Construction laser set-up

[Digger293]

Hello everyone....I wasn't sure where to post this but here goes.....Can anyone explain to me how to set up a remote laser to dig a basement....Putting it on the tripod and leveling it is a no brainer but how do you set up the pole for the right height. I've dug plenty of basements but a foreman always set up the laser before I tracked over..Thanks

[digger242j]

I'll assume you have an elevation for the bottom of your hole, and a benchmark, whose elevation is known. It's always best if the benchmark is on something permanent, that you know is still going to be there tomorrow, like a fire hydrant, or the top of a manhole. Your laser is set up and leveled.

There's a couple of different ways of figuring out where on your rod to set the laser sensor.

The more complicated way, is to get the elevation of the laser, and calculate from there. We'll use round numbers, to make it simple. Say your benchmark is at 1,000 feet even. You set up your laser, and find that the laser is four feet above the benchmark--your sensor reads level at the 4' mark. That means that the elevation of your laser is 1,004 feet.

Now, you simply take the elevation of the bottom of your hole, and figure out how far that is below the laser.

If the bottom of your hole is supposed to be 994 feet, you subtract :
1,004 - 994 = 10

You set your laser sensor at the 10' mark on your rod.

If you're going to be digging a number of holes of different elevations, from the same laser setup, this allows you to work from one standard number.

The easier way is this--you take your benchmark elevation, and figure out how much higher than the bottom of your hole the benchmark is. For the same numbers as above:

1,000 - 994 = 6

Your benchmark is six feet above the bottom of your hole. You set your laser sensor wherever it reads level on the rod. Then all you do is add 6' to that setting. (This is a good method for guys who aren't real good with numbers, or if somebody ran over your rod with a machine, and you have to use a piece of 2X4, since that won't have any numbers printed on it.) Once you've figured out how far below the benchmark you need to be, you can just use your tape measure to move the sensor 6 feet up the rod. (Using nice round numbers it doesn't seem that difficult, but if we were talking about say, 6' 2 3/4", you can see where it would save some head scratching.)

(I put up the rod in bold, because that's important. Move the sensor the wrong way, and you'll be way off grade. Remember, when you need a deeper hole, the rod has to be longer to reach the bottom. Shallower hole, the rod has to be shorter. This may also seem like a no-brainer, but I've seen guys get it bass ackwards, especially when the difference is only a foot or so. A foot error may not jump right out at you, but when they come to start setting froms and find out that you have another foot of cut, or worse, a foot of fill to do, it can ruin your day .)

Be aware too, that some rods are calibrated in feet and inches, while others are in feet and tenths of feet. Don't forget to check and be sure what your supposed to be using.

Confused yet? :dizzy

[Electra_Glide]

Another thing to keep in mind is that you want to set up your laser so that the sensor will be able to "see" it from anywhere in the area where you're working. These are line-of-sight devices, so if you set your laser up in a location where the receiver can't see it due to obstacles (spoil piles, trees, existing structures, etc.), you'll have to stop and reposition it. Any time you reposition your laser, you'll have to go through the procedure that Digger described again.

Also keep this in mind as you're placing your spoils. You may start out with a wide-open space, but if your spoil pile gets high enough to block the laser, then you'll have to reposition.

--
Joe

[telescooper]

In addition to good line of sight, If possible try to set up the laser where it will be protected. You don't want someone backing over, or hitting it.:mad:
Joe

[greywynd]

Okay.....now I've done the parts discussed above before, with both laser and the old optical transits. (Happen to have an old optical transit even, so often that's what I end up using, though it does suck needing two people all the time.)

I know on a lot of the laser guided stuff (dozers and graders, for example) that often the receiver is located on a long pole, so it can be adjusted to a height that works for the grading. Seems that when you get into an excavator mounted receiver, they are always mounted in the same spot on the stick. Does this mean the laser has to be adjusted to the right height for the grade you wish to dig at? Can someone fill me in on the basics of having a machine mounted receiver on an excavator?

[MKTEF]

OK

It depends on the type of system u have.;)

If it's very simple u only have one receiver on the stick.
Then the laser has to be at the right hight with the reciever on the stick.
Here u always got to have the bucket and the stick in the same positions as when u adjusted the system.
Put the bucket at desired hight, stick vertical and adjust the laser and reciever to the right hight.

If your system is a bit advanced it got angle sensors on the bucket, boom and on the stick. Then the onboard computer reads when the receiver passes the laser beam and corrects for the angles telling u the hight inside the cab.
U then can adjust the hight on the display inside the cab.
So when u move to a new spot u only pass the beam with the receiver and the height is calculated.

Digging a trench u pass the beam on the way down, and the system calculates as u lower the bucket and tells u when u are deep enough.(reading changing angles)

Laser beam is telling the system a height.
And u added the level u wanted compared to the laser beam height.
The lenght and angles of the stick, boom and bucket is programmed into the computer so that the movement of those gives a corresponding right height.

Next step is a gps system where the computer nows where the excavater is and has a onboard drawing of the wanted heights.
Calibrate the bucket at a known point and the system tells u where it is at all time, reffering to the drawings.
Here u need a basestation sending out correction values to improve the gps exactness.

Next is the doser and grader systems where the system controls the valves in the machine.
Computer then "drives" the machine/blade.

If u want millimeter/exact systems u add a gps system and a laser beam reciever at the same machine.
U then have the gps for positions and drawings, and the laser for millimeter presision.
The system then knows the height of the laser beam.
And the machines have a very long recieving area on the laser recievers.

Hope this explains the system differences.:)

[dayexco]

make sure you don't have any strobe lights from equipment running.....your receiver will pick up the strobe and drive you nuts beeping all the time

[greywynd]

Thanks MKTEF, I wondered if a single receiver on an excavator required setting the laser accordingly. Great job on explaining the more involved setups too...again, I had a good hunch, but that's a great explanation. Someday I would like to figure out a system that would work easily (with one person) on a mini excavator. I seem to get a lot of little jobs where it would speed things up a lot.

[Deas Plant]

Hi, Greywynd.
There are already magnet-based laser sensors on the market for excavators that you can stick on the dipper arm at a height that you have worked out to suit the level you need to cut.

To set up, you roll the bucket right out in the fully dumped position (That and fully closed are the only 'constants' with an excavator bucket.), put the cutting edge on the ground, measure up the height you need on the dipper arm and stick your magnet-based sensor to the dipper arm.

In operation, you simply roll your bucket right back with your dipper arm around vertical and the cutting edge VERY close to the ground where you want to check. The sensor will tell when the dipper arm IS vertical or which way to go to get there. When you ARE dipper vertical, set the cutting edge on the ground and take the reading.

You do have to be a bit careful about jarring the bucket/dipper arm with these systems or you may shake the sensor right off the dipper arm and it can be a PITA sometimes getting your dipper dead vertical but it beats getting in and out of your machine all the time.

For levelling areas where you can drive around with the excavator, our guys use a spreader bar in place of the bucket with a laser rod mounted on the spreader bar and the sensor stuck to the rod at the appropriate height. They then drive around using the spreader bar much as you would with a skid-steer or a loader with a spreader bar clamped in the 4-in-1.

These spreader bars are 10 - 14 feet long from side to side with a quick coupler head welded in the middle so they cover a bit of width on each pass. You can see some photos of one designed for a track loader here.

http://www.heavyequipmentforums.com/Forum/showthread.php?t=4405&page=2&highlight=fine+grading

Just substitute a quick hitch head for the grips for the 4-in-1 bucket.

Hope this helps.