540 rpms or less?

[theboman]

</font><font color="blue" class="small">( I agree with the others.. mowing at much less than 540 rpm is going to yeild non-optimal results. however mowing at excessively higher speeds than 540 may be detrimental to the mower..

Soundguy )</font>

That's a good point.. There's a big difference in pto RPMs and ground speed.

I'm not sure but if you open a throttle all the way open and engage a 540 RPM PTO I'd bet it don't get to 600 RPMs. Running a tractor a 1/2 thottle won't get a PTO up to speed.

 

[Villengineer]

</font><font color="blue" class="small">( I'm not sure but if you open a throttle all the way open and engage a 540 RPM PTO I'd bet it don't get to 600 RPMs. Running a tractor a 1/2 thottle won't get a PTO up to speed )</font>
That will depend completely on the tractor. Based on the gear reduction for the PTO on my tractor I can achieve more than 600 RPM at full throttle.

As far as the overall question of running attachments below 540 damaging equipment there are too many variables to make a general rule. Obviously there are resonable limits to what the manufacturers have built the equipment to handle, both above and below the stated operating rpm. Here are some things I think matter:
1) Obviously most implements will not operate properly at idle, but there has to be an acceptable range. A manufacturer would be a fool to design it otherwise. After all I've operated more than 1 tractor that either didn't have a tach or it was inoperable. For that matter the tachs aren't usually all that precise anyway.
2) Too low an rpm will probably affect proper lubrication as much as anything else. Most gear boxes rely on the gears "throwing" the oil/grease around to get everything nice a lubed. Most likely proper lube is achieved at a resonable rpm less than 540.
3) If you have balance problems below 540, you have them at 540 and most likely will do more damage at the higher speed. The reason it seems to be better at higher speeds is that you're "chopping" the amplitude by increasing the frequency of the vibrations. The bearings don't like either condition.
4) Each implement may or may not have specific issues with operating below the prescribed rpm. As far as a finish mower is concerned, the quanity and quality of cut will be affected. But I doubt that it would cut well at all if the rpm were so low to be a problem.

 

[OkieG]

<font color="blue"> Brett, are you sure that 2600rpm = 540pto rpm on your tractor? That sounds like top speed on most diesel compacts, with 540pto rpm at about 2200 engine rpm. </font>

Norm,
It seems to me that engine rpm to achieve PTO speed varies plenty from tractor model to model. My little JD is hanging out at the end of the bell curve. PTO speed of 540 is at just over 3000 rpm engine speed. Top engine speed is just 100 rpm or so over the PTO mark on the tach, so I can't overspeed my implements by much. On the other hand, the engine itself sometimes sounds like it's overspeeding for the task at hand when it's running at rated PTO speed.

OkieG

 

[BrettW]

normde2001,
thats what I was told by other owners of a Kubota B7800. Sure seems high to me also. But the posts on this thread talk about 540 rpms being about 80% of engine power. Hope someone else will confirm it for me. bw

 

[Soundguy]

</font><font color="blue" class="small">( I'm not sure but if you open a throttle all the way open and engage a 540 RPM PTO I'd bet it don't get to 600 RPMs. Running a tractor a 1/2 thottle won't get a PTO up to speed.
)</font>

That's going to depend on gear ratio.. On my 8n.. 1500 engine rpm is right at 540pto rpm./ Tractor maxes out at 2200 rpm.. with 2000 being pretty much usable top end., and that is the belt pulley speed.. that makes a pto speed of 720 at 2000 rpm.. and 792 at max of 2200 rpm. That.s a 1 : .36 ratio. eng/ : pto rpm for my tractor. Other tractors vary.. My JD B doesn't even get to 2000 rpm.. more like 1500 or 1200 rpm.. etc.

Soundguy