Drainage trenching - maintaining slope

[DraftHorse]

I checked a smattering of prices for your level and came up w/ $700 list, available at one store new for $500 and one used on ebay for $200, the detector about $50 so for my occasional work it is in the spendy bracket. For a project like yours well worth it seeing as it will get other use too I'm sure.

Your level also has fairly good specs for a reasonable insturment. Accuracy is stated as .2mm/m and if my math is right this converts to just shy of 1/4in/100ft. It seems robust and up to the task.

Tell us. On the quickie info sheet I read it talked about "manual leveling" via two leveling screws. How does this work? Do you set the instrument level then adjust leveling screws? Is there any indicator to tell you what slope you are setting? Does the beam slope 360 degrees around the instrument or only in one direction?

Here's something to consider for those using marginal quality instruments. The accuracy is extrapolated the further you get away from the instrument. So Peter's quite decent 1/4"/100ft will still be 1/2"/200ft and 3/4"/300ft, etc. When I am using a marginally accurate instrument I make sure I don't take extremely long shots. For fine work I'll set level bench marks spaced 100-200 ft apart with my best instrument (1/16"/100ft) then reset the cheaper one so I'm never shooting more than about 100ft in length.

Ray

Ray - Thanks for the comments. I checked at the lowes web site and they have the updated version manual level DW073KD for $360. The difference between the updated one and mine is that it uses their standard 18v battery pack, while mine uses 3 D cell batteries. The price for the detectors is about right.

You are correct that the accuracy is 1/4"/100' - that is radius. Therefore, the 135' x 165' area (67.5' x 82.5' radius) that I did would have a better accuracy.

The beam actual rotates 360 degrees. It is variable speed up to 600 rpm. The slower the rotation, the brighter the laser. for outdoor work, you would want to keep it at about mid range.

To set the laser level, I do a rough level using the bubbles with the tripod legs and then finish off levelling with the two levelling screws. You are level when both bubbles are centered. ( they make it easy for you because they have an additional set of marks on the bubble.)

On a side note, if you turn the laser on and leave the speed at the closes point to off, you can use the laser as a single spot that you can position by depressing the top knob and turning to the desired location.

Doing slope can be rather involved, but the simplest way to describe it is this way.

As described in my privious post, find what would make the plot level. Then decide what slope you want, lets say 2", then take your measure pole to the first upper corner, read the measurement, calculate where level would be, then add 1". record what that measurement would be. Do the same for the other upper corner.

Using an assistant, addjust the tilt on the laser so that the detector registers level at the specified mark. Do the same for the upper corner. Repeat until both read the recorded values.

you now will be able to laser the area with a 2" slope from the high side to the low side.

Tell me that I confussed you !

Peter

 

[SpringHollow]

For the price of that manual level laser, i bought on Ebay this used highly accurate long distance grade capable unit:

David White AutoLaser 3175 Interior/Exterior Dual-Grade Split-Beam Rotary Laser (48-3175)

This Rotary Laser has a Grade Feature, where you can enter a grade percentage into the keypad and it will tilt the laser to the percentage slope you tell it to.

Interior/Exterior Dual-Grade Split-Beam Rotary Laser, Electronic Self-Leveling.

# 635nm "High-powered" visible split-beam, class 2M
# Horizontal/vertical applications
# 1/16-in.(1.5mm) accuracy at 100-ft.(30m) with up to 2800-ft.(850m) range
# Horizontal and vertical self-leveling range of ±5 %
# LCD Display with dual dial-in grade, range of ±10%
# Durable plastic housing
# Scanning mode angles (0-359)
# Variable speed (0-1000 RPM)

Obviously, you take some risks buying used but this laser lists for $2300. One other feature i liked was field calibration.

Ken

 

[RedDirt]

Ray -

Doing slope can be rather involved, but the simplest way to describe it is this way.

As described in my privious post, find what would make the plot level. Then decide what slope you want, lets say 2", then take your measure pole to the first upper corner, read the measurement, calculate where level would be, then add 1". record what that measurement would be. Do the same for the other upper corner.

Using an assistant, addjust the tilt on the laser so that the detector registers level at the specified mark. Do the same for the upper corner. Repeat until both read the recorded values.

you now will be able to laser the area with a 2" slope from the high side to the low side.

Tell me that I confussed you !

Peter

Peter,
No, you explained the process well, I think I got it. I use a somewhat similar process to set an incline with my transit. The result is the same, the instrument is set to shoot an inclined plane.

The Lowes price for your instrument now looks a bit more affordable for someone doing a lot of grading. Ken's David White and my Leica auto-level are good examples of buys on ebay. I'm getting anxious to pick up that bottom of the line HF laser and see if I can get acceptable results from it.

For some weird reason I was thinking the beam itself could be possibly tilted up or down so that when it rotated, the beam would be describing a cone shape. What good this would do I am not sure but I am thinking drainage trenches and most eventually turn direction.

My misguided thinking was leading me to the hope that one could set up an instrument and it could stay in one spot while still giving you a slope depth no matter which way the trench angled or curved. But a cone shaped beam would not do this either as the slope of the trench is a function of its length. For instance, if the trench was "U" shaped in plan and the instrument was set for a down cone slope at the beginning of the "U" and one was targeting a fixed point on the dipper, the first leg would slope down, the second would be near level, and the third would climb uphill.

To keep an instrument in one spot and have it give you slope despite the horizontal direction of the trench would take a quite sophisticated instrument. With my company's theodolites I can program the trench bottom with x,y,z coordinates and use an on-board reference line program to keep the trench bottom at perfect slope while the trench zigs and zags, all while the instrument is stationary in one spot. But it is an optical device and the process would ideally take three men, an instrument man, a rod man, and an equipment operator. I tele-commute so getting one home is not an option. If a laser device could do this it would be ideal. Leica, and others make robotic theodolites that could be adapted to this work but the robotics add another 5K to the 17K instrument cost. Sounds like a government or highway contractor's instrument! I think we just have to move our instruments at every zig and zag.

Ray

 

[RedDirt]

Peter - DraftHorse

I forgot to ask. When your detector is mounted on the box blade what is the distance (inches?) up/down the detector can be above/below the beam and still get a reading? If it is only a couple of inches is it difficult to know if the detector is too high or too low without going back and physically raising the beam to see if you get a reading? Your vertical slide mount would make this easy enough but would require getting off the tractor. Maybe a lever mechanism could be set up to slide the detector up the mounting post from the seat (I don't have a cab) to "probe" for the beam. If you slid the detector up and did not get a beep you'd know you were still too high.

Your post mentions detector angle of 170 degrees but I don't know what that angle refers to. I presume that is 85 degrees horizontal from perpendicular to the detector?

Ray

 

[DraftHorse]

Peter - DraftHorse

I forgot to ask. When your detector is mounted on the box blade what is the distance (inches?) up/down the detector can be above/below the beam and still get a reading? If it is only a couple of inches is it difficult to know if the detector is too high or too low without going back and physically raising the beam to see if you get a reading? Your vertical slide mount would make this easy enough but would require getting off the tractor. Maybe a lever mechanism could be set up to slide the detector up the mounting post from the seat (I don't have a cab) to "probe" for the beam. If you slid the detector up and did not get a beep you'd know you were still too high.

Your post mentions detector angle of 170 degrees but I don't know what that angle refers to. I presume that is 85 degrees horizontal from perpendicular to the detector?

Ray

Once the laser detector is set on the box blade, I get about +/- 8" from level in course mode and about +/- 4" in fine mode. I use the course mode for leveling.

From experiance using this setup, if the tone was emitting a high signal (rapid beeping) and then drops out, I just lower the box blade and it comes back into signal range and vice versa.

Once you have set the detector to grade requirement, you do not want to move it. Just raise or lower the box blade. The only time that I would reset the position of the detector is if the angle of reception is too great. That is why I have the lower collar on my rod. It allows me to change the reciver angle without losing my grade setting.

The 170 degree is the reception angle from the laser, 85 degrees left or right from center.

On a side note, I did some research on my laser and noticed that I can turn it to shoot a verical line. So if I can rotate it 90 degrees, one would assume that it would operate at any angle in between.

That being said, if one were to place a sub-base under the laser that angled in x-y axis, then you could set a compound angle with the laser.

Just a thought

Peter

 

[RedDirt]

Thanks for the explanation Peter.

Hey, I was going through my stuff and remembered I had a reasonably bright pocket laser pointer. It has a flat, beam parallel, bottom on one surface. I've also got this neat bubble level some guy left on site that has one of the level vials graduated for 1/8, 1/4, 3/8, & 1/2 in/ft slopes. I've never seen another like it but they must be around. Must be a plumbers level. I'm going to try the Tommu56 method with this set up once I devise a way to keep the laser push button depressed. The graduated vial level will eliminate Tom's second level in his method.

Ray