do you allways have to run tractor at full rpm for work?

[Dr. Bob]

Ditto on the post hole digger! When that thing gets going it can bury itself pretty fast and it dosn't have a reverse to get it back out!!! If you've ever got one stuck in a hole, you know how much fun it is to get it out.

For mowing with the brush hog, I run at the rpm at the lowest speed that give me the cut quality I want: mow a little and look behind you to see how its cutting. It depends on the blade sharpness, too.

 

[Reg]

Ditto on the post hole digger! When that thing gets going it can bury itself pretty fast and it dosn't have a reverse to get it back out!!! If you've ever got one stuck in a hole, you know how much fun it is to get it out.

For mowing with the brush hog, I run at the rpm at the lowest speed that give me the cut quality I want: mow a little and look behind you to see how its cutting. It depends on the blade sharpness, too.

The REAL trick with the post hole digger is to not get it stuck (-:
I do this by closing my lowering speed valve and then opening it just a tiny bit, so if/when the auger grabs it won't screw itself down, it will/SHOULD either pull something up and out, or break the shear pin and quit.

Not suggesting or recommending this, but it CAN work to free a stuck auger.
With the PTO in neutral, get the FEL bucket up on edge and use the curl/dump to "rock" the tractor back and forth a LITTLE BIT !, but not enough to bend the auger, while trying to raise the 3pt.
According to how your shear pin is located you might have to replace the broken one before you can try lifting, in which case;
Shut the tractor down, the PTO should already be in neutral at this point but check it anyway. Rotate the shaft by hand until you can replace the shear pin. Start up the tractor and LIFT ONLY.

 

[Ken45101]

I haven't seen the EXACT wording that you refer to, but it is sometimes the case that a tractor puts out it's maximum POWER at an engine speed different to it's maximum SPEED.
Some manufacturers might design for and recommend an engine speed that produces 540 at the PTO maximum torque, or maximum power.
A design choice.

I understand. From what I've seen of the torque curve on the M5040, it's pretty flat from 2100 rpm (540 pto) to WOT at 2600.

Ken

 

[ezlife]

Do I understand correctly that the 540 pto speed is only achieved at full throttle? Not to be dumb, but I thought for some reason that the pto speed was always at a constant 540 regardless of engine speed. I know I've seen farm machinery connected to a stopped tractor at idle speed working along just fine. Somehow I thought that was the point.

 

[pdowling1]

EZLife, your assumption is incorrect. PTO speed is directly proportional to engine RPM. The ratio varies from one model to another, but always if you double the engine speed you double the PTO speed. 540 PTO RPM is generally achieved at 80-95% of max engine RPM. Keep in mind, as others have pointed out, you don't always need or want 540 RPM. A post hole auger is a good example where slower is better. Mowers generelly work best at high RPM.

 

[Ken45101]

pdowling is correct. PTO speed is directly proportional to engine RPM. Some tractors need flat out full throttle to reach 540 rpm, others reach is as much as 20% below full RPM. That's one of the reasons I didn't like the Kubota MX5100, it had to be run at max rpm (2700) for the PTO whereas my M5040 and M9540 only run around 2100 rpm evne though their max is around 2600.

Most implements don't have to be run at the full 540 rpm although my Bush Hog rotary cutter manual recommends not running slower as it will cause more wear on the blade pivots.

Ken

 

[RadarTech]

Lets see brush hog says run at 540 rpm and you cut the throttle to half and its running at 300 rpm tip speed on blades drops and and you blame the mower for bad cut?

The guy that designed said run it at 540 run at that point and adjust my ground speed to conditions.
tom

ya know-- the guys that designed the tractor and the attachements are a whole lot smarter than me... So if they say.... then I have to listen -- albeit with a grain of salt sometimes..

J

 

[arrabil]

I've always found with any HST I've ever used that the whine becomes more of a begging for mercy type sound at engine speeds below 2000rpm or so. With a BH or PHD you're stationary and I wouldn't have much trouble running the engine much lower. But in motion I try to keep the tranny pump happy. Maybe I'm being overly concerned but I don't like that point where the whine turns to squeal.

 

[Reg]

Do I understand correctly that the 540 pto speed is only achieved at full throttle? Not to be dumb, but I thought for some reason that the pto speed was always at a constant 540 regardless of engine speed. I know I've seen farm machinery connected to a stopped tractor at idle speed working along just fine. Somehow I thought that was the point.

Partly right, partly wrong.
GENERALLY: PTO shaft speed is directly proportional to engine speed, so there will be an engine speed (maybe 2 or 3 if there is more than one selectable output shaft gear) at which the PTO shaft rotates at 540 RPM (and/or at 1,000 etc).

HOWEVER, that isn't necessarily "full throttle" (a misnomer on a diesel), neither is it always the engine speed at which maximum rated power is produced, or maximum torque.

This is HARD for some folk here to acknowledge, but not ALL attachments have to be run at 540 "all the time".
Many/most are merely spec'd to be run at NOT MORE THAN 540 and without knowing what you have seen run on a stopped tractor at idle - it is not possible to comment further.

There might be exceptions to this, e.g. one that matches your misconception.
I don't know of any in the small tractor context, but I wouldn't bet against the existence of such a transmission SOMEWHERE in the agricultural industry (-:

 

[powerstroke444e]

The biggest killer of hydro's and over heating of engines is from running at less than rated rpm. That is why I will take a new machine or well used machine over a machine grandma only used on sunday and never worked hard. WFO all the time, with a few exceptions like the posthole digger or bale elevator. Gear tractors you have to use the throttle for loader work to adjust the speed but on a hydro wfo.