540 rpms or less?

rswyan · Dec 9, 2004

( Noise probably, fuel consumption I don't think so. Speed your motor up and go a bit faster, getting done faster and you won't see a bit of change in fuel consumption. )

The only problem with that logic is that it would require the purchase of a kidney belt. /forums/images/graemlins/frown.gif

Seriously, even at the rpm/ground speed range I was running (in high range) I would not have wanted to go any faster becuase I would end up being beat to death from the bumps - even with the suspension seat.

rswyan · Dec 9, 2004

( If I mowed my "fairly" flat yard at 11 mph, I'd be airborne half the time, have blood in my pee, and need the crinkles taken out of my spine by the time I was done. )

Amen, brother, amen.

( If the grass is thick or long and the engine starts to bog, I bump up the throttle and/or travel slower. )

Same here - for the most part I'm not cutting all that much off - I have the deck set to 3.5 or 4 inches I think and the grass varies in height when I cut it from less than 3.5 inches to maybe 5 inches at most. And when I say 5 inches I don't mean all of a particular section is 5 inches, but that maybe 15% of any given section is 5 inches tall - interspersed with blades of a lesser height. I also have a small section that used to be an old corn field that was turned into pasture that I cut a few times a year which is much taller when I cut - 12 inches - on this I run the rpms up.

have_blue · Dec 9, 2004

I ascribe to the "sweet spot" theory. That is, mow at the lowest RPM and highest gear that runs smoothly and quietly, yet cuts cleanly and without lugging. This will probably not be too far from the arbitrary 540 RPM figure, but 50 RPM can make a big difference.

Personally, I try to mow often enough that I have few weeds. I run my tractor RPM at ~1800 and keep my blade very sharp. Things work very quietly and efficiently, the grass is cut cleanly, and it makes a big difference in fuel usage. It's obvious this is not harmful to my tractor or RC, because of greatly reduced noise and vibration. If I kick my RPM up to 2200 (or whatever it takes to get 540 RPM), it just wastes a ton of power by re-grinding the grass, and noise and vibration are a lot worse.

Just an aside: It's amazing how much longer my blade stays sharp and how much fuel I save by running a bit under 540 RPM.

YMMV!

theboman · Dec 9, 2004

If you mow and you go "airborne" the problem is not RPMs it's how fast you're mowing. Keep the RPMs up and lighen the foot on the hydro. Remember the hydro is not the gas pedal, it's a speed (and torque) control.

have_blue · Dec 9, 2004

( "I have never had a mechanic, manufacture or dealer tell me to run one at low RPM's."

I'm a mechanic and give you permission to run at less than full 540 PTO speed.

Rich )

If 2200 RPM were the best speed for tractor engines, the manufacturers wouldn't bother to put throttles on them! /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif

JerryG · Dec 9, 2004

540 rpm is the max rpm that most of our implements are rated at. This does not mean that they can't be run at a reduced rpm, (ex. Post auger) if the implement is doing the job required and the tractor engine is not bogging down. The engine is bogging down or is at the verge of doing so any time the fuel is increased, but the rpms do not increase.

theboman · Dec 9, 2004

If 2200 RPM were the best speed for tractor engines, the manufacturers wouldn't bother to put throttles on them! /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif )

The MID PTOs are 2400 or whatever but rear the most I've seen is 960 but 80% or more of the implements are 540 RPM.
That's why most tachs have a 540 RPM mark so you know when the implements are up to working speed.

I've never read any manual that said run the PTO lower than the desired speed. I have one or two saying running below the RPMs may damage the implement or the tractor. It's about balance too, they have these things call bearings that and things turn really fast and if not fast enough there's wobble....

OkieG · Dec 9, 2004

The engine is bogging down or is at the verge of doing so any time the fuel is increased, but the rpms do not increase. 

Hi Jerry,
Yes, I've been there, when I've bumped up the throttle, but the rpms didn't. I think that is definitely lugging the engine.

theboman,
Just read your bio. Man, I love bluegrass music. I could find it when I lived in Virginia. Around Oklahoma there's plenty of country music, but not much bluegrass. I have a banjo in the closet that gets dusted off a couple times a year.

OkieG

theboman · Dec 9, 2004

Ahhh bluegrass when I grow up it's all I want to do! /forums/images/graemlins/smile.gif
3 radio shows in 7 states on 15 stations, or close to that.
I MC a ton of shows too.

BTW, I had to get my 'Bota for mowing and now have to make time to garden, bush hog, etc... I love my tractor too and I never run implements below the recommended RPMs.

I mow grass in 2.5 hours and use about two gallons of diesel. With the rider it was 5 hours and 4 gallons of gas...a lot louder, a lot more vibration, slower and rougher ride.

Now, 'bout that banjer....

Soundguy · Dec 10, 2004

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