Collapsible Flettner Rotor Project

Discussion in 'Projects & Proposals' started by Yobarnacle, Jun 4, 2014.

  1. Yobarnacle
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    Yobarnacle Senior Member holding true course

    I calculate the lateral area as 58 sqft +/- and includes rudder. I removed the original rudder and closed in the propeller/rudder aperture.
    Pers Brohall claimed the Albin 25 is a trawler with sails. Said the rudder was too small to sail well without prop power.
    I dislike underwater thruhulls anyway.
    I found/purchsed a transom hung rudder 150% larger immersed area than original rudder.
    Being a couple feet further aft should also improve steering.
    I'm planning for it to be kickup and lowering and easy dismountable for trailering. Plan on using an adaptation of rudder in a drum as Eric Sponberg describes in http://www.boatdesign.net/forums/boat-design/rudder-drum-25041.html

    I'll use a glassed over drum shell to house the rudder cassette, of course. :)
    Since a rudder only functions up to 35 degrees or tiny bit more, the drum doesn't need to surround entire rudder chord when it's transom hung. The drum/case only needs to rotate an arc of 70 degrees.
    The case can be open at the rear and part of the rudder be external of drum and case. Also this allows the axis of the rudder to be where you choose (size of drum), and provides for kickup as well as vertical adjustment.
     

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  2. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Still having difficulty locating an appropriate continuous rotation suspension swivel.
    Might have to have something fabricated.
     
  3. rwatson
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    rwatson Senior Member

    The bearing doesnt have to be suspended, in fact its probably better not to be.

    Looking at crazy alternatives, you could bolt a car hub to the cabin top, put a hole in a shortened stub axle, and let the stub revolve on the end of whatever you have.

    I would be very wary about 'assuming' that your tripod will support the cylinder without actually designing the cylinder, and knowing the total weight that has to be supported. Also, in the 'Tracker' project, getting an easy to use braking system to allow reversal of the rotor on each tack was a pain, and removing vibration from the tower also.
     
  4. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Thanks for all your posts.
    In the cutaway and description of the 'Tracker', the mechanism supporting the rotor weight was in it's middle. No wonder they had vibration problems. If it were not for the steadying wheels at the rotor's bottom, it could have twirled like a majorette's baton! :)
    I think suspending the rotor under tension, attached top and bottom, would minimize vibration problems. Kinda difficult to oscillate, tied hand and foot.

    The spars will indeed have to be suitable to the load, once that figure is known.
    Fortunately, extruded aluminum sailboat spars can be had in a wide variety of dimensions. And used ones are relatively cheap, selling for scrap prices. A sad benefit from hurricanes is salvaged boat gear. :)

    You mention agricultural equipment in earlier post. Anything particular come to mind?

    The bottom swivel may indeed use a wheel hub and disk or drum brake. Good idea. Something from a gokart or skooter might be light and strong.
    Or a boat trailer hub. small, inexpensive, plentiful, and a 'Bearing Buddy' grease cap fits. (Spring loaded grease reservoir for the bearings to keep water out.)
     
  5. Yobarnacle
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    Yobarnacle Senior Member holding true course

    The boat trailer hub might be adapted for the upper swivel as well. A little heavy compared to a roller furling barrel swivel, and not stainless. hmmm.
     
  6. Yobarnacle
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    Yobarnacle Senior Member holding true course

  7. Yobarnacle
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    Yobarnacle Senior Member holding true course

    As to brakes. The friction or pinch drive I posted awhile back? what damage would occur to an electric motor trying to turn one direction but being forced to turn backwards until it braked off the momentum and could turn the right way?

    Actually, an advantage of diesel electric is instantaneous reverse. Even spinning 12 foot bronze props weighing more than a ton. hmmm.

    Would being instantly reversed hurt the rotor?

    Probably bicycle caliper brakes could be install on top and bottom endplates. simultaneously hand operated from a single lever. I believe there would be time during a tack to brake and release before counter rotation.
     
  8. rwatson
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    rwatson Senior Member


    I guess if you got a cheap rusting solution working, you could order a stainless equivalent when it rusted. Getting stuff to work in the first place will be your big headache.

    Instant reversing of electric motors shouldnt be a nono, but I would defer to more expert opinion. Maybe it would scrub out the friction drive arrangement quickly. We must work out the power levels for the drive.

    For something light and effective as a brake - are there any motorcycle wreckers around your area ? Even a slightly deformed bike brake rotor, ( very cheap ) would be good enough for this app I would think. Easy to install and operate too, with a brake handle in the cockpit.

    There would be a good case to set it all up on land and try it out before wrecking the boat. If you put it on some small trailer, you could take it down to the breezy shore and get a good workout.

    The Uni of California built some light trucks on rail with Flettners rotors to generate power as the wind blew the trucks around the circular rail, so you could test it on land easily.
     
  9. Yobarnacle
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    Yobarnacle Senior Member holding true course

    all good ideas. thanks.
    I looked at trailer brakes but they are sold as LH and RH. Apparently only work in one direction. Since bikes don't have reverse, I wonder if they work both directions like car brakes or one direction like trailer brakes?
    An automatic brake might use the electric clutch from car A/C compressors. One on top and one at bottom. Whenever power to the motor was turned off, a solenoid engages the vee belt pullys of the two A/C clutches. But not as a drive source. These vee belt pullys work like brake drums because the vee belt doesn't move. It's working as a brake band. Only need piece of vee belt. One end bolted down, the other end of vee belt connected to a tension adjustment.
     
  10. daiquiri
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    daiquiri Engineering and Design

    I don't get the point about brakes. All manufacturers of electric motors have the self-braking motors (also called brake motors) in their offer, and it costs just a tad more than a base model with no brakes.

    Brake motors have a solenoid-activated disk brake attached to the shaft. As long as the current is flowing, the motor revs and turns the load. As soon as the current stops, the solenoid gets de-energized and allows a spring to push the brake pads against the disc. The load rating of the brakes is at least equal to the maximum motor torque and they act in a fraction of a second, so you're safe that if motor can spin it, the brake will be able to stop it.

    It is a very reliable system and I don't see why you should waste your time reinventing the wheel. I would use as many off-the-shelf products as possible, because they are tested and covered by the warranty. And if you use components sized according to industrial standards, you will be able to find spare parts anywhere.

    I am attaching the brake motors catalog by ABB, just as an example. You will be able to find local producers who will offer the same type of motors.

    Cheers
     

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  11. Yobarnacle
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    Yobarnacle Senior Member holding true course

    I didn't know that. That's wonderful! Thanks for ALL your help, daiquiri. :)


    These are some big motors. The 4kw size to produce the 5hp needed weighs 86 lbs. And 400v 4 phase doesn't seem right to call low voltage. My brother is an electrician and claims 1.5v or less is LOW voltage. Everything above is dangerous ie: HIGH voltage. :D
     
  12. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Big motors. The 4kw weighs 86lbs.
     
  13. daiquiri
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    daiquiri Engineering and Design

    Those are cast-iron AC asynchronous motors, and are indeed not small. But aluminium-casing models are also available, and I am pretty sure you can find DC models too. However, the DC models require pretty big-diameter copper wires for continuous duty, the cost and weight of which might offset any gains from adopting the DC system. If you opt for DC, don't go for less than 48V voltage (96V is even better), or your wires will have to be really big.

    You should search for DC motors for hoisting applications. They are mostly equipped with brakes or have them as an option. But even if you find a decent producer of other types of light-weight electric motors, a DC brake can be bought separately and mounted later on.

    This company here produces DC winches for hoisting, like: http://www.warn.com/industrial/hoists/DC4000.shtml. It has an integrated gearbox and a brake, too bad it's 24 V. So the solutions are available around, one just has to search for them. You could call them and ask if it is suitable for continuous duty (some are not), and if they could kindly indicate a producer of their brake motor. For the latter request, I think you will have to be very convincing... :)

    Cheers
     
  14. daiquiri
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    I have found this one: http://www.bonfiglioli.com/media/fi...fd7-663a5d073678/br_cat_bmd_std_eng_r01_0.pdf . Model BMD 145 is what you need. 16 kg weight, brake included. It is an Italian company we often work with, they have very good-quality products and are present worldwide (american site: http://www.bonfiglioliusa.com/en-us/company/). I have called them and asked some info. Here's what they have told me:
    - these motors can work in continuous mode, no problems about that. Just stay under the S1 curve at the torque vs. speed graph.
    - these motors use the electromagnetic braking for bringing the motor to zero speed, after which the electro-mechanical clutch engages and holds it there.
    - in order to use the electromagnetic braking, they require a dissipative resistance, which is bought separately.
    - they are available at voltages up to 400 V, thus allowing electric connections and wires of reduced-diameter.
    It looks good to me, but see if you can find something similar from your local suppliers.

    Cheers
     
    Kai Rabenstein likes this.

  15. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Actually, I prefer 3 phase AC over DC. I also, before we are finished, want to look at using wind power to produce SOME of the torque needed to spin the rotor by direct mechanical linkage. Faster the wind blows, faster the rotor spins. For free! If possible, this would reduce the required HP for motor, and reduce the electrical load.
    I can imagine how a number of conventional windmill setups could be incorporated. The problem I haven't solved with this issue, is how to conveniently, mechanically, reverse direction with a windmill? Probably need to be CP props I guess.
     
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