Announcement

Collapse
No announcement yet.

Electric power

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Electric power

    Any thoughts on using a 4 stroke motorbike engine to power an alternator/ generator to run an electric motor? As usual bike engine weight will be an issue but any other thoughts? I'm not concerned with batteries, pure generator output only for motor drive.
    Further ideas - motor to generator drive via rubber pulley suitably geared up to provide constant revs, thus low(ish) engine revs for correct generator speed. Thyristor controlled motor speed.
    There's a big electric motor on Afors that looks like it would do the trick.

  • #2
    Electric power

    Is that is a dc motor with brushes? Probably quite a low power to weight ratio and efficiency compared with a brushless motor. On the plus side, easier to control and cheaper.

    With no batteries the peak power output of the electric motor can't exceed the max rated power of the 4-stroke, minus a bit for generator inefficiencies. Adding some battery power would give a burst of power for take off.

    Comment


    • #3
      Electric power

      And a battery would provide a few minutes redundancy if the motor failed.
      Dave

      Comment


      • #4
        Electric power

        Is the proposal an alternative to a reduction drive? If so, the poor efficiency of smallish alternators (
        Pete T.

        "A closed mouth gathers no feet".

        Comment


        • #5
          Electric power

          Well, it depends - the power density of an electrical machine is roughly proportional to operating frequency. So a 500Hz machine will be an order of magnitude higher than a 50Hz one (leaving aside losses for the moment, which increase with frequency). Peak efficiencies for well designed rare-earth magnet motors/generators exceed 90% with power density in the 3-5 kW/kg range - see Joby Motors or Rotexelectric for examples.

          We use a Joby JM1 in our hybrid 'plane - it can deliver over 13kW at 6000rpm and has a mass under 3kg. One of the main challenges would be to develop the electronic controllers to handle the power transfer between the back-to-back machines - effectively to make an electrical CVT. Efficiency would be over 80%, but hard to say if the total mass would be less than a mechanical version, as found on scooters for example. Of course, as has been noted previously, with some batteries added (not too many or it gets heavy) then peak boosts are available.

          Comment

          Working...
          X