1962 Masset ferguson 65

Hello everyone i am a new member and this is my first post the problem I have is on two occasions whilst using a topper with my tractor I have accidently run over an unseen rock or other obsticle, (stupid I know but this is my first tractor and I'm very new to this )
now to stop the PTO extension shaft breaking at the coupling apparently i can fit an adaptor which allows the blade on the topper to stop suddenly but does not do any damage to the pto shaft. So do I need an overrun coupler or a slip clutch ? any help with this matter would be greatly appreciated. Thankyou Andy.

Can you clarify your post? I've never heard of a "topper". Are you concerned about your PTO shaft, or is the concern with some sort of PTO shaft extension?

A lot of PTO attachments use either slip clutches or shear bolts to protect things. A shear bolt is just what it sounds like. When the attachment encounters an obstacle, a cheap replaceable bolt shears (rather than breaking something more expensive). Slip clutches are normally built into the various attachments. I've never seen one that could be added between the tractor PTO and the attachment.

I've never used a PTO "extension" whose sole purpose was to increase the length of the PTO shaft coming from a tractor. I have used "extension" adapters on my early Ford tractor. The adapter fits over the original 1 1/8" shaft for use with attachments designed for a 1 3/8" PTO shaft. The ones that I have purchased in recent years were made in India out of what appears to be pot metal. They all seemed to fail after just a few months use. I finally got tired of replacing them and just replaced my PTO with a 1 3/8" aftermarket upgrade.

An overrunning clutch will not allow the tractor's PTO to continue to turn when the attachment is stopped by an obstruction.

Andrew, it sounds like you are posting about what is commonly called a brush hog or shredder here in the US. There are two things: First many mowers do have a slip clutch but many do not. You need to share your brand and model in oder to get help with what you may have now or what may be available for it. As tom said an over running clutch won't help you in your situation. Second, you can install a pair of chains from the hitch points of your mower up to the top link mount point, which will stop the front of your mower from dropping below the desired height. There are special brackets available from the mower manufacturers for this.

Andrew, it sounds like you are posting about what is commonly called a brush hog or shredder here in the US. There are two things: First many mowers do have a slip clutch but many do not. You need to share your brand and model in oder to get help with what you may have now or what may be available for it. As tom said an over running clutch won't help you in your situation. Second, you can install a pair of chains from the hitch points of your mower up to the top link mount point, which will stop the front of your mower from dropping below the desired height. There are special brackets available from the mower manufacturers for this.

If a topper is a rotary cutter, also known as a shredder or bush hog, you may need both an over running clutch(ORC) and impact protection. The ORC acts like a ratchet so the cutter can keep rotating and not impart its momentum to the drive axle of the tractor. On some tractors this momentum will cause the tractor to keep moving forward when the clutch is depressed without an ORC. It installs on the tractors pto shaft. Impact protection is acheived with a shear bolt or slip clutch. Both are typically installed right before the cutters gearbox. The shear bolt breaks when you hit something. The slip clutch is a spring loaded clutch pack that when adjusted properly slips when you hit something.

MF 65 will have 2 stage clutch. No need for over running clutch. Needs slip clutch or shear pin on hog. I prefer a shear pin. Must hogs have at least a shear pin.

Andrew might be in UK. I've heard them talk about topping.