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Poor man's emergency genny.

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DICKEYBIRD:
I guess this idea should go here as I haven't actually built it.  The idea occurred to me this morning after reading some old posts over on the HSM BBS.  I posted the idea there but one fellow said I was polishing a t*rd and wasting gasoline with a totally inefficient setup.  Prolly true but hey, I don't have a grand to spend on a fancy Honda genny.

The idea is to spin a junkyard auto alternator with a lawn mower engine, charging an auto battery which in turn powers an inverter to power up misc. household items when the power goes out.

The mower could be converted in the winter and converted back in the spring or as in my case, this oldie but goody Murray could be left in the converted state since it's my #3 spare. The wheels allow it to easily moved from the shed out back up close to the house when needed. Harbor Freight has a 2000 watt inverter for $149.95 or smaller ones for much less which I think would be properly powered by the 4 hp. mower at 1/2 to 3/4 throttle. I would use a junkyard alternator that has an internal, battery sensed voltage regulator so engine speed wouldn't be critical. Later model alternators have Power Control Model voltage regulation and a pain to rig a regulator.  Should be a snap to mount it with a few scraps of strap and angle iron. The belt would come right through the side discharge chute so no major mods would be needed to the mower deck. And no, I haven't thought this through far enough to work out any alternator/mower rotation direction issues. That could possibly complicate things a little.  It would need a chunk of scrap steel turned down to make a flywheel that would bolt on in place of the blade and then a pulley grafted on.

Seems like a reasonable emergency cobble job to me.  Apologies for the crappy CAD overlay. My old steam powered version of TurboCAD doesn't allow .jpgs to show up with rendered objects....hence the wireframe objects.

dsquire:
DickeyBird

Definitely nothing wrong with the thought process, that's how great ideas are born. I can't see any good reason why it wouldn't work as long as your rotation was correct.  :ddb: :ddb:

Cheers  :beer:

Don

Russel:
That isn't a bad idea. I've seen lawnmower engines converted to generators before. It usually takes most of the horsepower the engine will produce, of course depending on the load. One thing you must work out is the Alternator RPM to produce sufficient voltage. A small pulley at the crankshaft and a bigger one at the alternator won't usually spin it fast enough. Engines of this size and type have a max of 3600 rpm, that is usually what you have to use to develop enough power if the alternator is under a load. You probably know this, but if you multiply the required alternator RPM by the diameter of it's pulley and divide that by the engine rpm, that will give you the required engine pulley diameter. Also, I noticed that you labeled the pulley a flywheel/pulley. The engine has a sufficient flywheel under the cowling. It will run properly with nothing attached to the crankshaft under the mower, and considering the charging application, I don't think you need to add to the flywheel to stabilize the rpm.

Interesting project, I hope that this might help. If you decide to build it I am sure that I am not the only one that would be interested reading about your progress.

Russ

trevoratxtal:
Hello Dickybird
Your concept can and will work to charge a battery.
I made something similar back in the 70s when we had power strikes in the UK.
I run lights to a milking parlor, 12v and kept the milking machines running off a tractor but that is a another story. 
The rotation of a alternator works both ways as a 3 phase AC is produced then rectified to DC for charging!.
12v to mains converters will not work with most fridges, as they use a syncro motor and to match the perfect frequency and start current is not easy.
However lights Tvs and Radios mostly will work.
Wiring to the battery from the alternator is straight forward as the regulator is in the alternator, however either disconnect the battery after charging or fit a switch between the small plug on the alternator and the battery as this is the supply line for the activating coil and if left on will flatten the battery just like the ignition switch on a vehicle.

bogstandard:
Wot's that big red thing with all that green stuff under it?  :lol:

I went concrete and cement years ago.


Bogs

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