Excavator bending ram

[Jameshenry]

Been operating a 6 ton bobcat excavator for a neighbour, he bought the machine a few months ago and i noticed when he first bought it the dipper ram was slightly bent and the wiper seal had come loose, so he had a new rod fitted by a well thought of hydraulic specialist, anyway i had done about a days work with the machine since the ram was repaired, i changed buckets yesterday and went to pick up the grading bucket against the blade with the 3ft digging bucket that was on it, and i had oil flying from the top of the boom, i thought a pipe had burst , but the dipper ram was bent like a banana
We are baffled as to what has caused it ? Any ideas ? Might of been why it was sold possibly !

 

[john432]

Had a similar problem, long time ago with an old Hymac 580bt. Dipper ram seals kept leaking, fitted a reconditioned ram ,that leaked after some work, new set of seals, leaked in no time. In the Royal Welsh show, spoke to a chap from Concord hydraulics in Newtown, who diagnosed and explained the problem. A rough operator on the old Hymac's, fitted with a long dipper. If a loaded bucket came in too fast hitting the stop,the whipping effect would bend the chrome piston rod enough to wear the seals out. When checked they were both bent, a new piston rod from Concord and never had a problem with that ram again.

 

[Jameshenry]

Had a similar problem, long time ago with an old Hymac 580bt. Dipper ram seals kept leaking, fitted a reconditioned ram ,that leaked after some work, new set of seals, leaked in no time. In the Royal Welsh show, spoke to a chap from Concord hydraulics in Newtown, who diagnosed and explained the problem. A rough operator on the old Hymac's, fitted with a long dipper. If a loaded bucket came in too fast hitting the stop,the whipping effect would bend the chrome piston rod enough to wear the seals out. When checked they were both bent, a new piston rod from Concord and never had a problem with that ram again.

That's interesting to know

 

[box]

Check the pressures.

 

[Northeastfarmer]

I would imagine it’ll have a pressure relief valve which may not be working

 

[essexpete]

Would have thought it could only be happening with the dipper being drawn in and the ram extending. It does point to too much force on the ram when the bucket meets something solid. Another way it can happen is when lifting the machine with the bucket pushing down and the weight of the machine then pushing on the dipper ram. I did do that on a wheeled digger years ago.

 

[jd6820]

I'd be checking for pins and bushes badly worn or dipper/boom bent out of shape. If all these are okay then check relief pressures, if they are set slightly high or not relieving at all then it will bend cylinders for fun. Also check the cylinder is correct for that machine. A good workshop manual will have all the specs including cylinder dimensions.

 

[thesilentone]

Check the boom and dipper pivot pin is not seizing........

Or a build up of crap anywhere.

 

[Nearly]

@TripleSix

 

[shumungus]

A common way this can happen is moving the blade down against the point of the bucket when you have the dipper pulled in tight against the blade as there is more power in the down force of the blade than there is the geometry of the dipper at that point. The ram is at its most vunerable when fully extended, interesting you say the problem started again when you were lifting against blade. 121 Hymacs used to be prone to it when lifting a big stone against the track and tracking it into the bucket, bent them like a banana.