Fine grading with gps

[Whowho05]

Hello everyone this is my first post and I love all the advise that i can read from everyones posts on this site.. I have a question about finish blading with gps, the company i work for purchased gps for equipment about 3 years ago started with the topcon but just recently we switched to trimble because of tighter tolerances on an airport project we are doing. It seems like if i try to just "flip the switches and go" like the caterpillar guy said the blade tends to be really jumpy and that is after i get the grade watered and compacted i like to leave it about a tenth high then cut one last time to grade and compact again. We have had the caterpillar guys come out and look at the machine and they say everything is how its supposed to be. I end up usually only running the side with the mast on automatic and running the other side manually, I tried running both sides but our grade failed tolerances which is 3 hundreds, has to pass straight edge, 100% compaction, and pass proof roll. Is there anything i can do different or is it a machine issue? Any help is appreciated. The machine is a cat 140H tier 2 with about 8500 hours and i would call it good condition not great. I have been running a blade for about 4 years now. And its all the newest equipment from trimble to my knowledge with the robot that follows the prism on the mast.

 

[Vern B]

Hello everyone this is my first post and I love all the advise that i can read from everyones posts on this site.. I have a question about finish blading with gps, the company i work for purchased gps for equipment about 3 years ago started with the topcon but just recently we switched to trimble because of tighter tolerances on an airport project we are doing. It seems like if i try to just "flip the switches and go" like the caterpillar guy said the blade tends to be really jumpy and that is after i get the grade watered and compacted i like to leave it about a tenth high then cut one last time to grade and compact again. We have had the caterpillar guys come out and look at the machine and they say everything is how its supposed to be. I end up usually only running the side with the mast on automatic and running the other side manually, I tried running both sides but our grade failed tolerances which is 3 hundreds, has to pass straight edge, 100% compaction, and pass proof roll. Is there anything i can do different or is it a machine issue? Any help is appreciated. The machine is a cat 140H tier 2 with about 8500 hours and i would call it good condition not great. I have been running a blade for about 4 years now. And its all the newest equipment from trimble to my knowledge with the robot that follows the prism on the mast.

How tight is your blade? Seems you could easily have enough slop in the blade on an
8500 hour machine to throw your tolerance's off. If their is much movement/slop in the blade, circle and A frame the system might be overreacting to the movement in the blade and over-compensating for it.

Might have to have your mechanic check to see and make sure everything is tightened up.

 

[xcavate]

Go into the computer in the cab and try slowing down the hydraulic valve speed. If its turned up to high it will make the blade jumpy.

 

[Kman9090]

What everyone else has mentioned and also if you are new to GPS what are you finish grading? I'm guessing a highway with such low tolerances. My question is who built the model and how good is it? In the cross section mode zoom in real close and make sure theres no breaks no mistakes in the lines. Also when you are grading a road you need to move your focus point in a couple feet from the end of the blade or it will pick up the linework and break points for the shoulder and cause your blade to go nuts as it keeps jumping back and forth from side to side.

 

[Kman9090]

Also instead of ditching the Topcon why didn't they just buy the milimeter GPS head? Just normal GPS is good for getting it within a tenth, you need laser guidence to get it any closer.

http://www.youtube.com/watch?v=-4v5I_t2A5g&feature=relmfu

 

[390eric]

-I just started really learning gps on the dozer. Talking to the boss, who is our gps expert, he was saying with the grader he has to run it about ten feet before actually starting to grade. Our grader only has one antenna, he says that it cant triangulate the machine quick enough with just the one to be on grade instantly. Guess once it starts moving all the sensors pick it up, then makes everything more accurate amd smoother. I also learned about have rough grade lines in the model, really does make the gps confused, learned this first time trying to grade a 2:1.

 

[Kman9090]

Your boss is some what right but not quite. The GPS is always on, the reason why you cant turn it on and go is when your backing up the gps thinks your still going forward so it takes a few feet of going forward before it picks back up. Also if you have one antenna then the other side of the blade reads off of a slope sensor.

 

[390eric]

Thats basically what he said, didnt just explain it well in the post. Basically the gps is confused for couple seconds when changing directions.

 

[terrasmooth]

Hello everyone this is my first post and I love all the advise that i can read from everyones posts on this site.. I have a question about finish blading with gps, the company i work for purchased gps for equipment about 3 years ago started with the topcon but just recently we switched to trimble because of tighter tolerances on an airport project we are doing. It seems like if i try to just "flip the switches and go" like the caterpillar guy said the blade tends to be really jumpy and that is after i get the grade watered and compacted i like to leave it about a tenth high then cut one last time to grade and compact again. We have had the caterpillar guys come out and look at the machine and they say everything is how its supposed to be. I end up usually only running the side with the mast on automatic and running the other side manually, I tried running both sides but our grade failed tolerances which is 3 hundreds, has to pass straight edge, 100% compaction, and pass proof roll. Is there anything i can do different or is it a machine issue? Any help is appreciated. The machine is a cat 140H tier 2 with about 8500 hours and i would call it good condition not great. I have been running a blade for about 4 years now. And its all the newest equipment from trimble to my knowledge with the robot that follows the prism on the mast.

Like someone else said; you can go in to the controls and set the speed at 5 and see if it helps. I have had this happen with the Trimble Robotics. I tried turning the speed down, did a valve calibration and finally got a new box, that fixed that occasion, but other times it did not. I ended up running at least one side manually to get the job done.
Part of the issue could be play in moldboard and circle, this combined with a small amount of material will cause it to chatter.

 

[140Monster]

it sounds like the Gcs900 system, we have that system on our 140m, we have had little issues but the biggest advise it to calibrate your machine everymorning and if your on tight tolerances like you are, i would be doing it every 4 hours. . . once you calibrate the grader then start with setting up the robot, then bench your machine with the robot, never use uts station as bench, one you set all that up everything should be all good. oh and make sure you adjust your blade wear as often as you calibrate. we are having great success at the moment with this system.

 

[satmike]

When I ran a 140H, I couldn't run both sides on auto at once. It would duck walk. On the 140M I run now no problems with both sides, but I still usually run 1 side manual and every thing comes out smoother

 

[140Monster]

i wonder if the valve speed is too high, over corrects itself instead of correcting the problem, that would explain the duckwalk, i run both sides on auto with the 140m no dramas at all. thats using uts.

 

[terrasmooth]

it sounds like the Gcs900 system, we have that system on our 140m, we have had little issues but the biggest advise it to calibrate your machine everymorning and if your on tight tolerances like you are, i would be doing it every 4 hours. . . once you calibrate the grader then start with setting up the robot, then bench your machine with the robot, never use uts station as bench, one you set all that up everything should be all good. oh and make sure you adjust your blade wear as often as you calibrate. we are having great success at the moment with this system.

With due respect, I think it is a waste of time to calibrate more than once per shift, unless something drastic changes; such as new cutting edges or a low tire.
This calibration mainly affects how the machine matches up when switching directions. In my considerable experience I have found that it has little affect on accuracy or 'chatter' of the blade.

 

[Digger321b]

How fast are you going when grading??

 

[140Monster]

totally up to you terrasmooth, im just saying what i found best. the advice from SITECH whom we bought the gear from said some people calibrate 4 times a day. to keep it all good, he said at least twice, especially if your working super elevations all day. its just me but i would much rather be shaw that its not my fault when the job fails for levels and you have to redo it just because you choose to calabrate once. up to you.
if you think it dosent affect accuracy mate, your crazy, you dont want it reading 2 different levels when you switch ways im sure. . if you hit a rock, re calibrate, if you push too much gravel to spin the blade, recalibrate, if you hit a corner tip into the ground, re calibrate. each to there own, but know one will pay you the top hourly rate for the extra uts gear to find our your too lazy to calibrate it and dont use it to its full capacity. . not my problem mate, was just offering advice, we have a calibration station which is made up of sleepers and guidepost, so it only takes one minute and its a one man system and you dont have to leave the cab to do it.

 

[terrasmooth]

totally up to you terrasmooth, im just saying what i found best. the advice from SITECH whom we bought the gear from said some people calibrate 4 times a day. to keep it all good, he said at least twice, especially if your working super elevations all day. its just me but i would much rather be shaw that its not my fault when the job fails for levels and you have to redo it just because you choose to calabrate once. up to you.
if you think it dosent affect accuracy mate, your crazy, you dont want it reading 2 different levels when you switch ways im sure. . if you hit a rock, re calibrate, if you push too much gravel to spin the blade, recalibrate, if you hit a corner tip into the ground, re calibrate. each to there own, but know one will pay you the top hourly rate for the extra uts gear to find our your too lazy to calibrate it and dont use it to its full capacity. . not my problem mate, was just offering advice, we have a calibration station which is made up of sleepers and guidepost, so it only takes one minute and its a one man system and you dont have to leave the cab to do it.

You need to reread what I wrote; I will reiterate, this kind of calibration only affects the cross slope and main fall matchup… not vertical elevation accuracy. This is why you can’t completely trust these systems, like I have said they are ‘stupid’, just like any computer they only as good as what they being directed to do. Trimble systems did have a flaw with matching up on steep super elevations. I worked extensively with their representatives on a job with 10% ‘supers’. and NO amount of calibrations helped… I did as many as 6 in a day. I personally prefer the TOPCON system because you can turn adjust it to match much easier from the cab… with leaving the grade; it has nothing to do with being lazy. It does have a lot to do with production and knowing the quirks of the system in order to make it accurate. If I were to calibrate under the stipulations you state, I would never get anything done. Dont take it so personal; I am offering my input based on thousands of hours in the seat with these systems and very much frustration in finally getting their quirks figured out... take it for whatever you like.

 

[Whowho05]

Ok so after taking all the tips from you guys i came to the conclussion that it has to be the model. I turned the valve speed down, i made sure that the blade wear was correct every morning and i also got our company surveyor to set some bench stakes... after we would do all this it still "duck walked" with both autos on so i ended up running one side manually, when the surveying company for the general came out to verify grade i had him set up bench marks, between his bench mark and the grader there was .04 difference, after i benched it to his marks it was still out. We also figured out that the slope sensor was off but it still didnt get us within our tolerances... The reason why i think its the model is that we did another job and this time we had our surveyor build the model instead of another surveying company and it worked flawless never had issues with the grade, the tolerances werent as tight but everything matched when we shot it with the prism and uts. unless its something else that i dont know of? Anyways i thank you guys for all your advise much appreciated.

 

[Grader4me]

Reading this with interest..haven't been on here for awhile..been quite busy of late. I operate a 140 m cat grader with a trimble system. Now and then with the auto on both sides, the blade will jump..but I find this happens when there is less material on the blade. I also find this happens when you are going for example in second gear...just idling along. I find the higher you keep the rpm's the less bouncing\jumping the blade will do.
Now, I am leveling crushed gravel on the Trans Labrador Highway, doing the finish grade. I will level and trimble a section..I always leave a small windrow on the left side of the road after its all to grade...then I will tilt my moldboard all the way forward and brush this windrow from the left side to the right side of the road..this takes all the little washboards/etc that your auto had caused, leaving a smooth finish. Now I have question for you trimble experts...why do I leave the windrow on the left and bring it to the right instead of vice- versa?? Hint: my mast is mounted on the left hand side of the moldboard....lol

 

[bigshow]

Keeps a tighter blade angle by putting mast towards front tire and away from the cab?

 

[Puppy]

I do it that away so that when you tip your blade the mast is over your tractor and not out in the open for someone else to hit.