gas/electric bicycle?

Discussion in 'Introduce Yourself' started by Thomson85, Nov 28, 2008.

  1. Thomson85

    Thomson85 New Member

    Ok so I was going to buy one of those 2-stroke china 50cc engines, but I want something I know that will be dependable. So I am going to pick myself up a weed wacker/chainsaw/or leaf blower engine and using it instead. But I also had this idea, and am not sure if anyone else has thought about this.

    Taking a small generator... I found one on craigslist for $60, and have it power an electric motor that would run the bike. I think this would be interesting as the gas generator would practically be at idle (gas saver) and everyone knows the acceleration benefits of having an electric engine (they're FAST).

    Would this be practical? I think it's kinda like having the power of an electric motor with the benifits of not being dependent on batteries or charging. The fuel consumption should remain minimal as the load of an appropriate motor shouldnt drain the gas generator and should produce fast acceleration from a dead stop. Not to mention as far as "red-lining" an electric motor is practical not to blow the motor apposed to a gas engine!

    Any comments?

    Don't get me wrong this will most likely be a project of the future for me, for now I will just use a weed wacker motor.

  2. seanhan

    seanhan Member

    Sounds cool but you might need 2 batterys, one to charge and one too run on.
    and have a selector switch to switch from one to another.
    also you will need a charger to run between the genarator and batt..
    not sure but the weight might become a prob.
    thats going to require a lot of real estate to mount all that stuff.
    but I was reading about the Chevy Volt electric car, it will have a small engine too only charge not propell the car.
    Sounds like one heck of a project.. but you might be on too somthing !!!
  3. srdavo

    srdavo Active Member

    seems like someone here has attemped to generate power for their electric bike...?
    anyone remember? link, please.....

    here's a fun thread about homebuilt motored bikes...enjoy

    welcome to MBc.
  4. Thomson85

    Thomson85 New Member

    2 batteries? No I dont think so... Im not speaking of a rechargable electric motor, I mean one you would plug into a regular house outlet.

    So basically on a rear mounted rack you would first have the gas generator (not big at all with only 1 outlet... ill look for a pic), then after that you would have the electric motor from either a weed eater, leaf/snow blower (whatever size you desire).

    There would be no need for batteries, just plug the engine into the generator, start the generator and the electric engine will run....

    Or am I missing something? The generator will provide enough electricity to power the electric motor, meaning it should be able to do so at idle or just above idle, meaning major savings in gas....

    convenience of a gas engine (no recharging or distance restrictions) with the speed of an electric motor (Fast with LOTS of torque)
  5. Thomson85

    Thomson85 New Member

    Last edited by a moderator: Nov 29, 2008
  6. thescooterguy

    thescooterguy Member

    what powers the generator ? wouldn't it be best to have gas motor to run bike and charge battery for electric drive then switch back and forth like the hybrid car ? i have toyed with this idea but its just the wiring that gets me . i would use a gas motor with an e start to send power to batteries .then a hub type eletric motor on front or back wheel .
  7. Thomson85

    Thomson85 New Member

    Read above it's a gasoline generator... you know the kind people buy for natural disasters or construction companies... So it would be like this.... I have said it 2 times already!

    It's a 4-stroke gasoline engine generator, that powers the electric motor! So the electric motor is PLUGGED into the gasoline engine generator!

    Gasoline engine generator > Provides constant power to electric motor. Using less gas to produce electricity to the motor. No charging, quick throttle response.

  8. thescooterguy

    thescooterguy Member

    got it now , came in late , sounds good
  9. SimpleSimon

    SimpleSimon Active Member

    There has been substantial discussion of the idea in several threads here, and at least two members have built gas/electric hybrid drive vehicles - a bike and a delta trike. Gas powered generators (even small ones of 1 KW or so) have substantial weights and physical footprints. The smallest I have seen was 36 lbs and is about 14" x 20" x 16" high. Most such built commercially are designed to deliver AC, with a small capability to provide DC (usually around 6-10 amps at 12 volts), so you'd likely have some electrical work to do to get substantial amounts of DC power.

    Acceleration using an electrical motor as the prime mover of the bike requires fairly high draws of power, which represents a big demand surge. In the absence of a battery to serve as a reserve current source to meet peak demands, you'd likely blow the surge protector on your generator repeatedly.

    Don't get me wrong - I'm no electrical engineer, and mayhap you can make your idea work. Good luck, and keep us posted on your efforts.
  10. Thomson85

    Thomson85 New Member

    I wouldnt need to use DC power as I can just use a standard 120v electric motor... like a electric weed eater (that you plug into you house 120V). I wouldn't imagine it being a little past idle to power something such as a weed wacker motor (electric).

    Yes, weight seems like it could be an issue, and that's why distributing it through out the bike would be essential and preferable centered. That's why this re-vised drawing I would move the electric motor to where a lot of people place their 2-stroke engines
    Last edited by a moderator: Nov 29, 2008
  11. Mountainman

    Mountainman Active Member

    good luck with this project

    most of us have thought about this same THING one time or another

    SimpleSimon is pretty up regarding this matter
    I would take note of his comments made

    once you are up and running -- we are looking forward to seeing you

    ride that THING
  12. JinbaIttai

    JinbaIttai Member

    Interesting project. I hope this works. Will it really be more efficient on the wallet than simply going gas-powered or simply going electric? IMHO it could be, but only if you manage to get the generator to run at the RPM and load where it's at the best spot for $$$ efficiency, and then do the same for the motor. The Chevy Volt team had the resources to make sure they chose the ideal generator and motor combination to have made it happen.

    If you take a typical off the shelf weed wacker, and happen to pair it to a typical light weight AC generator, you're not matching efficiencies, you're guessing. I believe you will not get any better gas mileage than just buying a Chinese 50cc motor, or an ebike.

    Here's the math:

    This is probably similar to the generator you are considering:
    And perhaps this is a weed wacker you might also consider:
    Per the amperage ratings, a smaller generator will not power this weed wacker.

    We don't really know if the weed wacker is capable of reliably putting out the torque needed to propel a bike up to 20 mph (or higher). But let's just assume it will for the sake of demonstration.

    The weed wacker is rated at 7.2 amps.
    The generator can put out a max of 8 amps fully loaded. This generator will not simply be idling along.

    Since it will consume .66 gallons over 8 hours at half load, we're really looking at burning approximately .66 gallons over 4 hours fully loaded.
    This works out to .165 gallons per hour.

    Assuming the weed wacker is actually capable of getting you to 20mph, and being able to hold you there for 4 hours, the math comes out to 121 miles per gallon.

    The weed wacker spins at 7400 RPM. You're going to have to build a transmission for it. Good luck with that.

    The generator above weighs 28lbs, plus the weight of gas. The weed wacker weighs 6.9lbs, minus all the extra **** you can remove and toss out. Plus the weight of the transmission and miscellaneous stuff. say 35lbs total.

    A typical hub-motor electric bike + battery kit adds about 20lbs to a bike.
    A typical internal combustion bike kit also adds about 20lbs.
    So for a setup that weighs 15 lbs more, you get basically the same (or worse) gas mileage as a 50cc.

    Again, Chevy made it happen with the Volt, I think you could too, but not with just any motor and generator. I made a lot of assumptions, and I encourage you to prove my theory wrong by example!:biggrin:
  13. Thomson85

    Thomson85 New Member

    No, thank you for bringing up such examples! I do appreciate them. Now, I am not necessarily looking for a more fuel effecient motored bike.

    Basically I've seen a lot of these electric bikes, and they haul a** but have a very limited frame. So I figured that having an electric motor hooked up to a generator might give me the power of an electric engine, with the convienance of running off gas.

    So in my opinion, just getting the same MPG but with the power of an electric motor would be amazing. I'm sure that weed wacker motor would propel the bike to 35+ MPH

    But ultimately it's all speculation until some one completes this! I will begin working on it within 6 months time, as I am currently in transition of jobs.

    And my first project will be a home made chain driven bicycle using a weed wacker/chainsaw/ or leaf blower engine.

    I love this site and love that all of you put in your honest input on such projects like the one I have proposed... thank you!