PTO RPM range

[AllDodge]

Probably dumb question but does the 540 PTO have a min and max rpm range. Pulling my batwing up and down hills the motor rpms change and therefore so does the PTO

 

[Russell King]

There is one single RPM on the engine that will result in exactly 540.000 RPM on the PTO shaft. There is a mark on the engine tachometer that indicates a RPM speed that will be about 540 RPM on the PTO shaft. Unless your tractor has a digital tachometer I doubt that you can get exactly the speed on the PTO shaft.

In other words it is only approximately 540 RPMs when not loaded and will vary a bit down when the engine is working hard.

If very concerned with that then throttle up a little to get back to the correct engine RPM indicator when you see it starting to lug down.

 

[AllDodge]

Agree, just wondering if there is a Min Max (like 500 to 580) or does it really matter?

I'm thinking don't go over 600, and for the most part the tractor keeps it close.

 

[Palmettokat]

Alldodge think most common mention on the pto speed has been, "not to exceed the rated speed" or close wording to it. It would surprise me if a tractor's pto could reach 600 rpms in 540 gear or speed selector. Now if you have higher pto gearing say 750 then you could. If you are running a pto equipment you hear running listen to it. Often the sound will tell you are running it too slow or fast. So will the repairs.

 

[chim]

A PTO generator would of course be very particular about the RPM's to maintain frequency. Other implements aren't all that fussy. Most are designed to operate at a specific RPM for peak efficiency. I had a 3-point snow blower for a few years and 540 worked quite well. I've rarely exceeded 540 except for short periods because of a concern for any bearings, etc. An example of that would be for a minute or two when I used a side discharge deck to blow clippings off the driveway.

Since selling the blower, my only PTO usage has been with RFM's, and the one size fits all 540 RPM isn't as applicable. The tractor has a display to see the PTO speed. The speed at which the mower performs best varies with the condition of the grass. The deck cuts well at any speed, but has a moving sweet spot for spreading the clippings nicely. The amount of grass being cut off and the juiciness of it make the difference. We're coming off a streak of dry weather here and when I mowed on Friday the deck did best at about 450 RPM's. The week before it was just under 400.

 

[Palmettokat]

chim, of course there can be many variables in mowing. The type of grass, how thick it is, how tall and how much is being remove. Then there is the different type of mowers and blades.

But for the rpms you quoted what kind of ground speed are you running?

 

[chim]

chim, of course there can be many variables in mowing. The type of grass, how thick it is, how tall and how much is being remove. Then there is the different type of mowers and blades.

But for the rpms you quoted what kind of ground speed are you running?

I'll have to check that when I mow this week. Recently it's been working well in HI range. I find myself toggling between Turtle and Rabbit. With the throttle set to whatever RPM it is for the blade speed desired, HI Turtle can be a bit slow at lower RPM's. One short but steeper hill needs MED Turtle to prevent bogging down.

Rabbit is geared too high for the larger slopes if mowing in one direction, but not the other. The low end of the property is the NE corner and the SE corner the highest. In rough terms, grade change is such that travelling from the low point to the high point will either take you 3/4 of the perimeter in one direction or just 1/4 in the other if that makes sense.

 

[chim]

chim, of course there can be many variables in mowing. The type of grass, how thick it is, how tall and how much is being remove. Then there is the different type of mowers and blades.

But for the rpms you quoted what kind of ground speed are you running?

Mowed late this afternoon. Grass was quite tall and thick. Engine RPM's were around 2000, PTO was running 416 and speed was 6 MPH for most of the time. I did drop back to HI Turtle on a couple hills. Shaky pics below.

 

[Bmyers]

I mowed yesterday afternoon. Grass was thick and still damp from rain the day before, plus most of the day it was foggy. I mowed at 4MPH, RPM was going from 550-530 depending on the thickness of the grass and if I was going up a slope. Parts of the area being mowed have 15-20 degree slopes (I installed a couple of slope gauges since I have seen different ones talking about it and was curios what some of our slopes looked like; the biggest was a 20 feet 30 degree slope.)

 

[Mike463]

What AllDodge said RE: the tach marking. Ideally, this is the engine RPM to provide the 540 RPM at the PTO. I suspect this particular RPM ...which is probably different for the different engines installed ...is probably the torque peak for the engine in your Kubota. The torque peak is the point at which the engine runs most efficiently, is most stable and able to absorb and recover from loads placed on it ...it is also the point at which the highest load can be placed on the the engine. There is no "range" per se ...the range is determined by how the engine recovers from loads placed on it. Your job is to set the engine to that hash mark on the tach and keep it there. If there was a "range" then it would be stated in the owners manual and marked on the tach.