I have a D7H with the extended rail undercarriage, it doesn't have the upper roller like some of them do and I was wondering if I could add them as I would think they would work better, with less sag in the track. Mine calls for 5", but if you have the extra roller it is only 2.5" on either side of the roller.
You're talking about a carrier roller. Agreed that they reduce track whip because the suspended length of track between sprocket and front idler is effectively halved. For certain types of operation they have advantages, however I've always avoided them like the plague. Do NOT contemplate a carrier roller if your machine works in lots of mud and there is the chance the roller can stop turning. Always keep the track tension right on the specified 5" limit of sag and you'll be fine - IMHO. When elevated sprockets first came all we all looked at the track sag numbers with scepticism thinking about how much the track would whip, now they're just taken for granted.
In my experience having the top carrier roller removes the occurence of having the track slap up and down while in reverse, typically when climbing something a bit steep or backing through heavy mud. I am not familiar with a 7H specifically, but on many of the high drives the pad on the track roller frame exists, so adding the carrier roller is just a matter of bolting on the parts. If this is not the case then it would be quite a project to weld on the mounting pad.
Keep the track adjustment correct and in my experience track slap does not occur. Track slap gets rapidly worse as soon as the sag goes beyond the specified measurement. I don't have your Serial Number prefix but what I found was a spec of 115 +/- 10mm. The spec for your particular Serial Number prefix may differ. Also the comments about how to prepare the machine for track sag measurement are interesting.......see below Coast the machine to a stop on level ground. Lightly power forward with blade in FLOAT position to assure that no excess track slack remains between the rear idler and the sprocket. Apply the service brake. Position the transmission control lever to NEUTRAL. Apply the parking brake. Tracks should be adjusted under the same conditions in which the machine will be used. If packing conditions prevail on the job, the tracks should be adjusted with packing present.
I've owned a D7H , it doesn't have a carrier roller and it's given me many years of service with no problems..... a bigger problem is the tracks wear out from time to time.
This is what the cat undercarriage system management pamphlet says "Move the tractor forward and let it coast to a stop without applying the brakes. Make sure slack is between the sprocket and front idler. Then park the machine and turn off the engine. Place a tight line over the grouser tips from the sprocket to the front idler." which would probably give me a little different measurement then the procedure you listed, as I think the blade would be up for this one. The spec is 126 with no min or max like the regular length track. My ser# 79Z1723 The pamphlet is at http://parts.cat.com/cda/files/3070388/7/PEGP5027-06.pdf if you want to see it. Sounds like I need to play with the adjustment a little more, rather than add the extra roller. There is no frame there so I would have to weld it on.
Now I have your S/N checking the on-line O&M Manual for that prefix says exactly what I posted above, so I suggest you follow that procedure. The procedure in the pamphlet you refer to is somewhat generic and not guaranteed to work 100% for every model. The critical thing when checking track tension is to ensure that the track between the rear idler and the sprocket is absolutely tight, thus ensuring you have all your slack between the sprocket and the front idler when you measure. It's a common error, the sag measurement is "within spec" but the tracks are slapping. Pretty much guaranteed that there was some slack hidden between the sprocket and the rear idler when the measurements were taken. If it was me I'd just push gently against the blade to make sure all the slack was forward of the sprocket before getting the tape meaure and string line out. Try comparing the sag measurements produced by the 2 methods and post the results back here. The spec is confirmed as 115 +/- 10mm by the way.
I will get on the job, and post results. thanks
When I gave my serial number to get my undercarriage the companies all priced me for a standard track with 40 links, but mine has 8 bottom rollers and 41 links, is it possible they could have changed the rail? The standard 7 roller 40 link calls for the 115 and the extended is 125.
Measured the slack using the procedure above and I still got the same measurement as before so I must have had all the slack out of the back before. Still seems to be some slapping when turning so I will try tightening it up a bit and get it closer to the 115, don't want to overtighten it as I just put all new undercarriage on it.
Run it as close as you can get the the lower end of the specification for track sag and you'll be fine. Just a thought. Are your steering clutches and brakes adjusted correctly..? That might cause a final drive to "grab" and lead to the slap you say you're experiencing.
Have to look up how to adjust them, not sure if they are set correctly or not.
I just have to blow a few verbs on this top roller lark on high drive tractors, it makes me ill to see that track whipping and snatching about, I am told the top roller is deleted in the need to reduce the racket a Bulldozer can poke out, "give me strenght" who in the U.K. cares??? stuff the noise factor look at the damage it does to the frame etc, as for holding in a bit of muck well lets say the drivers usualy come with 2 feet and 2 hands if they cannot clear a bit of muck twice a day perhapse they need a new start doing something else, I am a big fan of top rollers on these bangers, all that track sag and whip is crap. tctractors
This is one time I'm going to have to disagree with you Tony. We don't use carrier rollers on our 10T's and our link groups go around 8-10,000 hours from new to worn out. We don't turn pins & bushes. Have tried it but the numbers don't add up. Hardly ever change a track roller, same for idlers - just the occasional one, the only time we really go into them is when the tractor gets overhauled. Pretty much the only thing that wear are sprocket segments & grousers. Up to now we've never even pulled a bogie of any type, and the rubber pads the bogies bounce on go from one machine overhaul to the next, about 15,000 hours. I don't think I'd swap that type of undercarriage performance with what I recall from years ago on 8K's and 9H's, track slap or not.
Like I said earlier in this thread,,,, I've owned one for years with no problems....... whatsoever.
guess its kinda like dirt farming, everyone has switched to zero till here, which is one pass but the land is rough to drive over, but old time farmers like to harrow it to make it nice and smooth, doesn't accomplish anything but burn more fuel, but it looks nicer. All about perspective.
Nige and Grandpa, I dont want to sound a Knob with my Left Wing top roller outlook, I see High Drives weekly with this piece of "Ballast" missing, just as a matter of interest Nige was there ever any study work done on the "To Roll or To Slap About" as you have quoted me a track group expected hour life of the "Slap About" undercart, its only fair that things should be a ballanced comment with possibly some hard facts to sort this Noise reducing deal that CAT think is GOOD??? if It was my D7H there would be a top roller stuffed on-board fast, perhapse I just am a bit stuck in the past??? but its a good topic. (the roller that is)
Tony, First up. I've been around high drives since the first D10 in the late 1970's and this is the first time I've ever heard the noise issue mentioned regarding undercarriage. Fan noise from a big belt-driven propeller, yes. That's why the engines went to ATAAC and hydraulically-drive fans. Thinking about it surely with another roller on top there would be more metal turning and track-related noise would increase with a carrier roller, not reduce. In the case of our 10's a carrier roller would be easy. The brackets are already for the support are cast into the track frame and we'd just have to bolt them in place. See the photo below. in the case of Shaun's D7H there is nothing on the track frame unless you either swap it for the track frame with the carrier roller mounting or weld something in place. I'm always more than a bit wary of welding on track frames, the buggers crack at the least provocation without adding even more stress-riser points by putting even more weld on them, especially of the home-made variety. Obviously my experience is all around mining. But from the 6-months dry/6-months wet of Central Africa to the dry desert conditions of the Chilean Andes to the current job in the Caribbean where it pours with rain 300 days a year I personally wouldn't have carrier rollers on a high-drive tractor if you paid me, and my operating cost calculations appear to bear out that stance. In some operating conditions a carrier roller could more than likely be beneficial, however I've yet to find those conditions on any operation I've been on. Regarding undercarriage operating costs, the answer is yes. We had a fleet of about 20 x 10N's in Africa working with a fleet of 651 scrapers about 15 years ago that all had carrier rollers on them. By accident one machine lost its rollers (no spare parts, usual story for Africa) and it was noticed on the CTS Inspections that the undercarriage wear had reduced on that tractor. We then did a comparative study "with" and "without" using more than one machine that confirmed the reduction in link wear and especially a reduction in spalling of the rail surfaces happened on all of them. As a result of that test we pulled the carrier rollers off the whole fleet. Good thing is that you don't lose them because they're a double-flanged track roller, so they can go under another tractor at overhaul time. The only thing that got thrown away was the brackets.
Well done Nige for a well balanced and interesting slant on the " to Roll or not to Roll" thing, but in the U.K the track is often dragging the top frame off with 2 massive gouge marks that spook me up some, plus the need to keep things adjusted that often beats any driver desire to undertake, plus the fact that CAT still leave the bolt location on lots of the frames to "cop a wheel" interests me??? the fact that you managed to snaffle near a full undercart from the top side of the tractor fleet I find interesting, the Noise thing checks out in the CAT book of Verbs, it fails to mention the fact that you get less tractor for your bag of coins, by not fitting the roller the overall din is reduced, anyhow the thing is all to do with personal choice, mine is I want it on my CAT if I was stumping up the coins even if at some point I stripped it off to put on the shelf. tctractors
Well lads,I have read this thread,and a few others, about the top roller debate on larger hidrive tractors. Having just purchased a series 1 D8R that will only see occasional use,I am in a pickle about what to do. I can assure you that I will be very watchful of achieving accurate track tension to the best of my ability. Digging tracks out is actually a quirky pleasure of mine,so I wonder if I might get away without sticking one on. I will get some some pics of the trackframes on this tractor asap.
There appears to be a rubber pad on the trackframes. The idler cannon bits appear to be rash free
Ok so does that mean I should adjust my tracks on the surface they are running on as long as it is level ? If so that is going to suck My 3 dozers run in a landfill its a big enough pain getting to the covers on the track frames . I could only imagine what my D8R and T would look like if they had carrier rollers The d8t has the pads there for it the d8r does not , Its a project cleaning out the D7E oval track as it is .
I have a question for Nige. Do all of your high-drives have 3rd gear disabled? Or maybe only in reverse?? Fair question.
Making sure Nige sees this thread again. Walker had a question, as did I.
The answer to Walker's question is yes, so long as the ground is level you should adjust the tracks with whatever underfoot conditions the tractor normally works in. If the undercarriage works most/all of its life in packing conditions then that's how you should check the track sag. Shimmy, it's a judgement call but we re-program our transmissions to remove 3rd speed in both directions right from the day we take delivery of them. Sorry for the tardy reply but my new challenge in the jungles of S.America has me working 13 hours/day 7 days/week by design, so not much spare time.
Thanks Nige that's the answer I did not want to hear .lol oh well it is what it is .at least I can doe the d6 sitting on the daily cover dirt not the trash . Historically we only get 4500 hours out of the d8 uc . Maybe adjusting properly we can get a few more hours out of them . I also recommended to run one d8 uc to destruction and do a pin and bushing roll on the other one to see what the difference will be per all the dozer knowledge you share on here.
If the operators are in the habit of flying round at top speed in 3rd gear a lot try removing it electronically using ET. It's only a 2-minute job and the same to restore it if that's the decision. We had a bit of push back from our Ops people but they were convinced in the end and the tractors were all left with 3rd gear blanked off.
That might not be a bad thing in our application also. Im sure the speed accelerates uc wear aswell
I think 4500 hrs for a set of U/C in landfill is OK. Way back when, I was looking after a fleet of Komatsu dozers in landfill and we were getting similar hours. At first we tried doing the pin and bush turn at half-life, but then found that by the time the rollers and idlers were worn out, we hadn't got the full usage out of the turned chains. That then meant we had a machine with new idlers and rollers but part worn chains and it quickly became a mess. In the end I worked out that the best overall economy was gained by monitoring when a pin and bush turn was due, at that time just bolt on a new set of segments and run it until the rollers collapse.
Spoken like a true manager. I already have some thoughts on this subject, but I'll play along for a little while. In keeping with the spirit of the thread, when I was running with my dad we had a 7H. No top roller. Majority of the work we used it for was clearing trees. What I'd like to know is how do you put a half-mile of trees in two piles keeping the tractor in second gear all day long. Time is money, and after the first row costs $10,000, the customer will find somebody else to do it for $5000.
Yair . . . Shimmy1. I too have wondered about this blanking off third gear thing. I suppose it depends entirely on the application. Nige's tractors never walked but, if they had, the fuel burn to travel four or five miles would be less if they were slipped into third and the revs decreased to maintain the same speed they would have done at full revs in second. With those large rakes I have posted pictures of there often often patches of light country in a paddock where a good operator can back the revs off and pick up a bit of third. As long as there's some load on and they are not rattling along flat out "loose", in general contracting, (I believe) third is there for a purpose. In the heyday of McAninch (spelling?) I would be surprised if those D11's pulling scrapers were locked out of third. Cheers.
I had two options. After getting my "load" to the pile, I was either going to walk out around in a circle to head back for another go, or grab third reverse and let her buck back for another push. While staying in forward gear would probably be better on the bottom end, after about a dozen times of ring around the Rosie (with no less than 30 or 40 more to go), the ground would look like a plowed field, not to mention I'd probably be adding lots of extra miles to my day.
With the advent of high drives and SALT tracks it no longer makes any measurable difference which way you travel to the undercarriage, or at least that's what the Deere and CAT factory reps all told me........
Yair . . . Bloody hell lantraxco. you can mind read from half a world away! I have been thinking about that and it was going to be my next question. Cheers.
Reading all this talk about 3rd reverse is giving me cold chills, I can still hear my grandpa yelling at anyone who backed up "hot" in a dozer. You hear that pop pop pop when you are backing up? That the sound of you killing my sprockets and bushings! It's funny how a thread can bring back memories good and bad!