Efficient electric boat

Discussion in 'Boat Design' started by Jeremy Harris, Jun 22, 2009.

  1. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Thanks Jeremy for all info.

    That is a nice piece of work. That is the kind of belt, I am looking for. I saw it at one of your English yards who makes the following boats.
    Bert
     

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  2. Jeremy Harris
    Joined: Jun 2009
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    Location: Salisbury, UK

    Jeremy Harris Senior Member

    One of the reasons that the belt drive is quieter is because it doesn't use any gears at all. To turn the drive through the angle at the bottom of the shaft (although not quite a right angle), I'm using a double universal joint. This seems to run completely silently, with virtually no power loss. It also doesn't have any angular velocity variation, as the aligned joints cancel each others variation out. Here's a photo of the double joint I'm using:

    [​IMG]

    I'm not too keen on using an idler, as the drive doesn't need it and it would add friction (and probably noise). I've got enough of a wrap around the small pulley to utilise the full tensile strength of the belt, so any more wrap wouldn't improve things. These belts are reasonably tolerant of belt tension, although I've found that they run with lower losses if run at a tension right at the bottom end of the allowable range. They tighten under load, as the teeth try and climb out of the grooves very slightly, so there is some merit in not over-tightening them from a bearing stress perspective, too.


    Jeremy
     
  3. Jeremy Harris
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    Location: Salisbury, UK

    Jeremy Harris Senior Member

    It's a standard industrial transmission part, Bert. This belt is a 3mm pitch, 15mm wide, HTD section. This is just about OK for the low power that I'm using, but these belts are commonly available in much larger sections, capable of handling many tens of hp at normal motor speeds. Years ago I flew an aircraft that used a 2" wide toothed belt as the reduction drive to the propeller and it was very reliable and completely maintenance free.

    Jermey
     
  4. BATAAN
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    Location: USA

    BATAAN Senior Member

    Here's a photo of an electric drive setup we did for a recent series of Pirate movies, working in the Bahamas.
    The boats are 18' pulling boats, typical 18th century, the 36 volt bow-mounted 360 degree drives are trolling motors with very shortened shafts so they fit under the front thwart of the boat. Worked like a champ! Little tugboats for towing around lots of other movies skiffs and small boats.
     
  5. BATAAN
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    Location: USA

    BATAAN Senior Member

    Ooops here's the photo

    OK here's the photo to go with my post, sorry.
     
  6. BATAAN
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    Location: USA

    BATAAN Senior Member

    try again

    Did it work? Oh the file was too big. OK now try.
     

    Attached Files:

  7. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Interesting consept, to have frontwheel drive. Something to consider. However how does it perform with a 2 - 3 meter (10 feet ) waves, which is the norm in our area.

    Bert
     
  8. BATAAN
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    Location: USA

    BATAAN Senior Member

    front wheel drive

    I have no idea. We used it only to work in mostly smooth water to make a movie, then we packed the boats in shipping containers and I never saw them again.
     
  9. Guest625101138

    Guest625101138 Previous Member

    Jeremy
    I am currently using a toothed belt on my pedal boat. The belt is slack at rest. I made a small ptfe pulley that engages on the back of the belt if the tooth try to lift out of the slot.

    This is certainly much more efficient at low power. I do not know how the efficiency compares at higher power but it can transmit much higher power than I could get with pretension in the belt.

    The idler pulley sits right at the slack side nip point on the smaller pulley.

    The need for the idler would depend on the length of belt relative to the size of the small pulley. However it also means that I do not have to be concerned about the belt stretching at least with horizontal shafts as the belt just sags like a chain.

    Rick
     
  10. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Hi Jeremy,
    I have something like attached in mind. Any names of good quality manufacturers for the pulley and belts? I will be on the way to Cape Town again tomorrow and can search for the agent while I am there
    Bert.
     

    Attached Files:

  11. Guest625101138

    Guest625101138 Previous Member

    Bert
    I order belts from here:
    http://www.piesau.com.au/shop/index1.html

    It will give you an idea of what is around and at what cost. Not sure if they operate in locations outside Australia. Their website is a bit clunky but it eventually works. They have a belt and pulley catalog you can download as well.

    Rick
     
  12. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Yes, you are right. I get the message, website under construction and struggle to get to 2nd and 3rd pages.

    Do I assume correct and I must look for timing belts? and Pulley's ?
    Thanks Rick
     
  13. Guest625101138

    Guest625101138 Previous Member

    Bert
    Yes the belts and pulleys.

    There is also a very good catalogue on them that gives useful design detail.
    Rick
     
  14. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Thanks, I will try to download it.
    Bert
     

  15. Jeremy Harris
    Joined: Jun 2009
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    Location: Salisbury, UK

    Jeremy Harris Senior Member

    Bert,

    If you do a web search in your area (just set Google to search SA sites only) and look for HTD belts you should find some local stockists I would have thought. HTD belts are a more efficient profile than the older H series timing belts, as their tooth form allows a lot more torque to be handled for a given size of belt. Better still are the Gates modified HTD profile belts, their GT2 series. A search on Gates and belts will probably find a local supplier.

    I get my parts from a UK company called Bearing Boys, who stock belts, pulleys, bearings etc, so are a sort of one-stop-shop for this stuff. Although it's of little use to you down there, here's a link to their timing pulley pages: http://www.bearingboys.co.uk/Timing_Pulleys-1042-c (the HTD section pulleys are described here by their pitch, 3m is 3mm pitch, 5m is 5mm pitch etc).

    I'm using 3m section belts 15mm wide to drive my prop. I can get away with this small pitch because I'm using a 72 tooth driven pulley and a 28 tooth drive pulley, so I have lots of teeth in engagement and the whole lot is going at a moderate rpm. Rick is going the other way, with very high peak torque, a low input rpm from his pedals, driving a prop at a higher speed and lower torque, so he's had to use a belt of much bigger pitch.

    The best way to size belts and pulleys seems to be to use the belt tooth torque rating. As electric drive, and a boat prop, present a fairly gentle load I don't think there's any need to use the derating factors based on duty that the manufacturers provide.

    Jeremy
     
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