Shear pin misery... only thing left is adding a slip clutch?

[Dadnatron]

I do not bring it up from idle. That is not a feasible situation in my real world. I cannot idle down every time I want to begin mowing.

I have no strange noises. Everything begins and appears fine. It begins spinning, and everything is smooth, but I think the stress of getting all that metal moving simply overcomes the shear force of the pin.

I am extremely limited on what I can add as far as size of a bigger bolt. There simply isn't very much 'meat' to drill out and maintain integrity.

If I try to weld it (and I'm not sure whether it is cast steel or iron) and add an adaptable slip clutch at the machine, will that 'work' as far as protection of the tractor? I was able to find a slip clutch at TSC which slips over the shaft at the gear box, and onto which the PTO shaft can be attached. At least that is what it appears to be set up for. I thought, perhaps if I weld the 'shear pin pieces' together, then I could still protect things with the clutch. Any thoughts about this?

The only other thing I can do is to purchase a completely new PTO shaft with a slip clutch integrated already. This is probably what I should do. Get a new PTO shaft Series 6 or 8 with a CV joint and a slip clutch. I am sure this would cure 'all' the problems which have arisen.

IF anyone has a recommendation on where I can find such a shaft collapsed length of 72" with at least 18" working expansion, please link me or give me a name. The length that is required is making it difficult to find.

 

[Gator6x4]

I do not bring it up from idle. That is not a feasible situation in my real world. I cannot idle down every time I want to begin mowing.

I have no strange noises. Everything begins and appears fine. It begins spinning, and everything is smooth, but I think the stress of getting all that metal moving simply overcomes the shear force of the pin.

I am extremely limited on what I can add as far as size of a bigger bolt. There simply isn't very much 'meat' to drill out and maintain integrity.

If I try to weld it (and I'm not sure whether it is cast steel or iron) and add an adaptable slip clutch at the machine, will that 'work' as far as protection of the tractor? I was able to find a slip clutch at TSC which slips over the shaft at the gear box, and onto which the PTO shaft can be attached. At least that is what it appears to be set up for. I thought, perhaps if I weld the 'shear pin pieces' together, then I could still protect things with the clutch. Any thoughts about this?

The only other thing I can do is to purchase a completely new PTO shaft with a slip clutch integrated already. This is probably what I should do. Get a new PTO shaft Series 6 or 8 with a CV joint and a slip clutch. I am sure this would cure 'all' the problems which have arisen.

IF anyone has a recommendation on where I can find such a shaft collapsed length of 72" with at least 18" working expansion, please link me or give me a name. The length that is required is making it difficult to find.

View attachment 514946
View attachment 514948View attachment 514949

Call these people by phone, Agri Supply has farm supplies, tractor implements & mower parts.

Everything Attachment is a real good source. Tractor PTO Shafts | The best quality shafts at the best price available and as always free shipping.

You may also want to review Everything Attachments video on how to measure and cut a PTO shaft. (The first one on this page) everything attachments how to cut a pto shaft - Google Search

 

[RandyT]

I have seen that exact shear bolt setup that uses a 5/16 bolt on a bushhog squealer SQ72 that belongs to my neighbor. I have to start all pto attachments at idle with my Kioti Otherwise you will get the chock load of your life. And a 1/2 grade 5 won't survive at anything above idle on my cheap rural king bush hog. Went to slip clutch years ago because of it.

 

[vvanders]

What's the side of the flail look like, does it have a belt? If so then there's you're slip protection. FWIW Caroni flails don't have a shear pin or clutch, just 2-3 belts.

I bring mine up from idle every time, helps with drivetrain shock and once it gets spinning it takes a good ~30s to spin down so I usually only need to do it once. You'll probably stop breaking shear pins if you bring it up from an idle.

 

[SPYDERLK]

I do not bring it up from idle. That is not a feasible situation in my real world. I cannot idle down every time I want to begin mowing.

I have no strange noises. Everything begins and appears fine. It begins spinning, and everything is smooth, but I think the stress of getting all that metal moving simply overcomes the shear force of the pin.

I am extremely limited on what I can add as far as size of a bigger bolt. There simply isn't very much 'meat' to drill out and maintain integrity.

If I try to weld it (and I'm not sure whether it is cast steel or iron) and add an adaptable slip clutch at the machine, will that 'work' as far as protection of the tractor? I was able to find a slip clutch at TSC which slips over the shaft at the gear box, and onto which the PTO shaft can be attached. At least that is what it appears to be set up for. I thought, perhaps if I weld the 'shear pin pieces' together, then I could still protect things with the clutch. Any thoughts about this?

The only other thing I can do is to purchase a completely new PTO shaft with a slip clutch integrated already. This is probably what I should do. Get a new PTO shaft Series 6 or 8 with a CV joint and a slip clutch. I am sure this would cure 'all' the problems which have arisen.

IF anyone has a recommendation on where I can find such a shaft collapsed length of 72" with at least 18" working expansion, please link me or give me a name. The length that is required is making it difficult to find.

View attachment 514946
View attachment 514948View attachment 514949

I think you should go with the new shaft with slip clutch. That will solve the problem.​

IF I were going to try to make what you have work, I would machine that hole out to half inch on a new center 3/32" inward from its present center. A very difficult operation on that extremely hard steel. -- But like you said, just drilling it bigger on center would critically thin the outer web.

 

[ruffdog]

Yeah, just plunge a 2 flute carbide end mill on the new location.

Caution...only go up one size at a time...a 3/8 has much more meat that the 5/16

 

[Dadnatron]

I tried bringing it up from idle and got it running full speed. It was pretty nice because it had absolutely no vibration, which really surprised me. I expected at least some vibration or shimmy but it worked well. I tried it out a bit, but must admit I didn't have a lot of confidence in that shear bolt. But from idle up, it held for at least 4-6 runs.

Cut well, recognize I need to work on the height adjustment. But I did a quick swath along the road and ran it vertically to clear off some things growing finto the road a bit. Worked great.

I'll do a full review of my experience at a later date. I saved about 75% from US based purchase, from what I'd found. There are likely others, but what I'd found was out of my willingness to pay.

I think I'll look to get a Series 6-8 shaft with a clutch. It has belts, but there are 4 of them and this is a pretty good sized machine so by the time the energy has it alll turning, I'm thinking those 4 belts might hold strong enough to still damage something. I don't know, but I know my peace of mind would benefit if nothing else.

I'll see what I can find this week.

 

[airbiscuit]

First/Best Fix - engage the PTO from Idle
Second/cheap fix - drill a second shear pin below the first one. (do 1/4" first to see if that is just enough extra and still maintain function).
Third fix - new PTO Shaft with slip clutch.

 

[vvanders]

I suspect unless you *really* hit something that shear bolt will hold. The flails should bounce off anything small they hit, the driveline shock of going 0 -> 540 is pretty substantial. I'd carry a couple extra with you and see how well it holds up but a clutch probably won't hurt.

 

[ruffdog]

The problem with clutches is they freeze up. If the unit sits for a while, it takes much more effort to break them loose and the tractor may be damaged.