I was helping a friend who threw a track on an EX 120. Terrible location to work, but we got it done. My question is on the guide for the front idler. There is a 1/2" clearance on each side in the frame which allows the idler to twist. In my opinion, way too much and may have contributed to the track coming off as tension was pretty good. It almost looked like the frame was sprung, but a straight edge showed it was ok. There was no evidence of spacers on each side. My Cat does not have this much play. Any thoughts? Thanks in advance.
That idler should not be able to twist. When I rebuilt the undercarriage for my 550 Deere we replaced all the guide shims for the idler. I have a sneaking suspicion that the guides for the 120 are completely shot.
It can't be wear, as there is hardly any movement...certainly not over the entire length. It's like there is a shim or something missing. Because the tensioning ram only pushes on the yoke, there is no support on the back so the guide must keep everything in line.
How old is this machine? How many hours on the clock? You should define where the 1/2" of space is at. If it is between the support block of the idler and the side of the track frame, that is kind of normal. If it is between the top of the support block and the track frame channel, then that is too much. There is a big different between dozer track frames and idler supports on excavators. The front idlers in excavators ride on the blocks at the ends of the shafts. The blocks ride in the ends of the track frames in channels. The channels keep the block from bouncing up and down very much. There is a lot of space usually which can allow the idler to tilt to the side. I have smoothed out the inside of the frame by grinding and then welding flat bar to the bottom of the channel to take up the space. There does have to be some space so blocks and idlers don't get stuck when dirt and debris fill up the space.
John C., I don't know hours on clock. Yes, the gap is between the sides of the blocks and the frame, nearly 1/2" on each side. Without the track on, you can twist the idler about 5 degrees. I guess it just seemed excessive to me.
Which EX120 model do you have? Info I have shows the EX120-5 to have an idler 300mm wide at the outside of the brackets. I had the same problem on a John Deere excavator one time. The track would not stay on. What I did was to take plate and weld it on each side to narrow up the gap some. That cured my problem. James
I welded some 1/8...3/16 plate on each side of ours but there is also taper from a bit of sprung in the frame so make sure you have the room when the idler is all the way back before making it permanent... also welded wear strips for the rest of it. I think we have 6-7000 on it now.