When mowing grass with my brown attachment it’s in third gear low range at 1800 rpms and its a comfortable speed and mows fine. Can it cause any potential problems not running the pto to the full 540 rpms. It’s basically flat ground.
Mowing at less than pto speed
- Thread starter Wolfbay farm
- Start date
It likely depends on whether the tractor has a DPF. According to what I've read here and other places, a tractor with a DPF needs to be run at higher PM's.
My tractor is pre-DPF and I vary the engine/PTO speed to suit conditions. My rear discharge RFM handles clippings better at different RPM's at different times. Amount of "juiceiness", height of the grass, presence of dew, etc all come into play. Yesterday I ran the PTO around 470 RPM's.
My tractor is pre-DPF and I vary the engine/PTO speed to suit conditions. My rear discharge RFM handles clippings better at different RPM's at different times. Amount of "juiceiness", height of the grass, presence of dew, etc all come into play. Yesterday I ran the PTO around 470 RPM's.
85Hokie
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BX-25D ,PTB. Under Armor, '90&'92-B7100HST's, '06 BX1850 FEL
This is an age old discussion ...... and even an argument.
So - lets start at the beginning -
Why does EACH tractor manufacture have a engine rpm to match an implement rpm?
Each implement makes their device operate efficiently at 540 rpms (forget all the other rpms for a second)
That decision is based on bearing, blades, tines, or whatever is being dragged or spun.
In a cutter - either horz or vert, a blade will spin with a certain rate, not RPM - rather feet per second at the tip. So a blade that is 24" in diameter has a spin that makes it cut well - so the gearing of that blade is matched to the 540 RPM.
This is a lot of science and calculation being used to determine blade spin - a rotary cutter of 60" Diameter may have 2 blades with the same FPM as a cutter with 24" Diameter - but if you look at how fast they spin, it will be completely different, even though the FPM is the same.
Now to answer your question.
It does NOT help the tractor to cut at a lower rpm than designed. A diesel is a torque machine - designed to run a "X" rpm to make everything work as it should - running an engine at a lower RPM to "think you are saving" the engine is bad choice. I will say, sometimes when using say the backhoe - it might be fine to run the rpms down a bit if you need MUCH more careful control in a very tight space between two item that you do not want to damage.
Getting back to the physics of cutting grass - sharp blades and correct rpms will do two things to always help - it will cut the grass better - Newton's second law, F=MA . Also - the clippings will be thrown out further, thus placing lest strain on everything under the cutter.
Ok -3th thing - the engine will be happier and MAYBE burn less fuel at the rate of cutting at the higher RPM - while this though may be counterintuitive, some engines will burn less fuel at 2800 rpm's than at 1800 rpms depending on the engines torque curve.
The real bottom line - are you going to "hurt" anything? Probably not, you are in full control of what occurs with your machine. In my opinion, is it speed of moving you want to achieve? In other words - I want to hurry up to cut the grass, or is it I don't want to run the engine at a high rpm for noise or stress?
So - lets start at the beginning -
Why does EACH tractor manufacture have a engine rpm to match an implement rpm?
Each implement makes their device operate efficiently at 540 rpms (forget all the other rpms for a second)
That decision is based on bearing, blades, tines, or whatever is being dragged or spun.
In a cutter - either horz or vert, a blade will spin with a certain rate, not RPM - rather feet per second at the tip. So a blade that is 24" in diameter has a spin that makes it cut well - so the gearing of that blade is matched to the 540 RPM.
This is a lot of science and calculation being used to determine blade spin - a rotary cutter of 60" Diameter may have 2 blades with the same FPM as a cutter with 24" Diameter - but if you look at how fast they spin, it will be completely different, even though the FPM is the same.
Now to answer your question.
It does NOT help the tractor to cut at a lower rpm than designed. A diesel is a torque machine - designed to run a "X" rpm to make everything work as it should - running an engine at a lower RPM to "think you are saving" the engine is bad choice. I will say, sometimes when using say the backhoe - it might be fine to run the rpms down a bit if you need MUCH more careful control in a very tight space between two item that you do not want to damage.
Getting back to the physics of cutting grass - sharp blades and correct rpms will do two things to always help - it will cut the grass better - Newton's second law, F=MA . Also - the clippings will be thrown out further, thus placing lest strain on everything under the cutter.
Ok -3th thing - the engine will be happier and MAYBE burn less fuel at the rate of cutting at the higher RPM - while this though may be counterintuitive, some engines will burn less fuel at 2800 rpm's than at 1800 rpms depending on the engines torque curve.
The real bottom line - are you going to "hurt" anything? Probably not, you are in full control of what occurs with your machine. In my opinion, is it speed of moving you want to achieve? In other words - I want to hurry up to cut the grass, or is it I don't want to run the engine at a high rpm for noise or stress?
I operate all of my mowers below rated PTO speed nearly all of the time and have done so for decades.
Absent extreme circumstances (abuse) doing so will damage neither tractor nor mower.
SDT
Treckerzeug
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Carraro tgf 7800 taijfun 4,5 t winch, trailer with crane, double bl saw
No worries, if it mows fine everything is fine,
A "torque" engines loves to work at low revs,
Max torque on a modern engine is available at a wide range of engine speed.
Most larger tractors today are designed to reach their top road speed at reduced engine speed, e.g. 40 kph at 1300 rpm
A "torque" engines loves to work at low revs,
Max torque on a modern engine is available at a wide range of engine speed.
Most larger tractors today are designed to reach their top road speed at reduced engine speed, e.g. 40 kph at 1300 rpm
My experience from watching individuals cut at low speed is that the deck belt fails far more frequently than it should.
Dave
Dave
No doubt about that. There must be a criteria for the design of a mower that fits an average usage. BUT, we don't mow astroturf that is manufactured to a certain specification. We mow live plants. All the grass I've cut has varied in moisture content (what I call "juiciness") through the season. It changes significantly between the first and last mowings of the season. The amount of grass that's cut off isn't always the same. Sometimes there's still some dew left when I start, and sometimes when I mow in the evenings dew starts forming before I'm done.
Cutting at rated PTO speed is no problem. Distribution of the clippings is. Varying the speed allows the mower to be tuned in to the current conditions. To suggest that the mower must only be run at it's spec sheet RPM because some engineer said so is like telling a welder he can't tweak the amps to suit the task.
If it cuts the grass and you are satisfied then you are doing it right and don't need full throttle.