Broken rubber track… what now?
We’re all familiar with that moment: you’re looking at a split rubber track and you know it’s time to replace it. The tricky bit: what’s the best way to handle it? Perhaps you start off by looking at the sprockets, and if they don’t look too worn, well, maybe you can keep using them with the new rubber tracks. So you just order a fresh set of tracks… and then, all too soon, a piece of the track snaps off or the track keeps slipping away from your machine. “Bother”, you think. “What a poor quality rubber track”.
Is this a fair assumption, though? Is it really the track that is at fault? Or could you have saved the bother and irritation by investing a bit more when replacing your track?
Things often go wrong because you only look at the defective part, i.e., the rubber track, and don’t take into account the fact that the damage might actually be caused by other parts of the undercarriage. Just like a chain-driven machine, the mini excavator undercarriage has a clearance height. This is determined from the diameter of the tread on the bottom rollers and the height of the lugs. Clearance ensures that the drive and front wheel are protected from the weight of the machine. The front wheel must be able to shift forward and back in its guides if something gets between the track and the other components of the undercarriage. It is also important that the drive, the strongest and most expensive part of the undercarriage, does not bear any of the machine’s weight.
Measure carefully before use
The crane log book for the machine usually specifies how far the tread of each component may wear. For example, for a 1.6 tonne mini excavator, tread wear of 2.5 mm indicates the part is 100% worn. The clearance value for a mini excavator is likewise very small. Some Takeuchi machines allow you to set the bottom roller lower down in order to create more clearance space. This enables you to use the bottom rollers and tracks for longer, since you have the necessary clearance for the drive and front wheels. However, you should still check the machine log book, which will specify the mm value for tread wear at which the roller or front wheel must be replaced.
Then and now
Sprocket teeth often used to become pointy as they would wear along with the inserts on the inside of the rubber track. A long-pitch rubber track typically has around 40 inserts – these are the pins that insert into the reinforcement plates in the track. We still find long-pitch rubber tracks on skid-steer loaders; these have a very different sort of undercarriage from the usual type of excavator. Almost all excavator rubber tracks nowadays are short-pitch, and generally have 80 inserts for the same circumference as the long-pitch with 40 inserts.
This furthermore means that while previously, the sprocket driving the track would only interlock with every other lug, now all the lugs are used. As a result, the front and back of the sprocket teeth do not wear as much as they used to with a long-pitch rubber track. Instead, sprockets wear more at the depth of the lugs. We are seeing steadily fewer pointed teeth, but it is becoming more common instead for parts to jump off the teeth when the sprockets have been installed for too long.
Knowledge is power
This makes it harder to determine visually when other components of the undercarriage need replacing. If you want a professional assessment before starting work, we will be happy to advise you free of charge about what you ideally should replace and what you can leave in place. All undercarriage parts will be inspected at no charge and assessed based on wear lists for each part. The assessments are combined into a wear picture that we can use to give you the right advice, taking your preferences into account. Since downtime is the biggest expense for a machine, you may be able to make savings simply through merging two maintenance downtimes into one.
You can be sure of good advice, quality products and support from Verhoeven.
We are always happy to help.
Salesman Rijwerk & Uitrustingsstukken
Region: Belgium North