After a days work on my 939C track loader I noticed the paint chipped off just one of my bucket arms, looks like it was stressed and bent a bit. Just wondering what would cause just this one arm to show stress. When i eyeball both the arms I can't see any difference between the two arms. By the way, the bend is normal!
I don't know that you have a problem, other than paint missing. It looks like rust where the paint is now removed, meaning, moisture had already got under the paint for some time and the paint just now flaked off. It could be poor metal/paint prep from the beginning and it just now showed up. As far as loader arms being bent, maybe not. Those could be ductile iron arms instead of plain carbon steel arms. If carbon steel arms bend (form stress) they stay bent. Ductile iron, unlike cast iron, has the ability to flex under a load but then come back to its original shape after load is released. These loader arms would be the perfect application for ductile iron. This "flexing" of the arms could be what caused the paint to release. But poor steel/paint prep is probably the reason the paint didn't bond well in the first place.
Im pretty sure thows things are going to flex alittle when the bucket is fully loaded. I think its Fine just watch it. See if it develops worse at all.
Hi idleup That's not normal! Those are bent like a pair of bananas. They should look like this.
When the paint chipped off it was perfectly clean under the paint - also on that model 939C they all had that arc to the arms.
Did you check out the drawing I attached to the previous post? The 939C only has one serial prefix, which is 6DS, and this is the drawing of it. I'm afraid they should be straight my friend....
Well I've seen maybe 10 machines with the same exact bend could they all be bent exactly the same on different machines? I think when you get the 4 in 1 bucket it has the different arms!
Here's one i just found on MT it has bent arms as well - if you look close his paint chipping off the one arm as well! http://www.machinerytrader.com/list...6662528&GUID=3104f9013d9c45a094c777c8c34f6cce
Yes, I suppose they could. But these haven't.... http://www.tqmachinery.com/Images/CrawlerLoaders/CAT-939C-4497LG.jpg http://www.ritchiewiki.com/wiki/files/Cat_939C_Hystat_-_facing_left.jpg http://www.catnewsinfo.cat.com/cda/files/351542/7/939c.jpg
There is one each on Iron Planet, Equipment Locator and E-Bay, all with those linkages straight.:beatsme The initial photos do look like they have bent some.
They are suppose to be straight. I demoed a brand new 939C and after I ran her hard the arms where bent.
Looks like it happens from pushing the bucket down with the tilt linkage, right? Do i have the linkage motion backwards?
Would seem to me the only way to bend them in that direction is to push the stick forward and all that would do is lift the weight of the machine. I believe most all the 4 in 1 buckets machines come with this special arm set.
That is the motion but not the cause. Mine where also bent outward and not just up so looking from above they looked like this ( ). It was done in a mater of months not as bad as Idles pics. I demoed a lot concrete swell and hard pushing in "sand stone" with some good size rocks 2.5'-. Maybe shaking the bucket back and forth hard? I would do that with the 4n1 open a ways hold large chunks of the swell to get the dirt out. Idle ours was a 4n1 with straight arms, before I bent them.
every 939 i have ran they are straight. I do not see a reason for them to be bent from factory, it is just a cheap desing. Our 935c arms are straight also.
This is, in my opinion how they could get bent. You see how the links anchor onto the bucket? The anchor forms a channel that extends right down to the bottom. If this channel is allowed to fill up with dirt, when the bucket is thrown hard over on tip, the links will be bent against the packed dirt. Note that due to the self levelling linkage design, you would see this the most when the loader arms are at full height. Lift the arms right up and tip the bucket. Have a look around the links and I bet you will find minimum clearances which would cause the damage if something get jammed in there.
Well, I suppose I must edit my original post. I was working under the premise that the bend was normal. I believe this is one of the craziest things I've seen though, so many of these loaders with "bent arms" when they're supposed to be straight??? Then again, maybe I was right; this looks like the perfect application that they "should have used" ductile iron arms. :beatsme
Let's blame it on the crappy Japanese steel, eh?
i agree with u on that one. Our 935 was built in japan and many cracks in the main frame later i am agreeing with u on that one. I was looking on machinerytrader and there were not to many bent ones, but a few were there.
Here here! I'll have a shot of Scotch with you on that one Cmark! :drinkup
OK, I have another one for all you experts - I don't have a image to show you but on my 4 in 1 bucket the pivot arms where the hydraulic ram attaches to open and close the bucket is cracked - looks like they tried to weld it numerous times without any luck. It appears that the piece is cast so it don't weld good. Cat wants $574 for each side and I'll have to cut the old one off and re-weld the new one in place. Anyone else having this problem and is there a cheaper solution?
We for sure want a picture of that.
Are the cracks where the bottom of the ram attaches to the bucket or at the top at the hinge casting? There were a couple or reworks out to address cracking at the bottom anchor point.
I'll have to stoot a picture but its the piece where the bucket opens and the ram is attached . . .
Only way I can think of is fabricate one out of steel and weld it in. You'll spend more time welding the casting than it'll take to snap it again. As for the the 939 arms issue, I think it may be that unlike the rear-engines (and Drotts) the linkage is back to front, in that the head end of the ram is used to dump the bucket and the rod end to roll back, so you can put more force on the link in compression than in tension, (opposite to Z-bar linkage)and the link just isn't up to it. The crowd link on a backhoe loader is more substantial.
I hear that welding a cast part like that is a waste of time - what do you think?
Cast can be welded ,but from all the problems out of the CAT 939 ,I think you would be better off trading up to a DRESSER 125 E high lift dozer.You wont have to weld on it or worry if the bucket arms are bent.
I have another idea of how the loader arms got bent.Alot of highlift operators will turn the bucket down and let the teeth run in the ground like a root rake when cleaning up a site.This works good until it hits something solid and "shock loads" the lingkage.If the highlift was backing up with the bucket in this position and caught a tree stump or rock I could see it damaging the loader arms easily.IdelUp might be able to staiten the arms & weld some renforcement to them,or have a welding shop do it.Now don't anyone start making fun of my art work.
Make fun of your artwork! Heck, I think it's dang good! I can't hand scetch lines that good. :notworthy But you did forget something...the operator! So I'm more than glad to help ya' out here...
Better put a seat belt on the operator ATCO.When it hits the stump It might throw him out of the cab.
Darn it, I knew I was forgettin' something! :Banghead
just thinking ,are there any other things that go wrong or falts with the 939c? Always good to learn befor you have one! thanks.
Nope that isn't what happened in my case. To sand and dry of material to build up like that. Again not in my case I didn't really run it like that. When I did I was working dirt out the concrete so I wasn't hitting anything solid. It must be a problem with the design of the arms that they all bent the same way. Maybe the holes for the pins ain't aligned.
It's a lousy design from Cat just like the pivot supports for the 4&1 bucket which cracks - this is what happens when you start building machines in China and Japan - all the quality control goes down th tubes.
I do not know on this model machine - but I have seen this on both rubber tired loaders and tracked loaders when bucket / bucket arm bushings were sloppy- -that does not mean all loaders do it, seems to depend on model