Operating rpm for m59

[Hersheyfarm]

Book says rated rpm is 2700. No redline rated. Any advise?

 

[rScotty]

Book says rated rpm is 2700. No redline rated. Any advise?

Well....maybe I'm not understanding the question. In my book the "rated RPM" is printed right below the HP rating, and since HP is a simple multiple of RPM....then I just kind of assumed Kubota is saying is that the HP was calculated at 2700 RPM. And then it would follow that they would design the PTO gearing to turn 550 when the engine is turning 2700. That would make it a "rated" speed.

Just speculating a bit farther...., but if Kubota follows the common practice of quoting the highest HP number that they can justify, then it is probably the case that 2700 is the RPM where the torque is falling off faster than the RPM is rising up. The crossover point.

Does rated RPM have anything to do with redline RPM? Maybe Kubota knows the answer to that one. Is it in the manual somewhere? ......but I don't see why they would have to be related.

For light work I run my M59 at a fairly low RPM.... about what we used to call a "fast idle". For heavier work I engage the autothrottle and let the computer choose the RPM.
Enjoy, rScotty

 

[Hersheyfarm]

When I am digging 8' sewers a couple hundred rpm's makes huge difference in hydraulic flow and speed. 2500 rpms is slower than 2700 but 2700 seems to high to me for a diesel. there is no mention of any operating speed other than 'rated' . ok.

 

[rScotty]

When I am digging 8' sewers a couple hundred rpm's makes huge difference in hydraulic flow and speed. 2500 rpms is slower than 2700 but 2700 seems to high to me for a diesel. there is no mention of any operating speed other than 'rated' . ok.

OK...I understand now. Mine is the same. At 2500 it seems to be working hard and at 2700 is seems to my ear to be revving too high.

This morning I went through the various workshop and parts manuals to try to understand more about how they set and define the engine speed.

First of all, Kubota seems oddly reluctant to commit themselves. For example, the engine governor is a mechanical spring type (not via the intellipanel computer)...and although the workshop manual goes into detail about uworking on the governor I could not find any refererence to what speed to set it to!! If the information is there it is in hiding.

BTW, I did see where the PTO is geared to turn 540 rpm at 2550 engine RPM. I'll probably use that rpm as my own set point for max RPM.

And I learned that the 2700 rpm "rated" speed comes from specifications for testing of the hydraulic system. All of the flow related rate tests are conducted at 2700 rpm for the main hydraulics and also for the PTO, PS, and swing systems.
The exception to 2700 rpm is for testing the relief valves. They are to be tested at "maximum" rpm - which is not defined anywhere that I could find. Just as you said.

The "max rpm" for the relief valve makes some sense. After all, if the governor springs are setting the engine to some fuzzy undefined rpm, then one ought to at least set the hydraulic pressure relief valves at the same rpm.

I think our M59 max rpm is about 2900 rpm - though I can't recall ever looking to see. Maybe I will try it out next time it is good and warm. Probably try it in low or medium range at max hand throttle. And with/without the autothrottle engaged. That should be safe enough, and we can read the max RPM on the panel.
rScotty

 

[art]

the best fuel economy, and over all running ease (performance) is normally about 2/3 to 3/4 throttle! This is true on most engines in the field.

 

[dstig1]

I find on my L3130 that if I run much less than full throttle, it can lug then engine with the work I do, and my steep lot. Now if I put it in L instead of M, that is much less an issue, but then that slows me down a lot. I have been burning through diesel rather quickly lately... Early on, when I was really new to all this, I ran at lower throttle settings and the fuel lasted a lot longer it seemed, but once I became attuned to the lugging issue, I increased throttle to max for most running time. I idle down when I stop. I do wish I didn't have the base motor for the L series, but then when you buy used, you have to make some compromises.