Using a Nitro Engine as a power source

Discussion in 'Physics' started by MachineHum, Nov 22, 2014.

  1. MachineHum

    Thread Starter Member

    Nov 3, 2014
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    [​IMG]

    The idea is still very abstract...

    I'm looking into a small power source that I can use to power a robot. It's going to use a lot of juice... 12V at somewhere in between 20-50amps ... depending on how many actuators are going at once. If I was to pick up a Nitro engine and couple a DC motor to the shaft and use it as a generator...

    When I start loading the circuit obviously the mechanical resistance of the motor goes up, thus loading the nitro engine. At some point, the engine will stall. Does anyone know the best way to operate the system over the whole "load range"? The first thing that comes to my mind is some sort of dynamic transmission or gearbox...
     
  2. ISB123

    Well-Known Member

    May 21, 2014
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    I think that you wont be able to get 20A-50A.
     
  3. MachineHum

    Thread Starter Member

    Nov 3, 2014
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  4. BR-549

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    Sep 22, 2013
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    Interesting......an outdoor robot.

    Or man-cave robot on race-day.
     
  5. BR-549

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    Sep 22, 2013
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    If you use a manufactured generator or alternator......I believe you will have to do some serious down gearing.
    I have not looked.....maybe there are some high speed ones.
    A gearbox and generator would probably be to heavy and bulky.
    You might try experimenting with mounting high quality magnet(s) to the shaft and building your own stator around it.
    I have never worked with high rpm without a large gearbox.
    I am assuming that glow engine has relative high rpm.
     
  6. BR-549

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    Sep 22, 2013
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  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Large nitro engines probably have the power. They are available up to a few cubic inches. However, they are not very fuel efficient, the fuel is expensive. A 2-stroke like you show has a messy exhaust. They also have a relatively short usable life. A 4-stroke nitro engine is cleaner. If you want an I.C. engine, I suggest a 2-stroke gasoline or gasoline-nitro engine. Gasoline is cheaper and the gas-glo fuel eliminates the need for an ignition. Since weight is probably not a big issue, then a small 4-stroke from a lawnmower might be a good consideration. That engine also will have a much slower rpm than a 2-stroke nitro engine.

    For real panache, there are also turbine engines with geared outputs (model turboprop engines), but again longevity and fuel consumption are detractors. ;)

    My first choice would be a small 4-stroke gasoline engine. I believe small diesel engines are under development. You might consider getting a used stand-by motor-generator set.

    John
     
  8. KJ6EAD

    Senior Member

    Apr 30, 2011
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    There are some rotary engine generators made for UAVs that may work for you or a Honda EX1000 generator may be enough.
     
  9. MachineHum

    Thread Starter Member

    Nov 3, 2014
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    Thanks for this! I know little about engines and just read a quick PDF of how they even work... The cost/size of these nitro engines are the main interest in using them for the project...

    http://www.ebay.com/itm/SH-ENGINES-...Control_Parts_Accessories&hash=item5b071d74e5

    I'll look around for a 4-stroke gasoline similar... but I doubt I will be able to match the cost/size
     
  10. jpanhalt

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    Jan 18, 2008
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    I don't think that engine will work well for running a 600+ watt generator. It is basically a racing engine (28,000 rpm) designed for relatively short runs.

    Fuel runs about $17 to $25/per gallon. I suspect you will be buying fuel at the upper end of that range. How long do you want your robot to operate before refueling? At that HP rating, you will probably burn close to 16 oz/12 minutes.

    John
     
  11. MachineHum

    Thread Starter Member

    Nov 3, 2014
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    10-20 minuets... 28,000RPM is the tricky part... I'm going to needs a DC motor with a rated speed of that... Unless it will run at less under load happily?

    http://www.ebay.com/itm/400W-High-s...583?pt=LH_DefaultDomain_0&hash=item486333e4b7

    I'm thinking something like this... then some work on the output side with a switching circuit and a transformer... some feedback to keep the output at ruffly 12VDC? maybe some clever work with a supercap to keep the load consistent? As I said this is highly theoretical but the more I think about it, the more interested I become...
     
  12. profbuxton

    Member

    Feb 21, 2014
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    Has anyone thought of building a robot powered by hydraulics instead of electric actuators. Just need a suitable pressure pump and rams to suit. Only needs a single source of power electric or IC motor.
    I suspect control could be very easy with hydraulic lines and suitable control valves. Don't know what sort of pressures are needed , depends on application. I'm sure one could get fine control also.
    I think the weight factor would also be lower than using all electric actuators.
     
  13. alfacliff

    Well-Known Member

    Dec 13, 2013
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    the hydraulic pump would still require horsepower to run. how about the engine from a string trimmer? uses a gasoline and oil mixture, small and probably cheap to find.
     
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  14. alfacliff

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    Dec 13, 2013
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    how about pneumatic? not as powerfull as hydraulic, but lots of small 12 volt compressors available.
     
  15. MachineHum

    Thread Starter Member

    Nov 3, 2014
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    Not really interesting in any mechanical power transmission. Typical accuracy is not that great, actuators and controls are expensive. Plus, I would still need electrical power to power my electronics.
     
  16. cmartinez

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    Jan 17, 2007
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    Interesting idea, but the problem with that proposal would be the the rotational joints needed, and precision of movement (since the fluid is compressible and behaves like a spring), not to mention lower efficiency. High pressure hydraulics not only require proper rigid tubing, but also a motor capable of sustaining working pressure even when no motion is being executed. The only advantage I see in using hydraulics is higher reliability, if the system is well designed. Considering all those factors, I'd say that electric actuators would be more practical to use.... in fact, next generation aircraft are beginning to drop hydraulics and are implementing electric actuators instead...
     
  17. cmartinez

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    Jan 17, 2007
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    On the other hand, following the initial idea, I'd say that one possibility would be to design a special generator whose characteristics matched those of the Nitro Engine. That is, a generator designed to run at optimum performance as the engine's optimum rpm's and torque... But I know nothing about generator design, so I don't know if I'm talking wisely here...

    edit: I mean, if an electric motor can be designed for optimum performance within a specific application, then why not the other way around? Couldn't a generator be developed for its direct coupling to your proposed engine?
     
    Last edited: Dec 21, 2014
  18. MaxHeadRoom

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    Jul 18, 2013
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    The only readily available device I can think of is a 12v alternator from a wrecker?
    But then you still require a means to drive it. Small gasoline motor?

    They have for quite a while now, servo actuated ball-screw for rudder, elevator etc.
    Max.
     
  19. cmartinez

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    I'm no aircraft expert, but arent't there some hydraulic systems still present even in most recent planes? Is the small emergency turbine manually deployed by pilots when they lose power a hydraulic pump or an electric generator?
     
  20. MaxHeadRoom

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    I'm sure there are both around, I know I was doing some CNC work in Air Canada Maintenance hanger about 10 yrs ago, I went in to one of the smaller Boeing's (787?) with stripped interior and could see the rear ball screw operating mechanisms.
    Max.
     
    Last edited: Dec 21, 2014
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