So today one of our field mechanics tells me their job got shut down because one of the pipe layers had the block fall off the stick!! Thank goodness nobody got killed, but it got me thinking about what caused it. So the unofficial story is that the cotter pin “fell” out and then the main pin rattled out, then the entire works came crashing down. As I understand they were walking it to another spot, so no load on the hook. We got looking at a similar machine in the yard, and there is No way that cotter pin just “fell out”. Its a beefy hunk of metal, probably 4 to 5 inches long, and around I bet 1/4” wide legs on it. Its a pretty hefty cotter pin. My question is, is that something others see breaking regularly? I can’t see there being much force on it, as it is just holding the main pin in? Unless the alignment of the pin bores is worn crooked causing the pin to walk and over time it broke or sheared the cotter pin? Of course the pin that came out can’t be found. I just wanted to pick other people’s brain to see if this is an issue that has a solution outside of the obvious, operators need to be a little more diligent on their morning inspections. Thats pretty scary when 2-300 plus pounds falls out of the sky unexpectedly like that! Pretty sure your hard hat ain’t gonna cut it
Perhaps someone "borrowed" the cotter pin? If the cotter pin broke off, it could only be from impact on the pin, or severe wear that would show up as abrasion marks on the metal next to it.
Yeah thats what Im thinking too. If there was enough force to shear or otherwise break the cotter pin, it would leave obvious evidence of it. I cant see a cotter pin that beefy falling out, even if the ears weren’t bent all the way around. Its so stiff, even if the Legs were only slightly spread apart, it still couldn’t rattle its way out!
Had a tow truck come to a job to lower a concrete cutting saw into a basement. I just happened to look at the end of the boom and saw the pin for pulley half way out. The driver pushed it back in to lower the saw but didn't think it was too serious. I think it was missing a snap ring but you would think it would be something you'd inspect on a regular basis. As far as sidebooms heard a story of one of the guys on a crew being a real jerk to one of the sideboom operators. Later in the day when this jerk was walking near bye the sideboom went crashing to the ground. Scared the crap out of the guy. Sideboom operator said something must have slipped. Never had any more problems after that.
You would be surprised at how many people don't know to bend the legs of a cotter pin once its inserted. Those thick hardened ones can be a bitch to bend the legs...........sometimes that part gets skipped.
Did the bearing seize up and shear off the pin ?
I don’t think it seized up, As far as I know they just had to put the block back together with a couple new cotter pins, nothing was really damaged per Say. The mechanic is going out this morning to go through all the equipment and check everything, because obviously having a major failure like this is a pretty big deal in the saftey world. So it will be interesting to see what comes of this. Usually they gotta completely reinvent the wheel after an incident like this!
Some cotter pins are quite brittle. I was turning the ripper shanks around to the work position on my newly acquired grader ripper. The cotter pins were curved almost the same as the pins. A couple broke just trying to straighten them a little bit. I wonder if over bending them stresses them too much where it doesn't take much to break them?? I had a kit with some new ones that seemed much softer and could be reused if necessary. I didn't need to curve them almost around the pin for this application. I just bent each leg about 30 deg's. They just have to keep the pins from falling out. A lot of applications only one leg is required to be bent.
True.
Well we’ll probably never really know what happened. They brought the parts into town today and the holes are definitely clapped out Anywhere from 65-75 thou clearance on the pin And one side is bell mouth quite a lot. I suspect either someone never put it in at all Put it in with out spreading the legs or put it in stupidly………. Buddy was out inspecting the other equipment onsite and found they had installed a similar cotter pin in a way I didn’t think even an operator could dream up They bent the legs wide open, Stuck one leg through the hole Then bent the free leg around and hooked it behind the other leg so it was like a hitch pin sort of?! I was like, well they get good points on creativity Ill say that much! Wowzers.
I was going to say the wrong size pin was put in and it fell out.