Do you mow at 540

[have_blue]

I have a Woods BB72. I cut at around 425 PTO RPM. I have found that 540 usually shreds the grass and makes brown fluff balls that stay in the field forever. 425 cuts the grass and weeds cleanly, and the plants fall over and lay flat, where they quickly decay. 540 makes a lot of whanging and banging noise as the weeds grind against the deck. At 425, all I hear is a nice swooshing sound.

I always take 15 minutes to touch up my blades every time I mow, and sharpen them truly sharp. At 425, they stay sharp, and only need a touchup next time. At 540, they start dulling out real quick, and look pretty sorry by the time I'm finished.

I don't think rotary cutters were designed to grind and shred thick grass and weeds like a mulching mower. That takes entirely too much power, and can really heat up the tractor engine and mower's gear box.

 

[greg_g]

I cut at around 425 PTO RPM. I have found that 540 usually shreds the grass and makes brown fluff balls that stay in the field forever.

Have you considered that your tach may not be reporting RPMs correctly?

//greg//

 

[Soundguy]

I also run my tach at the place where it gives me 540 pto rpm.. if perhaps not a few more rpm.. but never less.

Soundguy

I believe the engineers when they say blade tip speed is what cuts grass. That, and sharp blades of course. If their design (blade tip) speed is achieved at 540 PTO rpm, then that's where I set the throttle. On my KAMA that's about 2250 engine rpm. I apply the same logic to my rotary cutter. Same for the PTO driven spreader too. Those engineers calculated spread patterns based upon 540 rpm. So if I'm to go by the spread charts in the owner's manual, I'd best be turning 540 PTO rpm

//greg//

 

[Soundguy]

I always take 15 minutes to touch up my blades every time I mow, and sharpen them truly sharp. ...I don't think rotary cutters were designed to grind and shred thick grass and weeds like a mulching mower. That takes entirely too much power, and can really heat up the tractor engine and mower's gear box.

IMHO.. rotary rough cut mowers are not meant to have 'really sharp' blades.. but rather almost a 32nd flat... etc.

soundguy

 

[have_blue]

Have you considered that your tach may not be reporting RPMs correctly?

//greg//

That would be unusual on 2 different tractors.

 

[3RRL]

Same here...always at 540 pto rpm. I may accomplish this by using one or the other pto range (depends on cutting conditions) but the pto rpm is always 540. I also read a recent post written here on TBN where it doesn't hurt to spin faster than 540. I haven't tried that personally, since my results have been adequate so far.

 

[have_blue]

IMHO.. rotary rough cut mowers are not meant to have 'really sharp' blades.. but rather almost a 32nd flat... etc.

soundguy

Well, you're correct that 1/32" flat is usually recommended. But rotary cutters usually cut heavy stuff, which I knocked out years ago. All I cut now is grass and light weeds. Since I use it like a big lawn mower, I sharpen it like a lawn mower. I highly recommend sharp blades and lower RPM. Works great for the past 5 years.

 

[Turkeyman]

I cut at 1500 RPM with my MX6 and my Brown tree cutter, but if I want the best results I use the PTO speed of 2500 rpms. At 1500 rpm I can cut thru 5 ft tall Johnson grass ( looks like corn in a field).

 

[Neophyte]

my Brown tree cutter

How do you like your Brown Tree Cutter? Do you have any pics of it in action or the aftermath? We were thinking about getting one for our Ford TW30 (160HP). I'm not sure they are rated for this type of HP since the largest listed on the Brown site is 100HP.

 

[PineRidge]

I always take 15 minutes to touch up my blades every time I mow, and sharpen them truly sharp.

I happen to catch the highlights of your post Bob and the way that I 1st interpreted it thought that you were touching up your blades with paint after each mowing. Thought to myself, "Man wish I had that kind of diligence." Then the true subject matter of what you were saying hit me. Boy did I feel foolish!