Jam nut help shear bolt?

[wango tango]

I seem to have problems breaking my sheer bolt on my land pride RCR 1572. I don’t feel I’m terribly hard on it but that’s anecdotal.

I saw a land pride schematic today that shows using a jam nut. That is not something I’ve ever used. Will that help with breaking somehow or will that just keep things from coming loose? I’m wondering if it was starting to come loose when it broke, I don’t know - just seems like it happens pretty easily. Granted it’s grade 2.

 

[AWSubie]

I can’t see a jam nut helping. I have only sheared a bolt after hitting a rock or stump and when that happens it gets my attention quickly.

Are u feeling the blades hit something big when the bolt shears or does it happen during normal brush hogging?

 

[the old grind]

Shear bolts are by design 'soft' to give way. (grade 2, etc) By tightening the nut to hold one in place we're adding stresses with a tensile load. That also keeps the bolt from rotating in place which may prolong life. Shocks are cumulative and even vibration against the load can cause a slow shearing over time.

IMO a jam nut is just too cheap not to try. I used one the first time I broke shear bolt with the 6' BH behing my JD 5210, which happened the first time I used it. (bot old & rough btw) I never replaced the pin again before selling the BH so can't verify whether it'd help but I didn't break the replacement in 3 years of use.

Like 'em or not, PTO shear pins are easier to replace than clutches are to adjust/test, esp if one shaft is shared between implements. I use the same one for tiller & flail mower, might not for a PHD. If I've never 'slipped' the clutch, for all I know it's rusted stuck and wouldn't as intended before something broke.

 

[JethroB]

My take is a jam or double nut is to combat vibration in this instance. You can whomp down on the second nut a bit without fear of over-stressing or compressing the shaft housing or components.

Are you running at or near 540 when mowing? Too slow and the driveline takes more of the stress when hitting an object vs. letting the inertia of the heavy spinning blade absorb more of it.

 

[ArlyA]

Not sure about your land pride RCR 1572 but our Honda blower shear bolts came with lock nuts. Bolts and nuts were mid grade, stronger than 2. I thought lock nuts were standard on shear bolts so as to have a consistent shear off force. Doesn't your manual state something about this? If your share bolts are loose, the force to break them goes waaaay down. I'd say lock nuts are your friend.

 

[wango tango]

Not rocks - could be just too much load - some sticks / bramble. I’m going to try to just get the first but snug and go to town on the jam nut.

Also looking at selling the land pride and getting a brush mower for my cat 299d xhp. That will be a significant difference I’m assuming. My wife gets a nice discount since she works at Cat.

 

[ArlyA]

We've been to Peoria a few times. Good luck!

 

[MoKelly]

I lived in Peoria from kindergarten to freshman in high school. I had a son attend Bradley.

MoKelly

 

[3gunr]

On my farm king tiller the shear bolts are only 1/4 inch and they pop at the slightest bump , I bought grade 5 bolts and they broke easy also, Finally bought a slip clutch and a different shaft, No more breaking bolts but it is a pain adjusting the slip clutch every yr. I have 3 implements with slip clutches, Takes hrs to do them all.

 

[bigtiller]

If you are using a Nylock nut, in my experience, they can work loose so either back it up with a jamb nut or a dab of Loctite.