Collapsible Flettner Rotor Project

To review,

We have a triangle lattice tower 5.5m high (thank you Hans). I favor cutting two 4m lengths, and using oversize aluminum tubing as 'sleeves' to join them to make a new 5.5m length. I would use epoxy for this joint, to avoid distorting the lattices with welding heat.

This triangle lattice tower would sit on a trailer hub at the bottom, and have another trailer hub top center. The lower trailer hub would be supported on a frame, probably wood, and probably shaped from 4" X 4" stock. I am considering having this assembly mounted on rubber donuts, for sound isolation, and ease of alignment.

The 1m diameter bottom disk would be driven by a Golf Cart motor (brilliant Rwatson, i wish i had thought of that), possibly through a "V" belt, or toothed belt? At the top of the tower, above the upper trailer bearing, a sort of bridge, possibly made from the same triangular lattice as the tower (the spare bits?) will reach out beyond the ~2m diameter of the upper, end plate disk, and allow steel wire stays to stabilize the rig. As the vessel and/or rig will distort under stress, these stays need not be extremely tight, and the top of the lattice tower could move a few inches either way for tolerance.

Now I believe a tubular rotor from stabilized fabric, sailcloth if you wish, supported by foam disks at appropriate distances is most appropriate for a practical boat, especially a smaller one, and comparable with proper seamanship. It should also be the cheapest, though this may depend on the cost of 5.5m of lattice tower.

Please note; several thousand airplanes have been built using a sewn 'sock' of sailcloth as their wing covering, the sock simply lashed taunt at the wing root. No wrinkling or distortion, even at 110kt (VNE, velocity never exceeded, + 20%). RANS does most of their wing covering using this method, and it has proved very successful. Here is a RANS -6 as an example.

http://airprayer.wordpress.com/2010/09/10/rans-coyote-update/

Alternately, a 'solid' rotor of fiberglass could be attached around this triangular lattice, or some other form of pole, possibly an aluminum tube, of suitable (quite large) diameter for longitudinal stability.

 

The rotor drive needs to be harmonious with my other systems on board. The golf cart motors http://www.cartszone.com/golf-cart-electric-motors.html run from $430 to over $700. without controller or batteries.

I was planning to run my diesel as a gen-set to power the electric drive rather than carry a huge battery bank. Would it make sense to belt drive the rotor directly from the diesel using a scooter variator cvt belt drive?

http://www.monsterscooterparts.com/street-motor-scooter-cvt-transmission-variator.html

The fabric covered wings is interesting. Remembering when I was a kid, building balsa and tissue paper rubber band powered flying models. Once the paper was glued on the assembled skeleton, I sprayed it with a water mist and as it dried, it shrank drum head tight. Then I painted with airplane dope. Must be getting senile. Ancient memories I haven't thought about in half a century, coming back as clear as if they were last week.

 

Ah, pity about the cost of the Golf Cart drive system, seemed like a good idea.

Typically a DC traction motor, like a car starter motor, or a mine winding motor, is a ‘series’ DC motor. In this case, the rotor and stator winding are connected in series, so both winding must take the high current of the motor. This connection/winding style gives very high torque at standstill, but also continues to increase in RPM until a load balances the available torque. i.e. poor speed control. it is possible to control the speed of such a motor using a DC PWM controller, i.e. a single pulse train of probably 18V peak with little damage to the starter motor. Unfortunately, starter motors are NOT designed for this duty cycle, but below are verbatim suggestions on how to modify them to do so. I copy these suggestions across without permission, and with little data on whether they would work or not. The grammar is as is, i didn't attempt to correct it. Theoretically, the bearing modification, the change of lubricant, and the cooling modifications will defiantly help, and the PWM controller should allow reasonable speed control, BUT, speed will depend on rotor resistance and this might vary, hence the speed will vary too.
Please note; this recommends specific manufacturers starter motors, and the suggestions as to why sound reasonable.


Reproduced without permission, and without guarantees.

This is my electric go cart that I made many years ago. I still have it and it is over 10 years old. The best starter to use is a gear reduction type, my common on import Japanese cars/trucks. This is because it is easier to mount a drive sprocket to replace the pinion gear. To answer the question, yes, you can modify a starter to run at 30 minutes at a time.

a. remove all off the original grease used in the gear reduction assembly, this grease is almost gummy and was designed to lessen the impact of intermittent full power when starting a car. Replace with some very light grease, I used some Mobil 1 pink synthetic wheel bearing grease.

b. Drill cooling holes around the motor brush housing. Do this carefully and as not take too much metal away making it too weak to hold the brushes.

c. Sand the outer motor housing and attach cooling fins made of aluminum. I used JB Weld, it does conduct heat, but if you access to PC CPU heat sink adhesive, this would be best but significantly more expensive. I used what I had, 1/2" by 1/2" "L" shaped aluminum strip, could go with tall fins if you want.

d. I run a 12volt fan directly on the case, you can experiment with the placement, but mine shoots air from bottom to top at about a 60 degree angle. I also cut off the solenoid from the start as it was just in the way. The starter shaft is permanently pushed out from the housing using Loctite Red. It has never dislodged.

After bench testing the stock Honda Civic starter, I found in stock form the motor gets very hot quickly when running for only a few seconds. When I removed all of the thick gummy grease, the motor spun significantly more free and there is much less heat created.

I let me nephew loose with the go cart, he ran it into the ground running up and the street. After about the 1/2 hour, the motor is hot, but the windings are not burning up with the typical smell of a overheated starter. I am sure that everything could be more optimized, but many people have tried the go cart and it has not given out.

Pictured the go kart only has on/off via a continuous duty 12v solenoid. I do have a homemade PWM speed control going through 6 vintage MOSFET's. The PWM controller helps mainly with initial jolt of taking off from a dead stop. For fully power, the continuous duty solenoid is wired to kick in and disengage the PWM controller.

Another separate post from the same source.

Hi, I am thinking if you did a couple of things, then perhaps you could do it. first, I would think that the starter should be made mechanically sound I.e. cleaned of any grease and grime, new brushes, bearings, armature contacts cleaned and polished, etc. As you want to start with the best opportunity for success. Heat is a big issue., so if you constructed an aluminum "shell" to fit around the starter case that might be a good start. I was thinking something like a long strip of aluminum heat sink and wrapping it around the starter case, or more likely, A series of aluminum angles perpendicular to the axis of rotation with small slits in the end to accommodate a hose clamp to secure them around the outer casing of the starter motor on each end. Once I had a good heat sink identified or fabricated and fit snugly around the starter. After getting a very snug fit, disassemble and add a thin layer of heat transfer paste around the starter to maximize heat transfer from the motor to the sink. I'd find some way to place a fan of some sort on the output shaft of the starter (or an electric fan) to blow air around the fins to transfer heat away. The use of a Pulse width modulated controller (like an electronic speed controller for a golf cart) would tend to reduce the operating temperature. As the PWM delivers power to the motor in a series of Pulses rather than continuous DC current, this may also result in lower heat buildup. PWMs are somewhat expensive. A cheaper alternative might be to build your own using 12V mechanical starter relays and resistance wire as used in older golf carts. All you'd need besides that is a control switch from a golf cart to "ease the transition" between the relays and away you go. Idea behind the resistance controller is that by creating a resistance coil, and tapping at different points, more current or less current is supplied to the motor. Check this link for a good description of how to build it. It is for a "golf cart" but the same idea. download the PDFs and enjoy.

http://www.vintageprojects.com/go-kart/golf-cart-plans.html

 

I'm still wishing ac induction motors would work. I can belt drive a large motor as a 3 phase alternator off my diesel. Installing 3 capacitors (around 150uf to 200 uf) wired in delta, it will black start. Self excite. I only have to spin it about 3% faster than rated speed and it will output it's full load rating 3 phase at full amps and volts. Drive it 1840 to 1860 rpm for 1800 rpm 5KW rated motor and it will produce 5KW electricity. At least that's what I read/heard.
A lot of ac motors can be wired two speeds, 1800 and 3600 RPM. I'm thinking wire the motor up through a 3 way multipole switch, so it's power off in the middle, 1800rpm switched to one side and 3600 rpm switched the otherway. A different switch swaps a pair of legs, for reverse and forward.
Size the drive pullys so, the reversible rotor gets driven at either 200 rpm or 400 rpm or stopped. Fine control isn't essential. If you are spinning the rotor MORE than twice the wind speed, you get even BETTER performance/power. Double the wind speed is thresh-hold, not critical rpm.
I know a rewind shop sells rebuilt 3 phase motors for 20% to 30% new cost.

CDK said good things about 3 phase induction motors, reliable ect. Only BAD was heavy and inefficient. How inefficient? Or how efficient? Heavy I can deal with. Helium filled tires!

 

"Only BAD was heavy and inefficient. How inefficient? Or how efficient? Heavy I can deal with."

With the power coming from a diesel, efficiency becomes less important. 3 phase motors are cheap, so the air gap is wider than it could be and a handful of copper strips in the rotor is not the most sophisticated way to create a magnetic field.
My guess is that approx. 80% of the electrical power is available at the shaft. A bit more for big motors, a bit less for small ones.

Long time ago I made a controller for a number of 3 phase motors that could reduce the rpm to as low as 1%. The client was a machine factory that delivered a large installation for sorting and packaging eggs to an Arab country. They made similar machines for European countries but never thought about the conditions in the middle East. The machine could handle enormous quantities of eggs, but the Arabs were too slow to take the 6 and 12 packs from the end of the machine, so there was a pile of broken eggs around the installation.
My solution was a controller with hall rpm sensors that skipped complete 3 phase cycles as soon as the required speed was reached. At very low speed the motors turned in small increments; quite noisy but effective.

 

You already have that info, Yob.
Check the AC motor catalog in my post #85 and you will find it all there. The other producers have similar efficiency and weight values.
Cheers

 

Thank you gentlemen. I believe 3 phase ac is the motors I will use. Cheap, dependable, rebuildable, and nearly universal available if need buy replacements. Compatibility with other systems/components is important.
I have a homemade, retractable, 360 degree azimuthing electric propulsion drive, 2/3 installed aft of transom. The upper third penetrates the raked transom vertically well above the waterline, thru a waterproof stuffing gland. The electric motor and wiring and steering control is protected inside the boat connected to top third.
This also will have 3 speeds. Fast, half speed, and stopped. Fine control is manual. In and out of "gear" for quick bursts of power in maneuvering. Let her headreach (coast in neutral) is the rule rather than exception.
I also plan an electric anchor windlass. Old folks like wife and me, don't need to risk our health pulling up heavy anchors with our backs.
Many other plans for using electric motors on board.

 

Does the specs for these supercaps seem incredible to the rest of you?
http://www.digikey.com/product-search/en?x=19&y=16&lang=en&site=us&KeyWords=1182-1016-ND

350F ? Not 350 uF which is credible, but 350 FARAD? I think must be a typo!

 

For windless days, DIY and make some wind!

https://www.youtube.com/watch?v=uPabWOqnvsc

Might yet still be a use for that car alternator used as a 12,000RPM 2HP motor!
Shallow water?

 

Thanks for reminder. Since braking had been discussed and consensus was braking is unnecessary, I forgot about your motor catalog. The 50hz European motors are about 20% slower rpm than 60hz motors standard in USA.
I believe you regarding efficiency is fairly standard for type. The catalog chart also agrees with CDK's 80% ballpark estimate.
While efficiency in watthour consumption is of great concern for long distance cruisers and trans-oceanic racers, it is less a priority than initial costs for this experimental drive I'm planning.
Later, converting the induction motors to PM by purchasing off the shelf PM rotor conversion kits, or adding permanent magnets to the rotor DIY, IS a possibility.
I'm posting a capture from that catalog, outlined in red the motor I think needed for rotor. Another a bit larger needed for the alternator, to allow for loss. I can guess 10% to 20% larger is needed. Maybe one size smaller would be sufficient for rotor and the red outlined for the alternator.
Any professional opinions how much larger KW rating is required for motor used as alternator? I have a 20hp (2 cylinder) and a 10hp (1 cylinder) diesel. Both very fuel efficient medium speed heavy cast iron Albin diesels, with many interchangeable parts.
I'm still thinking hard about pros and cons of the plastic tank collapsing rotor versus the alternative sailcloth/multi-disk assembly furling rotor.
Time, money, and required skill factors, are the determinants.

 

http://www.boatdesign.net/forums/pr...lettner-rotor-project-50587-9.html#post692193

In these earlier posts, #124 and #125, I described how I believed ancient lateen rigs tacked so the sail didn't foul the mast. My drawing and explanation obviously were unclear, because Sailor Alan later remarked you couldn't set a lateen, let alone TWO lateens on the single aft leg of my tripod mast. I CAN, could, but my explanation and sketch were not easily understandable, apparently.

Here is a better drawing to explain the concept, how two rigid wing sails would tack seesaw fashion on a pair of Aframe masts. Maybe this will help make my earlier intent clear. Maybe seesaw is an Americanism, for the playground balanced lever over fulcrum kids ride on. Teetertotter? Same as seesaw.

The lateen yard or yards would flip over the single inclined aft leg of the tripod, in exactly the same manner as Hereshoffs sailing machine's wings teetertotter on their inclined axel. I believe lateen rigs of ancient times probably tacked this way, also, though differing by rotating at the top of a single nearly vertical spar. The tripod mast can serve as support for several light air lateen sails, instead of multiple vertical spars carrying several lateen yards at the truck.
I intend to experiment with lateen sails, using this "tactic" to tack, on the same spars deploying the rotor. Probably not simultaneously. But it's another reason I don't want a rigid rotor.

It is apparently human nature to discount the intelligence of members of other cultures, or earlier civilizations. I believe we do an injustice to the gentlemen of the age of exploration, in suspecting them of setting sails badly in ignorance. I think WE failed to understand the lateen rig. I hope this helps and no more BAD tacks fouling the mast..

 

Yes you can use a 3 phase induction motor feeding another 3 phase induction motor as you describe. Typical 3 phase induction motors efficiency varies between 96% and 85%, usually depending on relative air gap, windage, etc. As a generator, about the same, so don't worry about it. Note; efficiency or inefficiency is cumulative, and few systems are much better that your suggested system above. Power conversion, except perhaps for chain, is always lossy, its just a matter of minimizing it and being practical as well. Those capacitors must be a typo!

Unfortunately, when a 3 phase induction motor is started DOL, direct on line, or connected when the source of power is already in rotation (has some number of Hz), the stalled current of the ‘motor’ part of the circuit is very high (for various reasons). The alternator must supply this current, or itself “dip’ in frequency, up to and including stalling the prime mover, your diesel. Unfortunately as you run your diesel slower in RPM, so it too will produce less power.

To start the electric motor from stop (including the inertia of the Fletner rotor itself) you will need the diesel running slowly, and lets hope your flywheel is big enough to carry over until the diesel throttle can respond. The low speed winding/high speed windings are a very good idea, but make sure the rotary switch you use is a ‘break’ before ‘make’ kind. If it is “make’ before ‘break’, you will get an electrical fire, there is so much energy stored in the system. Absolutely use a single multi-stage rotary switch to change all these winding options, not two of them. Less chance of getting your wires crossed!! Look in the 'square D' catalogue.

I would suggest using a ‘V’ belt drive from the motor/gearbox to the rotor base, it has a lot of ‘give’ and so should reduce the inertia shock from the DOL motor start. Note; unless you use a true variable frequency drive for the 3 phase motor, there will be a very sudden start to the motor, and therefore rotor. A “soft" start, usually a kind of ‘chopper’ to reduce voltage whilst retaining frequency, are available, but are yet another complication, and expense.

Using the Scooter transmission would be a good idea except you need both directions. I do not think these ‘friction’ drives work in both directions, but have no data. Making the shafting etc to get from the diesel to the vertical rotor would be quite an effort, especially if you worried about alignment at sea etc.

 

thanks again for all your help.
My understanding is, if the diesel is running and spinning the 3 phase alternator(motor) but there is no load, then the alternator isn't doing anything except spinning.
This kinda goes against the advice I've always heard that a CAR alternator must never "look" into an empty circuit. Maybe ONLY for car alternators?
If I need to have some small load on the alternator prior to engaging the rotor, or if it's always needed so alternator doesn't "look" in an empty circuit, no problem. I'll install a small 3 phase blower pump air to the engine box. In addition to the dc blowers.
Necessary?

 

A car alternator without load generates much more than the 14.5V that is supposed to be the limit, because the regulator cannot deal with that situation. If a load is present, then suddenly removed, the voltage rises to 100V or more and destroys the regulator.

In your case there is no regulation, so no damage.

 

Thanks CDK