ilder and bottom rollers ok, installed new steering linkage(had play) and steering spool spring. swapped cross over relief valves on counterblanace steering valve, problem did not change. left hand rail has one link taken out
Why has the left hand track had a link taken out ? is it more worn than the RH side, if it is it could cause it to walk off line. Had it happen on a D 6 D, one track was worn more in the bushes/ pins etc because it was not a S A L T chain where as the other side was, the non S A L T side had the idler about 40 mm further out yet they had both done the same number of hrs, it would walk off line when going straight, bit like having a bigger wheel on one side and not the other.
Is the tractor a differential steer machine or steering clutch & brake..?
Now I've had a coffee and a bit of a think about it, RDG is correct. The tracks normally have 43 links, so your LH track now only has 42. I assume the link was taken out because you couldn't tension it properly due to pin/bush wear..? So now you will have one track where the master link passes the sprocket every 42 pitches and the other side where the master link passes the sprocket once every 43 pitches. So your LH track will be travelling faster than the RH track by something like 1 in 43, or a bit over 2%. This will cause the tractor to slowly track to the right over long distances when according to the controls it should be going straight. The short-term solution would be to remove a link from the RH track if that is possible. The long term solution (without having photos or wear measurements to hand) would appear to be an undercarriage overhaul if at least one of the tracks had sufficient wear in it that it couldn't be properly tensioned and you had to take a link out of it. Running the LH track with the pitch extended like that is eventually going to take the sprocket out because the bushes won't sit correctly in the sprocket teeth due to the track chain pitch extension.
This one caused me to have to stop and think about it a little, and on only my first cup of coffee so that was bit of a challenge! At first it did not seem to make sense that the number of links in a "chain"/ "track" would make a difference. Then it came to me to think of the "chain" as a "flexible gear". If the drive sprocket has say 20 teeth and you remove one of the links from the "chain" that is the same as if it was messing with a gear with one less tooth on the left side which give the change in gear ratio making the driven gear turn a little faster. Tried to word that better but as I said only on first cup of coffee! Glad I don't try to explain this one to some bosses I have had! Had one guy try to tell me that if I took off a fan blade and turned it around and put it back on it would go from being a sucking fan to a pushing fan! I think I finally was able to convince him that a fan was more or less a short thread that screws into the air. If you take a piece of threaded rod and "unscrew" it from a nut and turn it around 180º it does not change from a left hand to right hand threads. Yes I do know that most fans are directional and work better when turned the correct way so a backwards mounted fan can cause an overheating problem.
differential steer
link was taken out due to pin and bushing wear, machine is used on pipeline jobs to operator pushes dirt to one side causing LH side to wear faster
going to lift both tracks off the ground and check sprocket RPM per minute
Sprotcket RPM has nothing to do with it - or at least it shouldn't, but it's worth checking it just to make sure that the differential steer motor isn't turning one way or the other when it shouldn't be. Try this 2-part test. 1. Paint a mark on both LH & RH sprocket teeth and also to a point in line on each track frame. Do as you say and jack the machine off the ground. Run the sprockets slowly and see whether both sprockets come back to their respective marks at the same time after one revolution. That should indicate if the diff steer motor is operating when it shouldn't be. 2. While you're painting the marks above, paint a mark on each track chain and also one on the respective track frame in line with it. Somewhere around the rear idler might work well. Then with the machine still jacked up run both tracks for one complete cycle until one track comes back exactly to the mark. Then check the other track to see whether or not it's also back to the mark. I suspect what you are going to find is that if the LH track is back to the mark the RH track is going to be a hair short of reaching its mark. If that happens it explains why the machine is tracking in a curve when you expect it to track in a straight line. As a suggestion for the future if the type of work stays the same and you would like to remove the need for taking links out until both tracks are worn out then swap the complete track assemblies from LH to RH and vice versa long before you start to run into pin/bushing wear isssues. It will balance up the wear.
Took a link out from RH side, both rails have same amount of links now. Still pulling to the right. Did paint mark test. Tested ok Tested RH brake pressure ok
Both paint mark tests (sprocket & track link) OK..? Have you checked the equalizer bar end pins and the pivot shaft for play..?
OP states replaced steering linkage. Check to be sure it is not binding and returning to center on its own.
new steering linkage, no binding
standby pressure at 320psi high idle, and 280psi 2nd gear high idle checked LH and RH brake pressure ok. then oprate and checked brake temp, cut hyd filters open.. clean trans oil clean not burnt no play in equalizer bar/pivot shaft Could it be a bad steering motor counterbalance valve?
Measure the width of the tracks outside to outside at the front and rear of machine... When you reverse what way is it going?
I note that the D7 had been used on the pipeline job pretty much dozing into a cut one way.This appears to have worn one side out and got the link out to try and cure it.Surley taking a link out the opposite side just puts you back at the start again ??. I also wonder how good the 'good ' side is that you can still remove a link out and rejoin the track
Yair . . . How much does it veer and, all other things being equal, why is it a problem? When walking tractors for miles between jobs various machines would wander left or right and need constant correction . . . clutch and brake rigs of course. Cheers.
I cannot understand some comments on this track long and short thing so I might need some help?? firstly on tractors like a D6D or D8H/K with 4 gear F/Drives the sprocket speed is locked solid unless a steering clutch is activated, the track could be a mile long on 1 side and a mile shorter on the other, the tractor will only progress forward or backward at the rotating speed of the sprocket, the track is nothing more than moving ground that is picked up and laid down under the sprocket as the drive is solid and cannot change, on the high rim tractors the drive comes out to the outer half shafts again as a solid drive, the only change being the half shafts are connected to a planetary gear set that can speed change, the modification in speed within the gear set is the reason they are used, so I would check your hubs then check your clutch packs, if the tractor will spin turn well in both directions in N and both tracks will power under near stall load in 2nd its a good drive line, I went to a Landfill Site today to fiddle with System 1 tack on a D6R ser3 near it was a Komatsu with an interesting set of tracks on, lets say it was a First for me as I could not stop rubbing my eyes, I will post snaps in Shop Talk of the chariot as it still making me smile, the driver said it pushes well, its untrue the state of the thing. tctractors
I was going to say this but you said it much better and more thoroughly than I could have
Think about it this way Tony. One track runs out of tensioner adjustment because of internal pin/bush wear so a link is taken out of it. So now you have one track with 42 links and the track adjuster pretty well right back, the other one with 43 links and the adjuster almost all the way out, therefore one track must be shorter than the other one. If both sprockets are turning at exactly the same speed then the speed at which the track bushings are going over the sprocket must be the same for both sides. The master link on the track with 42 links is going to arrive back at the sprocket 1 link before the one with 43 links in it. Hence the shorter track (LH in this case) will be moving a hair faster than the RH track and over long distances the machine is going to track to the right. As someone else suggested it would be a good idea if the distance between the tracks (or to the machine centre line) was measured front and rear it may give an indication if one track frame is toed-in more than the other which would also cause the machine not to track in a straight line. Also the tractor is a diff steer, so if for some reason the differential steering motor is turning when it shouldn't be then the tractor isn't going to track in a straight line over long distances. That's the first issue but according to the OP he's checked that the sprockets on both final drives are rotating at the same speed. However maybe one revolution of the sprocket won't show up enough of a difference to be able to see it. It could need 10 or even 100 revolutions to spot something.
For what it's worth, I don't buy into this theory of the length of the track altering the travel speed. As TC said, the track is just a piece of road for the sprocket to run on. Imagine if the tracks were split and laid out flat on the ground. The sprockets would engage the tracks (assuming not a high drive, of course) and the machine would travel in a straight line, irrespective of how long the pieces of track were, would it not? The only thing affecting the ground speed is the radius of the sprocket. Look at it another way. Picture just one conventional track assembly, say 10ft long, on its own, rolling along the ground. Are we saying that if we somehow were able to extend it to say 50ft long it would move slower than the 10ft one? Or yet another way. Look at, for example a specalog for a D6R. Available in standard, XL and LGP undercarriage, each one with a longer track the other but all three have the same top ground speed at 7.1mph. Why would that be if a longer track travels slower?
This long track V short track thing doe's little for me as the track is as I said just moving ground with no change in the drive left to right via the steering clutch packs, the only factor that might/would cause a change of direction is the ground shape, on H/Drives with clutch or Diff Steer things are easy to test for control faults, but drive through the outer hub gear set does allow a speed variation, all that talk of the track reaching point A before point B I am to thick to grasp this " New Tech" also to old to need to invent this new Dynamic in my head. I still cannot stop laughing at the Komatsu Dozer that I spotted yesterday, the driver thought nothing of it that freaks me out some, but it is Off Topic. tctractors
Guess as I said in post #5 I should not try to "think" before coffee kicks in! The 10 foot long track would make more revolutions in a mile than the 50 foot one but that would not change the distance either side of the tractor travels. There may be some slight variation in speed due to different wear in the chains, but find it hard to believe most operators could see the difference. TC are you going to post what was so funny about the Komatsu?
ksh, I will post the Komatsu pic or even a few pic's of it in the shop talk spot asap, I did hear the komatsu working but failed to spot the Track Issue, you will be " Mouth Open " to see the way this tractor was performing, sadly it was Pissing down rain so the chance to see it working hard was not going to happen, when you see the pic's you will understand this point. Back to that track as a gear thing, I avoid Yoga, Witch craft, dodgy Females, spiders and tracks that are Magic, they all spook me out, the track assembly is just moving ground that runs under a set point the drive rim, no drug, beer or Who-do will change my outlook on something that can be over thought by people with a Brain, I don't have 1 the Bride tells me constantly? tctractors. p.s. I bet you are keen to see the Komatsu snaps, I still keep giggling like a little kid about it, when the driver said it pushes well considering, I was in tears its tragic really??
Guess I was kinda hoping that would work, I was going to put a longer chain on my Harley and move the rear wheel back a couple inches to get a little more top speed!
Yair . . . Okay I'll ask again . . . how much deviation are we speaking of, is it (say) a hundred yards in half a mile? How much is normal variation? As mentioned I have walked many different tractors for hundreds of miles and can say for sure and for certain none of them track straight. I have tried on flat open country lining up a target on the far horizon and they all take constant stabs of clutch to keep them running true. We often used to run the Allis's in reverse to get some relief from the dust and, sure enough, they would tend to be giggle headed the opposite way. A slightly bent track frame or twisted brace, a half shot Berco on one side versus a genuine Allis on the other, a few missing plates, mismatched tracks with higher grousers on one side, a whole lot of things come into play. As regards the track length thing, poor folks got poor ways and I knew a bloke who ran a D8 with a long and a short track frame and he reckoned the long side beat the short side every time and he worked the job to suit . . . the six roller frames with high set idlers were the preferred option when running a scoop (pan). Cheers.
As scrub puller mentioned a half shot Berco on one side versus a Genuine Allis on the other!!!! The machine in question has one track worn to the point where one track link has to be removed therefore its pretty well shot, so the sprocket would be be also and the internal wear in the pins/ bushes would also come into play so that would have to make a difference. Simply put, one track group on one side and one stuffed one on the other would have to make a difference, two tracks with the same wear on each side probably wouldn't make much difference. GO THE ALL BLACKS .
Come on Tony! Where are the pictures of the Komatsu? Don't leave us hanging
DB2, I need a few pictures of stuff that I am working on to give things a flavour, the next few days I should have some worth looking at, sadly I have been working on near new stuff for the last few days so I don't take pic's of that stuff unless it rare, plus my Son posts them for me so its on a visit from him that they are loaded up. tctractors
Thanks for this TC, I just could not wrap my feeble brain around the concept of one side traveling farther than the other, despite the difference in length.
Just to stir things a bit.... The sprockets are engaged on the bushes not the ground as such. You then get a good chain and an stretched chain that's been shortened. The pitch might differ by say 1/8". Now with the sprockets tied to the same speed they will both grab the same number of links but for every revolution of say a 44link chain there will be a 4 1/2" difference in travel? Hard hat firmly on!!!
Just to stir things a bit, if the tracks (moving ground) are worn some and the sprockets are worn some often the slack bit of the chain hangs around the lower section of the sprocket on flat drive tractors, also on flat drive 2or 4 gear F/D tractors there is no difference in sprocket speed, so all this crap even on H/Drive tractors is more to do with topography than anything, in the first page or so of this thread the man changed his track status making F.A. change in its wayward dance, you don't want to think about this drive deviation thing to much its not healthy, on High Drive tractors due to the annulus gear set up in the hubs other factors like rollers idlers and brake pack control will come in to play. I hate Hard Hats mine nearly always off. tctractors
Only having the craic tc... Life's too short to worry about it
The track sprockets move the tracks at the same rate of links; and the worn links are longer than the less worn links. The track links on both sides move at the same number of links per time, but the worn track moves more length per time, i.e. faster surface speed. Just like tire stagger on a sprint car. The rear wheels turn the same rpm, with a spool, but the larger tire travels farther, and the car turns left.
Jim D, the 1 item missing in your post is the Car being fitted with a speed adjustment device between the rear wheels, even if the Diff is locked like you find on 99% of track type tractors, its not the common thing to see someone fitting a larger sprocket onto 1 side? with it usual to find wear within track groups at around the same level the point is of little value, I have yet to be called to a dozer or tractor shovel with D/D or P/S with the complaint of 1 leg dragging but the drive to both tracks still being good, I look forward to other Mechanics comments on how they had to deal with this issue on standard drive tractors, as in 45 years of working hard on track type tractors I have yet to earn any coins from this unusual defect. tctractors p.s. jam I loved your post although it was not without its errors, as Hard Hats are all standard Gauge with fine adjustment left to the operator to get the correct pitch required.