Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

1.5 V simple motor increase rpm

  1. Nov 17, 2011 #1
    I am working on a simple motor and I would love input or tips to increase the rpm on it.
    The motor is built by having a 1.5 v D battery connected to 2 bobby pins for and a coil of wire that one side is fully stripped and the other side is on the other side is only stripped on the bottom. Then i have a magnet under the coil to cause to rotate. I got it to run abbout 800 rpm but i would like it to excede 3000 rpm.
    If i increase/decrease the diameter of the coil will it increase?
    if i increase the number of coil will it increase?
    If i add a stronger magnet will it it cause it to increase?
    What will be a better replacement for the bobby pins?
  2. jcsd
  3. Nov 17, 2011 #2


    User Avatar
    Science Advisor

    You could put another magnet above the coil with the magnetic polarity the opposite to the one at the bottom.
    This will give more torque and possibly more speed. Use the best Neodymium magnets you can get and put them as close to the coil as you can.

    Those motors are great for a simple demonstration of motor principles, but the simple commutator mechanism requires constant care to keep it working, This is because the enamel on the wire quickly wears off as the motor turns.
  4. Nov 17, 2011 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Welcome to PF sdnhatb.

    You could also try using 2 D batteries, connected in series.
  5. Nov 17, 2011 #4
    I could connect 2 batteries in series but its kind of a challenge i got from my brother to get the 1.5v motor to reach 3000 rpm.
    Will adding oil to the pivot points decrease friction causing it to go faster and stay cooler?
  6. Nov 17, 2011 #5


    User Avatar
    Science Advisor

    The motor coil is suspended on the paper clips, so very little friction occurs here and adding oil may increase the friction if it burns while the motor is turning. You could get the motor running and then put a drop of sewing machine oil on one of the support points and see if the speed increases.

    Adding extra turns to the coil will help, but increasing the coil diameter will make it worse.

    Also, if you can add mass to the rotor, the motor will run more smoothly. (Using soft iron for this will make the magnets more effective as the magnetic flux will be increased.)

    This is because the motor is unpowered for most of each revolution so it needs considerable mass to keep it turning while it is not being powered. It is important to keep the rotor balanced, though, so careful construction is needed.

    However, I would not put too much effort into this motor, which is really just a novelty. You can get kits to make up motors which will be much more efficient and longer lasting.
  7. Nov 17, 2011 #6
    I know the this motor design isn't very exciting but I want the maximum potential of it. :]
    Can you please explain a litle more detail about the adding iron to the rotor? And by rotor do you mean the coil?
  8. Nov 17, 2011 #7


    User Avatar
    Science Advisor

    With such a small motor, any changes you make will have to be experimental and depend on what you have available.

    As a test, you could try a few nails attached to the inner side of the coil with the same number of nails on the opposite side to keep the coil balanced. These will add mass to the rotating coil and may help to concentrate the magnetic field.

    In this case, yes, the coil IS the rotor, although it normally includes everything that rotates.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook