Cautionary tale. Check your Shear Bolts and get a fire extinguisher for your tractor

[aczlan]

I have only seen a grade 8 bolt used for a shear pin once. That was on an old bushhog brand cutter that had 2 1/4-20 grade 8 bolts that squeezed together a flat plate. Otherwise, I have only seen grade 2 or 5 used.

Aaron Z

 

[Soundguy]

i have an old, old servis ( rhino ) cutter that uses a flat plate and a single 1/4 gr8 bolt as the shear bolt.. those type are usually the exception to the rule.. and use a very small gr8

 

[RFB]

I have a Loftness 841 snowblower. All of the shear bolts, Auger sprocket, PTO shaft (both ends) are grade 5. the only exception is the drive sprocket, which is Grade 2. All verified by OEM Parts Manual.

 

[SPYDERLK]

Perhaps that pto shaft was too weak for the application and twisted, then wouldnt telescope. Not long from there to failure. Same issue if it was a little too short. Telescoping at hi load with low overlap is very hard on everything. This could explain the stuck coupling at the tractor. If that kind of thing failed it you need bearngs on both ends [tractor/implement] to be checked. They may have been compromised by thrust loading.
larry

 

[canoetrpr]

You know, the too short theory is sounding good actually. Still find grade 8 shear bolt to be wierd. Maybe a combination of too short and the shear bolt. I have in the past found it to be a pain to have enough room to get the shaft on. It was always just an irritant but perhaps there is a range there where it just binds.

Still curious to hear how much of this you guys think I should just be out of luck for vs expect the blower manufacturer to take on under warranty.

How can I go about checking the bearings and seals btw. Should I just be sending this off to thr dealer for a full checkup? I'm not the handiest guy in the world. I can change my oil, do normal maint items and changed an oil pan once.

 

[k0ua]

You know, the too short theory is sounding good actually. Still find grade 8 shear bolt to be wierd. Maybe a combination of too short and the shear bolt. I have in the past found it to be a pain to have enough room to get the shaft on. It was always just an irritant but perhaps there is a range there where it just binds.

Still curious to hear how much of this you guys think I should just be out of luck for vs expect the blower manufacturer to take on under warranty.

How can I go about checking the bearings and seals btw. Should I just be sending this off to thr dealer for a full checkup? I'm not the handiest guy in the world. I can change my oil, do normal maint items and changed an oil pan once.

In my opinion, and that is all it is, just an opinion, if you trust this dealer and I believe you do, then I would let him and his mechanic diagnose the causes of the failure and how to proceed forward. This is what I would do, as isn't your tractor nearly new?

James K0UA

 

[canoetrpr]

Finally got around to checking my manual for the blower. Sure enough, my service manager was right. This thing calls for a grade 8 shear bolt on the PTO! I'm surprised. But it's there in black and white. He's talking to the manufacturer of the blower. I hope they can come up with a good theory / resolution for what to do going forward. My problem now is I don't really trust using it as-is.... even when the shaft is replaced. Maybe it does need to be a heavier duty shaft for this application.

I'm using a Kubota M7040 tractor and the blower is a Meteor PT75. The rating on the blower says 50hp minimum - I can't seem to find a max rating. I think my PTO is putting out about 70hp.

I've also emailed my dealer to see if he would consider trading the blower in for a heavier duty push type one. Overall the dealership has been good to work with so lets hope I get a decent resolution to this.

 

[IndyIan]

Do you know how much overlap you had to start with? It sounds it wasn't enough and the friction of the shaft spinning with a bow in it, over heated the shaft over time. Does your tractor have telescopic lift arms on the 3pth? Mine does and I think the implement manufacturers aren't accounting for the extra length needed for their pto shafts. My rotary cutter's pto shaft is a bit shorter than ideal too, so your experience is a little reminder to rectify that... Hope the dealer will work with you on getting you back up and running.

 

[jimainiac]

Can't wait to hear how this story turns out. Sure seems like using a grade 8 hardened bolt defeats the purpose of having a shear bolt.

 

[Wagtail]

I also read that the constant vibration of being on the tractor can compact the contents of the extinguisher to the point where it might not work. Don't know if that's true or not, but I figure why take a chance. I'm putting this on the top of my to-do list.

Ah, the old vibration bugbear. I can honestly offer top advice to this = when clamping or bolting the FE mounting bracket to whatever surface, pad the bracket with 2 layers of 1/4" foam neopreme (the stuff that they make diving wet-suits out of or, in Australia, stubie/beer holders) and 1 layer between the FE quick-release bracket and the FE itself.

This advice is from my serving on Navy Mine-Hunters. EVERYTHING on those ships are shock mounted!:alert: