Stand alone power source for PTO generator

[Nicetoy]

I have a 80 something hp naturally aspirated Mercedes Diesel that is a miser fuel wise, and a **** good motor. I also have a 25K PTO generator. I typically run the generator off my Ford 1710, which works, however the tractor is slightly underpowered for the generator. Under heavy loads the tractor is strained to the point where the output voltage drops and some stuff doesn't run well, and puts a stress on motor loads in my house. That said, most of the time, everything works as it should and there is no problem. BUT. I am moving to a new property soon, and would like to keep my little tractor for doing strictly tractor related stuff. So i'd like to weld together a trailer and mount the Mercedes Diesel on it with a PTO shaft to the generator. My question to those smarter then I, What would I need to use in between the engine and generator to produce 540RPMs or 1000Rpms? I cannot just weld a pto shaft onto the flywheel and go, or can I? Any ideas?

 

[Mickey_Fx]

More important than how to mount a shaft to the flywheel, what are you going to do for a governor to control engine speed as loads vary?

 

[kevinwak]

You can get a bell housing to bolt to the flywheel that has a clutch in it and an output shaft for stationary use. That is how it was done on my Dads sawmill that I worked at growing up. You then connect to the input shaft of what you want to run with belts and pulleys in the right sizes to give the speed you are after. It might be harder to find one that bolts to a Mercedes engine, but they sure were easy to get and plentiful for the old Detroit diesels that we ran.

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[Nicetoy]

Like my tractor, I rev it up to a point where it is putting out the full 240V as tested on a meter, then just leave it running at that engine speed, there is no governor, and that is why I have a voltage drop when heavy loads are put to it because it is underpowered. To get full output, WinCo says you should have a 50hp tractor, so I'm thinking that with a 80-90 hp stand alone engine, even when loads are put to the motor, it should be way more engine then needed, and absorb those loads seamlessly.

 

[Nicetoy]

I know it can be done with belts and pulleys, I was trying to stay away from things that wear over time and crack.. Was looking more at some type of gear driven solution.

 

[Willl]

there is no governor

Sure about that ?

 

[Nicetoy]

I suppose I'm not sure, but there are no electronics of any kind on the tractor, so it would have to be something mechanical, likely part of the injection pump if anything, The mercedes also has zero electronics, and is 100% mechanical, which is why I want to use it.. Trying to keep this as simple as possible, something that can be parked in the barn, and pulled out and start right up.
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[joshuabardwell]

I suppose I'm not sure, but there are no electronics of any kind on the tractor, so it would have to be something mechanical, likely part of the injection pump if anything, The mercedes also has zero electronics, and is 100% mechanical, which is why I want to use it.. Trying to keep this as simple as possible, something that can be parked in the barn, and pulled out and start right up.
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Governors can absolutely be mechanical. Remember the two ball mechanism where as the motor spins centrifugal force raises them and conservation of angular momentum slows them down, and vice versa? I love that thing.

EDIT: This thing:

I'm not literally suggesting that such a thing is inside your Mercedes, just that an analogous mechanism could be.

 

[Nicetoy]

I have to imagine the mercedes motor has something built in already?

 

[unimog_jason]

There are couple engines I can think of that this might be:

OM312 - 6 cylinder truck engine, 5.1 litres displacement - very old engine, not likely.
OM314 - 4 cylinder truck engine, 4 litres displacement - somewhat common engine, used in vans, Unimogs, tractors and likely boats.
OM352 - 6 cylinder truck engine, 5.7 litres displacement - very common engine, used in Unimogs, MB trucks, tractors, boats, etc.
OM617 - 5 cylinder car engine - 3 litres displacement - common as dirt.

If you have one of the truck engines and it happened to come out of a Unimog or boat you're in luck, it will have the right governor and flywheel housing for your application. You can either buy an over center PTO kit and bolt it up to your engine and devise a system to step down the shaft speed to 540 RPM or remove the reduction gearbox from the generator and directly drive it (assuming you have a 4 pole generator that turns 1800 RPMs and not a 2 pole @ 3600 RPMs). Lastly you can look at buying something like this and bolt it directly to the engine:

Generator Alternator Head 184E 23KW 1 Phase 120 240V SAE 4 6 5 Stamford Type | eBay


If the engine came out of a truck or van it will have a different flywheel housing and the governor will not likely work very well for you. If it came out of a car your out of luck on both counts and you're likely better off looking elsewhere.

Jason