305CR boom swing pivot repair

[Phil_C]

Hello All
What started as a decision to remove the hydraulic pipes from the boom to clean the rust off them and repaint them has turned into a repin/rebush of some of the pivots as well as a crack repair on the stick.
The problem is the main pivot for the boom swing is worn. The pin is badly worn and the bushes slightly worn but the worst part is the bores through the housing are worn as well even though the pin does not rotate in them. The only solution I can see is to get them bored out and a hardened bush pressed in. My concern is that if I machine the bores out to suit a bush will there be enough thickness left. The pin should be 90mm and the nearest hardened bush I can get has an OD of 100mm so that would require 5mm removed from the thinnest section. Currently the top hole measured up at 91.5mm and the bottom at 90.5mm. I could maybe bore the new hole offset so there is little or no material removed at the thinnest part but that will change the dynamics of the linkage.
What do you all think? Anybody had this issue before?

Also one day I would like to fit a hydraulic thumb to this machine but it lacks the mounting lug for the cylinder. I seem to recall reading about a weld procedure and a kit for the mount but I can't find anything now. Does anybody know about this kit and procedure? Mine has the long heavy duty stick on it not the standard.

Regards

Phil

 

[Chrisso]

Cat had an expander-pin fix for this issue, but you'll have trouble finding the pins now. 299-8349 was the pin p/n for a 305.

Boom and stick cracking was an issue also. On the boom have a good look at the welds around the arch and where the stick cylinder mounts.

268-4100 is the correct Thumb Ar listed for your s/n, 265-5855 is the cylinder mounting lug for the stick, but downside is it's not listed as compatible with your heavy duty long stick so you'll have to get creative. I'm thinking this (or any) thumb arrangement is going to cause some weight/machine stability issues with your long stick... so as long as you're aware of that.

 

[Acoals]

but you'll have trouble finding the pins now. 299-8349 was the pin p/n for a 305.

How does this expander pin work? My 305c has a similar issue, I have figured it will need boring.

 

[Chrisso]

How does this expander pin work?

I can't find an exact picture of the 299-8349 pin but something like this...


Works the same way as a collet style pin arrangement. The collets took up up to 2mm of wear in the "static" area where the pin doesn't rotate.

And there was a special torque procedure. Once installed it has to be torqued again after an hour of operation, then 4 hours, then a day, then a few days etc. Seems fairly agricultural but I can see how it would get the job done.

Can't see anything listed for a C series machine unfortunately.

 

[Chrisso]

The other factor is obviously costs. The expander pins are expensive... availability doesn't look good either. It would be worth talking to a line borer before going down this path IMO.

 

[Phil_C]

Hello Chrisso
Thank you very much for the information. A quick search for expander pins and I found this website that even lists the 305CR.
Cat want $1008 for the standard pin so I am guessing the expander setup from Cat would be very expensive.
You mentioned line boring but even with the expander pin the bore would at least need the ovality removed or is that why the tension has to be redone at multiple intervals.

I may have to shelve the idea of adding a grab. If Cat don't offer one from factory then there is a fair chance there is a good reason for it. I did not realize mine had a longer that normal stick until I went looking on SIS. Makes a lot more sense now as to why it was so unstable with a full bucket at maximum reach.

There are multiple cracks in the right ear emanating from the radius on the top of the box section just above the arms pivot. I will vee the cracks out and reweld. The pin in the end of the stick for the bucket is also flogged out and one bush actually fell out when I took the quick hitch off so I have to fix that as well.

 

[Phil_C]

Went looking for parts on Machinery Trader and found this wreck with a long stick and a hydraulic grab so I guess they work after all.

Fortus in WA also make the expander pins and I have asked them for a quote.

 

[Acoals]

Hello Chrisso
Thank you very much for the information. A quick search for expander pins and I found this website that even lists the 305CR.
Cat want $1008 for the standard pin so I am guessing the expander setup from Cat would be very expensive.
You mentioned line boring but even with the expander pin the bore would at least need the ovality removed or is that why the tension has to be redone at multiple intervals.

I may have to shelve the idea of adding a grab. If Cat don't offer one from factory then there is a fair chance there is a good reason for it. I did not realize mine had a longer that normal stick until I went looking on SIS. Makes a lot more sense now as to why it was so unstable with a full bucket at maximum reach.

There are multiple cracks in the right ear emanating from the radius on the top of the box section just above the arms pivot. I will vee the cracks out and reweld. The pin in the end of the stick for the bucket is also flogged out and one bush actually fell out when I took the quick hitch off so I have to fix that as well.

How long is your stick? My 305c is the "long stick". I think it is like 5'2", but I would have to look it up. Mine has a Cat thumb, and is fine as far as balance goes. Mini's aren't much for balance in general, so maybe I don't expect much.

 

[Phil_C]

The stick is 6' from pin center to pin center.

 

[Chrisso]

I may have to shelve the idea of adding a grab. If Cat don't offer one from factory then there is a fair chance there is a good reason for it.

Possibly, or there was a marketing reason behind the decision, or both. These days people fit anything on anything. You know your machine best, just expect it to be slightly more tipsy when the stick's reaching out and you're not working over the blade. If you can handle that it will be fine.

You mentioned line boring but even with the expander pin the bore would at least need the ovality removed or is that why the tension has to be redone at multiple intervals.

I can't imagine any wear here that wouldn't have some amount of ovality. Cat simply stated the expander pins were capable of taking up 2mm (.080") of wear... that's the agricultural bit.

As for line boring, I see plenty of those guys building material with weld then boring it back to original spec.

 

[Phil_C]

Looking at the Nord Lock Expander website it says;
The Expander System is perfect for repairs even if the lugs are badly worn. The expansion sleeves expand to conform to the wear patterns and lock the system into place. There is no need for time consuming and expensive welding practices.

Fortus don't actually make them, they resell the Nord Lock Expander. I will see what they come back with tomorrow with a price.
Nord Lock are saying they have installed over a million of the pins in every thing from mini excavators to lift span bridges.

 

[Chrisso]

If you end up going down that path maybe post some feedback here and/or pics to show us the end result.

 

[Phil_C]

Heard back from Fortus and they don't do any pins for the 305CR. Will try Nord Lock direct and see what they say. Might have to just weld up the cracks and put it back together for now.

 

[Phil_C]

Finally got a price on the Nord Lock and it's $3175.00 for one pin and taper locks. Way out of my price league. Looks like I will be putting it back together as is for now. Maybe down the track I can look at welding the bore and boring it out. The Nord Lock cannot handle ovality and the bores would need to be machined to remove the ovality.

 

[Chrisso]

Probably on par with line boring at that price.

If you have to remove the ovality you don't need an expanding pin IMO

 

[John C.]

We used to weld and line for at $1,000 a hole. Makes the collet type pins over the market for a somewhat questionable fix.