DIY Miniature Gasoline Generator

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About: Being a science student i love to indulge in projects related to engineering as i love to learn things practically...

In this insctrutale, I am going to built a miniature DC generator that is powered by a four stroke gasoline engine. It can be a great tool for off grid power or charging your car battery when you are miles away from a power socket as the whole unit is quiet compact and wieghts arround 8 kg.

The idea is to built a small gasoline powered generator thats able to charge batteries or can power appliances using an inverter. To make it possible what we have got is a small four stroke 36cc Gasoile Engine. These are compact engines that are usually built to power tools such as a leaf blower or a string trimmer. Luckily we have got one in brand new condition and thats how we got through this project.

Ready set built....

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Step 1: Tools and Materials

The steps to this project might involve a bunch of tools but you can do the same with a bunch of other tools, inshort the goal is to get the job done so no comphrensive list of tools.

For the material and stuff , you are going to need the following:

  • A small Gasoline Powered Engine
  • An old hoverboard motor
  • chain spockets
  • Chain
  • Metal tubes and sheet
  • Nut and bolts
  • Aluminium spacers
  • A rectifier unit
  • Rubber pads
  • Fuel bottle. etc

Step 2: Selecting the Generator

To convert the mechanical energy into electrical energy we are going to need a permanent magnet motor. Now brushed motors are a simple way to go but they are most likely to get their brushes weared out soon and doest seems to offer a good efficiency. So, we have to go with a brushless motor to eliminate this problem.

One such motor is used in hoverboards, yes each wheel of a hoverboard is a permanent magnet brushless motor. With the outer casing containing the magnets that spins across the coils, so as you give the motor a quick spin it proudces electricity.

Now the good thing about this motor is that its highly efficient and it can produce a good range of voltage on a relatively slow RPM. To be accurate it produces 40 volts as you spin the motor at nearly 700 RPM. But the down side is that the electrical energy it produces is a three phase altyernating current which we have to convert into direct current.

Now the first thing we did is to extract the motor out of the hoverboard which is just a matter of removing the casing and unscrew the motor coupling.

Once we get our hands on the motor, we dismentalled the motor and removed the tyre which is no more needed. To drive the motor what we are going to do is to attach a spocket to the motor casing using a couple of 6mm nutbolts tighten across the motor casing.

Once we get that done, the motor is assembled and is ready to be used.

Step 3: Centrifugal Clutch

These engines comes with a centrifugal clutch assembly which allows the engine to engage to the external load when the throttle is pulled. Since I am planing to use this engine to experriment with fuel other than gasoline. So to make the tuning process easier I have attached a centrifugal clutch assembly. You can skip this step if you are planing to run it on gasoline only.

To drive the motor I have used a smaller chain spocket having 7 teeths.

Step 4: Framing

For holding everything together we are going to use 1 inch square metal tubing. A pair of tubes run across the length of the unit and holds everything with the help of 4mm thick metal sheet and a bunch of spacers as shown.

Step 5: Assmebling the Frame

The metal tubes are first attached to the enigne using a couple of allen bolts. Next the spacers are added with the metal plate in its place. Now with everything tightned up its time to mount the motor.

Step 6: Mounting the Motor

The motor is mounted to the metal plate using its original coupling that comes with the hoverboard. The chain is placed across both the spockets and the coupling is then tightened up.

Step 7: Base Mount

As we finished mounting the motor I have realized that the weight of the whole unit is shifted towards the front of the unit causing it to fall over.

To get the CG within the base frame I have added two metal strips on either ends with four rubber feets mounted across each corner. The gives the whole frame a nice stablity and stops the unit to move here and there due to viberation.

Next we have added a fuel bottle to the bottom of the frame using a bunch of cable ties. The fuel tubes are then connected to the carbeurator.

Step 8: Rectifier Unit

As we have discussed earlier, our generator is going to produce a three phase alternating current. Now to make it useful we have to rectify it to convert it into more useful direct current.

Upto thsi point the unit seems like a great built so to keep up the great work what I have decided to do is to built the rectifier unit using customized PCBs. Now that might sounds complicated and and expensive job but with JLCPCB you can get you hands on customized PCBs at a great price and the quality is just unmatchable.

So To order The PCBs I have uploaded the gerber files and after going through a bunch of options, the order is complete. And thats how simple is that, so have a look at their website for some great quality PCBs at an outstanding price.

Project files:

https://easyeda.com/diyking/diy-three-phase-rectif...

https://easyeda.com/editor#id=|31478ddb75014415afa...

Gerber Files Bill of Material and schematic:

https://drive.google.com/open?id=13J0mqBVomIx8cV9E...

Step 9: Assembling the Rectifier Unit

We have recieved the PCBs within just a week and the quality is flawless. Next we gathered all the components and witht that its just a matter of dropping all the compionents in place and sotter them.

With the rectifier unit ready its time to mount it on our generator and test it out.

Step 10: Final Results

With a couple of pulls on the kick starter the engine started and seems to run perfectly. As the speed of the engine is increased the centrifugal clutch engaged and started to spin the motor.

At nearly 40% throttle the generator produces nearly 36v and a total output of 250 watts which is quiet sufficient for unit this compact. Now this generator can be couplet with a buck/boost converter to power DC loads or to charge a battery. To power AC appliances, we need to connect the DC output to an inverter.

The generator wieghts around 8kg and can be a useful tool for charging your battery or powering you AC appliances when you are miles away from a power socket.

That was a fun project, will see you guys with the next one.

Regards.

DIY King

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    14 Discussions

    None
    PDM2

    Question 9 days ago on Step 10

    from whee did you buy the hoverboard? Are you planning to sell the rectifier board as a kit or fully assembled?

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    pixel tamer

    21 days ago

    Nice Video. The build sequence was well thought out. I was a little surprised that you didn't select an alternator from an automobile. The alternator should be easy to come by, and it uses the same principle of generating electricity. They usually have High current capability (60 to 120 Amps), and have a built in regulator for 12 volts dc suitable for charging a battery.

    4 replies
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    nic.bryan.73pixel tamer

    Reply 21 days ago

    I have to agree with you Pixel. An 80A sedan alternator from a junkyard probably costs about the same as the hoverboard, but doesn't need disassembled, has a built-in rectifier circuit, and operates at a much higher RPM (So flip the large and small gears.

    Also, the alternator comes with a mount better suited for tensioning the chain. It's what I'm intending to use for my steam-generator (Because I'm not worried about torque...I'll have more of that than I'll ever need...)

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    RaymondR6nic.bryan.73

    Reply 21 days ago

    A car alternator has one problem. It need a startup current to magnetize the rotor coil, so the stator can convert that field to electricity. You can prove this by spinning an alternator with no load and see that no voltage is generated. One solution is to replace the rotor coils with permanent magnets. This is what builders do to make a wind turbine. The use of a regular permanent magnet motor is ideal.

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    tytowerRaymondR6

    Reply 20 days ago

    Actually thats what the pilot/indicator/charge light does . On startup current is flowing through the field coil and the lamp to ground which excites the coil. Once current is produced the light charge is reversed and the light goes out.

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    nic.bryan.73RaymondR6

    Reply 20 days ago

    If it is being used to charge a battery, the battery can provide the starting current for the coil, correct? So you get the shaft up to speed, turn the starter to energize the coil, and it runs (Or disassemble it and put in the permanent magnets)

    Why don't they already use permanent magnets in them?

    None
    TimF10

    Tip 21 days ago

    I've thought about something similar but to use a car alternator ran off of the motor. Older GM vehicles had a "1 wire" setup with an internal voltage regulator. This could be hooked up to a car battery to charge the battery, or by hooking the alternator up to a battery and then using an inverter, you could get AC power out of it too.

    None
    tytower

    26 days ago

    I'd also refer you to these generator units that can be fitted to Honda and briggs & stratton second hand engines.
    https://www.aliexpress.com/item/32994050807.html?spm=a2g0o.detail.1000014.11.240b52aeIIjl4q&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.13338.128125.0&scm_id=1007.13338.128125.0&scm-url=1007.13338.128125.0&pvid=d5e977f4-81e1-4bfa-88c7-84ef41d03fa4

    Still need a rectifier board suitable to 3000w but if you are going to build one then may as well build big no?

    48Vgeneratorcoil.jpg
    1 reply
    None
    RaymondR6tytower

    Reply 21 days ago

    This works well because the rotor(attached to the shaft) has permanent magnets attached to the inner circumference. This also how the gas engine generates the spark energy to fire the cylinder.

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    RaymondR6

    21 days ago

    I like your article very much, although I don't need to build one, since I have a 2014 Ford Fusion Hybrid that does almost the same. The 2.0 liter gas engine generates electricity to charge the 400+ HVDC battery, which powers the traction motor inside the transaxle and moves the car. There is also a DC-DC converter to produce 12 VDC for all the accessories and charge up the small lead-acid battery. The same generator attached to the gas engine also starts the same engine by computer control when the main traction battery has a low charge. In the interior, I have 12 VDC outlets and one 120 VAC outlet, too, powered by that HVDC battery.

    So now anyone can see how this project is related to hybrids, and maybe motivate someone to convert a regular gas car to a small hybrid, using a large electric motor, a set of batteries, and this tiny gas engine charger. You cold get over 50 MPG. My Fusion Hybrid gets 54 MPG which is excellent for a 4,000 pound car.

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    WeliverGary

    21 days ago

    Very interesting project, Recycling is vitally important for our Environment!
    I have acquired a now good 1200W inverter from recycle (just plug it in to an accessory port) but seriously 250W, unfortunate will light 1 Lightbulb? And not start a car.
    The important thing is your thought process, your engineering and fabricating skills and you shared (OPEN SOURCE) and your computer skills (to make this fine and Awesome INSTRUCTABLE) plus you reused something and kept it out of a landfill!!! Thanks So Much!

    1 reply
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    nic.bryan.73WeliverGary

    Reply 21 days ago

    250W is actually a LOT of power (Average laptop is 80W on the charger, 30-50W running. LED lights are usually measured in quarter- or half-watts. At 12V (bucked down from 36) you've got 20A. That's more than any of your accessory outlets can handle without blowing a fuse. And is higher than the minimum needed to charge the car batteries. (This could full-charge an average starter battery in less than 5 hours. From DEAD. That is, not from too dead to start. From too dead to turn on a light))

    You have to take into account that most things used in camp power are designed to use very little power. Yeah, this thing won't power a microwave straight up (But neither will that 1200W inverter), but it'll run a crock-pot, or a GPS, or a phone charger, or even a small-area portable A/C unit (200Cubic Feet)

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    Josehf Murchison

    25 days ago

    Very nice I like the reuse.
    I watched the video twice and red the Instructable. I noticed after removing the circuit board from the hover board motor you didn't mention wiring the motor to a delta configuration. you might want to add that

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