Excessive wear from driving in reverse?

[Allan M]

I have a U55-4 Kubota. I only have about 300 hours of excavator experience cutting trails, removing stumps, etc... very basic stuff for the pros on this site. In the Operator's Manual it cautions against driving in reverse because of "excessive drive train wear". When cutting mountain trails I'm working uphill at 10 to 15 degrees and back track a considerable amount of time because I can't turn around--and cutting turnarounds on my steep trails seems counter productive (Have about 1/2 mile of trails cut on my 18 acres of hilly land).
If driving in reverse causes abnormal wear is this because the drive sprockets are pulling from the front (if in reverse) and the idlers in the back? Not sure I understand the mechanics of more wear driving backwards.
I'd appreciate any input on this from the wise ones on this site. Best, Allan

 

[skyking1]

Sure thing, Alan.
When you back up, and especially when it is uphill at all, the forces are pulling from all the way around the front idler, and pushing from the sprocket under the lower rollers.
The slack in the track builds right where it leaves the sprocket pushing forward under that first roller. The sprocket is prone to jumping or skipping with the track at a normal tension. Even if you don't feel it skipping, it is still causing more rapid wear at that spot.
None of that happens when tracking with idlers forward in the forward direction. The sprocket essentially walks across the chain or track with a pulling force, and the slack is building across the top of the track and this is optimal for wear and tear.
As you get more proficient you will find yourself turning around with a bucket assisted turn more and more so you can track forward. As you get more practice in you can do it without tearing up the ground or putting undue loads on the tracks.
The key to making a turn like that is picking the right spot. If you are down in a hole with a lot of weight bearing on the idler and sprockets and not the middle of the track, that is the worst place to turn.
If you are on a bump with more weight in the middle, you can make a more nimble turn.

 

[Tags]

Allen, skyking is 100% correct, but I feel in your application there's no chance of you ruining your undercarriage by doing the what you're doing. If you were working on an open site and tracking back and forth CONSTANTLY in high range you would see some potential issues. I had a a 161-3 with colose to 6000 hours with the original wide pad steel tracks and only replaced the top rollers once, maybe twice, and I tracked with that machine ALOT. Was the undercarriage in perfect condition when I sold it, no, but it certain had a lot left to give. If you can track it with the idlers in front when it's feasible, do it, but I would not lose any sleep over it if you can't. The only thing I would suggest is to change the final drive fluid more often than not, I usually change any final drive fluid when I service the machine weather it's due as per manual specs or not.

 

[John C.]

The only thing I told operators about direction of travel was to keep the sprockets to the down hill side of travel whenever possible. It's the same thing skyking1 said up above. Driving in reverse does cause more wear to the outside of the track bushings than going forward because of the construction of the links. It's a design issue and there is nothing you can do about it. They put that phrase in the OM to reduce expectations on undercarriage life and because some tech writer didn't know what really happens.

 

[uffex]

Good day
Is this not a subject of overspill from tractor applications, excavator undercarriage burn out between 3 - 6000 hours depending on use and working surface irrelevant of forward or reverse use. This same discussion existed in the seventies if the excavator should dig over the idlers depending on if it was a front shovel or back hoe.
Kind regards
Uffex

 

[Willie B]

Several years ago i did some research on bulldozer tracks.
well matched tracks will be exactly as far between the pins & two gullets on the drive sprockets.
As the undercarriage wears, the gullets on the sprocket wear closer to the center, therefore become closer together. Simultaneously, the track chains wear further apart. As they wear, the pitch of track chain becomes greater than the pitch between every second sprocket tooth.
Going forward, only the first tooth fully engages the sprocket gullet. (Yes, it is the gullet between teeth we want doing the hard work, not the teeth.) going forward, the chain follows the sprocket, but not much force is exerted except under the sprocket.
As mentioned earlier, the sprocket walks itself along the track chain laying on the ground. The track chain isn't under a great deal of tension.
In reverse, the sprocket must pull on the chain to drag chain with shoes up & over the rollers to place it under the sprocket. It is under a lot more tension, causing wear in the track chain. As the weight of the machine is not on it at top of sprocket, the chain tends to lift up the tooth placing strain higher on the tooth, causing wear on the track bushings.
This is true of bulldozers. I can't say how true it is in excavators . Excavators don't push all day like dozers do. I'd presume you can get more hours from excavator chains, and you might only move 100' in a given hour of operation.
I'd guess some newer excavators with actual dozer blades, not just backfill blades, will wear faster.

 

[Allan M]

Skyking1: Thanks for the technical explanation. I get it! A lot to learn. I really didn't understand the physics of how the tracks work. What you say makes total sense. Tags and John C. very helpful input. Thanks guys. I really appreciate it. Too bad that the operator's manual doesn't really explain what is going on in the machine when they issue a caution or warning. I would think more detailed information would help extend the life of the equipment they sell--leading to a better reputation. Best, Allan

 

[Allan M]

Willie B: Your observation is very interesting. I've been told a number of times that the "dozer blade" as it is called in the excavator manual is for backfill only, "not excavation". I read this as meaning don't cut virgin ground with an excavator backfill blade even if it is referred to as a dozer blade by the manufacturer. And, I can tell the tracks are working harder if I pushing a lot of loose fill or occasionally cut some virgin soil while pushing as I clear my cut. I have a four way blade. I can't image that the tracks on small excavators, like mine at 12.5k pounds, will hold up well with a six way blade (on some machines now and I'd love to have one)...because it would be hard not to cut virgin soil when angling down to keep a trail, road or pad level.

 

[skyking1]

Willie B
Thanks for adding all that detail.

 

[Willie B]

Willie B: Your observation is very interesting. I've been told a number of times that the "dozer blade" as it is called in the excavator manual is for backfill only, "not excavation". I read this as meaning don't cut virgin ground with an excavator backfill blade even if it is referred to as a dozer blade by the manufacturer. And, I can tell the tracks are working harder if I pushing a lot of loose fill or occasionally cut some virgin soil while pushing as I clear my cut. I have a four way blade. I can't image that the tracks on small excavators, like mine at 12.5k pounds, will hold up well with a six way blade (on some machines now and I'd love to have one)...because it would be hard not to cut virgin soil when angling down to keep a trail, road or pad level.

In the history of mankind excavators are brand new. The first I saw were in the aftermath of a flood in 1976. I'm sure before that they existed, but I hadn't seen one.
My first did not include any blade. Later I saw them equipped with up down only mounting. Only in the recent few years have I seen dozer blades, taller than the backfill blades, and capable of tilting & pitching. They are advertised as true dozer blades able to dig.

 

[Tones]

Good day
Is this not a subject of overspill from tractor applications, excavator undercarriage burn out between 3 - 6000 hours depending on use and working surface irrelevant of forward or reverse use. This same discussion existed in the seventies if the excavator should dig over the idlers depending on if it was a front shovel or back hoe.
Kind regards
Uffex

Pre planetary hubs it was recommended to dig over the sprockets. Today I still operate them like that for a number of reasons.
1 extends track life no pulling on the top of the chain.
2 eliminates lidler, grease adjuster, coilspring and threw bolt failures.
3 gives the machine and operator a far better ride .

A new Hitachi UH 083 I operated from new was sold with 11000 hrs and 4 years old with ALL its original parts including bucket pins and track gear. Sure the digger needed new tracks and new bucket pins and bushes but the hubs never failed. And boy that machine never had an easy life, if the boss thought it could do a job then it did it.

 

[uffex]

Good day
As to the best of my information telematics do not differentiate between tracking forwards and backwards which suggests that no firm data exists to support the original thread.
My memory recalls this was important with both crawler loaders & dozers, in the early days the running gear manufactured for tractors were found to be unsuited to the excavator applications as the hard surface of the components were prone to chipping and spalling. The shock loads from the machine dropping onto a individual link in the chains proved to much, a softer version of the chain evolved by Inter-tractor.
Kind regards
Uffex

 

[John C.]

I produced this little training video awhile back as a general knowledge piece. Hopefully it will show some of the things being discussed here.

 

[skyking1]

that's just an outstanding video may I repost it?

 

[John C.]

You absolutely can. There are also videos for oval track dozers, high drive dozers and new technology undercarriage if you are interested. Check out my channel for those and others here;

https://www.youtube.com/channel/UC9ZtvgWG-EtmGZhvtMeBMEQ