Slipclutchs, any downside?

[Anonymous Poster]

Most everything I read says slipclutchs are the way to go for rotary cutters. My NH dealer, while a fan of slip clutchs, offered this caution: He said slip clutchs can freeze up and not provide the protection they are supposed to if you don't perform proper annual maintenance on them. This includes loosening the bolts, slipping the clutch and retightening the bolts to establish proper torque slipage. It all sounded straight forward until he started explaining how you set the bolt torque to get the proper slipage torque and I started thinking this sounds exactly like something a neophyte like me will mess up. Has anyone ever heard of driveline damage caused by a poorly maintained slip clutch that didn't slip? Is there really an issue here to be concerned with and if so how do you know how much to tighten the bolts so the clutch slips at the proper torque?
Thanks,
Newland

 

[Bird]

Your dealer is right; regular maintenance is needed.

 

[BOTAMAN]

To make sure your slip clutch is working properly it is necessary to do as you dealer instructed. After the cutter has not been used for an extended period of time such as over the winter the friction discs may stick to the metal plates locking the clutch up, should you hit something solid with the clutch in this condition it could damage the mower drive shaft or possibly the tractor pto shaft, have seen both of these things happen.
Woods on their larger cutters are starting to coat their metal plates with a non-stick coating, but as far as I know they are just begining to do this and it is not available on their smaller cutters yet.

 

[beenthere]

<font color=blue>and if so how do you know how much to tighten the bolts so the clutch slips at the proper torque?<font color=black>

As long as you don't initially tighten too much (follow the manual), then if not right, the clutch will slip. If it slips, tighten some more. This adjustment routine, IMO, is easier to do than having to replace shear bolts (as they usually shear when it is the least convenient to repair).

And now that you mention the subject, I need to do that to my rotary mower clutch before using it the next time. It is an often neglected practice (which is probably what your dealer was trying to help you with). Thanks for the post.

 

[gerard]

Just from personal experieince on my land I don't need and don't want a slip clutch for my mower for the stated reasons. (freeze up if not "slipped" periodically). After two years of mowing I have not sheared one bolt and so see little reason for slip clutch. Due to the design of rotory blades (two piece design with the "blade" portion pivoting freely on the arm portion), if you hit an obstruction with the pivoting portion it'll just deflect. I guess if you mow a lot of really rough stuff and regularly shear bolts, you may want a slip clutch but I would evaluate YOUR mowing needs to determine if you really need a slip clutch. (Now on my post hole digger I shear bolts ALL the time and would LOVE a slip clutch!!)

 

[Robert_in_NY]

If you chop brush any amount you will go thru bolts like crazy. If you cut weeds only in a small pasture you can probally go 5 years or more on one bolt. I have a old ford chopper with slip clutch that is still going strong and recently bought a Woods chopper with slip clutch that I did make slip when it bit off more then it wanted to chew. You are right though if you only maintain a pasture or small fields you can buy a lot of bolts for the extra the slip clutch will cost.

 

[DFB]

Newland,

For the question "how do you know how much to tighten the bolts so the clutch slips at the proper torque?"

On the two clutch units I have, the initial preset spring length measurement is supplied in the implement's operator's manual.

The simplest adjustment procedure I've seen described is to simply back off the clutch spring retaining nuts
1 Full Turn Each, then engage the PTO intermittently (on/off) several times at low rpm's causing the clutch to slip. Then retighten back to within 1/64" of their original position.

Now that can be easier said than done /w3tcompact/icons/smile.gif depending on your access to the clutch pack, safety shields etc.

There's a lot of info pertaining to slipclutch adjustment in the TBN archives too. This link is to one of the other discussions on slipclutch adjustment too. <A target="_blank" HREF=http://www.tractorbynet.com/cgi-bin/compact/showflat.pl?Cat=&Board=implement&Number=59293&page=&view=&sb=&o=&vc=1>Slip Clutch Maintenance</A>

DFB

 

[Anonymous Poster]

Thanks for the help. The link does a good job addressing the issue.

Newland