Collapsible Flettner Rotor Project

Been studying different electric motors designs.
Picked up on a bit of intriguing info.
The ESC on R/C models isn't always fed directly from the LIPO batteries.
Some have a radio controlled throttle, which is a PWM unit, rationing the dc power. It's connected between the batteries and the ESC which converts the dc voltage to 3 phase ac.

Might be PWM running ESC is something worth considering in my application, minus the radio controls.

 

http://www.math.niu.edu/~behr/RC/pwm.html

according to this, an R/C ESC IS a PWM controller, or includes a PWM circuit inside.

Could a R/C ESC run a 220v 3 phase induction motor?

could a R/C airplane motor run a flettner rotor? Some are rated for multi kilowatt power (more than 5 HP)


Like this 5kw water cooled brushless motor.
http://www.hobbyking.com/hobbyking/...er_Cooled_Brushless_Motor_USA_warehouse_.html

RPM/v: 730kv @ "Y" config. / 1280kv @ "Δ" config.
Max voltage: 41V (11S)
Max Current: 128A @ "Y" 730kv / 229A @ "Δ" 1280kv
Max Watts: 5280w


1 hp = 746 watts
so this motor is tad over 7 hp

 

You are determined to use some of those drum chassis are you not!!!

IF I understand you correctly, you propose cutting a circular hole in your foredeck, such that a circular drum chassis can be fitted, recessed into the triangle represented by the two gunwales, and the foredeck? Is this correct?

Then you propose mounting the triangular lighting truss ‘free standing’ in this recessed area. If so fine, BUT.

The drum chassis will merely be a former, or shape, and the structural fiberglass will need to be pretty massive to take the (bending, looks like shear to the hub base bolts) stress imposed by the ‘free standing’ rotor. The sides will need to be 3/8”-1/2” thick, and the bottom more, with significant steel washers to spread the load from the hub base. I am extremely concerned in case the new fiberglass resin system does NOT bond properly with the old drum chassis. These resins are not necessarily compatible, and you might be better off with something else as a base. I would specify E-Beam, or chemical etching to expose the ‘free’ co-valent bonds, but i don't know how you could do this satisfactorily. The fiberglass bottom of this depression, or well, will also need to be extremely stiff and strong as well to transfer the strain from the ‘base’ of the hub to the sides of the boat.

The drum chassis needs to be large enough in diameter to accept the trailer hub (make it a large trailer, 5 studs for instance), and just deep enough so the disk on the hub itself clears the deck. This depression needs to have enough room for the drive mechanism as well, or that least that part that is not in the fore-cabin.

Putting the rotor right forward is fine, but will tend to drive the nose down in almost any situation. The boat will tend to ‘bow steer’ and might be a bit of a pig to handle. I would absolutely make the sail-cloth version, so it can be reefed or doused if necessary. Use builders foam alone for all the middle disks, attaching the sailcloth using metal strips and your suggested screw base. The bottom disk should be a sandwich with plywood as it will be taking the driving force from the motor/gearbox to this bottom disk. I would definitely explore using a multi layer plywood disk for the bottom disk, configured as a “V” belt pulley, so the motor/gearbox can drive it from the back. The top disk will have a larger diameter plywood disk as an end plate on top. Each disk, including the bottom one will have a triangular hole in it exactly corresponding to the shape of the triangular lighting truss. I would still use 3 separate halyards, internal to the lighting truss and the triangular holes in the foam disks to tension the completed rotor up to the top. I think this design is a huge step forward in the concept of Flettner rotors, and well worth prototyping. No other has even proposed dowsing, let alone reefing that i know of. I will include a cartoon soon.

I am concerned if you use a ‘solid’ rotor as with no capability of reducing area, you will be prey to any wind that is there. If the rotor is working, fine, but until you get the bugs out, being able to ‘reef’ it or douse it completely, will be a real boon. You can also power out to a quiet body of water BEFORE exposing the rotor to the wind etc.

If you insist on making it solid, use solid builders foam, and don't bother to cover it with anything. You can do that later when it works.

 

The notes on PWM are seriously confusing, and i was one of the developers of PWM for commercial use, 40 years ago. Most of his discussion is to do with the transmission of information, i.e. the Radio control bit, so no interest to you. PWM is only the WAY in which a wave is formed, not an end unto itself the way these discussions use it. In fact, the PWM waveform can be used to generate a DC waveform OR an AC waveform, including a 3 phase AC waveform.

The water cooled motor sounds remarkable, and at some level could possibly do the job. No one i have poled in Boeings electric radio control airplane group has heard of these motors, so tread carefully. They certainly know all about Hobbyking though.

I have never seen the KV description before, it apparently means RPM/Volt. In this case, either 730 RPM/Volt, or 1280 RPM/Volt. As the maximum voltage is just 41V, the RPM ate full power is either 29,930, or 52,480. These are prodigious RPM’s, and i am aware of few gearboxes that will handle them. As the motors are current limited to 128A, or 229A, these will represent hard power limits, i.e. torque will be a constant, not increased as in a gearbox.

You will need to use the prescribed power-supply for these motors too, and follow all instructions. I am suspicions the descriptive video is in Russian, yet the add claims the motors are for sale into the USA only?

See the size of the cables supplied, that is a measure of the power used by these tiny motor(s).

The main shaft at 8mm diameter will be only capable of ‘turning’ something, and not engineered to take side loads (like a gearbox), and quite possibly no end thrust (like a propeller) either. Mind you i cannot imagine propellers doing this RPM either, so i have to assume gearboxes exist somewhere.

See if you can find a suitable gearbox, you need about 2,000rpm output and, say a 1/2” shaft to take the final pulley before the “V” belts to the bottom disk. Note, the Electric RC airplane people at Boeing were always getting gearboxes made specifically for a particular motor and propeller, and NOT from the motor manufacturers,

You will also need a suitable power-supply. i suggest getting them all from the same source, Hobbyking for instance, to at least attempt compatibility.

To be honest, integration of such systems is one of Boeings major skills, and it usually costs several times as much as the components alone.


[/quote]Quote: This unique motor has two configuration options allowing you adjust the KV to your needs. When wired in "Y" configuration, it operates at 730KV. Switch the wire leads to the "Δ"configuration and it will be 1280KV. The adjustable phase wire leads w/connectors are included.

The AquaStar brushless motors are a great choice for your deep-V, hydro or catamaran race boat and will be sure to leave the competition in your wake!
Features:
• Dual Configuration Allowing for 730KV or 1280KV Operation********* 
• CNC Machined Billet T6 Aluminum Motor Can** 
• High Purity Copper Windings*** 
• Powerful Sintered Neodymium Magnet**** 
• Precision Engineered for Maximum Energy Conversion
• Water Cooling Jacket Pre-installed
Specs:
RPM/v: 730kv @ "Y" config. / 1280kv @ "Δ" config.
Max voltage: 41V (11S)
Max Current: 128A @ "Y" 730kv / 229A @ "Δ" 1280kv
Max Watts: 5280w

 

not arguing, and I accede to your greater expertise. just for trivia and giggles, the meter long drive shaft for the British Seagull "5hp" Century Plus, is a hollow square steel tube 3/8 inch id (.375), supported only at ends. Spins 4000 rpm full power.
Slips over a 3/8 inch square stub gearshaft for the 4:1 red gear in hub.

This 8mm shaft on the R/C motor is 5/16 in od (.315).

Less robust than the Seagull certainly, but not a lot less, and not an unsupported meter long either.

A number of 1/4 inch and 3/8 inch electric drills have a threaded gear motor shaft in this size range, that the chuck screws on. 1/2 inch chucks screw on a 5/8 in shaft.

Dremmel tools spin 30,000 rpm with1/8 and 1/4 inch mandrels to which fair amount of side force is applied when cutting/grinding.

Maybe this isn't really such a delicate motor after all?

 

The outrunner motor cage is rigidly connected to shaft and both spin together See illustrations.
A water jacket surrounds all.

 

You are correct, this motor is probably tougher than i originally imagined, and thank you for keeping me focused.

A few caveats. An electric drill (which i originally suggested as a possible variable speed and direction motor source) has a gearbox. This gearbox has an output shaft with quite large bearings designed to take side and end load abuse. I suspect this motor does NOT have this bearing robustness.

Let us assume the bottom rotor, and therefore the bottom pulley, is 1m in diameter, ~39”, and the final drive pulley on the motor/gearbox is 3”. Possibly not very practical, as 3” may be too small to get a good enough ‘wrap’ from the “V” belts. A ‘tensioning’ roller can be added, to increase the ‘wrap’ and this may help. Note; i recommend “V” belts as they have lots of ‘give’ in both directions, and are cheap and easy to install.

This gives a final drive ratio of 13:1, so for 200rpm on the rotor, we need 2600rpm on the motor/gearbox. If we connect the small pulley directly to your suggested motor, then we apply 2600/730 V, ie 3.6V @ 128A. This gives a power W = I x V, of 460w, or 0.6 horse power. This is the MAXIMUM power this system can apply. Even a 2:1 gearbox will give 1.2hp, a large gain. This is the advantage of a gearbox. The closer the motor gets to its maximum rpm whilst the gearbox output is at 2600rpm, the greater the amount of power (the ability to do work).

These PWM power supplies are typically current limited, technically unable to be overdriven, and therefore burn out/fry. Even if mismatched to the wrong motor, they will either not function, or work fine. Most electronics have a high infant mortality rate, they either fry in the first few seconds, or work more or less forever. A failure after 100+ hours is fairly unusual. I can only conclude you were habitually driving too many volts into a poorly matched ‘motor/load’ set, and the motor eventually failed (shorted turns perhaps) and took the power supply with it. As the motor was cooled by water, its failure might have been delayed by good cooling for a long time.

BTW, the century multi-blade propeller looks like no propeller theory i know off. In fact, i think it breaks nearly every rule i ever learned. Blades of constant section root to tip, constant angle root to tip, constant chord root to tip. Its like they didn't know the propeller was rotating, and has different local velocities from root to tip. Perhaps I'm missing something, and they have some secret no one else knows. If so, submarines, closely followed by most other commercial ships, should be told. Submarines especially spend a fortune getting their propellers just so. In their case, quiet and efficiency are synonymous, and i assume the same can be said for all other slow speed commercial propellers.

Just as an aside, the two electric motors i used for my original scale model “Flying Sport Bike’ are geared 4hp @ 4,500rpm motors from ‘skill saws’. No idea where they came from now ( i just found them again), i cut all the non motor bits off, and the nameplates are in French and Spanish? I used a perfectly ordinary heavy duty ‘light dimmer’ as a voltage reducer, no reduction in frequency, and they worked extremely satisfactorily. I don't know how one would reverse these for your application, but i might suggest hooking both up, and driving one in each direction alternately!

 

I have several identical 5 bladed Seagull hydrofans. Always looking for more.
They are very aggressive pitch near hub and decreasing toward tip. About 60% of diameter out from root (3.5in), pitch is 10 inch. Diameter over all is 11 inch. 1/2 inch shaft hole. Blades are cupped. Only intended for ahead propulsion. No reverse.
The square tips fit shrouds/nozzles nicely. Seagull aluminum alloy, extremely resistant to salt water corrosion.

I'm also looking for century lower units. Seagull alloy. 4:1 reduction. Bronze bushing type bearings, not roller bearings. No seals. Designed to leak. Hub filled with very heavy oil, not grease. Water intrusion intentional, mixes with oil as emulsion, to a GOJO hand soap consistency providing lubrication.
Simple, functional, durable, easy disassembly and repairable.

I would suspect Seagulls benefitted from alien technology influence, except that those old British thread sizes make replacement screws difficult to find.
I redrilled, retapped the two lower units I own, to use USA fine thread.

This fellow seems to be like minded to yourself.

But no denying they work. Seagull 5 blade props high thrust has been known to destroy outboard motor mounts. I think I remember reading Donald M Street reporting such an incident.
[THE OCEAN SAILING YACHT DONALD M STREET JR First edition 1973 This is a classic for the cruising sailor. 703 pages
On page 560-561 Street recommends using British Seagull engines and gives solid reasons which still apply today. Mind you he does get his gear ratios wrong. ( the big seagulls have a 1:4 reduction gear not a 1:2 gear. And you still need to be a good mechanic to get the dependability out of them that they are capable of. ]

The bumblebee of the props? Aerodynamics can prove by scientific principles, that a bumblebee can't fly, or is that a myth?

 

Seagull Propaganda

http://www.britishseagullshop.com/faq.html

"How can Seagulls have five HP ratings with only two block and piston sizes?

You may notice that Seagull produced several engines with different hp ratings but with only two block sizes and only two different pistons. Unlike other motors, I have been told that seagull measured its' HP rating by the pull the motor could exert on a bollard. . There is a small block - the 64cc block that is shared by the two and three hp motors and then a 102cc block that is shared by the 4,5, and 6 HP motors. The gear ratio in the gear boxes and the size of the propellers determine the HP ranges within each block size. But remember horsepower ratings were measured differently over the years and it is difficult to say exactly how many hp each engine produced. In fact I ran across references to fractional hp ratings such as 1.5, 2.5, 4.5 and 5.5. Very confusing if one wants a single number. Lets look at some examples:

•1 to 2hp featherweight - has a 10:21 gear reduction and a 4 blade 6" prop with an engine turning up to 3500 rpm


•2 to 3hp forty plus -has a 10:35 gear reduction and a 4 blade 9" prop with an engine turning up to 4000 rpm


Both rated horsepower engines were generated from the same cylinder and piston.

The prop is very interesting. It's called a "hydrofan" and at first looks deceptively simple. But take a closer look and you will see not square blades but blades with a compound pitch to them. Seagull also provided a modern looking "weedless prop" of more conventional design. The 11" hydrofan on the 6 hp seagulls is awesome! Imagine a 37 pound motor swinging an 11" five bladed prop! No wonder they have so much torque!

•5.5hp Silver Century Plus - has a 12:48 gear ratio, a five bladed 11" prop with an engine turning at up to 4000rpm. There is world of difference between the 26 pound forty featherweight and the big seagull - the silver century plus longshaft. But is it a 6hp , a 5.5 hp or a 5 hp? Who knows! ( in fact if anyone can explain this better than I can I will include the answer here!)


The huge advantage of keeping to only two block sizes is that many parts are interchangeable! A tremendous amount of excellent engineering went into your seagull. But don't go around spouting off gear ratios and prop diameters- a seagull is a working motor that likes to be taken out and used. Also, HP ratings changed over the years as different measurements methods were used. The bottom line is that your seagull with its lower gearing will provide a surprising amount of thrust at displacement hull speeds. And is there anything more fun than seagulling? Probably not! Well ...maybe one thing."

http://forum.woodenboat.com/showthread.php?166819-British-Seagull-Outboard/page2

"It may be of interest to note that the Brittish Seagull Outboard Motor was, purportedly first developed, for the intended invasion of Normandy. It was used to push heavy barges across the English Channel, a job which this high torque engine was and is well suited for. According to information from various Seagull afficianados, a simple, reliable and easy to maintain engine was needed for wartime use, hence the development of the Seagull Motor."

"The National Aeronautics and Space Administration ( NASA) announced today that it has covertly stored thousands of pounds of rare and expensive unobtainum. During the 60's the 70's the agency cast the metal, which fetches $18,000 per ounce, into the flywheels of British Seagull outboards, a cold war ploy that kept the world supply from falling into the hands of the former Soviet Union. " Its the last place anyone would have thought to look," stated an agency spokesman.

British Seagull was chosen since, unlike other outboards, they just dont die.

Seagull owners can redeem their engines for fair market value of unobtainium on the date of redemption. Todays COMEX unobtainium close reached $18, 102.

end "

 

I long suspected the Seagull designers of having extraterrestrial help, and your note about the toxicity of the gearbox oil, and the apparent necessity for a “Hazmat” suit for humans to handle it, AND the complete non-availability of the thread types they use on this side of the Atlantic confirms it. In fact they may well have extraterrestrial manufacturing as well for all i know. Witness the exclusive use of ‘unobtainium’ for their flywheels (see your note), and the fact that their ‘aluminum’ does not corrode in seawater.

On closer inspection, i do notice the root is slightly different section and has a slightly greater pitch than the outer blade, pretty subtle, and clearly i didn't notice it before.

With regard to multiple blades, i believe something to do with ‘disk loading’ vs “blade loading’ but i am checking some very obscure aerodynamics.

Just as a complete aside, 3,600rpm is a ‘natural' speed for a 60hz electric motor, and is fairly close to the 4,000rpm input of a Seagull gearbox input. Perhaps a ‘normal’ single phase Skill Saw or other cheap electric motor might substitute, and get the electric motor out of the water itself. I wonder if turning the seagull “hydrofan” sideways in the water reduces its resistance to acceptable levels.

As a further aside, 110V/60hz inverters running from 12V car systems or battery’s are getting cheaper and bigger by the day. i wonder if the time has come to review your complete electrical system in this light. I have found some excellent used power tools at goodwill (or your equivalent) for very little money, and used a hack saw to convert them to my purpose. I usually start with Skill Saws, as i need the motor only, but drills, especially large ones, have substantial gearboxes. In a way it comes down to usage, is this a ‘proof of concept’ and can have a life measured in hours, or is it a permanent installation, with a life measured in years. My suggestion would be a bit of both, and things like the electric drive could be quite temporary as I'm sure improvements, possibly quite dramatic in terms of installation, will make themselves known over the course of tests.

 

Seagull proprietary alloy is supposedly "secret".

Metallurgical analysis would be interesting. Is it closer to Inconel or monel, or an aluminum bronze, or one of these alloys?


"Marine Alloys


These alloys are used for boat building and shipbuilding, and other marine and salt-water sensitive shore applications.


5052 Aluminum Alloy


5052 is one of the higher strength non-heat-treatable alloys. It has a high fatigue strength and is a good choice for structures subjected to excessive vibration. The alloy has excellent corrosion resistance, particularly in marine atmospheres. The formability of the grade is excellent and in the annealed condition it offers higher strengths than 1100 or 3003 grades.


5083 Aluminum Alloy


5083 is an aluminum alloy suitable for cryogenic applications down to design temperatures of minus 165 °C, since alloys of this type do not show the ductile/brittle transition phenomenon. Apart from aluminum, the main other ingredient is magnesium.


5086 Aluminum Alloy


5086 is an aluminum alloy, primarily alloyed with magnesium. It is not strengthened by heat treatment, instead becoming stronger due to strain hardening, or cold mechanical working of the material.Since heat treatment doesn't strongly affect the strength, 5086 can be readily welded and retain most of its mechanical strength. The good results with welding and good corrosion properties in seawater make 5086 extremely popular for building boat and yacht hulls."


Actually the entire seagull castings are unobtanium.

 

Ref the photo of the gear oil label in prior post. EP 140 is Viscosity, not environmental protection Toxicity. I know YOU were being witty, and YOU know you were, but there are some folks with agendas, only too happy to interpret things the wrong way. Just clearing up the potential haze.


R/C outrunner motors:

Because the can and shaft are "one" on outdrives, the diameter of shaft can be enhanced by the can design, as in photo below.

Since these 3 phase motors run either direction equally well, two motors could be installed nose to nose to work in harmony, with a vee belt pully bolted/trapped between. Doubles the power and improves rigidity, as combined unit has a mount base at both outer ends.

I suspect that being identical size would not be necessary. As long as kV was the same. A lower amp motor and high amp motor could be hitched nose to nose. Gives three power options. Lowest power when the small motor driving alone and big motor is only freewheeling, medium power when small motor freewheels while big motor drives, and highest power/torque when both motors are energized.

Your idea about using universal 110v motors is interesting as proof of concept.
This boat is a platform for several experimental propulsion systems.
I invented none. None are new or emerging technologies.
The experimental aspect is, viability of DIY with off the shelf repurposed components.
And info applicable to rotor may be applicable to other systems on board. Compatibility.

I was and am interested in 220v 3 phase induction motors for continuous operation.
These R/C motors are lower voltage 3 phase AC PM motors and much smaller/lighter for the hp.
Price is similar or lower than AC induction motors.
But can they withstand multi hour continuous running?

 

After reading, studying, and thinking a lot on this rotor project and having considered the various problems individually and together, I have arrived at these possible solutions I am about to post.
They fall short of conclusions because (1.) I am keeping an open mind and (2.) I value the input from the members here.

First I want to mention the problems perceived before I suggest solutions.

Supporting rotor on cabin top and heavily reinforcing same is too heavy in wrong place. Installing at stem is restricting visibility and wrong for center of effort.

A free standing rotor, while having some advantages, creates numerous engineering problems, that require expense, weight, and complexity to overcome.
it doesn't eliminate any rigging since I insist on ability to set sails also.
IntrepiDos is not to be PURE Flettner rotor, as comparison with other propulsion is important. I plan a number of experiments on the same hull.

A spinning vertical rotor in the winds eye imparts heeling force rather than a forward impetus. Some say a dangerous amount while others say not to worry. It's an 'unknown' to me. Contingency planning is the correct strategy for survival at sea, and ingrained in me. Need to plan on it MAY be dangerous and have a solution in advance.

A large mass aloft isn't something I'm happy with in strong winds. A cylinder has lower windage compared to other shapes. None (windage) is preferred. Hence the collapsing rotor agenda. But that (collapsibility) also adds expense, weight, and complexity.

The Flettner rotor I originally imagined has evolved into a much more expensive proposition. What if it doesn't work very well? Wasting money rots my socks and earns my wife's ire. Can I recoup anything if the rotor is a failed experiment?

What am I to DO? (gnashing teeth)

 

If the rotor had another, alternative use, that would ease my conscience about the investment. And versatility always appeals to me.

These articles are VERY interesting

proceedings.ewea.org/.../allfiles2/202_Ewec2007fullpaper.pdf

www.prh.fi/stc/attachments/innogalleria/savonius_kirja.pdf


I'm not suggesting here, a wind powered rotor. It would be electric motor powered as a magnus rotor.

But if it failed at propulsion, it could still have some value as a wind generator. And just MAYBE, it can do BOTH!

According to the above studies, if I read correctly, the Savonius rotor developes GREATER magnus effect than a smooth cylinder.
I am posting the pdf from the ist site. The second site you will need to download yourself as the pdf is too large to upload.
Please do treat yourself. It is Savonius' experiment papers in his own words.

 

https://www.youtube.com/watch?v=8VMRPi7y8ZM

This is interesting and open source