Stupid Shear Bolt

EdKing · May 6, 2002

Well, due to problems with my lawn tractor, I hadn't been able to mow the field across from my house. As it had got pretty high, I figured I cut it with my brush cutter first, then go back over it with the lawn tractor later. I was suprised with how nice a cut I got with the brush cutter. As I was finishing up, I hit a small log (left over from the guys who timbered my land this winter, thank them very much) and sheared a bolt. There was just a little left so I figured I'd go down to the house and get a drink, then change the shear bolt, and finish mowing with the string trimmer. When I looked at the PTO shaft, I noticed it had slipped back over the remnants of the shear bolt and had gotten jammed up. After about an hour and a half of tapping, prying, jiggling, beating, and swearing I finally got the shaft off to get the shear bolt remanants out. At this point my wife gets home and asks me "Why didn't you finish that patch over in the field ?". So I said the heck with it, put the tractor away, and decided to have a beer. I'm going out in a little while to finish the patch today, and do the rest of the trimming.

Now, the whole point to this tirade,

Is the PTO shaft slipping back over a busted bolt a commn occurance ? I have sheared a few in the past, but I changed them right away, instead of driving down to the house first. I have a Rhino LT5 brush cutter, there is a retaining ring to keep the shaft from coming of the gear box, but nothing to prevent it from sliding back like it did.

OverlyRun · May 6, 2002

Ed,

When mine shear, they shear clean off .... so the PTO shaft turns freely, leaving the rotary cutter blades at rest. To punch out the remnants of the bolt, I need to rotate the outer shaft to line up with the inner shaft and bolt piece. It always seems to turn easily...so easily that I need to punch the bolt piece quickly while the holes are briefly aligned. But this takes seconds, not minutes or half hours (especially if the PTO end of the shaft has been disconnected so it turns freely).

Not clear from your description if you are doing more than rotating the two shafts to expose the broken bolt, perhaps taking the shaft off the gear box in order to replace the shear bolt? On my Land Pride cutter this is not necessary and if it were it would be occasion for more than an hour and a half of cursing, skinned knuckles etc!!

While there is some lengthwise play on the shaft, it is less than an inch and is easy to line up while rotating the inner and outer shafts.

Perhaps someone with the Rhino LT5 will have specific experience.

Chas

EdKing · May 7, 2002

<font color=blue>To punch out the remnants of the bolt, I need to rotate the outer shaft to line up with the inner shaft </font color=blue>

Thats normally what I do. For some reason the yoke that attaches to the gear box slide back over the bolt and jammed up. I had to stick a 4x4 under the deck and engage the PTO at full speed to get the yoke to turn freely with out engageing the gearbox. Then it was a matter of getting the yoke to slide back up the shaft so I could line up the bolt holes to remove the old bolt and replace it. I have sheared a few bolts before, and never had this problem.

centex · May 8, 2002

There should be some kind of device to prevent the yoke from comming off the shaft when the bolt shears. My mower uses a C-clip and my PHD uses a set screw that engages a groove in the shaft. It sounds like whatever your mower uses is missing. You should fix this since it would be dangerous to have the PTO shaft swinging wildly about if it came off the shaft.

EdKing · May 8, 2002

There ia a snap-ring that keeps the PTO shaft from coming off the gear box shaft. The problem I had was there is nothing to keep the PTO shaft from sliding back over the bolt and jamming up. I was wondering if this is a common occurance, or just a fluke. It happened once in about 8 bolts sheared, so I was hoping it is a fluke. I am assuming from the few responses I recieved that no one else has encountered this problem.

Wingnut · May 9, 2002

Ed,
I've certainly sheared my share of shear bolts (there's a tongue-twister!) ... on my KK rotary cutter. I keep powering through the thick stands of brush and clogging the poor thing.
I haven't had any problems at all with the PTO shaft moving back and sticking. My only problem has been the hassle of trying to remove the bolt (remnants) and replacing it with the stupid darned shield in the way. I don't know about yours, but mine has a boot over the area where the shear bolt is located and it's pretty inflexible .... making me use a viariety of means to wedge it as out-of-the-way as I can.
Bottom line ... no problem with the shaft moving to where it's not wanted, it just spins so that I have to spend a little time muttering and aligning ....

pennwalk · May 9, 2002

To me it sounds like you had a bad shear. Normally when the bolt shears it shears fairly cleanly and there is nothing to jam the yoke. In that case, unless there was something designed to prevent it, the yoke should freely slide off the gearbox shaft. Sounds like a metal burr that screwed up under the yoke and jamed it. /w3tcompact/icons/sad.gif

Chris

EdKing · May 9, 2002

<font color=blue>To me it sounds like you had a bad shear</font color=blue>

That's what I was thinking, I just wondered how common an occurance this was. I was trying to determine if it was worth the effort to put a retaining device to prevent the shaft from sliding back over the bolt towards the gear box.

Thanks everyone for the replies.

pennwalk · May 9, 2002

If it was a burr then it could have jammed in any solid part of the yoke. I'm not sure it would have made any difference if the yoke hadn't moved down the shaft at all. With a little luck you won't shear any more bolts for a long time. /w3tcompact/icons/smile.gif At any rate you will probably be a lot better at fixing it the next time.

Chris

beenthere · May 9, 2002

Consider that the bolt used may have been very soft (softer than shear bolts normally are) which caused the jamming of soft bolt material. That was my conclusion years ago when this happened to me on a post hole auger. Have not had a problem since.
Also, for the boot or cover (shield) over the PTO, I cannot imagine what it is there for, other than good looks. No one will be riding on the deck to get caught in the PTO. I think they are there because of some GOvt. safety-hype regulations that include all PTO-driven attachments. I would take the shield off if it is in the way of replacing shear bolts.