Laser for house pads
Hi, CM1995.
I spent seven years cutting house pads with laser monitoring equipment on track loaders, 941's, 943's and 953's, and on a Cat D5B wide gauge dozer, 44X series.
The system we had was only grade checking, not grade controlling, that is it only checked the levels as you worked and gave you the readings and it only read about 3 1/2" above or below grade. Still it was well and truly worth having for the time it saved getting on and off the machine to manually check the levels.
Basically, it was the normal laser emitter (sender) unit set up where would do the most good, ie., somewhere between 7 and 8 1/4 feet above finished grade and where it had unrestricted coverage of the site. Then there was a laser receiver with a magnetic base that stuck to either a canopy leg or a vertical rail fitted to the door of the cab. We had survey staff scales stuck to these rails and/or the canopy legs to eliminate wasted time measuring the height at which the sensor needed to be set. Once we had the height worked out, we just looked it up on the survey staff scale and stuck the magnet at that height.
That company only had one machine, a 953C, with the electronics built in to run a laser-controlled system.
When working, I simply started cutting at the top, watched the sensor for when it indicated that it was getting close to grade and started spreading my load when the sensor showed grade. I always worked my fill up in layers so that I could track roll it as I came up.
Some clients wanted the fill compacted with a vibrating sheepsfoot roller. We always used a drawn vibrating roller for this work 'cos you could hang it over the edge to compact the batters too and still get it back. If you were using a self-propelled roller and hung the drum over the edge like we did, the only way from there would be down. Yes, there were those who said that these drawn vibrating rollers are antiquated and I have to admit that they are. However, they do the job where nothing else will.
The sensors that this company used indicated 'on grade' to about 1/2" above or below and then read 'high' or 'low' as the case may be for 3" above or below that 'on-grade' range. Once you got used to it, it was fairly easy to keep the 'on-grade' light flashing right across and all over a house pad if you were trimming with a track loader with a 4-in-1 bucket. It was a little harder with the D5B but still emminently do-able. And most of this company's clients only wanted +/- 3/4" anyway.
The only real problem that I had, other than the odd defective laser emitter or receiver, was with reflections from windows in existing houses around the site. To stop this, I used to drape a heavy cloth over the sides of the emitter facing these windows. At one stage, I made up a cardboard shroud that simply dropped over the emitter and did the same job.
I have never used laser-controlled grading equipment on anything but believe from the reports I have heard that is very quick and very accurate.
Over longer distances on hot days, heat haze can affect the laser beam making it do strange things but I never had that problem over the sorts of distances that we were working on even quite large house pads and a few even bigger factory or shopping centre pads.
Hope this helps.
