I received a couple of letter from viewers, both revolving around driveline protection in their rotary cutters or brush hogs. The topic of today's video is whether slip clutch or shear bolt driveline protection is better.
The two letters came from opposite ends of the spectrum...one viewer is constantly breaking shear pins and they're hard to access on her cutter. The other viewer ran over a 10" stump and the slip clutch or shear bolt protection didn't work.
Shear bolts are designed to break when you encounter an object that doesn't move. Problems arise when they're breaking all the time and/or they're difficult to replace. Some driveline designs have a mechanism built in that is very easy to access which puts the shear bolt out to the side. Others run the shear pin through a shaft and they can be difficult to access because they're buried up under shielding at the end of the shaft.
Sometimes the tractor is the cause of the frequent shear pin failures. My tractor has a very abrupt engagement of the PTO. If you don't move the lever back very slowly, you'll break a shear bolt every time. Also, sometimes the manufacturer's recommendations for the grade of bolt is pretty conservative. If running a grade 2 bolt and constantly having to replace it, you may have to move up to grade 5. The customer who hit the stump may have a grade 8 bolt in his driveline protection, offering virtually no protection.
Slip clutches, therefore, would appear to be the favored version of driveline protection. They are usually about $50-$600 more expensive, but if you hit something, they're going to stop the machine, then you can get back to work without getting off the tractor seat. The problem with a slip clutch is it has to be maintained. Loosening the bolts and "burning in" the clutches every year insures they're functioning properly. Especially in humid climates, a little moisture in the clutches and they weld themselves together and again, they don't offer protection, which could have been the issue when the viewer hit the stump.
In the end, which system is best? If you maintain them, slip clutches are are great way to go. If you're not the most meticulous at maintenance like I am, I'll stay with my shear bolt.
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