Range Extenders?

Discussion in 'Model 3' started by Geoff Shelley2, Oct 10, 2018.

What are your thoughts about this range extender www.youtube.com/watch?v=u4b0_6byuFU

Poll closed Wednesday at 12:15 PM.
  1. Great idea

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  2. Bad idea

    0 vote(s)
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  1. Geoff Shelley2

    Geoff Shelley2 New Member

    I'm interested in your opinion about electric traction drive range extenders. Both generally and more specifically linear generators like this one www.youtube.com/watch?v=u4b0_6byuFU . Please comment.
     
  2. bwilson4web

    bwilson4web Well-Known Member Subscriber

    The example has too much vibration. Opposed piston engines have similar efficiency and inherently less vibration. The proposed Wankel even lower vibration in a smaller package and more compatible with smaller generators.

    Bob Wilson
     
  3. Geoff Shelley2

    Geoff Shelley2 New Member

    Bob
    Can you point me to a website or other information about those two options. Because I thought 40% efficiency pretty awesome and the size 535 mm x 210 mm x 200 mm quite awesome too. Perhaps my conversion math is off, but isn't that 21" x 8.26" x 7.87"? About the size of an average carry on luggage? And it weighs about 40 lbs. Is the Wankel + generator or the opposed piston engines + generator you're referring to smaller and lighter than that?
    Thanks!
     
  4. bwilson4web

    bwilson4web Well-Known Member Subscriber

    Each engine has its own challenges and we really need to see them sized for an existing range extender. For example, my BMW i3-REx, 24 kW, 640 cc, liquid cooled, motorcycle engine.

    Bob Wilson
     
    Last edited: Oct 11, 2018
  5. Geoff Shelley2

    Geoff Shelley2 New Member

    Thanks for the info.
    I could not see from the websites any stats on thermal efficiency or size or weight. I did find a website about why the Wankel engine had to died, https://www.carthrottle.com/post/engineering-explained-why-the-rotary-engine-had-to-die/. It mentions that thermal efficiency was low. Perhaps they've made some improvements. I did find an article about a rotary engine made by LiquidPiston which claims above a 50% thermal efficiency and has only 3 moving parts and less than 20 parts all together. Looks interesting.

    Regardless none of these have a generator built right into the design, and I'm going to guess that they wouldn't fit into my carry on luggage, and I'm going to guess that they weigh more than 50 lbs, particularly when a generator is attached.

    I think I'm still a fan of the linear generator for now, at least until more info on the LiquidPiston engine (size, weight) is available.
     
  6. bwilson4web

    bwilson4web Well-Known Member Subscriber

    No problem. It is my hobby.
    Try to find a BSFC chart. One of my favorite sources are the SAE papers.
    The vibration problem can be solved in a 4-cylinder configuration with piston motion timed to avoid rotary and linear motion. Alternatively, 2-cylinders along along the piston center would work but be a little long.

    Bob Wilson
     

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