Boom & Bust

[Jeremy Rowland]

Never had an excavator come into work until today the little Kubota broke the end of her boom fork leaving the dipper arm hanging loose; close inspection revealed that the crack had gone right through two bolt holes that are drilled in the end of the boom fork, the one for the dipper pin retention and the other helps secure the hydraulic hose that a hammer could be used with. Crap idea drilling two points through a fork in my opinion.
A quick but good repair was made.

Jeremy

[Jeremy Rowland]

The last three pictures.

Jeremy

[mechman]

The designer had a bad day.

[diggerjones]

How the he'll would that happen. It's got the ditching bucket on, so not hard digging. Also I would think there's less pressure on that joint. There's more pressure on the end of the dipper.
Will have to have a look at my Kubota

[essexpete]

Was it on one side only?

[Jeremy Rowland]

Was it on one side only?

Yes Pete it only broke on the side where the two bolt holes were; ironically the other side was drilled and tapped to hold the tab on the pin that secures the dipper arm mounting pin, this made better sense than re-drilling the repaired side.

Jeremy

[Dah]

Could it happen if it slewed whilst the bucket was in the hole?

[Jeremy Rowland]

Could it happen if it slewed whilst the bucket was in the hole?

I would not have thought that; I reckon it had been slowly cracking over a period of time and that this had gone unnoticed until it was too late, I doubt it was metal fatigue either, just not the best of designs having two holes weakening a stress point?

Jeremy

[FOWLER MAN]

Hi,
A neat job there
I had a similar problem with a Priestman 220 years ago.
I was on the machine myself digging a deep trench some hard stiff clay. I pulled the arm in and instead of filling the bucket it just broke away the end of the boom and pushed it away still attached to the dipper arm. I was lucky not to bend the ram.

I didn't have the luxury of a workshop or a MIG, just a diesel stick welder, cutting lamp and an air grinder working off the site compressor. I have no pics of the job in progress but you can just about see the repair, (rusty weld near the end of the boom), in the grainy pic. below.

With a lift from another Priestman and a couple of pull lifts we got it lined up, pulled together and veed out, Standing on a dumper I managed to make a successful job of the welding, I plated the top and bottom.
It stood up to another five years service before I parted with the machine anyway.

[pgplantservices]

had exactly the same thing happen last year to a customers Kubota {same model }.
had cracked thru the bolt holes ,but they were a bit less fortunate as the twisted the other side of the boom aswell.
costly day for the customer he required a new boom assy.
funny thing is Kubota had stock in the uk and was delivered next day.
a definite design fault