Mower shear bolts breaking

[kensfarm]

How fast are you engaging the PTO.. even at idle it takes a lot of torque to get that 72 cutter turning.. have you tried slowly engaging? Maybe there's a reason he said use a 5 hardness bolt.. what does the manuel say about the shear bolt hardness?

 

[Trev]

You know, it's weird.. I was mowing the other day, and somehow got into some chicken wire hidden under deep grass. It was the kind of thing people use to prop up tomato plants as they grow.

Anyway, it bound the mower up solid, stalled the engine, and took me about an hour to cut and pull all the wire out from under and around the blades.

Even *this* didn't cause my bolt to shear. I wonder if I even have a shear bold. Maybe it's just a slipping clutch arrangement? The time from first contact with the wire until full engine stall was about 4 seconds.. which could have either been a clutch slipping a bit or the wire getting wrapped up in there.

It's a JD4300 with a JD272 rear finish mower. Once the wire was removed, I continued mowing and all was fine. Ideas?

Thanks,
Bob

 

[mgrick]

If you have a slip clutch you will have something like this on your output shaft coming out of your gear box.Other wise you will just have a bolt going threw the yoke on your output shaft.

Rick

 

[monkeybreath]

Thanks - I don't have slip clutch - just the bolt.

 

[mgrick]

Sorry Trev,didn't notice you were using a finish mower.This set up is on a rotary cutter.


Monkeybreath...

maybe you should look into getting a slip clutch.

Rick

 

[Trev]

</font><font color="blue" class="small">( If you have a slip clutch you will have something like this on your output shaft coming out of your gear box.Other wise you will just have a bolt going threw the yoke on your output shaft.

Rick )</font>

Thanks, Rick.. I'll pull off some covers and see what exactly I have in there. I didn't see any reference in the mower manual to either a clutch or a shear bolt. Struck me as odd that all these people are shearing bolts, and I never have.

Thanks again,
Bob

 

[herbenus]

I didn't even know guard moved. Thanks for that info. I've wrestled with mine to the point I finally cut some slits in it with a knife.

My manual didn't tell me this, I discovered it on my own. There are actually 3 positions on my pto lever. On, off, and a midpoint. If I switch straight from off to on it can cause premature shearing. I've learned to do this slowly, and pause at the midpoint position. Perhaps someone with more tractor smarts can explain this better.

And now my story. I have a sheared bolt on mower. I went to change it the other day and couldn't get it out. Sheared one end only I think. So I figured a few minutes of mowing would loosen it. It didn't. I've mowed about 20 hours now with a sheared shear bolt. I'm concerned now that a piece got wedged in so tight that I've negated the shear pin affect and could damage something if I hit a stump. Anyone seen this before?

 

[Hoeman00]

Trev a finish mower has belts to drive the blades so they will slip some.
It isn't direct drive like a brush cutter.

 

[Trev]

</font><font color="blue" class="small">( Trev a finish mower has belts to drive the blades so they will slip some.
It isn't direct drive like a brush cutter. )</font>

Oh, yeah.. I didn't think of that! Duh!

Thanks!

 

[Bird]

</font><font color="blue" class="small">( Struck me as odd that all these people are shearing bolts, and I never have.
)</font>

Me, too, Bob. I know I had shear bolts on everything 'cause I saw'em; even had some spares on hand, and never sheared a single one on my equipment. I used to think I used my equipment pretty hard, but maybe not. /forums/images/graemlins/wink.gif /forums/images/graemlins/laugh.gif