Author Options:

How to design and build a belt driven generator for a small tractor? Answered

The storm that swept through Ohio last Friday (seems like an eternity ago) took out our power. It may not be restored until sometime next week (ah, life in the country). We are used to this sort of thing in the winter and are prepared for it. However, we are not prepared to deal with it when it is this hot. I have a small generator that can run a fan and a few lights and am prepared to sacrifice the contents of the fridge. My generator doesn't put out enough power to run a window AC unit much less our central AC unit. My neighbor has a gas powered generator that is big enough to do the trick but he is pouring so much money into the tank that he might as well stay at a hotel.

So anyhow I looked into getting a PTO driven generator to run off my Kubota BX1500 (think diesel engined, 4wd lawn mower on steroids rather than tractor-it's a tiny little thing). It really doesn't burn all that much fuel and it offers the option of using home brewed biodiesel (damn the Tax Man-full speed ahead!). Here's the rub though: you need about 2 hp/kw to run a generator off the PTO. My Kubota has about 12.5 hp. The smallest PTO driven generator I can find (Norther Tool) is a 10 KW unit. That won't work out very well. However, they also have a 2900 watt belt driven generator head that would be large enough to do the job.

I suppose I could mig together an angle iron frame that will hook to the three point hitch and mount the generator head and the driven jack shaft but I don't have any experience in building belt drive units. Soooo, anybody out there have any experience in cobbling together belt drive units from scratch? The tractor's PTO shaft turns at 540 rpm but the generator really won't work right unless it turns at least 3600 rpm (interestingly the ratio works out to be 6.66 to 1, possibly not a good omen). Grainger has a large (if over priced) selection of pulleys that will get me in the ballpark. This still leaves a lot of questions though, probably more that I can think of since I have no experience in belt drive systems. I am specifically worried about how to set up the necessary bearings to support the jack shaft that connects the PTO shaft to the drive pulley. For that matter I don't know where to get a shaft that has PTO splines on one end and a keyway on the other.

In any case, one of you guys have probably already done this or something pretty close to it. So how about letting the rest of us in on all the necessary tricks?




that tells you how to make your own wind turbine instead of making a wind turbine (which wouldnt be a bad idea those things can produce a lot of energy for very little money) make the little generator disks they are talking about gear up your motor to the magnet disk and spin that as fast as you can think of, heck connect your motor to a bike chain and replace the backwheel with the generator disks and gear it up that way those would all work

Zaronas, I really do appreciate your input but what you suggest is a little beyond my current capabilities. Besides, we live on a ridge in Southeastern Ohio. Outsid of the occasional hurricane force winds like we had 9 days ago and the odd tornado we don't have high enough or steady enough winds to use a wind generator. Just check the national wind mad and you'll see what I mean. Besides that AEP owns enough of the politicians in Ohio to ensure that we have a very unfriendly legal environmenwith respect to alternative energy ideas. hat said, anything that burns fossil fuel, like a tractor powered emergency generator is welcomed with open arms. Well, unless you do as I did and ask AEP about the possibility of a grid intertied, biodiesel driven generator. Thought I was going to get burnt at the stake over that one.

In the long term though I do intend to build a small wind turbine based on a 29 Inch bicicle wheel. I don't expect it to ever pay for the cost of construction but since we do own a small piece of the tallest ridge in the county I just want to see what one will actually do.


oh sorry i think you misunderstood me but yah you should build a wind generator too that would be coo,
but what i meant was i was saying you should make the generator from that page and spin it from the pto of your tractor and gear it up so that it is producing 60hz electricity at whatever wattage, or you could just use an inverter that would work too

and if you have any questions about that pm me

1000 W won't satisfy his power requirements, if you read the question. And its 1000W from your windturbine only if the wind is blowing strongly enough.

which is why i said gear it up, which could potentially double that and he could always make the coils and magnets bigger. and one thing too "strong winds" are with that model probably and dont wuote me on this around 500 rpms depending on the wingspan number of wings yada yada, but you could easily gear that up to much past that, if the pto runs at 540 two bike gears away and the generators going 2160 +-

Then he needs an inverter to turn it into usable AC.


6 years ago

Good point. Unfortunately I'm kindof in the same boat. Originally I was thinking of being able to have a few lights and some way to cool the bedroom but I was coming at it from the perspective of conventional thinking. You have made me take a different viewpoint.

What I am now thinking is that instead of trying to produce lots of amps at 110 volts I might be able to solve my two problems with less effort and power loss inherient in the conversion process.

What if I wired a separate 12 volt circuit into the house to power a few 3-5w 12 volt LEDs for emergency lighting in critical areas? Maybe then I could use the PTO to turn a salvaged automotive AC unit just to cool the bedroom?

This would require a bit of work and a little expense but during a power outage in the winter I could run the LEDs off a standard automotive battery kept charged and ready with a small solar cell. I would need to have a longer set of lines made up for the Ac unit. And a three point hitch mountable frame for the compressor, drive system (still need to learn more about pulleys, bearings, etc.), accumulator and hot coil w/fan. Plus a sheet metal box for the inside (evap coil and fan) unit.

I know this sounds like a lot of crap and expense but suffering through this heat and feeding a generator (which doesn't quite do the trick) just isn't cutting it.

Electrical specifics:10-5W LEDs, 2 12 volt automotive fans-12 volts, 80 watts, 7 amps (each). Sorry, didn't see an amp rating for the LEDs but I don't think they draw a lot of juice.

So, what with you being an electrical whiz (remember who you're talking to here-use little words in you answer) do you think the larger alternator would do the trick? Don't worry about the AC side of the deal however I would really appreciate some input about the pulley drive system.


Find a multi-pole alternator, not a single pole one - you can run multipoles at a fraction of 3600, 1800, 900, 450 RPM and still deliver 60Hz

How many kW do you WANT ?

Why use the PTO ? Just put another belt on the front of the engine, and leave the alternator connected - it won't consume anything if you don't wire it.

Steveastrouk, one of the reasons my "handle" here on Instructables is Ogg1 is that technology beyond fire is a bit challenging for me. With the help and advice of people like you though maybe I can get past that.

Honestly, I have no idea what a multipole alternator is. I really don't know what a single pole one is either for that matter. Thanks to you though I now know that that might be what I need to learn about.

As for putting another alternator under the hood-ain't gonna happen. There just isn't enough space. I might be able to replace the one that is there with a larger one though. A buddy of mine has two derelect Ford Festivas rotting away in his yard. The engines in those are about twice the size of the diesel in my Kubota. While they had about 4 times the horse power they probably only cranked out about twice the tourqe as the diesel in my tractor. So tell me, could I simply replace my existing alternator with one of those? Would I need to change anything else in the electrical system of the tractor?

Having a larger alternator might facilitate the use of an inverter or simply allow me to use 12 volts to power some LEDs and a couple of small 12 v fans. Still, I don't think it would produce as much power as I think I need. Coupled with a rethinking of my power requirements it might do the trick though.

Mmm. I think I'd need a better handle on your actual power requirements to comment.