Concerning feathered paddlewheels...

Articulated Paddlewheels

Built the wheels, with a design somewhat modified from those presented earlier. The paddle floats are rolled steel plate, and performance got me about half way to the performance goal I had calculated: (Simple wheels, 52 RPM, Articulated Wheels, 64 RPM, Design Goal, 75 RPM). This is a good increase in performance, but some further adjustment is in order. This winter I will change the spider links to a little longer length, which is an adjustment that will make the paddles exit the water more vertically, and that should improve the performance.

Building the wheels took more labor (and $$) than I expected, and now I have 72 joints in the water, possibly a maintenance headache, although all has worked well so far. The articulating joints are all 5/8 inch Nylon bolts turning in steel heavy nuts, and lubricated with a special food grade grease that doesn't wash off.

If you are interested, the building of the articulated wheels is documented at Thesteamboatingforum.net, under the section "Technical - Non Engines and Boilers", with the subject heading "Articulated Paddlewheels".

 

" an adjustment that will make the paddles exit the water more vertically,"

Based on that closeup photo, I would suggest that the paddles dont get straight enough, soon enough.

The bottom paddle actually in the water is at an angle, while the one about to enter the water should be almost straight at that stage.

The problem isnt having vertical paddles on exit, as the one just leaving the water is already straight up and down.

You need to have the paddle just entering at the angle of the one just exiting IMHO

 

http://amhistory.si.edu/onthemove/collection/object_1379.html

 

You may have too many floats or they are not large enough. There is a optimum distance between floats based on size to thrust ratios and rules based on angles may be linked to wheel diameter and float size. Realistically, the next float should be entering water that is not moving relative to the global system. If the floats are too close then the water is already moving aft, so thrust is less.

 

I saw a working model of a gearless paddle wheel, with weighted bottoms of the blades, very similar to the patent SamSam posted. At speed the centrifugal force caused the blades to flare out. They were feathered somewhat, but not even close to vertical.

 

"Realistically, the next float should be entering water that is not moving relative to the global system."
Actually, the floats should always be moving rearward when interacting relative to the water. Thrust is only developed when the floats are moving through the water, producing a drag force on the floats, this is entirely dependent on the relative velocities, or, in common propeller terms, "slip".

"If the floats are too close then the water is already moving aft, so thrust is less."
That is true for an individual float, but net thrust for the larger number of floats interacting with the water is a larger net thrust. Another way of saying this: with more floats in the water (closer spacing), the thrust force on each float is somewhat less, but the net total thrust force (sum of all float propulsive forces) is increased. For the same performance objective, more floats allows each float to have a smaller area, something of a tradeoff. As discussed previously on this thread, paddle floats can be too large or too small, always a compromise to arrive at the best performance. Many paddle boats have much closer relative spacing than is used on this sidewheeler, which uses 9 floats on each wheel.

The present configuration on the Margaret S. is with too much curvature where the floats exit the water, not at the entrance. This is verified by video examination, so the adjustment will be to lengthen the spider links somewhat.

 

The military tried this on amphibious vehicles.
Had the merit of simplicity of feathered paddles.

Forgive the very crude sketch.

 

Attached are a couple of very recent papers by researchers at the
Australian Maritime College (AMC) and Incat that might be of interest even
though are of a slightly different bent. At the least, the references
at the end of the papers are a valuable resource.
Good luck!

 

Thanks for the references. This subject, high speed paddle wheel propulsion, is really out of the realm for my steamer, but interesting none the less.

I understand that ordinary high performance snowmobiles can, in stock form, do better on the water than the equivalent high performance personal watercraft. The watercraft are of course water jet propelled, I guess for safety reasons they do not use propellers. The snowmobiles are essentially paddle boats, (similar to what Yobarnacle just posted here) and it is interesting that they perform so well on the water. But don't slow down, they sink like a rock if speed is not maintained.

 

Simple fix: PWC with snowmobile drivetrain. Don't know where the market for it is, though...

 

An important reason why PWCs use jet propulsion is the serious safety issue that comes with conventional open propellers. Any manufacturer that produced a PWC with conventional propeller drive would be out of business with lawsuits very fast. While putting snowmobile tracks on a PWC could improve performance, the same safety issue would certianly preclude any manufacture of this arrangement, and with good reason.

 

Anybody tried snowmobile track propulsion, inserted between catamaran hulls?
Might be a fast cat!

 

I happened upon a different way to feather paddle wheels so I'm posting it here for reference. It obviously would only work for a sidewheeler paddleboat.

Patent Model for a Feathering Paddle Wheel, 1877 http://americanhistory.si.edu/collections/search/object/nmah_843821





Description
This patent model accompanied Henry William’s patent application for “a new way to feather the floats of a paddle wheel” that received patent number 189164 on April 3, 1877. Each blade in Williams's design rides on the end of a shaft. T-levers at the ends of the shafts carry rollers set into grooves cut into a central, immobile cam. As the wheel rotates, the blades turn as the grooves direct, presenting knife edges to the water when entering and rising, but offering resistance to the water when in the optimal position to push the vessel forward.
While the last generation of ocean paddle-wheel steamships emerged from European and American shipyards in the 1860s, paddle wheels remained the favored means of propulsion for steamers on the shallower waters of rivers and bays until the mid-twentieth century. Consequently, inventors like Henry Williams continued to suggest improvements to paddle wheel efficiency. For most of each turn, a paddle wheel slices ineffectively through the air. Then, when it enters the waves, it wastes energy pressing down on the water. After a brief passage moving the vessel forward, the paddles waste more effort churning the surface as they rise into the air once more. Feathering paddle wheels reduce this waste and, at the same time, cut noise and vibration in the boat. Never universally adopted, feathering wheels with their many moving parts are prone to damage and expensive to maintain. Williams's design, although particularly elegant, is not had no commercial success.

patent number
189164

 

Have you ever come across volume 1? It is supposed to have more information in it (an understatement considering these are 1000 page PDFs!) on paddlewheels but I've only ever found volume 2.

Now, iirc, HathiTrust has vol.1 ... BUT you have to have access to one of their partners to download any PDF (they also have a more complete collection of The Rudder thanGoogle Books), something I don't have.

 

.
I found another interesting one. I think the central sprocket is stationary. This looks pretty simple with just a chain and sprockets, and that's usually what the final drive is, a chain and a sprocket, so it's apparently rugged enough. This doesn't have all those cams and levers in other designs, which schemes don't keep the paddles all that vertical anyways. These are perfectly vertical 100% of the time.

I don't know if any paddle feathering is actually needed though. I believe the normal paddle wheel is efficient enough without the added complexity, the problem with paddle wheels is the whole paddle wheel apparatus is just generally cumbersome and inconvenient compared to propellers. It just depends on if you want a paddle wheel or not.

Patente US1811031 - Water wheel http://www.google.st/patents/US1811031