less than 540/PTO dangerous?

[BrettW]

On another post (attachment area) the possibility of damagaing my B7800 engine came up because I run my finish mower at a lower speed than 540 on the PTO. Is this likely or possible? The engine doesn't sound loaded at all while mowing at roughly 1600 or so on the tachometer. Grass cuts well and there is a lot less noise.
thanks, brett w

 

[dmftoy1]

I don't know about damage, but I would bet that you're much more likely to stall the motor when brush-hogging. I don't know if that would be all that bad for the motor, but definately not as good for it as it just spinning. /forums/images/graemlins/smile.gif

I tend to run all my 540 pto equipment at 540. I figure that people smarter than myself came up with the specification for a reason.

Have a good one,
Dave

 

[beenthere]

I rarely run my rotary cutter at 540 PTO speeds. I usually am in brush and figure hitting a rock at that rpm is more dangerous and harder on the equipment than at less than that rpm. I rely on the PTO clutch to take the abuse if I hit something that might stop the blades. Works good for me. I don't think the engine speed less than the "540" PTO rpm is harming the engine in any way. I think the 540 rpm is a something that tells what the standard gear ratio is in the tractor, and what the attachment is rated for. But each can do what they want. I don't think there is a 'right' or a 'wrong' way to do it. I get a lot less debris flying around when running it at lower than 540 rpm.

 

[Larry_T]

I do not think you can hurt your engine. I run mine at less rpms a lot.In my brush cutter book it only said 540 was max.

 

[Henro]

What speed is the mower designed to run at? That would be my first question. IF it is 540 PTO rpm, why not run it at 540 PTO rpm?

BUT if the grass is being cut to your satisfaction at lower RPMs, what could that hurt. I think most of us will know when the engine is being lugged. If you are not lugging the engine, then why should easy work at lower RPM be any different than running the tractor across a field at lower than 540 pto rpm?

I tend to find myself on the "run implements at their design speed" side of the classroom.

But if the implement performs to your satisfaction at lower RPM, and you are not constantly lugging the tractor engine when using it this way, why should it matter one way or the other?

 

[frank_f15]

you could run it at less than 540 pto speed, and would not hurt, but i bet you won't run much less than that speed, so why not run at the pto speed it was designed for? it certainly won't hurt your tractor.

 

[ZackaryMac]

I run my MMM at less than PTO speed, but as I don't have a tach I can only guess at the engine speed. I find it is less noisy, cuts great, and uses ½ the fuel than running it at 540, which is almost full throttle.
The snowblower will be a different story, as it needs the impellor speed to throw properly.

Lower RPM won't hurt the motor, but lugging it will. Working it hard at too low an rpm is looking to damage the crank or bearings.
Boat motors, particularly outboards, will always fail (usually a broken crank) when run full throttle at less than the designed RPM.

 

[BrettW]

There must be some way to tell if you are lugging the motor down.
I always use my ears. The only time I recall lugging it was pulling a box blade around. That will lug it down fast.
As for mowing, would it be possible to check the rpms by setting the motor at X speed, lifting the mower deck and checking the rpms, then mowing and looking to see if there is an appreciable difference in the tachometer. Seems to me that would tell you if you were lugging the motor at all. bw

 

[DK35vince]

If you can increase the throttle and the RPM's will increase, you are not lugging it.
If you increase the throttle and the motor struggles or will not gain RPMs' you may be lugging it.