Hi GUYS ! I am trying to understand the principle of caterpillar undercarriage management system (CTS) more precisely the Percent Worn Charts. I would like to know whether or not, the relation between the percent worn of different elements (bushing, idler, etc) VS “used time” is linear? For instance when I have some measurement data (% worn of an element at several hours), and want to project it on an graph, am I supposed to represent the time on the X-axis, or the % worn on the X-axis in order to make an extrapolation ? I would be grateful If you can provide me some explanation. Thanx
If you're going to graph the results I suggest the X-axis should be time, the Y-axis % wear. AFAIK on the larger machines (smaller ones may be different) all undercarriage components show linear wear patterns EXCEPT track rollers & sprockets. For track rollers the wear is linear up to 40%, then the rate of wear actually reduces from 41% to 120% (scrap limit). Sprockets are the same but in their case the wear is linear up to 80%, then reduces thereafter up to 120%. If you assume wear is linear then your preduction of the hours to 100% wear will actually be slightly pessimistic for sprockets & rollers. IMHO you need at least 3 CTS measurements between 0% and 50% worn in order to predict what the hours will be at 100% wear with any level of confidence. More measurements will obviously improve the accuracy of the prediction. Of course all the above is based on the assumption that the type of work the machine is doing does not change throughout the life of the undercarriage system. Start hauling a machine from one jobsite to another where working conditions are diferent (especially abrasion) and all bets are off.
Thanks a lot Nige ! Regarding this « assumption »: Do you consider the CAT D9T/D10T machines as large ones or small ones? By (scrap limit), you mean the maximum worn that can be reach before the undercarriage component "collapse"?
D9T/D10T would be large tractors in my book. I had numbers for them to hand and you didn't specify what size of machine you were talking about, for all I knew it could have been a D3 ....!! 100% is classed as "Normal wear limit" - to be used if you plan on doing things like a pin/bush turn on link groups, re-grousering track shoes, rebuilding idlers, etc, then re-install them for a 2nd life. 120% limit is the "Run to Destruction" limit that you run the components to if you don't plan to do any rebuild work on them. At that point they should be still working and not have "collapsed" as you call it. However there will be very little wear material left on any part once it reaches 120%.
All right Nige, That's clear to me. I may come back again with "more" questions Again,Thanks a lot.
I've never found any measuring system that would accurately predict how long an undercarriage would last and I've worked with a few. Basically what I have done in the past is base my projections for budgeting on the history of current production machines. I've found that material, weather, production schedules, slopes, operators, different manufacturers and cash on hand all affect how long an undercarriage will last. I've simply monitored the wear and made decisions on my own about when to repair or replace. At one place I worked in the past it even made a difference when we replaced. If I replaced the undercarriage in the spring I could get about 3,200 hours on a Komatsu D375. If I replaced the bottom end in December I was lucky to get 2,400 hours. The rain season made all the difference. Small machines now days, and that is up to a D6K, it does not make sense to turn pins and bushings. Mid size machines, D6R to D8T, it might make sense to turn pins and bushings depending on the wear rates and some times your best bet is to change sprockets and run thing to destruction. Large machines you might do the full process of turning pins and bushing wet for mid life and replacing the sprocket segments. Then again I've seen bottom roller flanges riding on the track bushings before the rails are worn out. The long and short is to use the CTS report as a way to monitor where you are currently at. You might sooner look into a crystal ball to better predict how long you have left.
Hi John C. and Nige I understand your point of view regarding the difficulty of predicting how long an undercarriage would last. To do my “predictions”, I understand that I have to focus on the % worn. I have an idea of "the recipe" I am going to use whether it consists in changing/turning/regrousering the different elements. I have 4 questions: 1) Let’s say that I want to schedule a complete link change at 100% worn I think that I should focus on 3 components simultaneous :the % worn of Links, Bushings, and Shoes, to see which one is going to reach the final point as they "works" together. Is it correct ? 2°) But I also have the track sag measurement, is that last one related to the links (I think yes)? In that case if the data I got in my possession are “accurate”, I can correlate the track sag extension to the links. But still I can focus on %worn of links. Am I right? 3°) And also what is a frame extension measurement? Is it related to the track frame as we can see on this link? http://www.deere.com/en_US/docs/construction/non-product_pdfs/parts/parts_by_industry/undercarriage/DKB765.pdf 4°) Can I with one CTS measurement at an advanced age of a machine and before the famous 40% worn of the shoes (among the 3 components above, the shoes show the more advanced %worn) are reached and thanks to what the expert called the "experience feedback" or "reporting on the experience" do a correct prediction? Or do I absolutely I quote Nige , need 3 measurements for each components at differents hours ? Or Did caterpillar got a "map" to extrapolate/predict the 100%/120% worn hours. I do not think so, I Think that a solver can be used to do that. Thank you
My thoughts on your questions....... purely IMHO. 1. It would be very strange if ALL the 4 elements of a Track Group (Link, Pin/Bushing Internal, Bushing External, & Track shoe grouser height) were wearing at the same rate. In fact I'll go as far as saying I've NEVER EVER seen it happen before. Leave Track Shoe grousers out of it (shoes are bolted on anyway) and concentrate on the other 3 parameters because they are all "common" to the Link Group. 2. Track sag has NO BEARING whatever on internal wear because if the Maintenance Dept are doing their job correctly they will keep tensioning the tracks as internal pin/bush wear takes place in order to maintain track sag within the specified range of the Service Manual. 3. Track frame extension on a Cat TTT is definitely related to internal pin/bush wear but I've never seen a way of calculating "X" cm of extension as being equivalent to "Y%" of internal wear. You need to have data on what the extension measurement was when a new Link Group was installed to give you a baseline measurement. 4. In a word, No. The whole idea of CTS (or whatever other manufacturers call it) is to give a "best estimate" projection as to when major undercarriage work will have to be undertaken on a specific tractor. To give you an idea our tractors work on average 500 hours a month and we do CTS on them at every 250 hour PM, so twice a month, at least on track shoe grousers. Why, you ask..? Well our track shoes in really abrasive ground will not last much more than 1000-1250 hours, so even measuring wear every 250 hours we only have at best 3-4 sets of wear figures available to help us determine the point at which a shoe change becomes necessary. On the other hand our link groups will go up to 8-10,000 hours so we run them to destruction - 120%, simply figuring that it's not worth doing a pin/bush turn on a Link Group with that many hours on it. Track Rollers & Idlers pretty much go from one 12,000-hour major machine overhaul to the next, or maybe we might change them when we install a new Link Group (keeping the removed ones as part-worn spares), it's all a matter of what we think is best for a particular machine at a particular overhaul. Cat's CTS numbers AFAIK are/were not extrapolations but literally hundreds of actual wear measurements in order to produce accurate numbers.
Nige has everything down right. The only thing I might add is that the frame extension is a clue to look for dry links. Once you have dry links you are about done on the pins and bushings as they won't hold the seals anymore and there is no bushing protrusions into the outer links to help carry the tracks. I also go back to my initial statement that you can't predict how long your undercarriage is going to last with a CTS report or anyone else's reports. The best you can do is monitor and adjust as the components wear out. Good Luck!
Hi Guys! I have a better understanding of a CTS report. . In fact I didn’t know that shoes worn rate is estimated with the grouser height. I read in a previous post that “all undercarriage components show linear wear patterns EXCEPT track rollers & sprockets” and on the data I have in my possession the shoes worn rate is the most advanced (abrasive conditions), that’s why I figured that I should considered it in the “common” elements to the link group (Link, Pin/Bushing Internal, Bushing External, & Track shoe grouser height), as it is going to be first to reach the famous 100/120% worn. And I am well aware that the 4 elements do not wear at the same rate. ==> Alright. I've found an explanation on the sag measurement method (Whether there is or not a carrier roller). ==> I have data on external bushing %worn, and no data on what the extension measurement was when the new link group was installed (even if there is no way of calculating "X" cm of extension being equivalent to "Y %"). In this case, can I only rely on external bushing %worn rate instead of extension to do my “predictions” among the 3 elements of a Track Group (because the %worn rate of the external bushing is higher than the links one)? (Maybe the question is not appropriate , because the answer is in the 4th point and in a previous post were it’s said that even at 120% worn the different components will still work)... ==>OK! It is an excellent explanation, and give me a better understanding of what you were meaning in the 1st regarding the shoes %worn. Thank you all
A couple of quick comments regarding your points above. 1. I always consider the shoes as separate items from the rest of the Link Group because they bolt on to it and as such are not directly dependent on the wear in the rest of the Link Group components. That is unless a job site finds itself in the very lucky position that track shoe grousers are wearing at approximately the same rate as the rest of the components in the Link Gp. Another comment about shoes. If a site/customer is considering regrousering then 100% is the limit for grouser wear in order for that procedure to be effective. Any more wear than that and there is literally nothing left of the original grouser on which to weld the replacment grouser bar. Usually a shoe will have 3 lives (original + regrouser twice) before the base of the shoe becomes so thin that it would start to bend. Destruction limit for shoes is still 120% if you want to get the last ounce of wear out of them. 3. Track frame extension will be a measure of internal pin/bush wear , not external. As the pin/bush joint wears internally the overall length of the Link Group will increase. As previously discussed for the track sag to be maintained within specified limits the track tensioner will then need to be extended. The frame extension will increase as this is done.
Some questions about catepillar CTS-- part 2 Hi guys, How are you doing? 1st of all thanks a lot for your explanation about CTS report. I am back again with new interrogations. To sum up: A machine can be started with out “rolling” during a period, thus the real travel hours of the undercarriage will be different from the hour meter indication (of the engine). Some dealer considers the % travel of the undercarriage (effective Travel hour of the undercarriage divided by the Hour meter of the machine) which shouldn’t exceed a limit as an indicator to “monitor” the wear of the undercarriage. Does the principle of caterpillar undercarriage management system or any undercarriage management system consider the fact that a tractor can be started without travelling, in the interpretation the % worn? Thanks,
Ah-ha. The good old "mobile air-conditioner" syndrome ......... know it well. AFAIK (and I've never been a Cat PSSR responsible for measuring undercarriage) the program that is installed in the ultra-sonic measuring tool can make allowances for the hours worked, distance travelled, and time spent idling to predict the remaining undercarriage life. Also, so long as the % of idling time without moving (let's say for sake of argument it's 20% of engine hours) stays constant then the projection of the hours at which undercarriage intervention will be required should still be valid because the relative % or idle time to work time remains the same.
I know I'm reviving an old thread, I was checking to see if, in the first post, the Percent Worn Chart was an actual available chart and if so where would I find a copy?
You can sometimes luck out and find the cat undercarriage manual on ebay. It is a good reference, plus contains many tips to improve the life of the system.