Buying Advice Live PTO vs. Over-running Clutch vs. Slip Clutch

[Beervangelist]

I'm looking at old tractors in the 20 - 30 HP range and have been receiving advice in another thread. (Ford vs. Case)

I've gained a new perspective in regards to LPTO, however I am receiving some interesting information from sellers and tractors. I've been looking to confirm whether tractors had the overrunning clutch, and have noticed others identify a slip clutch.

Can you help me understand if these are the same thing? I'm gleaning that I can add a $60 slip clutch to any tractor's PTO. Is the "over-running clutch" a factory feature of the same intention?

I'm looking at a lot of late 40, early 50 Fords and other makes, but trying to stay under 3K. Not finding many of the later Fords (861) with Live PTO, but if I can add the slip clutch for the same effect, it opens up many options.

Thanks in advance.

 

[rankrank1]

Adding the $60 overrun clutch is not the same thing as adding a PTO slip clutch. The overrun clutch is a worthwhile safety feature though as it will prevent the inertia in the implement (e.g. flywheel effect of a bushhog blade still spinning) from pushing the tractor forward even though you have the clutch pushed depressed. Newer tractors with non-live PTO power will have the overrun clutch built into the transimission and perform silently in the oil bath of the transmission. Older tractors will require the $60 overrun clutch to be added on externally and you will here them click when you press in the clutch.

Slip clutches are a totally differnet animal and not cheaply added to a tractor. Allis Chalmers had the "factory installed" power director lever which was a 2nd hand clutch lever that when pulled stopped the forward travel of tractor but allowed the PTO to still have power. The power director clutch ran in oil so it could be abused. M&W also made aftermarket kits to install a on popular tractors like Farmall H's and M's back in the day that offered a similar feature. But finding something like this today might prove difficult and it will not be an inexpensive item if you do find it.

While independant PTO is definitely best or even Live PTO is definately better, most tasks can be adequately performed with non-live PTO. The biggest difference is with non-live PTO you have to plan ahead for some situations. With independant or live PTO minimal planning ahead is required so it is more convenient.

 

[beenthere]

Can't improve on rankrank1's explanation.

There can also be a slip clutch on the PTO driveline of some attachments, separate from the tractor.

 

[ModMech]

^ Right.

A "slip clutch" *can* be installed in addition to, or in lieu of a shear-pin for the PTO driveshaft. In some cases the Torque limit of the slip clutch is low enough to prevent the PTO operated equipment from pushing a tractor with a transmission PTO because the clutch will slip before the there is enough Tq input to the tractor's PTO shaft..... at least in theory.

This is NOT the designed use of a PTO "slip clutch", it is to prevent severe PTO damage in the event that the powered equipment meets an immovable object (stump, rock etc). Use of a slip clutch to prevent the attachment from pushing the tractor will result in rapid wear of the clutch, which is not inexpensive.

 

[Soundguy]

it's better to refer to an ORC as an over running coupler.. this is the one that prevents back feed.

a slip clutch is a torque limiter.. think of a breaker and a fuse... shear pin is a fuse.. slip clutch is a auto reset breaker..

with live or independent pto, you usually don't need the ORC, unless you have a pto brake on the IPTO and want to save it some wear and tear..

soundguy

 

[LAWALLSTRACTOR]

It would be a big plus if you could find a tractor with live PTO.

 

[AndyMA]

it's better to refer to an ORC as an over running coupler.. this is the one that prevents back feed.

a slip clutch is a torque limiter.. think of a breaker and a fuse... shear pin is a fuse.. slip clutch is a auto reset breaker..

with live or independent pto, you usually don't need the ORC, unless you have a pto brake on the IPTO and want to save it some wear and tear..

soundguy

The only thing I'll disagree with here is that a live pto does nothing (in fact it is a direct connection) if you suddenly reduce the rpm's to the pto with a attachment that carries a large amount of rotational energy (flywheel effect). The ORC clutch allows this inertial energy to not be transmitted back into the tractor gear box where it does nothing good other than strain everything right back to the engine.

Andy

 

[Soundguy]

unless you have an orc built in. I know some models do.

I'm surprised you are choosing to disagree with my conditional statement about the orc.. ie 'usually'

so far, I havn't found the lack of an orc to be a problem on a 95hp tractor and a 15' mower.. which I'd say classifies as quite a bit of flywheel load.

imho..if the drive train is capable of handling the driven load.. it can handle the load decelerating as well.

soundguy

 

[beenthere]

Am with you soundguy. Good explanation, and agree it is an over-running coupler....not a clutch.

 

[Soundguy]

I think it gets called a clutch as it essentially clutches int he opposite direction, or when the implement overspeeds the tractor.. IE a 1-way clutch or ratchet. to save confusion from the newbies with the differences in that an a slip clutch.. the 'coupler' term seems safer.. to me anyway..

soundguy