Mowing rotary cutter in tall grass - clutch smell?

InThePines · Jul 27, 2012

L3700SU HST, less than 200 hrs on clock. Using a rotary cutter, I got into some tall grass, and could feel the tractor struggle some and smelled what seems to be a clutch burning smell. I raised the mower and kept going, the smell was not very strong and did not last long. Any idea what I was smelling? How can I prevent putting too much burden on my mower and how do I know when I am?

Thanks.

big bubba · Jul 27, 2012

does your mower have a slip clutch? if so, when over taxed, it will slip as designed (to prevent damage to drive train) it's possible you smelled the friction disc much the same as brake material that will do the same when overheated. if you raised up the mower or disengaged the pto, no damage done. may want to consider mowing higher 1st on low range at a slower speed, then finish cut. the clutch was just doing it's job
if you do not have a slip clutch, possibly it could be related to the pto clutch on the tractor itself. i am not sure about that end though. and KEEP THE MOWER KNIVES SHARP! makes a world of difference. good luck.

Bluegill2 · Jul 27, 2012

Need sharp blades when mowing tall, thick grass!!!

AStanton · Jul 27, 2012

Don't know much about slip clutches. Perhaps you need to adjust the clutch to increase the resistance a little. But be sure to test it after doing so.
For my money, I would always try to buy a unit that uses shear pins over a slip clutch. This is only my opinion.

SPYDERLK · Jul 27, 2012

InThePines said:
L3700SU HST, less than 200 hrs on clock. Using a rotary cutter, I got into some tall grass, and could feel the tractor struggle some and smelled what seems to be a clutch burning smell. I raised the mower and kept going, the smell was not very strong and did not last long. Any idea what I was smelling? How can I prevent putting too much burden on my mower and how do I know when I am?

Thanks.

If you have a slip clutch on the implement it should be visible. Feel it carefully for heat. If it is more than barely warm it is slipping from the drive torque required to cut the thick grass. This should never occur. Slip clutches are to prevent severe catastrophic loads that happen when you hit rocks or stumps etc. Slipping under steady state power, even the max available from the tractor, should never occur. ... If that clutch is hot from cutting grass tighten it or youll burn it up.
larry

big bubba · Jul 27, 2012

the working tension on most slip clutches are spring loaded w/bolt adjustment. your manual should state the proper clearance in terms of bolt tension for the clutch. as you'd imagine, if it's properly adjusted, it will not slip under normal working loads, but in your case of tall grass, the stress may have caused it to slip (hence burning smell)...this is what it's supposed to do. like previous poster said, just check it occasionally for heat build up under normal loads. actually, some recommend to check it @ start of every season by backing bolt tension all the way on all springs and it of course should slip (but not burn) (sometimes they bind over time). then tension back to specs. for liability reasons, i am not recommending this...just fyi. i think you are fine the way you described. just be careful checking things with pto running! (sorry, i was a jr hi shop teacher) good luck

InThePines · Jul 28, 2012

Thanks for the info guys, it is an old Ford 908 series, I dont know how to tell what model, but it has a slip clutch and I will be checking that for heat. Much appreciated.

SPYDERLK · Jul 28, 2012

SPYDERLK said:
If you have a slip clutch on the implement it should be visible. Feel it carefully for heat. If it is more than barely warm it is slipping from the drive torque required to cut the thick grass. This should never occur. Slip clutches are to prevent severe catastrophic loads that happen when you hit rocks or stumps etc. Slipping under steady state power, even the max available from the tractor, should never occur. ... If that clutch is hot from cutting grass tighten it or youll burn it up.
larry

big bubba said:
the working tension on most slip clutches are spring loaded w/bolt adjustment. your manual should state the proper clearance in terms of bolt tension for the clutch. as you'd imagine, if it's properly adjusted, it will not slip under normal working loads, but in your case of tall grass, the stress may have caused it to slip (hence burning smell)...this is what it's supposed to do. like previous poster said, just check it occasionally for heat build up under normal loads. actually, some recommend to check it @ start of every season by backing bolt tension all the way on all springs and it of course should slip (but not burn) (sometimes they bind over time). then tension back to specs. for liability reasons, i am not recommending this...just fyi. i think you are fine the way you described. just be careful checking things with pto running! (sorry, i was a jr hi shop teacher) good luck

Definitely NOT what it is supposed to do. A slip clutch should only slip under catastrophic impulse loads -- not attainable steady state loads. The only exception there would be when the tractor was a vast overmatch for the implement. The OP tractor and implement are well matched. His tractor should not be able to slip the clutch unless it was quickly stalling concurrently.
larry