Electric ala Rube Goldberg

Discussion in 'Hybrid' started by Justaguy, Dec 24, 2015.

  1. cmckesson
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    cmckesson Naval Architect

    The "argument" is because I used a shorthand to describe my batteries (i.e. "Group 31"). Fred is right that they are not Gp 31. But I used that shorthand because I thought it would describe their physical characteristics well enough for purposes of this conversation.
     
  2. Justaguy
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    Justaguy Junior Member

    Follow up

    Hi Chris,

    A few follow-up questions if you don't mind:

    1) Generator type: Why would you prefer a diesel vs. gas generator?

    2) Motors:

    a) For someone trying to put together a DIY electric motor setup (not outboard), leaving brands aside, what generic characteristics would you say are minimally required in an electric motor? Your opinion is all I'm after here. If you've already explained that elsewhere, please let me know.

    b) Can you provide a link to an example of the type of motor that you'd prefer now?

    3. Charger Capacity: What exactly limits your charging capacity to 30A in your current setup?

    Thanks,

    Justaguy
     
    Last edited: Feb 4, 2016
  3. cmckesson
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    cmckesson Naval Architect

    1) Generator type: Why would you prefer a diesel vs. gas generator?

    I would prefer a below-decks installation, but I am loathe to put gasoline below decks due to its explosive qualities.

    2) Motors:

    a) For someone trying to put together a DIY electric motor setup (not outboard), leaving brands aside, what generic characteristics would you say are minimally required in an electric motor? Your opinion is all I'm after here. If you've already explained that elsewhere, please let me know.


    I quite like the torque/rpm characteristic of a series-wound motor, because it eliminates the need to carefully match the propeller. A Series-wound motor will basically produce full power at any RPM, thus matching to the existing prop. (This is of course an approximation, but it's close enough for DIY / Rube Goldberg purposes.)

    b) Can you provide a link to an example of the type of motor that you'd prefer now?


    Here is a page of typical motors: http://www.cloudelectric.com/category-s/41.htm

    I have the model 4001. For my 17,000 lb boat one could argue that it is undersized.

    3. Charger Capacity: What exactly limits your charging capacity to 30A in your current setup?

    Simply commercial availability. My chargers are commercial off-the-shelf golf cart chargers: http://www.ebay.com/itm/LESTRONIC-II-36-VOLT-AUTOMATIC-BATTERY-CHARGER-Fast-Shipping-/381531830189

    I have not found higher-amperage chargers at an affordable price.


    Hope this helps!

    Chris McKesson
    Happily electric since 1999
     
  4. Yobarnacle
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    Yobarnacle Senior Member

  5. cmckesson
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    cmckesson Naval Architect

    Love it!
     
  6. Justaguy
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    Justaguy Junior Member

    And what about 110/220 volts, phase, and "continuous operation" rated -- any important characteristics or preferences in there? "Series-wound" might imply some of that, but I don't know.

    As for power, two questions:

    a) If you were to increase it, would you simply look for a motor with more HP or some other consideration? I know that increasing HP on electric motors gets very heavy and very expensive quickly.

    b) Was your choice of 2HP simply a cost issue or electricity consumption issue?

    Thanks,

    Justaguy
     
  7. Yobarnacle
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    Yobarnacle Senior Member

    Folks get confused about horsepower.
    Given large enough space, you could load a 1000 Clydesdales, REAL horsepower but how would they turn the propeller?
    Horsepower doesn't spin propellers, torque does.
    A monstrous big engine, that reaches it's maximum torque at several thousands of rpm, would be as out of place as the horses, if you needed to start 100 loaded iron ore cars rolling from dead stopped.
    You need static torque in the above scenario. Applying torque at 0 rpm.
    Fortunately, electric motors produce their GREATEST torque as static torque.
    That's why trains are diesel electric. Of course they used to be steam. Steam is the OTHER energy capable of static torque. Internal combustion engines accomplish nothing when they are stalled.
    I didn't mean to preach.
    To solve any problem, first analyze. :)
    For motive power for propeller boats, calculate required torque at the range of rpms desired, and find the motor or engine fits those requirements.

    My boat has 25ft waterline, which computes to hull speed of 7 knots. The motors and props I chose are capable of pushing my little boat 6.9 knots+/-. Adding more power is waste. Unless I want to plane, using enormous more power.
     
  8. Justaguy
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    Justaguy Junior Member

    Hmmmm ... (while untying the horse from the drive shaft)


    That's good. Actually I took your horse example as good practical advice, simply explained, and appreciated.


    Couldn't agree more. And good to remember its logical partner: Lack of knowledge in a specific subject area doesn't indicate lack of analytical ability.


    Couldn't I just pick the box in the motor store that's labeled "New and Improved: Tons of Torque!" ?


    Excellent point. My original question related to HP was due to Chris' comment that some people might argue that his electric motor system was under-powered.
     
  9. Yobarnacle
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    Yobarnacle Senior Member

    Wasn't trying to make anyone feel small or foolish.
    I suppose my point is, just as you would need to calculate for the correct motor/prop combination, for new gear?
    It would need to also be calculated based on desired performance, to determine if an existing installation was too small for the present owners needs and for potential buyers needs.
    It might be too small for YOUR requirements, and just right for perceived needs of current owner.
     
  10. Justaguy
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    Justaguy Junior Member

    Yobarnacle,

    Understood. It was my attempt to inject some humor into discussions that can get awfully dry and serious. Thanks for the good info and perspective. Please send more my way when you have it.

    Justaguy
     
  11. Yobarnacle
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    Yobarnacle Senior Member

  12. Justaguy
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    Justaguy Junior Member

  13. cmckesson
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    cmckesson Naval Architect

    And what about 110/220 volts, phase, and "continuous operation" rated -- any important characteristics or preferences in there? "Series-wound" might imply some of that, but I don't know.

    I believe that "Series Wound" implies that the motor is DC, thus no frequncy or phase.

    I have heard of fellas installing 120VDC systems, and then simply rectifying their AC shore power to drive them. Personally I start to get squeamish when the voltages get that high.

    As for power, two questions:

    a) If you were to increase it, would you simply look for a motor with more HP or some other consideration? I know that increasing HP on electric motors gets very heavy and very expensive quickly.

    b) Was your choice of 2HP simply a cost issue or electricity consumption issue?


    As with most things, the choice of motor was driven by multiple factors, including taking a pathway of baby steps to build the system, not wanting to commit too much money or energy at one time, in case it turned out to be an impractical solution. But that "baby step" approach also meant that some decisions constrained other ones.

    My only complaint with the current motor is that when I DO have to run it at 10kW (which it will do) it gets hot. The 10kW rating on that motor is only for 5 minutes, due to heat build up. I have exceeded that (one time bucking Greene Point Rapids comes to mind...) and there was indeed smoke starting to rise. But we made it, and no permanent harm was done. But clearly it would have been nice to have a bit more "overhead" so that I could go to such high throttle for a longer period of time.

    Thus my "more power" issue is not so much "more power continuously" but "longer time at high power." That, in turn, might be as simple as installing a cooling system.

    Hope this helps!

    Best regards,

    Chris
     
  14. Justaguy
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    Justaguy Junior Member

    Chris,

    Excellent info and summary, as usual. Thanks a bunch.

    Justaguy
     

  15. Yobarnacle
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    Yobarnacle Senior Member

    I think this interesting.

    http://www.rcgroups.com/forums/showthread.php?t=905411

    Old Aug 07, 2008, 04:00 PM

    #6

    IBCrazy
    Engineer for Christ
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    Amherst, VA
    Joined Jun 2006
    11,369 Posts

    "Get an alternator from an old motorcycle at a salvage yard. Many Yamaha's and a few Honda's have outrunner style alternators that can be hooked up directly to and esc and run as a motor.

    Some models I believe have an outrunner style alternator:
    Honda: CX500, CX650, GL650, GL500, V30 Magna/Sabre "


    Old Aug 07, 2008, 08:21 PM

    #8

    mjsas
    Registered User
    Joined Nov 2007
    991 Posts

    It is very easy to convert an alternator to a motor, remove the diodes and regulator and it's a motor. Buy a cheap 80 amp Mystery ESC off Ebay and it will run at a low RPM. Alternators have a KV in the 100 to 200 range. To get full power it may require an ESC rated at 200 to 300 volts and 100 to 200 amp.

    With a KV of 100, a 200 volt ESC will give about 15,000 RPM which is well within the operating range of an alternator. Just about any newer alternator would be rated at 100 amps or more.
    The area of the stator times 2 N/cm*cm gives about 20 HP for many alternators. "


    For those who might not know, an 'OUTRUNNER' is a brushless A/C motor where the center part is a stator, not the usual rotor. Since it doesn't move, it's direct wired without brushes.

    The outside case of the motor is the rotor, ie: spins.

    Kv is rpms per volt, measured in kv. 100 kv is 100 rpm per volt.

    Give anybody ideas?
     
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