Back in the dark ages when I was being taught to run a dozer my employer said never run in 3rd gear reverse due to increased undercarriage wear. This was pertaining to a D7G, but he also did not want me to back his 17A or 9U tractors in the higher gears. I understand the mechanics of the track slack bunching between the sprockets and the ground on conventional tracked dozers, but it would seem that the high drives would be less likely to have a problem with this. I now will travel in 3rd gear in the high drives, but only at a reduced throttle level that roughly matches 2nd at full throttle, and even then I can hear my old employers words in my head and feel a tinge of guilt. When finishing topsoil or cleaning up (going forward) I find myself in 3rd gear quite often, unless the topography is is such that you have to chase the contours quite a bit. I am curious to hear others thoughts, and I enjoyed the slot dozing thread so much that I thought this may be interesting as well.
HAHA Oxbow, I know exactly what you mean. I was told "never put a dozer in 3rd gear unless it's an emergency." and I too have done it on occasion depending on the circumstances. ( for the same reasons you describe. When finishing topsoil, etc.) The same thought goes through my head, "should I be doing this?" and feel the same tinge of guilt. Anytime I am on a job and hear the sound of a dozer in 3rd, I immediately look towards it because the sound is unmistakeable.
The newer dozers (tier4) actually kick the dozer into ECO mode when trying to back up in 3rd gear which is just about as slow as full throttle 2nd, but if you have to back up at an incline forget about it. That being said i have been running a new 7E (not tier 4) And its geared different 2.2 in the 7E is the same as 2.5 in a 6T, and it recommend to backup in 2.6-2.8, and 2.8 in the 7E is about what 3rd is in a 6T
The deal about reversing at high speed is to do with the way the track links (rails) are built. If you think about it each link is "cranked", as shown by the diagram below. The link assembly is designed so as to work properly when pushing forward because obviously that's when the most load is on it. When pushing forward there is no relative movement between the bush (which is pressed into the narrow end of the links) and the teeth of the drive sprocket. In reverse the bush "rolls" round the sprocket teeth and so you have relative movement between the two which will cause accelerated bush/sprocket tooth wear. This is why using high speeds in reverse is not recommended. On our tractors we blank off 3rd gear reverse so the operators can't use it.
To add a comment, it's nothing to do with bunching or the slack in the track, high-drive or low-drive. It's the simple mechanics of the sprocket tooth/bush contact in forward and reverse directions, especially at speed. Maybe I can explain it a bit better. in the diagram is looking down from above the spocket on the RH side of the machine. The left side of the diagram is the rear of the tractor, the right side is the front. You'll have to imagine the whole thing being inverted as the link group on the bottom side leaves the track rollers and arrives at the sprocket. So when the machine is moving in the forward direction the links/rails are moving left to right. The track bushing (3) that is presed into links (9 & 10) engages the sprocket and the next pair of links (5 & 6) which are pressed to the track pin (4) trail behind it. But because of the relative rotation of the bushing 3 & pin 4 the position of the bushing stays pretty much fixed with respect to the tooth of the sprocket from the time it picks up at the bottom until the time it lets go at the top. It's different when the machine is moving in reverse. As links 5 & 6 arrive at the sprocket (moving from right to left) they rotate along with the pin 4, then when the bushing 3 arrives at the sprocket because it's fixed to links 9 & 10 (that are now trailing behind it instead of leading it) it will rotate somewhat as it engages the sprocket teeth and also will rotate again with respect to the sprocket teeth when it disengages as it leaves the bottom end of the sprocket. That's where the difference lies.
Thanks Nige, I new there must be more to it than the bunching. I still am foggy as to why higher speed would wear the tracks proportionally more than lower speeds, but understand what you are saying about more wear in reverse than forward. So, if I understand correctly, the new style chain on a D6N for example (System 1?) that has links that both ends are either inside or outside the adjacent links, are less prone to accelerated wear in reverse? After reading the System 1 thread I understand that there are other issues with them.
With the issues of which I am aware of with SystemOne undercarriage (and I've never had to maintain one so it's all anecdotal evidence) high speed reversing should be the least of the tractor owner's worries ............... Because of the lack of relative bushing/sprocket movement in the forward direction high speeds forward are not majorly detrimental unless of course the ground the tractor's running on is so uneven as to cause major impact wear issues. The fact that there IS relative bushing/sprocket movement, which will obviously cause wear, in the reverse direction the higher the travel speed the more rapid the relative bushing/sprocket movement therefore the more pronounced the wear will be. Imagine taking a variable-speed grinder to a piece of metal. If everything else remains the same (e.g. the wheel, the pressure you apply on the metal, etc.) then the faster you rotate the grinding wheel the more metal you will remove in a given time. Same principle applies with undercarriage.
High gear is where it's at (when safe to do so). All the foreman I work for, want stuff done now. Even pushing scrapers, if you use high gear backing up, you could probably ad another scraper. The bosses/foreman I've been around want to see how much more you can do today than yesterday. Go Go Go. Oxbow, my first boss (dad) never liked high gear either. He always said "make every move count", you will have less passes than the operator in high gear not making every move count. Now, I operate in high gear (sorry dad) combined with making every move count, keeps my boss happy, keeps my job, happy happy happy. I don't plan on changing bosses, but if I do, and the next boss don't like high gear, I will respect him and do it his way. I also think the slot dozing thread is interesting.
The thing is of course that the foreman generally isn't paying the bill for the replacement undercarriage, neither is he the one who has to get greased up to the elbows changing tracks, rollers, & sprockets. That's why we don't give our ops foremen the choice, they get the tractor from the shop with just 1st & 2nd speeds in reverse and that's it .......... Your dad had wise words about high speed reverse, you should listen to him. My first thought any time I see or hear a dozer in 3rd speed reverse is "cowboy", working without thinking ahead and planning his moves.
Yair . . . I have often wondered what the point was of the third slot on a Cat, even in forward. The two speed on the Allis worked well and should have been more simple and reliable, they were plenty fast and responsive . . . I suppose converters work better at twenty one hundred. It was quite an elegant design, the side to side movement of the shifter selected the range and direction in the transmission and the back and forth movement actuated a clutch in front of the converter. Cheers.
I learned in the 50's. My Dad had a cowboy and an operator. The operator some times looked like he was in slow motion compared to the cowboy but at the end of the day he did at least a third more work with half the wear and tear. Clearing land or pushing dirt, he was the one to learn from.
I believe Nige has already answered the question that I am about to ask, as he is probably as knowledgeable about large scale outfits and the cost per yard/cost per our/etc. as anybody, but: It would be interesting to see a graph of cost per cubic yard running no faster than 2nd gear vs using 3rd. In other words, is there a point at which cost per cubic yard goes down due to increased production at a rate that is higher than the increased cost per hour caused by running faster? I suspect that in some scenarios where operator pay, bonuses for early completion, seasonal time windows, etc. are factored in there may be circumstances where it does indeed net a higher return, although they are probably few and far between. Food for thought!
Another good dozer thread, Nige hit it head on as usual. My neighbor is our master mechanic and I worked/hung out in his shop while still in high school, so I got to hear all about this topic long before I had a seat. Him and Nige explain almost exactly the same way too. I don't make a habit out of high ballin but every now and then on a hot to trot trim project I'll bump it up. It all depends on what the situation dictates, I'm usually a 2nd and wide open kind of guy, I don't touch the decel, usually sit with my legs crossed and trim away. So now that brings up another controversial subject, decelling when changing F-R, I generally don't, haven't since I never believed it to do any noticeable damage. Any more I'm on smaller hydro trim tractors just doing trim work, I don't believe it hurts them, but I've been wrong before. Now if I'm on bigger tractor working up and down slopes I'll decel when I get to the bottom before shifting to go back up. Shall I start another thread, as to not hijack this one?
This reminded me of a new operator we had on the 988H pit loader a few years back. Boss tried to tell him he had to pick up the pace. They then switched to a couple other operators who were "faster". Thing is when they kept track of the number of loads each one sent to the crusher in a day they found out the "slow" guy was actually getting more loads a day!
Slow is smooth, smooth is fast. Simple as that, consistency pays off. I have found routine helps as well.
Yair . . . bigshow . I believe that's exactly right in most callings, for instance the top tally hand (ringer) on a sheep shearing board often looks relaxed and slow. I have no experience and am quite unqualified to comment on the modern machines and the decel question. I would have thought the main issue was for the machine to come to stop before changing direction . . . apparently these days it isn't necessarily so and some transmissions are built to modulate and accommodate full power/speed direction changes. Rather than building complex transmissions for dummys I believe in most cases improved production could be achieved by a bit of tuition in machine control and basic operation techniques such as slot dozing. Cheers.
I was on a job years ago with two D8's. One in the T model insisted on doing everything in 3rd gear "cause it gets stuff dun faster", while the guy in the R never went higher than second... The second guy would constantly get more done. For one simple fact, the higher the gear, the less power to the tracks you have to push, so the smaller the "blade full" Course that's got nothing to do with reverse. I think it's standard that the reverse gears are set a bit faster than the respective forward, but I could be wrong.
The decel thing with going from F to R is another thing i love about the 7E! I dont know how it does it but no matter how fast your going or how quick you do it, its always so smooth. Does anyone know anything about the tracks on the 7E and why they recommend you back up in that high of a gear???
Jim makes a good point. The amount of torque available in 3rd gear (forward or reverse) is almost non-existent, pretty much just enough to drag the machine itself around let alone do any meaningful work with it. I probably have the "Big Load Slow" video clip somewhere, maybe it's even on YouTube. Get the biggest amount of material you can in front of the blade on every push, and like a chess player plan a dozen moves in advance and you don't need to charge around like a horny rhino .... When it comes to decel a lot of the modern electronically-controlled transmissions are allegedly capable of going from full power in one direction to full power in the other without needing to hit the decel pedal simply by the electronics figuring out what the machine needs - a true powershift if you will. If you're in the seat you can feel it, you flick the shift to change direction and you can hear the engine decel, plus then you feel the clutches start to slip. The whole process takes about maybe 2-3 seconds. I'm still sitting on the fence on that one as to how transmissions hold up. One thing I can tell you it doesn't work on 16M's (doesn't make the tranny live any longer than it), but that's a story for another day......
Accelerated wear on the bushing due to highspeed reverse is a non issue What it does to the sproket tips will get in your pocket
Houston dozer "operator" are the kings of 3rd gear. When I hit 3rd I'm at 1/2 throttle because I'm traveling. I have a green "dozerhand" on my site now that I'm working on making an operator out of. He ran around for 5hrs in 3rd gear with a new D6K and barely spread 240yards. And wasn't keeping up with the trucks...I got my work cutout for me.
Two things I hate to see a dozer do is spin around short and run in 3rd
Just because it will counter-rotate doesn't mean it has to.
I wish I could have made a video of one operator. I was working on a transmission problem in a 988 87A Cat with a dealers mechanic and we wanted the normal operator to run it while seeing how it was working. The dealers mechanic could not believe how this operator ran the machine. Only way to describe it would be a violent attack on the controls! We both wondered why the machine didn't have more problems. Another time I was checking out a problem with loss of power in an old Mack tractor, found a bad fuel suction hose. After replacing it driver asked me to go for a test run of his normal 30 trip. This was one of those good old Triplex 5 speed with 3 speed aux. Twin stick transmissions. You would swear those levers were not hooked to anything. He would go through the gears so slow and smooth with never even a click as they went into gear while running through city traffic and some Interstate miles pulling a bulk trailer full of stone dust from a BC plant.:notworthy
We had about 6 old D-9 G`s and H models where I worked at years ago. The slot for reverse had a bolt in it so there was no way to back it up. All set up with push blades and rear cushion blocks. If memory is correct the reason was the ungodly cost of the planetary final drive set up it uses
Nige and others have explained the reverse wear well. One thing I would add that I have not seen mentioned is the internal stress on pins and bushings. During forward travel, there is stress from the contact with the sprocket, down to the ground, and just a slight ways forward. In all, probably less than 1/4 of the track length. During reverse travel, the stress is from the sprocket, all the way to the front idler, then about halfway to the rear. This would be about 2/3 of the length of the track. I seen a very good pictoral description of it in a John Deere manual once. Another problem with high speed operation, forward or reverse, is heat build up. This can cause seals to fail in the sealed links, rollers, idlers, as well as hurting the heat treatment of the steel, further accelerating wear. On the issue of decelerating for shifts, the new iron seems to be made this way. When I run my D-8T, I will sometimes go for hours without touching the decel pedal. One day, the pedal fell off, as I had not noticed the bolt cam loose. I ran for over 4 hours that way. I will pause in neutral during the shift to let the tractor slow before engaging the other direction, and there is no harsh shift. The older machines would jerk and bang when shifting wide open, and I am sure that is not good. Running H and K model D-8's I would always idle down between shifts.
I'm interested to know why you think that should be so, because if you do a Rockwell hardness test on a bush and a sprocket segment they are as near as damnit the same hardness. So if that's the case why should one wear different to the other..?
OPERATION TIPS... Page 8. http://www.deere.com/en_US/docs/con...ts/parts_by_industry/undercarriage/DKB765.pdf OCR
Regardless of wear or stresses on the machine, I don't like third gear because I don't like beating myself up.
Yeah, it gets damn old... mighty fast. OCR
Thats the one OCR Thanks for helping out. That little book has some good operating tips in it, but what stuck in my mind was the track picture of forward and reverse. It makes it easy to see for some people who struggle with understanding the issue.
:thumbsup... Any time if I can... OCR...
Out here, there are some big companies that love to see an 8 or 9 going 3rd gear wide open in reverse. Those are the outfits I wouldn't want to work for. I think beyond the wear on the machine, as someone else pointed out, 3rd gear is just too hard on the operator. Dare I say a safety concern for long-term well being of the hands running the dozers? I ran an 824C wheel dozer that had the worst seat imaginable, so I started wearing a kidney belt and everyone gave me weird looks. 2 jobs later I came across the same unit, seat was replaced.
Something no one has mentioned is the increased distance a machine travels per day when using 3rd Rev is also a big part in the sprocket/ bushing wear rate. You might get more production using 3rd but you travel more mies in doing so, so therefore there is a correspondingly increase in wear and tear on the track system because of the increased distance travelled per hour. I have been on several machines lately that have 3rd blocked out on them, both fwd & rev. Just my 2 cents worth.
Higher the speed = more revolutions the sprocket does in a given hr = greater distance travelled / hr = more times the sprocket & bush rotate against each other which in turn creates more wear. So a machine does a 1000hrs in 1st 2 @ 2.5 mph is going to travel 2,500 miles in that time, one that does 1000hrs in 2nd gear @ 4mph is going to travel 4000 mies in that time, the same would go for using 3rd gear would mean a much greater distance travelled therefore much more wear has taken place because of the greater distance travelled.
I'm not sure about that. To me it appears as though the reasoning for using 3rd speed is generally to get the tractor from A to B faster. I think we are all in agreement that you wouldn't be pushing a load in 3rd speed forward. During operation "A to B" is generally (but not always) backing up the cut from the end of one push to the start of the next one. So in that case the distance (100m, 150m, whatever) is fixed, the only variable is the time taken to cover that distance. All the undercarriage components will move pretty much the same number of rotations to travel that distance whatever the speed (1st, 2nd, or 3rd) that is selected. Also there's plenty of evidence out there that the operators who are able to move the most dirt in a shift are the smooth steady ("Slow is smooth - smooth is fast") ones, and I can't say I've ever seen one of them tracking in 3rd gear.
3rd gear in reverse = greater chance of something flying off the track and shattering the door glass. Also I’ve seen someone doing the high speed reverse thing and struggle to open the door from the crap thrown onto the step.
High speed reverse in a Cat LTTT such as D9,10 or 11, for extended periods,...apart from UC problems, has anyone seen problems with the final drives due to an issue with the change in dynamics of the 'oil splash lubrication' when the unit is continually operated in this manner? I vaguely remember a service mag or other dealer document that stated to avoid this situation due to the poor lubrication characteristics in the FD compartment when operated for long periods, such as tramming the unit in reverse. Appreciate any relevant feedback. Thanks
If my memory serves me correctly that was for low-sprocket tractors a generation ago, not high-drives. I'm prepared to be proved wrong though. Any operation using D9 size tractors and upwards that does not electronically disable 3rd speed (in both directions) is asking for problems IMHO. We blanked 3rd speed off on all our big tractors and I can't say I've ever seen final drive issues on any fleet, other than normal wear and tear plus the occasional catastrophic failure which would be expected on a big fleet.
3 Gear is put on the tractors for a reason. Not every tractors tor is in a production slot dozing operation. I love how narrow minded some guys get. Now 3 rd gear reverse running not wise... but when you absolutely have to get from point a to b now, you use every thing you can. I have run 3 rd reverse wide open to travel multiple miles, like 8..., As did the guy next to me... Driving forward in 3rd isn't going to cause much difference in wear, running empty I often run 3 rd reduced throttle... And yes, I am a slow is fast and accurate operator... And for the guy who says why didn't you load it on a truck... trucks don't do well on 300' of snow.
All those gear positions where put there by the maker for a reason. Back in the day when the attractive roach coach driver was showing up for our lunch, and being probably 3/4 miles in the woods or more, clearing, 3rd gear reverse is very important at full throttle, oh and heading out at quitting time as well. The reverse speeds are always faster than forward. Now when doing work especially ripping only 1st allowed. I've done things that affect the finals etc way worse, and never had a final fix job other than seals.
RG's explanation makes no sense at all. If you have to back up 100 meters or 1000 it's still the same no matter how fast it takes to do it. Wear may be 3 or 4 times more but the distance is the same.
It does though. If you are going faster, you get there sooner and can make more passes per day, which in turn makes for more distance travelled over the course of a shift.
No, the distance traveled is the same. He was trying to say you travel a longer distance in a faster gear. you don't. It was nothing to do with more production. If the undercarriage wears out faster the cost per yard moved needs to be considered. I forget who but awhile back this issue came up. One of the members on here (Oz dozer?) knew an experienced operator who used 3rd gear but was also much more productive to warrant the increased undercarriage wear. Other operators going faster weren't any more productive than operators only using 2nd. gear. They just wore the undercarriage out faster. A lot depends on the experience of the person in the seat. Experienced smart operators can get more done at a lower speed than less experienced operators at higher speed. If max. production is paramount you want the best operator and it may warrant using 3rd gear. If you just need steady production and want the undercarriage to last longer it's better to not use 3rd. gear. Nige has mentioned many times of 3rd. being locked out or disabled and even of operators being run off for using 3rd. gear. He also mentioned slow and steady wins the race a few posts back. I don't use 3rd. because I want my undercarriage to last the longest and don't mind if it takes a little longer getting to the job site. I'm the one that has to pay for the undercarriage. My loader only has a single speed reverse and I don't miss having a 3rd. gear. I'd like to have a 1st. gear in reverse though for greater drawbar pull. Reverse is a little slower than 2nd. gear. I think owner/operators or smaller firms are often more concerned with undercarriage wear and replacement cost than operators who are employee's.
That's actually not what he was trying to say from what I can see. It's a simple concept, if you move faster, you travel faster. Since you travel the same distance faster, you are able to make more cycles in a fixed time. This means you do one of two things, either travel more distance in the shift, or park and wait after you have travelled the distance you would have at a lower speed. I don't know of many companies who would be ok with that.
No, in his first post he says you travel further in 3rd gear. It's the same distance no matter how fast you go. You go further with more pushes but it costs more in the end. You can also push more material in 1st gear than you can in 2nd. Why do a lot of large operations disable 3rd gear if it's so much more productive? The bigger picture is cost per yards moved. If your undercarriage wears out faster your cost per yard goes up. If you get another 1000 hours or more out of the undercarriage it pays to not use 3rd gear reverse. For long pushes there are better options than dozers.
Yes, he says you travel further in a day . That is due to more cycles, due to higher speed.
Not necessarily higher production if as you say the operator is getting beaten up. Nige's post 36 supports that higher speed doesn't equate to higher production. I've got lots of hours on a skid steer. It's very similar. I see inexperienced operators hop in and try to go as fast as they can bouncing around like a ping pong ball. There's no way they could keep that up for 8 hours let alone 2. The real trick is to let the machine do the work instead of forcing it or trying to be a hero. High speed bouncing around like that takes a big toll on the body. I've seen several semi and dump truck drivers that have drove for years that can barely walk now because of all the pounding and even getting in and out of the trucks. Going faster can be counter productive not only for the machine but the operator too. Too many operators think it's a race and it isn't. Going too fast often leads to more mistakes too.
Snow often causes packing that makes the chains too tight that really accelerates wear.
I have walked machines through deep spring snow many km’s and have seen a 1/16” inch of clear/hard ice form on each track bushing….very hard on track chain as will become tight as a ‘banjo’ string. To the point of the chain skipping on the sprocket with a loud bang. Grouser pads have ‘clearing’ holes but do nothing in this situation… Regarding third gear, I have often seen a physical lockout. Our dozer is old and personal use, so only use 1st for work. 2nd for travel.
Track chains tightened by ‘ice rime’
Please show me where I said anything about increased production. I simply pointed out that the comment on travelling more distance in a day due to higher speeds is in fact correct.
Daaaaa? Use a dumb truck as an example then. And use some dumb speeds and times. Truck drives as slow as possible on this 1/2 mile trip to get loaded and back to the dump site. Yeah its like slow dozer speed, 1 stupid mile per hour. So 1 total dump trip is going to take 1 hour to complete the trip. Now if that truck speeds up to almost light speed, say 10 miles per hour, then it gets to take 10 trips in that hour. I'd say production will increase with speed.