Electric Twin Surface Drive

Discussion in 'Surface Drives' started by mitchellleary, Jul 14, 2015.

  1. mitchellleary
    Joined: Jul 2015
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    Location: UK

    mitchellleary Junior Member

    Hi all,

    I'm working on a scratch boat-build which is quite unique and I need some advice please regarding which surface drive motor would be best.

    The motor will need to power a 5m (around 16foot) motorboat that will weigh less than 500kgs(total) and will be powered by solar power. For this reason, the motor needs to be the most energy efficient possible. So it doesn't need to be a monster, just one that uses the least electricity possible(these is the main requirement, oh and obviously reliable at sea)

    If you could recommend the one you think would do the job, why you think it will be best and its power rating, I would be very grateful.

    Thanks in advance and I look forward to your help.
     
  2. Jamie Kennedy
    Joined: Jun 2015
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    Location: Saint John New Brunswick

    Jamie Kennedy Senior Member

    What sort of speed and power were you looking at for a cruising speed and top end? I think brushless permament magnet DC motors are the most efficient, and if you get one that is relatively large in diameter, and a propeller that is relatively large in diameter, then that is even better. Larger diameter motor means less reduction gearing, or none. Large diameter prop means less slip. That said it depends on what is available, but smaller motors can be custom built and even home built. Here is an interesting article, but design for efficient cruising at 6 knots. Perhaps you are interested in planning speeds.
    http://www.westsystem.com/ss/ted-s-jewel-box/
    [​IMG]
     
  3. mitchellleary
    Joined: Jul 2015
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    mitchellleary Junior Member

    Hi Jamie,

    Thanks very much for your reply.

    The cruising speed I would be looking for would be at around 10-12 knots with as high a top speed as possible and bursts of power if necessary as at see, it may need to fight currents etc at certain times. I have heard of solar vehicles similar to mine that had a top speed of between 23 and 30 knots which to me sounds incredible but if it's possible, it would be nice to have that capability.

    Do you have a link to an example of one of your recommended motors?

    Thanks,

    Mitch
     
  4. Jamie Kennedy
    Joined: Jun 2015
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    Location: Saint John New Brunswick

    Jamie Kennedy Senior Member

    Mitch,
    No I am sorry I do not, but you could contact one of the people in the article above.

    Bear Mountain 30 Hybrid Electric Launch
    LOA: 30'
    Beam: 6' 11"
    Displacement: 6,800 lb
    Power: 7.5 kW Perm DC motor
    Cruising speed: 5-6 knots
    Designer hull: Steve Killing
    Designer electric: Jonathan Killing
    Builder/owner: Ted Moores

    The speed and power depend a lot on weight and length also. The boat pictured has a displacement of about 3000 kg, but given it's length and design is able to do 6 knots on the 7.5 kw motor. In your case you would need perhaps 1/5th the power due to the lighter displacement, but 8 times the power due to twice the speed, and then some additional penalty for operating above hull speed, assuming you don't take extreme measures to reduce wetted surface. But ballpark you might get by with a similar motor but perhaps 15 kw or say 40 horsepower.

    From the sounds of things however this was a specially built motor, designed for maximum efficiency, and designed operate at the same speed as the propeller shaft to avoid transmission losses. The propeller itself is 17 inches, but it might have a pitch of 12 inches for a shaft speed of 600 rpm. So I would imagine this is a large diameter electric motor for higher torque and lower speed. For your needs you might need something very similar in terms of pitch, but smaller diameter prop and perhaps twice the rpm for twice the speed through the water, but still relatively a moderate speed.

    If you were to look at a Torqedo, for example, in the 40hp equivalent range, you might come up with this one...

    40hp 1400rm Inboard...
    http://www.torqeedo.com/en/products/inboards/deep-blue-40-80i-1400/M-3302-00.html

    40hp 2400rpm Outboard...
    http://www.torqeedo.com/en/products/inboards/deep-blue-40-80i-1400/M-3302-00.html

    I think the inboard would be a better choice as the rpm better matches your speed of 10-12 knots. Of course they run $20,000 plus accessories, but it gives you an idea of the technology available, and something to compare options against, even custom options. These motors tend to be heavy too, relative to their power, so an inboard might be better for that reason also. Still it is only 40hp so perhaps not too heavy. The Torqeedo outboard weighs 300 pounds plus another 300 pounds for one battery. The Torqueedo inboard is probably similar.

    So if not out of your price range they might be out of your weight range. If you could reduce your speed requirements down from 10-12 knots to 7-9 knots your power requirements would get down to say 16hp equivalent for which you might use a pair of Torqedo 4.0 like these...
    http://www.torqeedo.com/en/products/outboards/cruise/cruise-4.0-r/M-1232-00.html

    Not sure what the price and weight would be, and I am not sure if you can get those to spin in both directions for twins, but for certain the more you slow down, the lighter everything gets, which again means less power, and ultimately less money. Now if you can plug in at your dock and just go for short hauls you can save a lot of weight and money that way also. Less battery, and less weight, and shore power is still cheaper than solar power.

    Good hunting.
     
  5. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    PERM G.m.b.H in Germany makes the type of electric motor you need, for example the PMG132 that is sometimes offered at bargain prices. There is a lot of torque because these motors have a large diameter and short length.
    For your power requirements you would probably need several motors stacked behind each other or placed around the prop shaft using a timing belt. Output in HP is proportional to rpm: the PMG132 delivers 7.5 KW at 3500 rpm peak.
     
  6. mitchellleary
    Joined: Jul 2015
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    Location: UK

    mitchellleary Junior Member

    Thanks very much CDK. I've had a look at those motors and they look very good. Thanks for the tip!

     
  7. blisspacket
    Joined: Jun 2005
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    Location: st augustine

    blisspacket Junior Member

    I would look long and hard at Heinzmann, which you've probably encountered, since they took over PERM.
    In particular, the Heinzmann PMS 120 series, which is a synchronous AC motor with permanent magnets. It requires use of a controller, and therein comes another expense. If you're intent upon 10-12 knots and up, count on having batteries on board with solar to help. A Torqeedo Cruise 4 powering a 15-footer 500lb at 9mph will consume 90 amps, 48 volts. Those numbers come from experience.
     
  8. Jamie Kennedy
    Joined: Jun 2015
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    Location: Saint John New Brunswick

    Jamie Kennedy Senior Member

    Just got back from a long drive with my 15 year old daughter to pick up an old laser hull and spars for spares and a fun reno project. She chose the music, which I've decided I need to share in this particular thread because I now can't get it out of my head, and I really shouldn't have to suffer alone. Sorry.

    Electric Feel
    - warning -
    may contain a brain virus
    https://www.youtube.com/watch?v=MmZexg8sxyk

    All along the eastern shore
    Put your circuits in the sea
    This is what the world is for
    Making electricity
    You can feel it in your mind
    Oh you can do it all the time
    Plug it in and change the world
    You are my electric girl

    Said ooh girl
    Shock me like an electric eel
    Baby girl
    Turn me on with your electric feel
    I said ooh girl
    Shock me like an electric eel
    Baby girl
    Turn me on with your electric feel
     
  9. epwd
    Joined: Oct 2015
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    Location: tucson

    epwd New Member

    Mitch, 2*1hp bicycle hub motors should give you close to your requested speed, built into paddlewheels.... very inexpensive and extreamly efficient!
    26" wheel will have a tip speed of ~22 Mph, 27" wheel ~25 Mph.
    3 to 5 floats, 4"dip * 18" wide if you truly want twin drive.
    because of the reliability of these i would highly suggest combining both motors into one wheel and articulate it for steering. 1 2hp wheel should have again 3-5 floats 4-5" dip and 36" width.
    for self trimming (important for max efficiency and getting away with such a small wheel) email me, i have built several solar powered boats. U.S. Patented but willing to share...
     
  10. epwd
    Joined: Oct 2015
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    Location: tucson

    epwd New Member

    Go Green Brother!

    Mitch,

    that is a fair choice in motors, I like brushless because of no wear components other the sealed bearings, am not a great fan of GM's controllers, there are far better, such as ????????????????, will discuss latter.

    i do not think GM is as efficient as they claim, but they are not bad either.

    direct drive is always most efficient, i.e. bldc hub motors, low rpm, traction motors... AND SIMPLEST TO BUILD!

    Please read my Patent, #7448930 uspto.gov
    The images and claims 1st, will help get you thru the descriptions which is written for a third grader to understand. (lol)

    obviously you will need a drive train if you stay with that choice of motor; i.e. gear reduction, slip clutch (belt drive), and drive lines.... for that much power, you may wish to go to tractor (endless line) drive, the dieing gasp of paddlewheel evolution, good stuff!

    I can not emphasize enough the value of the trailing "fin", this is your main trim device under power (should be initially adjustable until cruise trim is found), as it is effected by the output (effectiveness) of the PW.
    it also greatly reduces uplift, generation of splash and trust waves....

    always shroud the paddlewheel(s), small wheels can swamp a boat if they some how run away (over volt) and provides other safety factors!

    also wish to mention, Intel makes a pure 12 volt nominal motherboard dn2800mt, and many monitors can be ran directly from battery power!. this can enable full control, monitoring of electrical systems, navigation, AV media and security.... if you buy components pc enabled! reliably and low cost. I like ssd (Fast) for programs and operating system (lean (clean) and mean!) and several tb's for media-data.... well worth the fore thought!

    for detailed assistance please direct email, but please do post choices and progress....

    Glad to, hope I can help, tell me of you mfg tooling will aid in my suggestions....

    Go Green Brother!

    Peter
     
  11. epwd
    Joined: Oct 2015
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    Location: tucson

    epwd New Member

    why tractor drive

    only a small portion of the wheel is effective in the water,
    a smaller portion of that arc has optimal thrust generation.
    by using a belt around two axle-wheels that portion of the arc is lengthened giving stroke, STOKE = TRACTION = EFFICIENCY! :!:

    SIZE IS A CONSIDERATION:

    float entry into the water can waste much energy and creates splash.
    float exit efficiency is greatly assisted by wheel size and the use of the trimming fin!

    a smaller front wheel at an elevation higher then the back is an easy solution.
    this way the float does not slap as it enters the water, and less float immersions (depth) is required because now you have real stroke power....

    float alignment (timing (staying parallel to each other and perpendicular the belt line) is CRITICAL if you have more the one wheel per axle, i.e. belts (endless lines).
    some type of timing cogs should be used when multiple wheels per axle, and obviously wheels on a common axle must be timed....

    high quality rope, several lashes joined at ever float, is by far the easiest and cost effective endless line to maintain.

    larger rear axle - wheel "drive" assists in keeping tension on belt.
    but this also increase the drive train requirements if not going direct drive axle.
    V belts are a good clutch and simple drive train that can provide wheel protection and power ratio - transmission...

    tractor drive can eliminate the surging as known with single axle paddlewheels, and all power is transmitted in the desired direction.

    single axle wheels are obviously the simplest to build, and still will blow any screw away with much less power required.
    surging can be greatly reduced simply by V shaped floats which can also focus thrust generated.
     

  12. jimburden
    Joined: Oct 2015
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    Location: Lincoln NE

    jimburden Junior Member

    Look at Hobby King for the largest out-runner motors available and any needed commutation and speed controllers. These will give you about 7 hp to 9 hp, at about 8,500 RPM, at usually 48 volts, in a package that weights about ten pounds. Batteries are the real weight problem. You can use the cheapest available AA cels that are rechargable and place them in thin wall water cooled plastic tubes in a plastic box to improve the biggest problem, heat in fast charge and discharge cycles. Jim Burden, Lincoln Nebraska
     
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