Collapsible Flettner Rotor Project

Yob, I'm still thinking of ways to raise the rings up the center pole. What about compressed air in the center pipe or the top ring with appropriate nozzles???? Stan

 

We considered making the entire rotor inflatable, then tensioning it in suspension.
The space frame as the internal spar kinda deflated that idea.

 

Air tight roller bearings to attach to the center pipe supporting the rings should overcome that problem.

 

Those sealed bearings wouldn't work with this space frame truss. but thanks for the suggestions.

 

Inflating is just adding weight without stiffness, plus the problem of retaining an airtight solution.

Your first idea of circular cylinders that slide up over each other is going to be the best solution if you have to have 'on water' lowering power.

 

I think so too

 

With a five metre tower, you are probably only going to need say a 2,5 metre top tube that can slide down,

A bottom tower of 2,5 m can be 'permanent', as it will never be a problem in even huge winds,

 

back to hunting suitable sized prefab cylinders.

 

"If you obtain two alternators, you may use one as a generator and the other as a motor. The steps needed to prepare an alternator as a three-phase generator and as a three-phase motor are the same."

True, but in your case useless.
An average alternator delivers 60 amps @ 14 volts = 840 Watts (1.12 Hp) but it needs 8000 rpm to do that. As an electric motor it performs even better because there is no field current regulation: I estimate up to 2 Hp @ 12000 rpm.
However, you have no use for such speeds, you need approx. 2000 rpm and a 5:1 reduction to obtain 400 rpm cylinder rpm. The output in that case is only 0.4 Hp, not nearly enough to spin a laundry dryer.

 

Thanks for setting me straight, CDK.
I keep hoping to find a free lunch.

 

I cant think of any, with the strength and dimensions you need.

I reckon you are going to have to do the hard yards and run a couple up from fiberglass. Its not going to be much more work than some of your other potential methods.

Look into my eyes .... deeeply ...... You are going to make a half shell mould and build four identical half tubes ..... you are going to bolt them together ... and assemble the rotor from them ....


Here's a tapered half shell to inspire you. I would be happy to do the drawings for the frame dimensions for the mould if that would help.

 

being mesmerized :idea:

 

https://plasticstoragetanks.com/cgi...on&product=Open_Top_Tanks_PE&ppinc=1a&maxp=50

36 inch diameter x 50 inches tall open top plastic water tank. 74lbs each. $300 per in Texas.

stack 4 of them for the 5 metre+ height. $1200

looking for some similar but a slight taper, so can nest.

 

I agree, if a 'solid' or stiff rotor is an acceptable solution, it could be made to work satisfactorily. But, one of the original requirements of this forum was that the rotor should be able to be retracted, or folded, on the water. This is admirable, as few other rotors do this, otherwise we are merely repeating what others have done. If the object was to get a rotor to work, then by all means follow previous practice.

If we are to make a 'solid' rotor, fiberglass is a viable option. If the rotor surface is to be in 4 segments around, then the axial joints MUST be flush, ie butt joints, with countersunk fasteners. These segments need to be exact semi circles too, any ridges, proud fasteners, or slight out of round will be a serious aerodynamic penalty. We had extremely serious issues with spring back from the mold, and indeed slight differences in temperature, and even resin batch would alter the surface shape. Airbus use a 4 segment design for their A-350 fuselage, and created a stick for their back, whilst Boeing used a full round barrel, creating a different stick. The 737 uses an upper and lower segment, and rarley has issues?
Local stiffness needs to be built in to this skin, and I recommend foam, though a separate corrugated skin might work as well.

Using the plastic tubs as described might work, but that form of plastic (i think) is not self supporting. It will need rib or bulkheads as well as some form of central column, all of which adds cost and complexity. If I understand correctly, and unlike fiberglass, this form of plastic does not adhere very well, so special arrangements for bonding will have to be made. Circumferential joints need not be butt joints, they can be 'stove pipe', and can even have exposed head fasteners. $1200 seems a lot to pay for just the surface, not including shape retainers, a tower and etc.

I do not personally believe retracting, or telescoping this solid rotor by 1/2 is of any point. Ample evidence has been given that it's bulk and volume will have little effect except in very high and destructive winds.

On the other hand, the rotating triangular lattice tower, with hoisting sailcloth rotor, supported by foam disks will retract into a pile about 0.75-1m high, and the exposed lattice tower. Whether this is a benefit or not is up to Yobarnical. I also believe it should be cheaper too.

 

Found these trusses in Virginia and these tanks in Texas. Url for tanks in post above and not repeated here.
Url for truss here:
https://www.displaysexhibits.com/aboutus.asp

Back in post 81 I priced trailer hubs, bearings and stub axel. less than $100 for complete set, times 2 ends, $200. Truss and endplates, less than $350.
Two 36in by 50in tanks, $300 each, and a 6ft tall tank, 35in dia, $380. Tanks roughly a grand.
Roughly speaking total, $1500.
Leaves $500 for motor and control. I either have or can scavenge most of the other materials.

I am aware rwatson thinks I should build the rotor myself. I have done a lot of fiberglass work on my boats. Smooth after much filling and sanding. Strong but heavy in places. I don't think my skills are commiserate with building a balanced rotor.

The nesting tanks are 36 inches dia top and bottom, 35 inches middle portion, and 14 feet high deployed. 8 feet high collapsed. a bit less than the one metre by 5 metre rotor. So maybe I get 5.5 kts instead of 6kts.