building an electric generator

If someone has an old dumptruck motor that was fully functional, what would he have to do to make its output powerful enough to run everything in his house when the power goes out b/c of a hurricane or snowstorm?

I assume you mean dump truck “engine”. (Motors are electrically driven.) What you would need is a generator and a speed regulating system. Assuming it is a diesel, you would probably want to find an 1800 rpm, 60 cycle, 240 volt generator. Then you would need to find a governor system you could fit to the engine to keep it at 1800 rpm plus or minus a couple of percent.

Given that the engine is probably in the 200 horsepower range at 1800 rpm, that’s about 150 kilowatts and well over 100 kW electric even with all kinds of losses. Since the average house generally will only need a few kW in an emergency, you can power the whole neighborhood. However, in the end it will probably more economical to just buy a small home generator. You can get a 5 kW generator for $500 to $700:

I doubt you could home build a functional generator for less unless you got very lucky in finding a generator and came up with something unique on the engine governor.

I mean motor with it’s necessities (turbo, water pump, etc) so call it engine if you want. that says internal combustion and i’ve never seen an internal combustion electric motor:confused:

That link you have is just for buying a generator. I can order them at cost thru Ace Hardware if i wanted to and they are still kinda small. But the guy i know would want to do it himself (he built his own sawmill and this motor is going to power it when he cuts firewood for his house. He wants to be able to use it to power his house when power goes out). This is the kind of d-i-yer that does things bigger and better than the average d-i-yer.

No need for snarkiness, SlickRoenick, KenGr gave you a perfectly sensible answer.

That’s wrong on two counts:

  1. most of the things on that page are motor/generator sets.
  2. what you actually want is just a generator, and there’s one of those on the page as well (they call it a “generator head”).

You’d need to buy the “generator head”, make up brackets for it, fit a drive pulley and a belt, then arrange some method of making the engine run at constant rpm despite changing load - sorta like a cruise control.

All in all, it’d be a real pain in the ass, and would probably cost more and use more fuel than the simple motor/generator sets.

Dictionaries can say what they want. When I was in Engineering school, calling an IC engine a motor would get you slapped up side the head. Anyway, if you’re serious about this, the cheapest way to get a generator is to get a PTO (Power Takeoff) unit. These are intended to be powered by tractors.

You will note that these develop 20 to 60 kW which is pretty hefty in that 5 kW will power most houses. Cost is $2500 to $5000. The reasons these work well with tractors is that you can just set them to run at full throttle. The tractor governor will then limit the engine speed to give an industry standard PTO speed. Obviously, the truck engine won’t do this.

Maybe buy an old tractor also?

You will also have to consider some method of switching between the two supplies, whatever means you employ to generate the power.

If you wish to connect into your domestic supply with your genrator, then you could use a simple changeover switch, however you would likely have to inform your utility as you would be making an alteration that could affect them, and other customers if something goes wrong.

Is 5000W all that is really needed? B/c thinking about it, a microwave uses about 1000, a stove, furnace, television sets, computers, etc etc. . . . I don’t think 5000 would be nearly enough. Would a large enough generator head just connect to the flywheel with a pulley like Desmo said?

Didn’t mean to get smarky KenGr, i just worded my reply in a smartass way.

      • On a survivalist forum I saw a discussion of how to build the cheapest possible generator to run AC appliances off of. The easiest way would be to make a large coil-shaped stationary wire winding (like a slinky stretched out and circled into a loop) and then mount a magnet on an armature inside, and rotate at whatever frequency you needed the AC at. The problem here is that the voltage and current would be heavily dependent on the load, so this thing would only run one appliance really well. Another problem would be that you’d have to rather experiment with the number and spacing of windings–but it would avoid needing any sort of invertor or brushes at all. -And of course that most engines don’t spin well at 50 or 60 RPM’s, so that would be another problem–but the question mainly concerned how to get around needing a power-invertor crcuit or 3–>1 phase convertor.
  • If an appliance doesn’t use any synchronous motors however, you can run the AC at higher frequencies, which makes things much more convenient. One guy had build a generator out of an old gas-powered push-lawnmower, by making a coil that fit underneath the mower deck, and mounting a magnet and conterweight on the lawnmower blade.

The PTO: Its a “dumptruck engine”. Most dumpers I’ve seen use a PTO to power the hydraulics that raise the bed.

Cruise control: Lacking a PTO you could cobble up a criuse
controller to maintain an RPM.

Once you have a method of automatically governing engine RPM you’ll need to figure the pulley sizes to get the generator to spin at its operating RPM.

If you can, try and find last months (or this months i dont recall) issue of Backwoods Home. They had a nice article on the basics of living ‘off the grid’. The magazine can be a bit off the wall, but they offer a good starting point for survival and living away from the rest of society.

5000 watts is the general rule of thumb for emergency power. Of course, that assumes you won’t running your air conditioning, christmas lights, etc. Think of it this way. Most of your 120 volt circuits are 15 or 20 amps. They generally don’t exceed half load with every thing on. Can you get by with 5 circuits? Microwaves have a pretty big load but that will be very intermittant. If you have a Sub Zero walk in refrigerator and a big freezer, go for a bit more power. If you want to just live normally and not worry about what it on, the 10,000 watt models might be better.