Maintenance – September 2009
| September 29, 2009 |
More than just a way to move the machine, the rubber tracks on compact track loaders are engineered systems that have a direct bearing on the performance of your machine.
Emerging as it did in the late 1990s the compact track loader wouldn’t have been possible without the unique design of its rubber tracks. But unlike steel tracks, the high-flotation, turf-friendly rubber tracks aren’t bullet proof, and unlike skid steer tires, they’re not inexpensive to replace.
But there’s no denying the CTL has opened up productive new possibilities for contractors. Even in harsh applications that shorten the life of the tracks, users agree CTLs are well worth the cost. They can go places, work in weather and continue to produce in conditions that would stop any skid steer cold.
There are three elements to maximizing the life of these tracks: one, understanding what they’re designed for; two, selecting the right track for your application; and three, good operating techniques.
Built for brutality
Unlike the rubber tracks on compact excavators, CTL rubber tracks are real workhorses. They not only have to move the machine, they provide the traction needed to dig into a pile and they support the load when the bucket is full.
Excavator tracks only move when you move the machine, transitioning from the trailer to the worksite or moving from one digging position to the next. The CTL is in constant motion. So an hour of engine time is generally about an hour of track wear on a CTL, whereas an hour of engine time may only produce five or ten minutes of track wear on a compact excavator. As a result, CTL tracks are beefier; they contain more rubber and heavier tread, more steel cabling and thicker drive lugs.
The longevity of CTL tracks depends on the applications, underfoot conditions and operating techniques. And there is a huge range.
On average, a set of tracks properly maintained should last on average from 1,200 to 1,600 hours. If you’re in soft dirt or sand or non-abrasive soil conditions, and your operators don’t abuse the machine you could see tracks lasting 1,800 to 2,000 hours.
The harshest application is usually concrete or asphalt paving and milling, but there’s also demolition, excavation and disaster cleanup. In these you’ll encounter sharp-edged aggregate or milling spoils on a hard surface, abrupt transitions from soil to hard paving surfaces that can rapidly wear down the rubber on your treads. Rebar and broken concrete or asphalt can gouge the treads or tear the edges of a track. Under these conditions a set of tracks may only last 600 to 800 hours.
Diesel fuel, oil and hot asphalt are also commonly encountered on a paving project. Over time these often degrade the rubber compounds used in the tracks. And heat can be more of a problem than some contractors realize, because the track puts a lot more of its surface area on the asphalt than would a skid steer with its small tire contact patches.
Still, if you look at most paving jobs today, you’ll likely see a CTL in the mix of machines. Contractors have found that even if the machine rides on hard surfaces 80 percent of the time, it’s still worth their while to replace the tracks frequently and have that flotation rather than struggle with a rubber tire machine that might bog down in softer soils 20 percent of the time.
While there’s not a lot you can do about the conditions you find underfoot, you can get a lot more life out of a set of tracks if you train your operators in the proper techniques. Good operating techniques in harsh, high wear/low hour conditions can often extend the life of a set of tracks 25 to 40 percent. Some key pointers:
· Don’t counter rotate or skid turn the machine on hard surfaces if at all possible. This just grinds off rubber for very little effect. Instead create a V-shaped path when loading materials into a truck and make wide turns whenever possible.
· Don’t spin the tracks when digging into the pile. Back off on the drive lever and lift and curl the bucket slightly.
· If you have to do a lot of tight turns on hard surfaces scatter some sand or dirt on the surface to help reduce the abrasion.
· Observe the tipping load limits of the machine. Some attachments such as tree spades can easily exceed the design parameters of the machine and all this weight winds up in the tracks.
· Be vigilant in wet conditions. Tracks give you great flotation in wet, swampy or muddy conditions, but hitting a sharp rock, rebar or root with a wet track will often create a worse gash than running over the same obstacle dry.
Unlike tires that come in dozens of tread patterns, CTL tracks offer just a few different designs. A more open tread pattern (more void, less lug) with deeper tread will give you more traction and better cleanout properties. These are used primarily in soft soil and muddy conditions. For operating on hard surfaces you want more lug, less void and a shallower tread. Some designs split the difference so you can operate on both types of surfaces without excessively shortening the lifecycle.
A key element of a high quality CTL track is its anti-vibration characteristics. CTLs are relatively high-speed machines and a track that’s not designed for low vibration will shake the machine and operator, fatiguing both. There are a couple ways to reduce vibration. One is to put the cleats so close together that there’s very little transition from cleat to cleat. The other is to split and offset the cleats so you don’t have the entire width of the cleat hitting the ground all at once. If the tracks use pads instead of cleats, these likewise will be offset or configured in a zigzag pattern to reduce vibration.
Snow treads are also offered in cold areas of the country. These typically have a lower lug-to-void ratio for better traction and cleanout and are made from softer rubber. Snow treads can be left on the machine year round but using them in non-snow applications will reduce their life by 25 to 30 percent.
CTL tracks resist the lateral forces that would spool them off the undercarriage by virtue of the flanges on the rollers and idlers and the engagement of the teeth on the drive sprocket with the lugs on the inside of the track. Maintaining the correct tension on the tracks and avoiding lateral travel on side slopes should be enough to keep you from detracking.
The proper track tension will be spelled out in the machine owner’s manual. On a new machine, however, check the tension daily as the tensioning mechanism may need a bit of a break-in period. You should never over-tension the tracks to avoid detracking. It won’t solve the problem but it will force the machine to work harder to turn the tracks, stress the undercarriage and burn extra fuel for naught.
In some sandy soils where abrasive particles work their way between the track and the undercarriage components, contractors sometimes reduce the tension on the tracks a bit to reduce the wear on the drive sprocket and undercarriage.
When it comes time to replace a set of tracks, you’d be well advised to opt for at least the same quality as came with the original new machine. A cheaper track will fail early and in the long run and add downtime and cost you more unless you’re in severe applications where the tracks are destroyed before they wear out.
Note also that you should examine your machine’s drive sprockets when replacing tracks. Putting new track on a worn drive sprocket creates a loose fit on the drive lugs and will compromise the performance and longevity of the track. In abrasive soils, some contractors replace both at the same time. Just remember sprockets are a lot less expensive to replace than tracks. In more forgiving conditions your sprockets may last through two sets of tracks. Eventually you’ll need to replace the rollers and idlers too, but these often last through multiple sets of tracks.
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