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Need help creating a gasoline electric bike

  1. Apr 1, 2015 #1

    I have been thinking about creating a Gasoline electric bike. The reason being is that good batteries are very expensive. In fact more expensive than a good quality gasoline motor. I don't want a direct drive gasoline motor do to it being less stealthy and more cumbersome running a second chain to the rear hub.

    Let me start with the motor first. It is a mid mount electric motor (mounts near the pedals) that is rated for 48v/750watts. I know I need a gasoline engine and some type of generator that outputs 48v and roughly 750w. the question is where can I find this device and what exactly is it called? Searches for "48v generators" yields cumbersome devices that cannot be mounted on a bike. Can I use a 48v dc motor like this and connect the shaft of that motor to the gas engine, using a belt and pulleys? If you spin the shaft on an electric motor, will it generate the right voltage, or am I spinning my wheels (ha ha)??
    Description of potential DC generator below

    http://www.aliexpress.com/item/Electric-Scooter-Motor-48VDC-600W-DC-Motor-with-CE-appliance/318755784.html [Broken]

    Mid mount motor:
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Apr 1, 2015 #2

    Vanadium 50

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    Why do you think a gasoline engine, a generator and a motor will be less cumbersome and more stealthy than just a gasoline engine?
  4. Apr 2, 2015 #3
    Hobbyking sell many large electric brushless outrunners such as this one http://www.hobbyking.com/hobbyking/...oMax_80cc_Size_Brushless_Outrunner_Motor.html
    however if you want to use a motor like that you have to spend about 60-$200 more buying a speed controller, furthermore hobby king sell very cheap good lithium polymore batteries but you would have to have a combination of series/parallel to have the power you want.

    Many people simply choose gas over electric bikes because electric bikes are much more expensive. Here is a complete gas kit for a bycicle http://www.ebay.com/itm/New-Engine-...0cc-/251687352420?hash=item3a99bc3864&vxp=mtr

    I made 2 bycicle engine kits from the gas kit above and I can say that they work well and they are worth it but they are crude and cheaply made.

    Lastly I would not suggest the motor that you put a url for, it looks like it is brushed and I do not believe that you will be able to achieve speeds greater than 8 mph with that motor, I think you will be able to achieve speeds of around 50mph with the electric motor I posted above and you will be able to achieve around 30mph with the gas engine I posted.
  5. Apr 4, 2015 #4

    Thanks for responding. I don't want to go pure electric for the limited range. I have seen that 80cc motor on youtube and the two things that make me hesistate are its size and its noise. With the small honda, I envision placing it and the dc generator in an enclosed, almost sound proof box on the rear bike rack, and having just a wire running to the mid mount motor.

    Connecting the engine to the electric motor that you linked would produce the necessary voltage and watts? And the speed controller would regulate the dc generator and I would be all set?
  6. Apr 5, 2015 #5


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    You are speaking as though you intend your petrol-electric drive to not include storage batteries. Do you plan to speed up the engine revs when faced with a steep incline?
  7. Apr 5, 2015 #6
    That is correct. No battery storage. I was planning to include a throttle for the engine
  8. Apr 6, 2015 #7
    you speak strange conditions friend; do you want your bike to be a hybrid? Using a gas engine's magnetos to provide power to an electric motor on a bike is unrealistic. If you need power for that large motor simply get around 4-6 turnigy 11.1volt batteries in series and a few in parrell that should cost less than $100. However a pulse modulating speed controller used for brushless electric motors rated at around that many amps would be a little pricey. I am not sure if I answered your question so let me know please.
  9. Apr 6, 2015 #8


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    Staff: Mentor

    @Bikester I notice in your OP you have a link to a product at aliexpress.com
    That site can be a risky place for international buyers, among their thousands of honest sellers are some scam artists. Regardless of what you might be told, the only protection you have is that offered by your credit card on purchases.
  10. Apr 7, 2015 #9
    To add more to that that motor is not going to have enough rpm, torque or HP to drive a bike. The motor the OP posted is a brushed motor, he should get a brushless motor instead.
  11. Apr 8, 2015 #10

    Let me try to explain myself more clearly. Here are the compenents of the drivetrain. Petrol engine-> dc generator->dc motor attached to the crank (aka the 'mid mount motor'). So there are three compenents I need to buy and spec.
    Lets start with the petrol engine

    The honda GX25 produces about 650w at 6000 rpms. I can go up in size if necessary to spin the DC generator

    The DC generator has to output 48v. If I hook up a pulley to a DC motor and spin it, it should generate power, at least that is what I read. That is why I selected the DC motor I did. I did not consider brushless vs non-brushless. I will look into that

    Mid mount motor.
    This dc motor will be connected to the bike chain to drive the bike. This motor will be wired to DC generator.
  12. Apr 10, 2015 #11
    It is interesting that you are using a gasoline engine to output power for an electric motor. I do not have much experience in that area, I think you should ask around at rc hobby forums instead like rcgroups.com

    This is going to be difficult, from my experience with motorized bikes finding a mount to the wheel that is not going to break the spokes over time will be expensive, furthermore mounting the gas engine and electric motor on a bike will most likely lead to incompatibality issues because bike frames come in a variety of ranges. The honda engine will also cause vibration on the bike frame which is not good for the bike. So make sure you make the correct measurements and have the proper equipment to mount the attachments on the bike

    If I were you I would go all electric instead, it should cost less than $400 in high end parts to make a very nice powerful electric bike.

    If you want to go all electric and need a parts list I can help you with that friend.
  13. Apr 11, 2015 #12
    I am going to mount the gasoline motor and the DC generator to a block of wood that will be secured on the rear bike rack. I will then run a power cord to the mid mount electric motor that is local at the crank (between the pedals)
  14. Apr 13, 2015 #13
    Have fun with the project friend, I can imagine that the result will be very original and different.
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