Power Generation - Time to Get Serious

Discussion in 'Electrical' started by Fabian, Sep 21, 2009.

  1. Fabian

    Fabian Well-Known Member


    I've looked at a few posts, ok, more than a few about electric start systems for our Chinese 2-stroke motors.
    Haven't really found anything that's suitable and can double up as a 'decent' electrical generation system.

    Apart from being thankful that i've installed a SickBikeParts Jackshaft Shift/Shifter Kit, and looking for solution for a power take-off method to drive a generator, the solution could prove workable for those who already have a practical power take-off system on their bikes - as-in - the jackshaft from the SickBikeParts Shifter kit.

    Calling Jim - Calling Paul - Calling Jim - Calling Paul

    What about utilising a secondary 17 tooth sprocket as an accessory drive to a reasonable spec DC Motor - say 200 watts power output (for a decent automotive quality lighting system) and 200 watts power input to drive the jackshaft and assist in turning over the 2-stroke motor so the pedal start is more relaxed.
    The DC generator/motor could sit in an attachment fixed to (and sitting above) the jackshaft kit - it could have a tripple function in adding an extra 200 watts of power to the internal combustion engine for emergeny overtaking maneuvers, or towing a heavy trailer, in my case.

    Is it a foolish concept, or is a do-able concept that can be practically engineered.

    That jackshaft is looking at me - power take-off is just so practical as the shaft is sitting there waiting for an accessory drive to be fitted to it.


  2. augidog

    augidog New Member

    i agree...power-takeoff can occur many places on a chain or belt drive. i have a 24V motor i tried to hang in various places on my bike, including a rough "draft" of a separate small pully lashed to the spokes and a small belt driving the motor, & friction-drive right off the tire...it's a tantalizing concept alright, onboard charging...i'm not ready to give up on it, but i have given up on the starter/generator offered on the scooter engines...auto-quality lighting has sure made a difference in MY comfort/safety level, not to mention the peripheral accessories it could power.

    a huge aftermarket opening, i would think...IF someone can achieve universatility.
  3. Fabian

    Fabian Well-Known Member

    Quote "augidog":

    auto-quality lighting has sure made a difference in MY comfort/safety level, not to mention the peripheral accessories it could power.

    I also agree whole heartly - auto-quality lighting would make a huge difference to MY comfort/safety level.
    Why would i waste my time and money spending $400, even $500 or $600 on an fairly ordinary bicycle lighting system (compared to automotive illumination) - give me 3000 lumens on high beam!!!

    I would in a heartbeat spend $400 purchasing a decent electrical generation system from somebody (or company) that produced a reasonably powerful, reliable and warranty backed accessory attachment to the SickBikeParts jackshaft kit, to give me enough lumens (at least 1000 of the little critters) for safe navigation and good forward vision at night in areas with no street lights.
  4. loquin

    loquin Active Member


    An automotive level output is huge overkill for a Motorized Bike. An automotive headlight has to provide you with enough light to see objects far enough ahead to stop, when you're traveling at freeway speeds... 70 MPH.

    The amount of braking energy needed to stop a vehicle is proportional to the square of the speed. And, the amount of lighting needed is dependent upon the square of the distance. So, all other things being equal, you need to have 4 times as much braking distance to stop at twice the speed, and this means that you need 16 times more lighting power to be able to see an object in time to stop in time at 70 mph as you do at 35 mph.

    So, 3000 lumens at 70 is equivalent to 188 lumens at 35.

    The upshot of this is that you really do NOT need 200 watts (which,when you consider inefficiencies of generating electricity, is an appreciable portion of our small engine's total output) of electrical power for lighting for motorized bikes. Given today's LED technology, a 20W generator would provide more than enough power for lighting at 35mph, AND have enough left over for LED taillights, brake lights, and to keep a battery charged for a horn and LED turnsignals.
    Last edited: Sep 21, 2009
  5. augidog

    augidog New Member

    correct, lou...we can scale things down a bit, and without sacrificing our daylight needs.

    i won't bore anyone with talk of lumens (because i'm clueless) but locally we rely on a single auto foglamp/driving-light (H3 35-55W) for plenty of nitetime illumination & extreme daylight visibility. we buy them in pairs on the 'bay & split the cost. finish it off with a $3 10W red clearance light for a pretty safe system.

    after a ton of configs, i've personally settled on a dual 21W headlight and a 36- LED "1157" motorcycle-size taillight. i can see everything i need to at nite @ 30mph, and the reflector-headlight really sparkles during the day.

    but i still have to remember to keep the batteries topped, so anyone comes up with onboard-charging i can use, i'm buying it.
    Last edited: Sep 21, 2009
  6. Fabian

    Fabian Well-Known Member

    I've tried a 400 lumen led headlight and it was a complete waste of time.

    Zooming down a steep hill with winding curves at night and rain added to the mix you want a good 200 meters of full illumination, like your car headlights on high beam.
    Add a decent sized trailer pushing you from behind and you want all the forward light projection you can get your hands on, especially if riding in a forrested area with wild animals feeding just off the edge of the road.
    Getting light reflection from their eyes (at a long distance) gives plently of warning to avoid potential disaster as has nearly happened to me a few times with the useless bicycle lights available for reasonable cost - sure you can get more powerful lighting systems, but i'm not prepared to pay in excess of $500 for a bicycle lighting system that can't even get close to automotive headlights.

    Two 100 watt driving lights (for high beam) is already 200 watts and we haven't takin into consideration, front and rear turn signals, brake lights for the motorised pushbike and if you have a trailer, you will need another set of rear turn signals, brake lights

    188 lumens - please - that's a complete joke.
    1000 lumens is where your starting point needs to be on low beam, then add all the other lighting systems into the mix.

  7. Fabian

    Fabian Well-Known Member

    Been doing some more thinking about setting up a proper electrical generator on our motorised pushbikes.

    This link lists some good permanant magnet electric motors that could be used as generators and are relatively light and fits the bill for a minimum of 200 watts power generation.
    The highest 24volt motor draws 350 watts - perfect and exactly what i need; can always step down the voltage to 12 volts.


    Been looking over the jackshaft system and a perfect location for power take-off would be the 17 tooth sprocket recieving power from the Chinese motor's output shaft.
    My concept would be to have another hub made with dual sided 17 tooth sprockets on the same hub.
    If you have a SickBikeParts Jackshaft system, (any person who uses their motorised bicycle as regular transportation would have one fitted) look at the 17 tooth sprocket and imagine another sprocket attached to the opposite side of the hub.
    It would not cause any interference issues with the chain drive system.
    The 24 volt DC electric motor could reside below the frame space where the top tube and the seat post tube intersect and have a chain drive running to the motor at an appropriate gearing ratio, determined by the size of electric motor sprocket.

    On my bike (full size frame), i have plenty of space to fit the motor and mounting brackets - the installation looks to be quite easy.
    24 volts DC could be stepped down to 13.5 volts DC to charge a small lead acid battery to provide power output to the electric motor as an auxillary assist to the Chinese 2-stroke engine when requiring a bit of extra oomph when going up hills or even as an electric starter motor - that's a tantalising option.

    The 350 watt motor only weighs 6 pounds or approx 2.5 kilos.

    I'm past the point of thinking about it - it's onto the design stage of setting up the mounts when i purchase the electric motor and getting a custom made 17 tooth sprocket manufactured.

    Now we are talking about some REAL LUMENS and ELECTRIC START and AUXILLAY POWER FEED to the Chinese 2-stroke motor.

  8. Fabian

    Fabian Well-Known Member

  9. loquin

    loquin Active Member

    350 watts is half a horsepower, Fabian... and when you consider that to get 350 electrical watts out of a generator, you're going to need to provide quite a bit more engine power than that, as small generators aren't that efficient. So, count on at least 3/4 horsepower engine power loss to drive a generator of that size.
    Last edited: Oct 3, 2009
  10. machiasmort

    machiasmort Active Member

    Interesting point Lou and something to consider in the equation...

    You guy's are on the right track and that's why I'll share an idea with you. That and because you sound pretty serious!...

    I've been thinking about using a PM blower motor from a car. The motor that mounts to the squirel cage and brings you heat. Can probably get one a the Junkyard for $10. Just make sure it's PM and not brushed! All I ask is that somebody PM me if it works!
  11. 210061741

    210061741 Guest

    Well now this is a very interesting concept.
    Working on a Jackshaft kit design lately.
    I'll have to see if we can incorporate this without loosing too much HP.
    Hope you guys post some more great suggestions for the Jackshaft.
  12. professor

    professor Active Member

    I just went downstairs to the laboratory (garage), clamped a 12volt cooling fan motor (from the Mustang inventory), spun it with my drill (2250 rpm) with a spare headlamp for the Mustang.
    At full speed, the light was vary bright (forgot to check voltage output) - so much so that the camera blacked out everything but the light. Here is a pic at 1/2 speed or so:


    This bulb was a hi/low one. There really wasn't much resistance to my hand holding the drill from torque reactiononce I got it to speed.
    Your challenge would be to detirimine what rpm (oh, I forgot, aren't you the guy who made a speedometer into a tach?) to gear the motor to at the rpm you use for normal use- because the bulb will blow out if you give it too much juice (rpm).
    Forget using it for starting. The cool thing is that you would not need a battery at all.
  13. machiasmort

    machiasmort Active Member


    That appears to be a cooling fan motor, (goes infront of radiator), please correct me if I'm wrong? Believe me, we appreciate your bench test!

    A blower motor that heats the cab of a vehicle is smaller (lighter) and would be even more efficient (lower rpm)... A cooling fan motor would generate more power, I guess it depends on what you need?

    I believe, but am not sure, you can simply put a resister on the hot line to only allow a limited amount of volt through the line (eliminating spikes), caused by varried rpms.
  14. professor

    professor Active Member

    Back downstairs to learn voltage-
    9.8 while running the headlamp, 12 something with it off (same speed). Adding a tail light dropped voltage to 9.6 or so with the big lamp still on.
    Therefore, the more load you apply- the less voltage you get.
    More rpm needed?
    Set that properly and you have a winner.
  15. machiasmort

    machiasmort Active Member

    Bulbs add resistance like a resister! LOL! Took me years to understand! I still don't understand motor phasing and how to wire the coils within. Once I do, I'll be able to make a dummies guide for making your own generator. Bridge rectifiers to make the voltage dc are also confusing to me.

    All said, I'm not sure that more rpms would be the answer on that motor as per our bikes? If you listen to a cooling fan run, they really whiz compared to a blower motor. This leads me to be strongly suspicious that the blower motor will produce higher V's at lower RPM's.

    The thing we have going for us is that lights are forgiving of voltage!!!
  16. loquin

    loquin Active Member

    A permanent magnet DC motor can be treated as a voltage source in series with a resistor. The smaller the wire used in the motor, the higher the resistance of the wire, and the greater the resistance of that 'series' resistor.

    When you draw current from the generator, the greater the current, the greater the voltage loss across the internal series resistance. Adding the tail light increases the current drawn from the generator, and when it did, the the voltage across the internal resistance increased as well. That, in turn reduces the available voltage to the load.

    You can calculate the internal resistance with three simple measurements. First, at a fixed generator RPM, measure the voltage output from the generator, with no bulb or headlight connected. Then, connect the headlight, and take the same voltage measurement, across the headlight terminals. Finally, at the same RPM, measure the DC current through the headlamp. To calculate the internal resistance of the motor-generator, in ohms, take the the difference between the two voltages, and divide that by the lamp current in amps.

    A 55W headlight SHOULD pull about 4.5 amps. If we assume that that was the actual measured current with your test, (and with the voltages you mention, above) the internal resistance would be

    (12V-9.8V) / 4.5A = 0.489 Ohm

    The power loss would be

    4.5A * (12-9.8) = 9.9 W

    The headlight power would be

    9.8V * 4.5A = 44.1 W

    The power lost divided by the total is 9.9 / 55, or 18%

    You could increase the RPMs of the motor, so that it produces about 20% more voltage, unloaded, to compensate for the power lost to heat with the series resistance of the wire. You can also increase the RPM to compensate for increased current load. But, there comes a point where the internal power loss due to heat will slag the motor/generator, or the increased voltage would short out windings in the motor.
    Last edited: Oct 4, 2009
  17. professor

    professor Active Member

    Very good explaination Lou (I want to think about it some more when it isn't bed time).
    Mort- I think the bigger motor woul be more forgiving of wrecking it.
    I remember messing with a blower motor and it seemed to spin about the same rate as the cooling fan when they both were run on 12v
    Actually, what you guys need (I never ride at night) is just to upscale and refine the drive of one of those tiny DC generators that rub on the tire- the only thing is that unless you run a battery, when you slow down or stop- the lights go out.
  18. professor

    professor Active Member

    One other thing- when I spun the motor at 2250. I got 12 something volts. Does this mean that, used as a motor, the thing would spin at a little more than that? What would it spin @ 14.5 volts (alternator output setting)?

    Car systems run off the alternator (in my experience, once running, the alternator supplies ALL the electrical energy to run everything on the car- it will burn out if the load becomes too great -( Go real small on that winch for your 4x4!).
  19. 210061741

    210061741 Guest

    Good work here.
    This info will be invaluble.
    Test on and report results.
  20. machiasmort

    machiasmort Active Member

    You just took my idea!!! You said it and didn't realize it!

    Mount that motor under the belly of a rear bike rack, friction drive it off of the tire and charge a battery.

    How would I construct a diode to keep the current flowing one way? When you'd stop, the motor would want to run w/o something there to stop the current from the battery you were charging (on top of the rack)!