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They are 2 completely different devices. An ORC allows theimplement, like a mower, to freewheel if the tractor pto slows down lower than the implement rpm. this is usefull in older single stage clutch, non live pto tractors like the ford 8n, NAA, etc.. because if you step on the clutch, the pto inertia will still be transmitted back to the transmission and drive the tractor. Live and independent pto machines do not need the over-running capabilities of an ORC from a safety standpoint.. There is however one use for an ORC on an independent pto machine.. many of them have a pto brake to slow the pto down when you disengage it. if you have a large mower on a machine.. like a 10' mower.. when you disengage the pto, the brake gets quite a bit of wear . with an orc. the pto will stop immediatly, and the mower will coast to a stop. In general, to minimize pto break wear, you should idle the engine down very low before disengaging the pto.. and similarly.. to prevent driveline shock, the pto should only be engaged at enough rpm so that the load won't stall the tractor.

Now.. for a SLIP CLUTCH.. that's a torque limiter and goes inline with the driveline.. if the mower hits an object that stops or slows it.. instead of shearing a shear pin.. or perhaps damaging the driveline or the tractor, the clutch will slip at a pre-set torque value. torque value is usually adjusted by spring tension on bolts onthe clutch. also.. slip clutches should be 'exercised yearly by loosening them til they slip a little, then retorquing them.. this prevents them from rusting up and not slipping when needed.

buy a slip clutch that will match the needs of the implement. for instance.. if you have a 60hp tractor, and are using a mower that has a 40 hp gear box.. get a slip clutch that you can set to slip at 40.. etc..

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