Kubota D722, belt driven, 7500 watt, generator project…

[Henry W]

I missed that post. Thanks.

[keith71]

It may have worked being extended that far but I really did not want to take the chance. The belts should not be that tight anyway I imagine. Not sure how to figure the side load it would put on it anyway. And I did not want to spend a ton of money coming up with a bearing and bellhousing support solution.

[keith71]

Meant to ask you guy's,what oil do you like to use in these small Kubota's? Maybe a grade that is close for all season if that is possible. Might have to start up in the winter when it is 25f or in the middle of the summer when it could be 85-90f for a few day's. Thanks.

[Henry W]

For older engines such as your Kubota. I use Chevron Delo 400 SAE 30 mono-grade.

The stuff has a total base number of 10.1. A high TBN helps neutralize acids that build up in the crankcase.

And, it has a bit more zinc than other oils.

Amsoil makes two specific multi-grade oils that work well with small industrial diesels.
They are expensive and they work fine in colder weather.

Note: some older engines have oil seals that might not be compatible with synthetic oils and the seals can start leaking.

Product codes  for quarts: (Gallon jugs are available)
   ADNQT-EA 10W-30
   AMEQT-EA 15W-40


(Open the attachments below for Chevron Delo 400 info)

[Henry W]

Keith,
I'm looking forward seeing the project come together.

The Kubota D722 is a great engine. It has the same bore and stroke as the Z482 engine. Peak torque on the Z482 and D722 comes on at the same RPM's. (2600) A person that you spoke to not too long ago mentioned to me about ten years ago that it's best to keep the RPM's over the peak torque curve by 200. The reason is when the generator is loaded, the engine RPM's could drop as much 200. This will keep the engine operating at or just over peak torque. I've also had this discussion with an application engineer at Kubota about the same time. This confirms that 2800 is a healthy speed for the Z482 and D722 engines.

About engine life, Some D722 engines and others have been known to operate 20,000+ hours. The maintenance had to be exceptional to achieve it. That is a long time.  So, I feel there is no concern for the engine having a long life when the engine is properly maintained.

The Engine should have no problem pulling the load that your generator is able to produce.

Henry

[keith71]

Hi, Henry,yes that custom generator company told me that 2850 is the absolute sweet spot for the D722 for best effiency. And they run their belt driven generators at that rpm. On the other side of that They said that a D722 puts out enough power to make a little over 5000 watts at 1800. They have many units that are direct driven at 1800 rpm. Main issue is harmonics. The oneissue with the kubota super mini series is balancing, or the lack of it.Not very well done in their opinion. There is now a harmonic balancer that attaches to the flywheel available for these engines. They have seen bad vibration at different rpm levels depending on the load and drive set up. It would be great if these guy's were a member of the forum as they can explain alot better than I can. Maybe they will join in the future who knows.                         

[keith71]

I have a few different ratio's I am going to try. What I really want to get is a belt drive setup that has been in use for awhile now. It is a cogged style drive belt and pulley setup similiar to a harley davidson belt drive. A 35mm wide belt can handle 125 horsepower harley pretty easily, would be great for a kubota setup.. But super expensive.  Stub shaft will be here tomorrow morning. Then it is time to get serious..

[Henry W]

Hi, Henry,yes that custom generator company told me that 2850 is the absolute sweet spot for the D722 for best effiency. And they run their belt driven generators at that rpm. On the other side of that They said that a D722 puts out enough power to make a little over 5000 watts at 1800. They have many units that are direct driven at 1800 rpm. Main issue is harmonics. The oneissue with the kubota super mini series is balancing, or the lack of it.Not very well done in their opinion. There is now a harmonic balancer that attaches to the flywheel available for these engines. They have seen bad vibration at different rpm levels depending on the load and drive set up. It would be great if these guy's were a member of the forum as they can explain alot better than I can. Maybe they will join in the future who knows.                       

2850 would be pretty much on the mark when the generator frequency is set up near 62Hz. When the generator gets loaded some the frequency will be near 60hHz.(2800) It sounds right.

I've tried 1800 with the Z482 and I did not feel comfortable running it loaded. Yes it ran but, it exhibited harmonic (Critical Speed) issues. The Kubota application engineer and I spoke about this issue in depth and this was one of the reasons why I  started  looking at other engine options. And, shortly after, I located the D1005 engine. It took some time to set it up as close as I could to the BG series. It was costly but worth it. What a sweet running 1800 RPM, direct drive generator that was. But it was too large for my needs. Belt driving the D722 at 2800 - 2850 is a great compromise.

A person at the generator company does visit the forum from time to time. They are so busy that they don't have much time. They know about us. And we have helped each other. That is a good thing. They are great people to work with.

[Henry W]

I have a few different ratio's I am going to try. What I really want to get is a belt drive setup that has been in use for awhile now. It is a cogged style drive belt and pulley setup similiar to a harley davidson belt drive. A 35mm wide belt can handle 125 horsepower harley pretty easily, would be great for a kubota setup.. But super expensive.  Stub shaft will be here tomorrow morning. Then it is time to get serious..

Sounds good! A dual pulley BX belted setup should work fine. Bob G has a Browning hand book. He might be able to help. If a double belted setup is marginal, a triple belted setup is available.

Your right, A cogged style setup will be expensive. But it would work very well.

If your able, please take a picture of the stubshaft.

Henry

[keith71]

A few pics of the stub shaft. it has 1-1/8'' shaft about 3'' long.

[keith71]

more

[keith71]

another one.

[keith71]

last one.

[Tom Reed]

Looks beefy.

[Henry W]

Keith,
That is the one I've used on the Z482. It's one nice piece. The critical point from the shaft to the hub has a radius. The radius reduces the possibility of stress cracks. You will be able to mount the drive pulley very close to the flywheel face.

Henry