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How to make a mini generator??

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  • How to make a mini generator??

    I would like to make a small generator able to give about 16volts @ 10amps, and power it with a small constant speed model airoplane engin, would this be possible??

  • #2
    I doubt your plane engine will be able to provide the power necessary. To get 16V @ 10A (1600W) you would need about 3.5HP (standard lawnmower engine) and your plane engine is probably only about 1HP or so.

    Once you get a decent engine, an alternator from a car will work fine...Most alternators should produce about 15V at light load, which should be close enough to your 16V...
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    • #3
      Why make one when you could get a electric motor to use as a genarator.
      Sure you could get the pefect size then

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      • #4
        I dont know what you are trying to do with this, but if you are going to use it @ home, why not just get a 120-->12v transformer, and some diodes to make a full wave rectifier. This will give you a large amount of current to play with depending on the size of the transformer that you can scrounge up. Remember that the 120v that you read from the wall socket is the RMS voltage so after you rectify it on the 12v end you will end up with about 16.4 volts DC.

        just throwing out a few more options.
        Monger
        ICQ-7207702
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        • #5
          Originally posted by Aaron Cake:
          <STRONG> To get 16V @ 10A (1600W) you would need about 3.5HP (standard lawnmower engine) and your plane engine is probably only about 1HP or so.
          </STRONG>
          Isn't 16v @ 10A is 160W? This is 0.2 HP...
          Enjoint life!

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          • #6
            Yeah, its 160watts, and so, therefor, would a small model plane engin be big enough??

            I dont know what you are trying to do with this, but if you are going to use it @ home, why not just get a 120--&gt;12v transformer.
            well, I actually wanted it to power my computer..
            Like when we go on camping trips and stuff..

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            • #7
              Originally posted by SkinnyBoy:
              <STRONG>Yeah, its 160watts, and so, therefor, would a small model plane engin be big enough??

              well, I actually wanted it to power my computer..
              Like when we go on camping trips and stuff.. </STRONG>
              Yaa I was wondering about that too, last I checked 10 times 10 was 100 and not 1000. Yes a plane engine would be big enough to do just that. 1 horse power is about 746 watts. I know an OS FP40 is about 1/2 of a horse. The alternator method would probably work great, assuming that you can build the mechanical parts. It would probably be eaiser to search the used adds for a generator. And it would probably be a lot less noise. Personally, for camping I would buy big batteries and store them in the trunka and charge them on the driving part of the trip before I would try something like this.
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              • #8
                Ahhhh, OS engines. That takes me back. I have a 40 and a 45 somewhere. Bute why would you want to use one? They're not the easiest engines to start, they spray fuel everywhere, they're loud, and the fuel isn't exactly cheap. I'm not sure, but I think I remember paying something like $15/gallon for that glow fuel.
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                • #9
                  The engin I have is a glow chief 35, and I have only succedded in getting it running 3 times..
                  The fuel cost my $10 for 1 litre..

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                  • #10
                    I wanted to build something like that years ago when I was involved in R/C. I wanted to build a gas powered R/C tank and since the transmission parts, clutches, gear boxes with reverse were very hard to fabricate in my workshop, I thought that I could use an internal combustion engine to turn a DC motor for electric power generation and two separate motors (through two separate speed controllers) to drive the tracks. It is feasible and I found out later that a lot of people have already done it in R/C submarines and to charge the batteries while the ship is surfaced. I also use it in one of my .60 size R/C helis to power an onboard video camera without the use of a very big (heavy) battery pack.
                    However, for this paricular use I don't think it will be practical because:
                    1) R/C engines (4 strokes too) are VERY noisy (even with a big muffler)
                    2) Dirty
                    3) Difficult to start (unless you carry a heavy electric starter - which means another 12V battery)
                    4) Need a 1.5 V battery for the glow plug, during starts
                    5) You guys already mentioned that glow fuel is expensive
                    6) A static airplane engine needs to have prop on it's crankshaft to be properly cooled. Without it, it will overheat very fast, lean, overspeed, be inconsistent, unreliable - not to mention that it will be destroyed in a few minutes running time (loose compretion, bearing failure etc).
                    7) You have to find a way to adjust the throttle as the load will not be constant (it depents on the current you draw).

                    The only way you could (but shouldn't after all)do it is with a R/C car engine that has a pull starter at the back of the crankcase ,a head with big cooling fins and a small fan somewhere on the crankshaft blowing air on it.
                    Of course all the other technical problems are still there for you.

                    I hope I convinced you Skinnyboy, because this is way out of the subject of this forum.

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                    • #11
                      Originally posted by Dima:
                      <STRONG>
                      Isn't 16v @ 10A is 160W? This is 0.2 HP... </STRONG>
                      Yep, it is. I'm an idiot.

                      Anyway, now that I've demonstrated my stunning lack of ability in mathematics, I will talk about the generator....There are several problems with this:

                      1. Engine is hard to start...I've played with these engines before, and it usually takes me a few minutes to get one going...Thi smay or may not be a problem.

                      2. Weird fuel. Won't run on regular gas...Might run on deisel once it is warmed up, but you will need to mix in oil.

                      3. High RPM. These engines run extremely fast to make so much power from such a small size. You will need extreme gearing to bring it down to a useable 3000RPM or so.

                      With that said, I'm not sure if a 0.5 HP engine will be able to drive an alternator producing 10A...The inefficiencies of the alternator may be too much for it...
                      Player: Pentium 166MMX, Amptron 598LMR MB w/onboard Sound, Video, LAN, 10.2 Gig Fujitsu Laptop HD, Arise 865 DC-DC Converter, Lexan Case, Custom Software w/Voice Interface, MS Access Based Playlists
                      Car: 1986 Mazda RX-7 Turbo (highly modded), 1978 RX-7 Beater (Dead, parting out), 2001 Honda Insight
                      "If one more body-kitted, cut-spring-lowered, farty-exhausted Civic revs on me at an intersection, I swear I'm going to get out of my car and cram their ridiculous double-decker aluminium wing firmly up their rump."

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                      • #12
                        Skinnyboy,

                        Sounds like a neat idea, how about this:

                        Use some high RPM high load DC motor. Like a RC car motor. If you can find a DC motor spec'd for the gas motor's RPM, great. If not the gearing for that high of RPM will need to be pretty good, although maybe you can use a gearbox out of a gas RC car? Use a flexible coupler for the DC motor shaft connection.

                        Hook the leads of the DC motor to a gel cell battery through a switch.

                        Use a SMPS PWM IC to output a PWM signal to a RC servo motor. Connect this servo to the throttle control. Set the throttle to only go down to idle, and you'll also need to limit the max RPM somehow I'd guess.

                        When you need to start it flip the switch. This will use the gel cell to start the motor, and when it gets going, it will self regulate with the PWM IC.

                        The DC motor efficiencies should be pretty good I'd think, although I'd shoot for 50%. You'll probably need to heat sink the motor, maybe put a fan on it. A fan would be great for the gas motor, as it is used to moving air across it's fins. Also you'll need to find the right DC motor winding for your application.

                        You could even come up with a glow plug circuit, and auto start/stop.

                        Just some crazy ideas, who knows if any of them will work..

                        Presslab

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                        • #13
                          Originally posted by SkinnyBoy:
                          <STRONG>I would like to make a small generator able to give about 16volts @ 10amps, and power it with a small constant speed model airoplane engin, would this be possible??</STRONG>
                          Skinny,do you want this for your PSU with linear regulators? That's why u need 16v?
                          Enjoint life!

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                          • #14
                            Aaron is right,
                            motors, designed and winded to work like motors are not the most efficient alternators. Considering that a stock automotive alternator, that was designed to be an alternator, has an efficiency somewhere between 40-60%... you get the picture.
                            Presslab,
                            Do you think that the most powerfull RC motor has the torque to crank an engine through the gearbox that is needed to reduce the engine's RPM? Have you ever seen how big the motor of a starter is?
                            And yes, diesel is an (cheaper) alternative to glow fuel, if you can find a conversion kit for your engine, and you loose the need for glow plugs and their power supply.

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                            • #15
                              Presslab,
                              Do you think that the most powerfull RC motor has the torque to crank an engine through the gearbox that is needed to reduce the engine's RPM? Have you ever seen how big the motor of a starter is?
                              How much torque will it take to turn over a small engine? I don't really know for sure. I have seen how big starter motors are, I own one.

                              The better RC car motors can put out 1.5in/lb of torque and will spin at 20,000rpm. RC gas engines will spin at 10,000 to 30,000 rpm. So a gearbox might not be necessary. It would be easy to measure the starting torque of a gas engine.

                              A brushless motor would probably work better for this application but it is more complicated to work with.

                              Remember those vehicles that had the starter/generator setup? That's what I'm thinking of. A RC car motor might not be the best motor for the application though.

                              Presslab

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