P.T.O. ....R.P.M. Question

[1Lawman]

I've always mowed with a 10' mower on a 82 H.P. Kubota..Now I have a John Deere 5093E that 93 H.P. I just finished my pasture mowing with the J.D. and it doesn't seem like the cut is as clean..I know ground speed is one of several variables not to mention gear selection, grass height and toughness but it just doesn't seem like my P.T.O. turns as fast on the Deere..All things considered am I likely turning my blades faster on the Kubota than the John Deere?

 

[SSdoxie]

If running engine RPM of both tractors to the PTO mark on the tach, they should be the same. Were you running at the PTO mark on the JD or running at same engine RPM as the Kubota? Engine RPM @ 540 PTO is likely different.

If running both at PTO mark, tachometer might be off a little. Check it with a photo tach.

 

[1Lawman]

If running engine RPM of both tractors to the PTO mark on the tach, they should be the same. Were you running at the PTO mark on the JD or running at same engine RPM as the Kubota? Engine RPM @ 540 PTO is likely different.

If running both at PTO mark, tachometer might be off a little. Check it with a photo tach.

Now that you mention it I can tell you I run the Kubota at or near the PTO mark but not the JD...The J.D. has much more power and doesn't slow down as much as the Kubota in taller/tough grass.. My pasture is rough and I think my Kubota has a longer wheelbase and probably rides smoother...So if I understand correctly the blades may be spinning at different speeds when both engines are turning 2100 r.p.m. ??? correct???

 

[SSdoxie]

Now that you mention it I can tell you I run the Kubota at or near the PTO mark but not the JD...The J.D. has much more power and doesn't slow down as much as the Kubota in taller/tough grass.. My pasture is rough and I think my Kubota has a longer wheelbase and probably rides smoother...Will the blades be turning equally if both engines are turning the same r.p.m.?

Not necessarily, more likely probably not. The PTO speed is usually designed to be at or very close to optimum torque speed of the engine. Based on engine torque at given RPM the PTO gear reduction is established. Could change with every engine even in same manufacture.

 

[1Lawman]

Not necessarily, more likely probably not. The PTO speed is usually designed to be at or very close to optimum torque speed of the engine. Based on engine torque at given RPM the PTO gear reduction is established. Could change with every engine even in same manufacture.

okay...that helps...I believe the PTO mark on the Kubota is at a higher rpm than the J.D.

 

[Tx Jim]

By chance were you operating JD in the E-PTO mode?

 

[Gary Fowler]

About the only thing to degrade cut quality when using the same mower is less PTO speed and more ground speed, so if you did either or both of those, you can surely expect less cut quality.
If your pasture is like ours, I doubt you would be going too fast but slow PTO speed might be the culprit.

Does your tractor have multiple speed gear box for the PTO or just a single speed? MY LS has 3 speeds so I can shift to a higher speed (750 RPM) and reduce throttle setting appropriately(72%) so the PTO still spins at close to 540 RPM and safe some fuel since I don't need all the engine's power to turn the mower.

 

[1Lawman]

This JD is new to me so I was doing a lot of experimenting..I cut some in E-PTO and some not and at higher engine rpm's..At first I did not like the E-PTO mode but after using it a couple of hours I can say it really makes a lot of difference on fuel consumption and this tractor has plenty of power...

 

[sunnyside360]

Have to agree with the responses above but I would add one more factor --- blade condition. I mow about 75 to 100 acres once a year on this old farm and have found that keeping the blades sharp helps a great deal in getting a nice finish while allowing the tractor and rotary cutter to run at lower rpms which saves fuel and is easier on equipment. I usually adjust the ground speed according to how well the cut is, ie, just below where "skip" occurs. The blades are sharpened when cut quality starts to degrade which is usually about 1 or 2 times per year.