Cheap home made generator

Discussion in 'Back to Basics' started by monkeyman, Sep 2, 2005.

  1. Altoidfishfins

    Altoidfishfins Monkey+++ Site Supporter+

    Hmm. Looks like a good thing to do with my 10 HP horizontal shaft Tecumseh. The 120 volt AC generator head attached to it really sucks. It starts out just fine with 125 volts AC output but within a few minutes the voltage drops to about 85 volts, whether it is electrically loaded or not. The output frequency stays at 60 HZ so the engine is doing its part in keeping the proper speed. Good engine, junk generator head.

    Replacement generator heads can be had, but none that will match up to a Tecumseh engine because it was the only one manufactured with a tapered shaft. No current replacement generator heads are made to this non-standard configuration.
  2. ghrit

    ghrit Bad company Administrator Founding Member

    You can get tapered bushings that might work for ya.
    oldawg likes this.
  3. techsar

    techsar Monkey+++

    I've seen where a bad capacitor can do that...about 20 bucks for a replacement (or it used to be about that much).
  4. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    Yea, many cheap Genends use an AC Cap for excitation, and voltage regulation... Replace the Cap, and try again... The Copper will not cause what you are seeing.
  5. Altoidfishfins

    Altoidfishfins Monkey+++ Site Supporter+

    Tried replacing the cap. Same thing. Also checked two stud mount diodes that rectify the field current. Both checked good but replaced them anyway just in case one of them had a thermal issue. Just for a test I placed a DVM across the terminals of the cap. The excitation voltage starts out at close to 90 volts DC, then drops to below 70 volts over a period of a few minutes. Of course the generator output follows. After running about 30 minutes or so, the cap gets hot although it's never vented. It probably would eventually.

    Was pretty careful about watching polarity on the cap but come to think of it, maybe I made a bumbling idiot error. Done dumber things. I'll check it next time I'm on the remote property.
  6. oldawg

    oldawg Monkey+++

    Not for everyone but check into ST gen heads. They are heavy but give good service and do it at 1800 rpm. Power can be supplied by any horizontal shaft engine of appropriate hp. 20 bucks keeps spare electronics in hand.
  7. overbore

    overbore Monkey++

    McMaster-Carr has what you need in bushings. pulleys or what nots.

    Laus Deo
  8. jlutzcurtis

    jlutzcurtis Monkey

    Thanks for the ideas. Looks complicated task but looking forward to give all of these instructions a try to make a cheap home made generator. Since I needed one urgent.
  9. T. Riley

    T. Riley Monkey+++ Site Supporter++

    What size wire is needed to wire a small house for 12 volt LED lights? I have an inverter that can supply 110v current to ever fixture and receptacle in my house but I would like to have a 12v RV LED fixture in every room to bypass the inverter and resulting power loss. Max run would be 40 feet from the battery bank.
  10. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    I would use standard #12 or #14 Romex for that, as the current draw for those is small, so the Voltage Drop, on a 40' run wouldn't be significant.... I would also use a different Color Romex, to make the two different Systems, easily Identifiable...
  11. T. Riley

    T. Riley Monkey+++ Site Supporter++

    @Cruisin Sloth Yeah, lights only, using my solar system battery bank. I figure there is no use in going thru the inverter when so many 12v light fixtures are available. Figure on putting one in each room. #14 romex would be an easy option for me if that would work along with a DC fuse block.
  12. zombierspndr

    zombierspndr Monkey

    Alternators are no longer internally regulated. The parts may be there, but the car's computer is what controls them. Many even have temperature sensors now to lower charging current at high temps, or increase it at low temps. As far as the connections go, they're all simple. You only need to find the wiring diagrams for the vehicle the alternator was intended for. You can also purchase replacement pigtails to make connecting to the terminals easier...or just go to a junkyard and cut off the pigtail when you remove the alternator.

    I suspect your engine was struggling because your method of connection had the alternator "full fielded", meaning it was producing full power all the time. The other issue would be the pulley ratio. A larger pulley on the engine would spin the alternator faster, but is more difficult for the engine to turn under load. A smaller pulley on the engine would be easier to turn, but may result in reduced power output of the alternator. A side note here is that an alternator needs to spin at a certain rpm in order for the fan to provide full cooling of it. If it doesn't, the least that will happen is that output will go down as a result of heat, and the worst is that you burn up the diodes or damage the windings of the rotor or stator.

    If a heat treated steel tool is placed in a fire, there is a very high probability that it will be ruined. Cutting tools need to be hardened and tempered(two different processes) if they are to maintain an edge in use. Unless you happen to know how to heat treat them properly they will either be too hard and thus brittle, or too soft to perform their intended function. I could do this, but I am a machinist, so I have experience with it. The vast majority of people will have no idea.

    Junkyards are better sources for high amp alternators. I have less than $100 in a 320 amp heavy truck unit after having a local alternator shop go through it, test it, and install a new pulley. It would be futile to even try setting it up on a typical 3-6hp engine. It may prove too much for the 18hp briggs I plan to use it on. Most alternators can be fitted with several different pulley diameters and/or belt styles. Here's a source for rebuild parts, pulleys, etc.. Alternator Parts - Starter Parts & Repair kits

    That is false. There are two common crankshaft tapers used in small engines to direct drive generator(alternator, actually) heads. If you have the less commonly available version, you could swap the crank out to a standard straight shaft and then belt drive an appropriate generator head.
  13. Tempstar

    Tempstar Old and crochety Site Supporter+

    I built a 15 KW ST genny using the 26 horse single cylinder Chinese diesel. I coated everything inside with Glyptal, and added American made bearings before I ever started it up. That was 15 years ago and it has had no problems. Yearly oil and fuel filter changes is all that has been done in all that time. These things are beasts. I would have replaced 10 big-box store generators by now. My total 2001 build cost was around $1800. If I ever find a 10 horse diesel a new 3kw will be built with another ST head, as the 15kw is a little much in most cases.
    Gator 45/70, BTPost and oldawg like this.
  14. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    The Bearings are the Prime Failure Point in most Chinese Clone Diesels.... You were very smart to do that rebuild right off the start....
    Gator 45/70 likes this.
  15. Tempstar

    Tempstar Old and crochety Site Supporter+

    Nahh Bruce. Changed the bearings in the ST head. They come coated in Yak Grease and have flat spots in the balls. The Diesel I converted to a radiator system using the radiator with fan from a Honda ST 1100 and a 220v water pump. I did coat the little alternator windings under the huge flywheel with Glyptal as well. The main bearings were checked and they were some beefy units with huge balls (lol) and looked great. Popped the oil pan back on and haven't looked back.
    Ganado likes this.
  16. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Pictures would be great plz !

    Ganado likes this.
  17. Ganado

    Ganado Monkey+++

    an interesting thread bumping in hope pics will be posted [winkthumb]
  18. Tempstar

    Tempstar Old and crochety Site Supporter+

    IMG_0051.JPG IMG_0050.JPG
    birchtree, Ganado and Cruisin Sloth like this.
  19. Tempstar

    Tempstar Old and crochety Site Supporter+

    Forgot about this! First pic is the trailer I built with the Honda ST1100 radiator/fan and the outlet breaker on the left and control panel on the right. The second pic is inside the trailer with wire from another project tossed in. It has a 220v water pump, 12v diesel pump,100 amp GM 1 wire alternator (on the back side). The top plate I made to get rid of the water tank on top, and run the standard 5 psi radiator cap. It's good for 65 amps at 1800 rpm, 15KW at 230v. I have run the entire house with the A/C on, basically like the power isn't off.
    Ura-Ki, Ganado and Cruisin Sloth like this.
  20. Ura-Ki

    Ura-Ki Grudge Monkey

    Should combine this thread with the wind turbine thread, I can see a convergence with these two.
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