The latest talk on the 'New guy no clue' link about making sure to work over the idlers when clearing trees made me think of an incident I saw way before I even thought about owning heavy equipment. I was in San Antonio creeping along a construction site since the six lane road was choked down to a two lane so they could work on it. I saw an excavator propped up, sitting on its haunches with its front tracks in the air as the operator was trying to cowboy up on some chunk of concrete and dragging/skidding the excavator trying to pull it out. I remember thinking 'Wow- that guy is abusing that piece of equipment and should be fired'. Within a few secs I heard a loud metallic snap and saw the idler rolling around next to it. The guy was placing the hoe's full weight on his idlers while also dragging the tracks so no wonder he did that damage. When I got closer, I snapped this pic. You can see the operator standing on the back side while another guy is wildly waving his arms...probably the site foreman. LOL! So my question to the experienced: Is the idler side weaker than the drive side? I ask because every now and then on my 325BL when I'm digging up cedars is I will rock forward on the tips of tracks trying to pull a stump. Of course as soon as I do that I will back down and try a different angle. But does it matter if idlers or drives are taking that teetering stress?
After witnessing multiple years of shovel logging in the northwestern US and having rebuilt dozens of idlers and final drives both while working for dealers and end users, it is my conclusion that it makes no difference. The components are built to with stand that amount of abuse for thousands of hours. When there are problems it almost always on machines that are worn out through heavy use over thousands of hours or operation.
High hours & stupid. The idler failed a while ago the break is not clean & bearings look to be gone dragging on inside of yoke plus drive side track looks taut over greased adding extra stress & wear to that side if also not failed
My thoughts would be the idlers are designed to take shock loads hence the big spring
As other's have said that's an old machine and that idler shaft appears to have been breaking for a while. We put the full weight on the idlers on a regular basis. Once broke an idler shaft on our 953C and have no idea how it happened, it just did.
Having full weight on the idlers and falling/dropping off a big chunk of concrete would put an even heavier sudden load on the idler. In a case like that a brand new idler might break. Lousy operator. See excavators trying to pull out stuck machines standing on the idlers all the time. The difference is it's a controlled load being applied and released not a sudden slam.
In the operators manual of the Hitachi UH series there was a clear instruction to dig over the sprockets. That didn't change when they changed from a conventional final drive to planetary reduction hubs. Working that way is a whole lot easier on the track chains and idlers and I still work all breeds of excavators that way and never experienced any failures at the sprocket end. Blades on excavators is the biggest killer of planetary hubs.
Other than working on trees or similar situations I've never worried about whether I was working over the sprockets or the idlers. I've seen the debates about which end to dig over and unless the manufacturer specified working a specific way I just figured I'd spend more time and get additional undercarriage wear always turning the machine to dig one way or the other. If I'm going to be tracking more than a couple hundred feet I will turn it so it's traveling forward. No sense in purposely putting extra wear on an undercarriage... I will agree with @Tones on the blades killing drives, and, I would add chains. We get markedly fewer hours on the undercarriages of excavators that are wearing blades.
Digging conditions could help determine if you should dig over the sprockets or idlers. Permafrost or hard ground, digging over the idlers might be a better idea. General digging shouldn't make much difference.
I won't disagree with you. I'll just say that we've put many hours (think 10k-13k+ hrs.) on different brands of excavators in hard dirt, rock, stumps, etc with no failures or problems. Never had the privilege to work in permafrost but I've pried up more 3'+ deep frost than I care to remember ...
I wouldn't think it would make much difference unless you were digging close to the machine and constantly lifting the opposite end off the ground putting maximum weight on the sprocket end. I don't know if excavator tracks get much longer life if you drive with the sprockets at the back going forwards on long trenches. Much slower than dozers or track loaders.
First off all what is this frost you speak of? We dig over whatever side is there when we go to digging. Been doing this for 30 years without any noticeable failures. Our 321DL has over 8K hours on the original motors with one set of duo-cone seals replaced by Cat under warranty over it's lifetime. Like Mike said if we're tracking a distance we make sure the idlers are facing forward for chain wear. The job site is always a mixed bag of tricks where you can't do it by the book every time.
Frost is what we get for not having to deal with Red wasps, cottonmouths, and the privilege of stepping out of the house at 6 AM to temps of 70 or less.
In the shovel logging use, the only recommendation was to keep the sprockets to the downhill side of your direction of travel. The keeps the idlers from being pulled in against the springs and possibly knocking the tracks off the track frames when traveling idler first going down the pitch.
I can deal with the wasps and snakes - however this time of year is hell on earth and will be until the end of Sept. However when ya'll are shoveling snow in the winter, I will enjoy and gloat over our 50 degree temps.