bottom.
There is the environmental damage to consider, so a dedicated path would be necessary to limit that only during construction of the path.
The infrastructure cost of the dedicated path for the tractor. Grand guess of more than $50 million per mile ( a approximate ( high value ) tramway cost per mile above ground ( don't really know if we can use that as a valid base , but 100 miles of river using that as a base for cost figuring would be a 5$billion dollar investment )

And the incentive for the users to actually move towards the thing while paying a fee.

I can see the Panama Canal having the incentive of saving transit times across the seas, and the St. Lawrence Seaway having the ability to move farther up the river, for cheaper transit.

What would be the incentive for anyone to use this system, besides government decree that all boats/barges must use the tow system, and equip their flotilla for said function.

 

[Vanadium 50]

Underwater rails would quickly sink in the silt and in my opinion are a nonstarter.

Yes, but if the conditions of a towpath are too rough, just think what it's like on the river bottom.

(For most rivers - the Los Angeles River is an exception, being rice and paved)

 

[Baluncore]

There are two ways to interpret the word tracked.
One is tracked like a bulldozer or a army tank.
The other is tracked like a railroad with underwater rails.

The bulldozer is called tracked because it is a "tracklayer" vehicle. It lays track ahead as it advances, continually picking up the track and passing it forwards, to lay it again ahead of the vehicle. A tracklayer advances along the tracks with roller-chain pinions locked to the track chain rollers.

The driven wheels of a railway engine rely on friction between the wheels and the permanent way. Permanent underwater rails, (lubricated with mud), would need to take the form of a gear rack so as to give positive engagement with a tractor drive pinion.

While pinion lubrication by mud would be an advantage, abrasion of the track and pinion by sand and silt would be a problem.

Corrosion of steel track in an oxidising environment would be rapid as the oxide would be removed by each passage of a drive pinion. Stainless steel would corrode rapidly in anaerobic mud. That is the material selection problem.

 

[synch]

A) downstream : go with the flow
B) upstream : use the propeller as a water-driven turbine to drive a winch, and drag the barge/ship against the flow. Maybe use a generator to drive an electric mule. It would be slow but still work.
No fuel cost !

 

[synch]

caveat : it would require a larger turbine than normal ship propellers I guess.

 

[sophiecentaur]

Grand guess of more than $50 million per mile

For a lightweight cable car system, the costs are around $20m per mile so your estimate is on a par but an overhead ship tow would be more chunky than a simple cable car.

Permanent underwater rails, (lubricated with mud),

And abraded by mud and grit. Plus the problem of build up of silt around rails. And there's erosion of the river bed around and under the track.

No fuel cost !

Who pays for the electricity?

 

[jbriggs444]

Who pays for the electricity?

What electricity? The thing is water-powered.

We are talking about something very similar to a tethered turbine that uses the generated power to reel in the tether. And yes, this would likely be even less economically feasible than burning fuel or paying for electricity.

 

[sophiecentaur]

Whoops! So it's a water equivalent off sailing against the wind. Wouldn't the craft also need a regular propellor (when it's traveling elsewhere)? I guess a design that worked both ways would not be too efficient. What sort of speeds could be achieved, I wonder? The capital cost would need to be justified against the existing engine and speed is relevant in transport systems. The Canals died out largely because the railways were quicker. Not relevant for coal transport but, for many items, you can't have idle money during slow journeys.
The economics are very complicated - as complicated as the interesting Engineering factors.

 

[jbriggs444]

Whoops! So it's a water equivalent off sailing against the wind.

Yes, indeed.

Wouldn't the craft also need a regular propellor (when it's traveling elsewhere)?

If the thing needs to nose into a protected and current-free anchorage to load or unload then yes, one would need propellers, maneuvering thrusters, tugboats or some such. A battery and reversible turbine strikes me as the most elegant approach. Make sure not to cut the tow line, Captain Queeg.

If one were to take the craft out on the open ocean, one would need to un-tether and, perhaps, reverse the turbine to act as a propeller. But then one would need sustained power...

For a Rube Goldberg vessel such as this, perhaps one would launch a kite carrying a turbine.