The Steamboating Forum

Fred, You're welcome on the drawing, I tried to handsketch it - they are much like my handwriting, only I can understand it

One thing I noticed and you probably have too about your arrangement, there will be considerable force on the linkage and spider hub as opposed to a design that just rotates the floats.

-Ron

The geometry is needed here to act sort of like a reduction, so the engine will turn faster and give more power. Yes the spider rods will have much more force than with conventional articulated wheels. Independent of that, when the floats are working in water the forces are low, around 15 pounds on each float, and the lever mechanism results in 3x to 4x that amount, maybe 50-60 pounds. The spider arms can take about 700 pounds force before shearing a nylon bolt. The event that really increases the forces is hitting a piece of wood in the river.

The fiberglass lunch trays on the non-articulated wheel never broke on water forces, but every outing I usually broke one or two on something floating in the river. I'll have to keep a close watch on the Delaware River, but on lake Noximixon there is usually nothing floating around. Being nearly balanced, conventional articulated wheel spiders had almost no force when just pushing water, but they indeed got big forces when hitting a nearly submerged branch or log.

Thanks for the info. I'v never found much information on paddle wheel performance.

These will be very interesting to watch in operation.

DCSmith, I have searched for years trying to find real technical data about articulated paddlewheels, plenty of drawings and explainations, but never the real engineering formulas. But recently I came across the real technical equations for them. I will send files or a link if you wish.

Working on the articulated wheels, have made 16 floats so far. Most of the work is putting together a jig to hold the parts together for welding. After the jig is made, the parts cut and formed, then welding one together takes only about 15-20 minutes. Still plenty of work, spent Friday Saturday and Sunday on the floats alone. Still have to make 18 spider links, plus the outer strake on the paddleboxes (probably 2 x 4 red oak), plus the spider bearings plus.... plus... Hope It is all together for the first steamboat meet in June.

Fred,

Will this panjandrum back up? Not that there is some reason for efficiency while backing but I assume you have looked into the linkage forces when in reverse.

Mike

I would be interested to know the % advantage of the curved blade face, over straight, and would the effect be different %wise if it was curved in the other plane. As Lopez Mike has intimated it must surely have an effect going astern.

Sorry, I just have that sort of brain.

The technical parameter here is called the "Coefficient of Drag", and various fluid mechanics handbooks list the coefficient for various shapes. For the articulated paddle floats the Cd = 2.0, for the paddles in reverse, about 0.8, so much worse propulsion efficiency going astern with the new articulated floats.

For comparison, the flat plate floats on the original non-articulated wheels had a Cd of about 1.2, aproximately.

Of course, if all you want is efficiency, you use a propeller. The H.M.S. Rattler tests of 168 years ago settled that. Paddle wheelers exist today because they work in shallow water and we like them.

I've speculated occasionally whether there might be some in between solution like the Pelton Wheel where, instead of dealing with stalled flow on the paddles as we do now, you could get some attached flow as with a propeller or a wing.

Wings have attached flow. When airplanes stall, we read about it in the news. A dramatic reduction in lift followed often by a good deal of fire!

Perhaps there would be a way to deflect the water out to the side by flowing across the blade. With wheels on each side of the boat the side forces should cancel.

Too much ice cream late at night.

Mike

fredrosse wrote:DCSmith, I have searched for years trying to find real technical data about articulated paddlewheels, plenty of drawings and explainations, but never the real engineering formulas. But recently I came across the real technical equations for them. I will send files or a link if you wish.

Fred. I would appreciate a copy of the technical equations. I see this question from time to time and would like to publish them in Steamboating Magazine. Credit would be given.

There is a whole section on paddle wheel design in Hydrodynamics in Ship Design, Vol 2 Chapter 71 by Saunders. This is technical stuff, but the only real analysis I have ever come across, it is a 1907 book, probably OK to re-publish without copyright issues.

http://openlibrary.org/books/OL6242487M ... hip_design.

There are several other marine engineering books from around that time also available on the internet, but generally their treatment of paddlewheels is more empirical than analytical.

Ron, no credit for me, I was not there in 1907