Setting slip clutch on Woods BB60.30 brush cutter

[John_Mc]

I finally replaced my old Woods BB60 rotary cutter. It had been beaten to death mowing rocky trails over the years and more was broken on it than was worth fixing (or so I thought until I saw the price of a new one).

I'm having some issues with the slip clutch. The manual says to loosen the 8 adjusting bolts until you can spin the springs freely, run it to slip the clutch, then tighten the bolts back down until the springs are compressed to a length of 1.12 inches. There is no table of spring lengths to set for different HP tractors, just the single notation of 1.12", despite the fact that it is rated for 25-50 PTO HP. There is no mention in their procedure of making sure it slips when hitting a solid object.

The first issue I ran in to was that it is a real pain in the butt to even get to the bolt and nut behind the shields. Even worse, it's just about impossible to measure the length of the compressed springs: the access holes allow you the reach the heads of the bolts, but it's hard to even see the springs, and there is just no room to get a caliper on them. I finally gave up and asked the service manager at the dealer. His advice: we just set them before we put the PTO shaft on the mower. Duh! not sure why I did not think of pulling the shaft off. I did that and had a much easier time tightening them down. I went to 1.20", so it should be a bit easier to slip than what the Woods spec calls for.

My tractor is 33 HP, or 27 HP at the PTO, so I'm near the bottom of the HP range (but have always been satisfied with the performance - I did not even consider going with a smaller mower). I hit a few rocks and stumps as I was mowing and it would stall the tractor, unless I was quick on the clutch. No sign of slipping. Do people generally set theirs to the factory specs, or loosen them up until a solid hit makes them slip? Do you intentionally set it down on a stump to test?

My old one was set about where I thought it should be when I bought it: slipped (and made a very distinctive noise) when hitting a solid object, ran normally otherwise. All I had to do was loosen it at the beginning of the mowing season, slip the clutch, then tighten it back down the same number of turns that I loosened and I was good to go. Every few years if it loosened up, I'd tighten all of the nuts just a bit.

 

[wirlybird]

I'd set them as stated to start with and work from there. If it slips too much then tight 1/4 to 1/2 turn on each bolt. Same if it never slips.
I wouldn't want it to slip except under extreme cases but personal preference here. I also run a grade 5 bolt rather than an 8. The idea is that the grade 5 may break quicker in an extreme case if the slip clutch fails for whatever reason.

Did you get another Brushbull? I love mine.

 

[John_Mc]

Yes, a Woods Brushbull BB 60.30

I was happy with my original one, so figured I’d stay with the same brand.

I was considering going to a flail mower, which would be easier to maneuver on some of my trails. I was a bit concerned with that option, since they don’t seem to do as well when mowing high. (Though I think they do a better job when mowing short). I was very tempted by all the MechMax adds I’m constantly getting spammed with. Their flail mower that side shifts and tilts down into ditches or up vertical certainly looked interesting.

 

[repete]

I would take it apart and clean it to start with. The clutch will likely have two sides that slip, simply loosening the bolts may only alow one side to slip.
I have found these to frequently be rusted and locked so a clean surface is necessary.

Also, I put a line across the clutch so I can see if it slips. I want it to slip under REALLY heavy loads. Carry one of those point and shoot thermometers and monitor the temperature. If it gets overly hot tighten it a bit. If it is 10-20 degrees above ambient temps then it is doing its job of protecting your tractor.

I do not think it is an absolute "adjust to this setting" but rather what works to protect your particular machine.