Making my own!

[Baloo]

So out come the Onan 5.0 KW and in that huge spot now sits a Kubota 6hp diesel ready to get to work. The question I am kicking around is what size belt driven generator head to buy. I am thinking 3KW is perfect for my rig. Given the 749 Watt to a hp, I should be able to run the engine at 1800 RPM vs the 3600 RPM required by the generator head. Gotta love the ability to size up and down pulleys. The lower RPM will not only reduce the wear on the engine, lower fuel usage and greatly reduce engine noise. Am I on the right track? Or have I lost my mind? There is not a whole lot of info on this subject that I could find on the web. Any thoughts?

The old setup



It’s out!


Sent from my iPad using Tapatalk

The new setup in work

[Blacktank]

the maths shouldn't be that hard to get close,2 pulleys the same size would be 1 to 1,know the generators optimal rpm?

[B and C]

Most generators run at 1800 or 3600 rpm to keep a 60 Hz sine wave. You could put just about any generator that will fit in it. Even if the generator is oversized for the motor, the motor will only work as hard as how much load you put on it. If you end up putting more of a load on the generator than the engine can keep turning, the engine will die. You'll know not to put that much load on it next time.

[Baloo]

Thinking about this one:

https://www.northerntool.com/shop/tools/...1008_21008

If I use a 4” pulley on the engine and a 2” pulley on the generator, I should be 1800 RPM engine speed and 3600 RPM generator speed.
The engine is only a 6hp, but has more tq than the required 5hp gas engine.


Sent from my iPad using Tapatalk

[Blacktank]

here's a calculator for pulleys https://www.blocklayer.com/pulley-belteng.aspx

larger pulleys have more surface area for the vbelt to grab onto,if you go pulley and belt with teeth or chain drive you wont have to worry about slipping

[B and C]

That should be sufficient. My Onan is 2800 watts. The van manual says to start the air conditioner before turning on the microwave. The microwave that came in the van was only 600 watts though. I changed it out for a convection/microwave so I could have an oven. I generally only run the air conditioning getting out of Texas and don't bake. It consumes 1450 watts of power so I can't run the A/C.

Just figure your loads before turning them on.

[sternwake]

Can the engine itself make enough torque at 1600 rpm to support the loads you plan on putting on the generator head?

No snarky tone intended, genuine question, I don't know.

[Baloo]

Can the engine itself make enough torque at 1600 rpm to support the loads you plan on putting on the generator head?

No snarky tone intended, genuine question, I don't know.

Great question. The best part of a diesel is how they build power in the lower RPM range. The chart by Kubota puts 1800 RPM as the sweet spot. However it is good to 3600 RPM, so worse case I end up changing my pulley and belt configuration to work with the loads in use.


Sent from my iPhone using Tapatalk Pro

[Gr8ful]

I have a very low hour 6.0 Onan diesel from a fire truck. I like Onans gas or diesel as they run at 1800 rpm where most are 3600.

[Roadtripp]

The small diesels were used for electricity in sailboats. You will find a lot more written about how to set it up on the boat forums. The slow-speed Kubota 4-8 hp diesels are commonly used with a large frame alternator to charge the house and starting batteries. 
 If you want to attach a generator head look up the slow-speed Lister Diesel engine forums. Or the clones they call Listeroids as Listers have been out of production for a long time. They are popular for powering off grid systems. 
  I did read to be careful not to overload the small Kubota diesels. Some of the boaters were trying to charge at over 100 amps and it was damaging them. The 6-8 hp Kubota could go slightly over 100 amps but not the 4 hp.