2 dc motors

Discussion in 'General Electronics Chat' started by macataq, Sep 15, 2007.

  1. macataq

    Thread Starter Member

    Sep 15, 2007
    11
    0
    helo all
    i have the following motor;
    Leeson Direct Current Permanent Motor Model C4D17Nk10C.Cat. No. 1800 RPM, 1/2 HP 24 Volt, Type DN, 20 Amps, Ser. Fact. 1.0. Duty.Cont., Max AMD 40degrees C. Frame VS56C, Insul Class F3. Torque 17.5, inch lbs FF1.0Encl TENV
    i plan on putting this on a riding lawn mower(yes i have been told.. i'm nuts)
    i also plan to use PV panels to charge the batteries.
    using the general theory that an electric motor of 1 HP is equal to an ICE
    motor of 3-4 HP, i believe i have close to half of the power of the original
    ICE(5 HP B&S) that is on the mower now.
    my plan is to use 2 dc motors for this project; 1 for drive and 1 for the cutters. (if i can find another one ,cheap)
    i have a couple of questions regarding my plan:
    is it possible to control the speed of these motors from a single source?
    i have been looking over the info here on PWMs, but i am a bit of a noob.
    because i dont know yet what amp draw will be under load, i am not sure any of the PWM circuits i have seen will be sufficient.
    second question, if i cant get another 24v motor would it be possible to use motors of different ratings..i.e a 24v & 12v(or 36v) and still use a single control source.
    i would appreciate your thoughts (except on my mental state, LOL)
    thank you
    Mac
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The motor spec's come out to 480 watts - 24 v times 20 amps. One HP is 760 watts. Don't think you're going to get the mower going too fast.

    Possibly you could expand on the "single control source" idea. The motor running the blades should be running full out at all times. You only variable would then be controlling the speed over ground, which may be zero with only 480 watts to do the motivating.
     
  3. macataq

    Thread Starter Member

    Sep 15, 2007
    11
    0
    thanx for responding beenthere

    i was concerned about being under-powered, but this thing will do a wheelie with the existing 5 HP motor and generally goes too dang fast. i am hoping to aquire a 1 HP+ motor to be used for the drive and use the 1 i have already for the cutters. but 1 HP + motors seem to be very expensive(ETEK $700 + controller) with regard to your suggestion on the cutting blades, i was thinking that i should have some method of controlling the speed for times when i wasnt cutting(driveway from front yard to back yard) but i suppose a simple breaker/switch would work for that.
    my "single source" idea is to power both motors from the same battery bank,
    suggestions on the size and configuration of this would be appreciated.
    thanks again

    Mac
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    In addition to what beenthere said, a typical mower engine is running at about 3,600 RPM when it's producing it's rated horsepower. Your motor spins at half that speed - not nearly fast enough for the blades. It wouldn't even make a decent weed whacker. You'd have to use some mechanical means (ie: gearbox, V-belt drive, etc) to double the shaft speed of the motor, but you would lose a great deal of power in the doubler.

    As far as a speed control - you might want to take a look at Gar Woods' ancient invention. He invented a speed control for golf carts - can't remember exactly when, but I think it was in the 1930's. It basically consisted of a conducting bar of copper, which made contact with a series of other copper bars; each connected to the + supply via a successively lower value power resistor - that's my recollection anyway. (Gar Woods grew quite famous in the powerboat racing circles) His design has been used for many years - although it's probably been superceded by now.

    Anyway, I suggest you go over to your local golf course, and have a look at one of their electric carts - or just do a search on the web. That'll give you a good idea of a direction to head in.
     
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