Extreme metal fatigue with total boom failure

[someotherplace]

I know this truck...it's a 22 year old light duty selfloader; I'm not faulting Miller, not even implying the unit has been abused - it's just seen 22 years and a LOT of use.  Very surprising though to say the least.  I haven't noticed any signs of impending failure, and the break looks clean although the pic quality isn't the greatest.  Here it is:

 

Richard

Edited March 16, 2020 by someotherplace

[GRUMPS The Towman]

It does happen. It is rare but possible. (obviously). The lower pivot pins on the one that I had seen do it were seized and we came to the conclusion that that was a contributing factor due to the excess stress when moving the boom up and down. I believe it was a jerr-dan unit if I remember right.

[someotherplace]

I can definitely imagine it on a JD unit if it's got the "greaseless" pins.  Terrible idea.  I've seen Miller units with greaseable pins get neglected to the point that they sheared off the keeper bolt before seizing up in the bore.  Not fun to remove either one of those messes.

 

One thing I will say about that old unit is that I know it gets greased regularly; the owner has a full time mechanic in-house.

 

Richard

[KYTOWBIZ]

I wonder if the pivot pin was frozen and this was a effort of hydraulic force that sheared this boom ,or what was on this unit a few jobs back ,and I have a few years of doing Miller warranty repairs that I was doing Holmes warranty when Bill bought Challenger ,so a few days have passed and quite a few issues have gone thru my business .

Phil Kavanaugh Sr

[someotherplace]

I bet you've seen plenty!  In this case I don't believe the pivot was seized, but I can try to find out.  I know the man that does the repairs and maintenance on this fleet.  The units get greased at every oil change, and he greases the hell out of them.  With that in mind though wear is wear, that unit is old, and has seen lots of work.

At time of failure it had a midsized FWD car on the hook.  I don't doubt it has been used prior to load things heavier than it should have from time to time, as that company has to haul whatever they're called upon to haul - commercial accounts, you remove the vehicle or they'll find someone else.  They do have heavier duty trucks that get sent for those jobs, in general.

 

Richard

[Guest better update]

Richard , we have had several of these that broke the bolts off at the bed because of that problem, and they both had appearance of a good grease job, so a good inspection of that pivot point would be advised ,

 

Kyttowbiz