problems with a mini excavator

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I have a mini ex that the track  on the left side keeps throwing off the only thing I can see is the sprocket gear has a bend to it ( I don't know if you can see it in the pics)I don't see any signs of damage on the housing no cracks,twists stretch, I don't even see chip paint. When it moves there's no wooble to it thinking there a bent rod inside the unit  anyone run into this and any ideas on how to repair any input would be great thank you Attached Images
Reply:How's your track tension?  Does it walk off the track on the sprocket end or come off on the idler?  How much is the sprocket bent, how much run-out is there when you turn the sprocket over without the track on? Is your tensioner broken or the spring broken on the tensioner?  Is the sprocket skipping or the track "snapping" when load is applied? especially when turning?  Is it a rubber track, steel track?  What size of mini excavator is it? Brand? Year?Details, details,Last edited by bennyboy; 02-22-2010 at 07:44 PM.Can u build it?Fix it?I can build or fix anything you want...just add money
Reply:A bent sprocket makes a perfect derailer, because it walks the chain to one side and then rides up on the links next time in..Check the drive hub for run-out.I'll assume that the heavy hub is probably true, and only the sprocket is bent..Pull the sprocket and straighten it in a large shop press.Good LuckLast edited by denrep; 02-22-2010 at 07:45 PM.
Reply:What's the condition / age of the tracks? We had a rental tracked skid steer that kept throwing one track. After putting it back on the 3rd time in one day, we had the rental place send out the service tech. We were running in river silt, so his 1st thought that we were abusing the machine was quickly scratched ( He figured we were twisting on balast and getting big rocks in the sprocket). Turned out the steel cords had stretched and failed leaving the track loose and there was no more take up on the adjuster.We had a similar issue with our 15 K baby excavator. When the track stretched and failed, it would throw the track if you were not very careful. After #1 went, we knew #2 wasn't far behind. We got about 6 more months before that one had to get replaced..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:My red line is supposed to be straight.  I think I see your problem. Attached ImagesMy name's not Jim....
Reply:I can't see the sprocket from the side, but are the teeth pointed?  If they are,  the sprocket is worn out.  Look at the curve closely on the drive side compared to the back side.  If they are much different, this could also be your problem.  I like the picture above DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:I'm with bosstin.The whole sprocket area looks crooked.
Reply:It may just be an optical illusion but it appears to me that a force (black arrow) caused the the hub structure to twist outward forming an angle to the chassis (yellow arrows) as a result of the hub support stretching at the inboard edge (red arrows) due to the gussets (blue arrow) on the outboard side.If that's the case, I suggest notch the top and bottom plates of the hub support (red pie slice), pull back straight to chassis centerline (black arrow) and weld up with 7018.  Fishplate as needed/desired.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:boost  got it right  the thing is it looks like it was build that way nothing I can see as far a bent or twikin the housing the sprocket is  bad new one it on the way  they thought it was that at first till they took the track off I think it a kamotsuo (spelling )  rubber track ,needs a top idler on the same side or so i was told I didn't take it a part I just looked at it today while I was fixing a plow .
Reply:smart cookie duane.... real smart
Reply:Kamatsu. I've never used a small excavator from them, but have run the big ones..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Komatsu.... Attached ImagesMy name's not Jim....
Reply:I knew that and my fat fingered typing screwed it up. .No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Wow,  Living in Germany I thought Big Foot was just a myth. I guess I was wrong!It looks to me as if there is a torsion in the drive housing.  Before I would replace the sprocket I would first check the alignment of the drive housing.
Reply:Originally Posted by BoostinjdmKomatsu....
Reply:Originally Posted by duaneb55..If that's the case, I suggest notch the top and bottom plates of the hub support (red pie slice), pull back straight to chassis centerline (black arrow) and weld up with 7018.  Fishplate as needed/desired.
Reply:zip there's lines and a some sort of valve body  on the other side of the sprocket. The last thing I wantto do is take that all apart but I think I have to ..
Reply:Sorry about the sprocket straightening tutorial. I misunderstood the first post.And as unlikely as it seemed, with that misunderstanding in mind, to me, the pictures made the sprocket itself seem bent. I thought maybe it was rock damage. With that, I'd say it's going to be tough to locate any alignment problem from just the pictures.How about using a straight-edge or string-line over the hub, to check parallel with the track frame?Any misalignment needs to be specifically identified before working up a straightening plan.Good LuckLast edited by denrep; 02-23-2010 at 07:22 PM.
Reply:Another thought.. Is it possible to shim the unit back to alignment?  With steel machinist shims or washers?.. It would certainly be a lot less messy.. I'm assuming that final drive is bolted to something, and not welded in place.  Also, you never said.. does the drive on that side spin 'smoothly' ?  There are no problems with the internals are there (chipped gear tooth, dead bearing, brake pads , brake rotor, etc...)  Been there, and worked on that!For the alignment, take a string, metal carpenters square and layout the offset.  See how far you have to go.  My suspicion is the unit was designed with a little bit of adjustment in there.  Just because its a welding forum, doesn't necessarily mean welding is required... :^)zip.Last edited by zipzit; 02-23-2010 at 07:43 PM.
Reply:denrep I wish it was a bent sprocket that would be an easy fix (there's a new one on the way)if you look closer a the pic there's a string line that's straight in line with the front hub
Reply:Lenny, if your still stuck I will come over tomorrow(Wed), and give it an eyeball.Disclaimer; "I am just an a$$hole welder, don't take it personally ."
Reply:Have you tried to contact komatsu and see if this has been a common problem on this machine???  dont talk to the dumb bumkins at the local dealer you got to call komatsu corporate and see if they have a technical help department.  chances are they may have seen this failure before if it is a weak point in the design.  I just cant imagine how this bent in this manner other than some extreme abuse or design flaw.