Determining Correct Cutting Speed

[cnl390]

I have a John Deere 870 tractor and a 613 rotary cutter. How do I determine the correct speed of the tractor when shredding? I would like to go as fast as I can but still get the optimum cut.
Thanks

 

[J_J]

Listen to the engine to know if your cutting speed is matched to the PTO speed. If you have a tach, use it to judge correct speed. A good sharp blade cuts better, although some say they never sharpen. Trying to cut to much grass/weeds is not good. Make half cuts until you can manage it on a one cut regular cycle.

 

[whistlepig]

On most pastures if you are going too fast the tractor will beat you to death long before you run out of mower capacity. If you are going too fast on smooth ground in tall grass/weeds the quality of the cut will suffer. The grass/weeds won't have time to "stand back up" before the blades hit them. This will like tall tufts of twisted weeds and grass where the blade didn't have time to cut them and just twists them up.

 

[Soundguy]

Set the engine to pto speed.. now try your gears to feel the ground speed.

find the one that lets you run without bogging the engine down and gives you a decent cut.

plan your ground speed based on obstacles and any hidden treasures.. obviously clean pastures you are familiar with you can get some higher ground speeds on.. vs virgin thick terane..

soundguy

 

[have_blue]

I have a John Deere 870 tractor and a 613 rotary cutter. How do I determine the correct speed of the tractor when shredding? I would like to go as fast as I can but still get the optimum cut.
Thanks

It's something you'll have to learn. With a little seat time, you'll learn to read the signs.

Start off with a sharp blade, in a real low gear, at or near maximum PTO speed (usually 540 RPM).

Observe the cut quality and tune your ears to the engine sound.

Go up 1 gear at a time, each time observing the cut quality, and engine sound.

The object is to go as fast as possible, without your kidneys being pounded too much, while getting an acceptable cut quality, and without the tractor's engine sound changing too much. Lower engine RPM is always desirable, and reducing it a tad can save wear and fuel. Some cutter/tractor combinations need to run at PTO maximum, some tractor/cutter combinations can be run ~500 RPM lower and still cut fine.

Black exhaust smoke, strong diesel smell, or more than a 100 RPM engine RPM drop (not PTO RPM!) are indicators your gear is too high or your blade is too dull.