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Generator conversion  RSS feed

 
pollinator
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I have inherited two generators that are driven by small gas-powered small engines. These kinds of generators are pretty ubiquitous. However, the engines on them don't run. My question to the group is, can I used these set up by removing the engine and attaching them to a wind mill and generate electricity?  If so, what would I need to do, what should I look out for, what are your thoughts?

Here's a photo of one very similar to what I'm referring to:

Maybe the first photo didn't work. Here's another example:
 
pioneer
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If these are the common gas powered 2-pole generators that are found for sale at all the big box stores, they generate 60hz electricity at 3600rpm. So first your windmill would, with gears, need to turn the armature at 3600rpm. The second challenge to overcome is when more current is being used from the generator, the more torque it takes to maintain 3600rpm. When something with considerable amperage draw turns on, like a refrigerator for example, the sudden increase in power draw requires immediate torque compensation, this results in the brief "bog down" sound of generators as the engine compensates for the additional torque requirements.

If the generators are 4-pole, then they turn at 1800rpm, but also have the same power requirement hurdles as mentioned above.
 
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Those generators are designed to run at approximately 3600 rpm, it  is enormously hard to get a windmill with adequate torque to run the reducing set of gears to transfer the 8-900 rpm a windmill can achieve.
A large flow of water would be adequate, but still the gearset would be required, and an enormous amount of the power you create would be used in friction and drag losses.
There are many low rpm gensets and plans to build the same on the net.
If you could find one, an old Lister-Petter, single cylinder or a Changfa, diesel could be harnessed (still with a gearset!) to make an extraordinarily long lived genset.
Or.......Harbor Freight sells a six hp motor for $99.00
Or... the parts to rebuild a small engine around $34.00 to $75.00 and the tools to do a bang up job around $150.00 and you'll be able to use them for the rest of your life.
 
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Red Smith wrote:
Or.......Harbor Freight sells a six hp motor for $99.00



Keep in mind these generators commonly have a tapered shaft on the motor specific to generator heads. The motors are usually very difficult to separate from the gen head and if you do then you'll need to modify the tapered hole to accept a pulley or straight shaft motor.
 
Dan Grubbs
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Red and James:
Thanks for the replies. I figured the gear reduction would be a problem. I was simply wanting the generator to charge a battery pack and skip the inversion altogether. Does that still make using these a problem with a wind? Or, am I faced with the same issue that it won't generate power slower than 3,600 RPM?
 
James Freyr
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Dan Grubbs wrote:Red and James:
Thanks for the replies. I figured the gear reduction would be a problem. I was simply wanting the generator to charge a battery pack and skip the inversion altogether. Does that still make using these a problem with a wind? Or, am I faced with the same issue that it won't generate power slower than 3,600 RPM?



Oh they'll generate power at less rpm's, but it won't be 60hz or 110v.
 
Red Smith
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For bang for the buck nothing beats a 35 amp Chrysler alternator from a junkyard.
Research "Savonius rotors", their efficiency is horrible but their economy of construction and maintenance is remarkable. Remember, one rotor can run multiple alternators, a fifty five gallon drum creates an massive sail area, it's self limiting in the case of high wind and can be made of scrap materials. The only significant investment is good quality bearings.
 
Dan Grubbs
pollinator
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Thanks Red:

I'm trying to be good and "use what's on hand" and not buy a generator or alternator. I have two of these units on hand and don't want them to go to waste. Actually, I was thinking of making a vertical axis turbine from barrels driving these two generators. That is, IF someone can tell me these two generators will charge my battery bank.  I'm still unclear on that.  I assume it's a matter of speed and time. My draw from my batteries is low and intermittent. So, even if the turbine had to turn for an hour to help charge the battery bank, I'm good with that. The battery bank is also tied to a very small PV array. My objective is to ensure good charge during cloudy days (which are usually windy days for us).

Love to hear from more of you about this.
 
Red Smith
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Well......
FWIW, in thirty years of browsing alternative energy schemes and home experiments, I've never seen anyone successfully accomplish what you're trying. I'm sure it can be done if you can draw a picture of it on the back of a large enough check......
Home small scale projects factor in time as a variable that is ignored in generator equations, I.E. the generator creates 3500 watts immediately solar, wind or water (at small scale) create 1200 watts or ( sometimes far) less  that can build over hours and create a pool (battery) of energy be drained.
The reason that such low values are attained is a result of the fractional horsepowers achieved, a six foot diameter sail (or prop?) still creates fractional horse power at far less speed. At home user scale there is simply not enough power to turn that strong of a magnetic field through that many windings at a usefull speed.


So what has failed on the motors as they sit?
If they turn over, there are very few things that fail on these simple engines. The foremost enemy is alcohol in the gasoline, alcohol is brutally corrosive eating brass and nytrophyle floats, and slowly destroying the castings on old carburetors, if it is left in the carb for long storage as it evaporates it will leave these dissolved metals in fine passages and simply clog off fuel flow, an hour with a can of carb cleaner and some fine wire probes will do miracles. after that a point set or a cheap electronic ignition module, and finally if the key that holds the flywheel in relation to the crankshaft can bend under rapid braking, or after years of pounding and that simple key will make a world of difference.
Finally if its completely worn out (very rare comprising hundreds of hours use or deliberate abuse such as failing to add or change oil...) a set of rings and seals cost practically nothing on Ebay.
Ebay and Harbor Freight is your friend.
Youtube will show you bolt by screw exactly how to do it.....
Youtube will also show you how to create (from scratch!) a slow speed, permanent magnet generator that is appropriate for windmill use.
 
Dan Grubbs
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Thanks, Red.

I actually haven't looked into what is wrong with the two engines. I was just told they weren't running. I know I should explore that first. I was exploring the other idea intellectually which I why I asked for expertise, such as yours, to weigh in. I appreciate everyone comments.
 
pollinator
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Could a solar charge converter be used between generator and battery? Not sure bout ac vs dc. Gen is ac, solar is dc?

If it worked,  it would convert to usable voltage for batteries and shut down when fully charged regardless of rpm?
 
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My short answer is that if you want to learn how to work on small engines, dive in!  I like the youtuber "donyboy73" .  http://www.youtube.com/channel/UC6MEb54vwjicHs7L39sS4hA
If it had old gas in it, it might need a carb rebuild, which isn't too difficult.
You'll have to troubleshoot it and decide whether you want to repair it or use it for parts.
If you don't want to be a small engine mechanic then you should probably sell the generator(s) and buy what you need.

A more compatible energy source for a genset may be a biogas producing "digester" (anerobic composting), or a woodgas gasifier.

A wind turbine that can produce multiple horsepower sufficient to run this generator will be quite large, and so will the tower to put it on.  That may be your limitation.  I'm skeptical of the claim that the generator requires unusually high starting torque.   I think it probably does require a lot of torque at normal operating speeds, but I think that's because it is a multi-horsepower generator, not because of some unusually high dead-load (zero-speed torque load).  Gearing it down by 4:1 would *increase* the torque, and should make it *more* likely to run, not less.  Although a better answer is that power-transfer is maximized through impedance matching.  That's just a fancy way of saying "pick the right gear-ratio".

If you're familiar with the multi-vane (water-pumping) windmill that became an icon of the rural american landscape, one of its characteristics is relatively high torque in low wind speeds.  It will have a lower minimum windspeed at which it starts turning.  While the design doesn't produce as much energy overall as a modern 2 or 3 blade horizontal-axis wind turbine (HAWT), it does produce small amounts of power more often, which can be more useful for off-grid applications, given that most of the time windspeeds are low, and energy storage is often expensive.   A Savonius type is like that as well.  And there are other VAWTs like it, including one that came out recently. 

Wind energy has a lot of appeal, but justifying it tends to require surprisingly high windspeeds and/or lower power requirements, especially with small turbines that cost more per watt than the megawatt sized ones.  If you live on a coastline or on a mountain, great.  If I was on a sailboat I would get one.  However, solar cells are getting so affordable that I think small wind generators will have a tough time competing.  Biogas and woodgas can probably produce a lot more energy where load-requirements are in the HP or kW range. 

I think small-scale wind energy has to be justified some other way, either as being low-maintenance, or as a way to diversify energy sources in order to reduce storage requirements, or for an emergency source in situations where weather-related natural disasters might tend to be more windy than sunny.  Unfortunately, even then it's not as reliable as one might like, since a storm that can knockout the grid can also knockout a wind turbine, unless extreme protective measures are taken to prevent storm-damage.  That seems like a situation where something like a large battery, or a solar cell or a fuel cell seems like it would be much more reliable. 


 
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