Drainage trenching - maintaining slope

[RedDirt]

Volp's thread, Device for emptying backhoe bucket
http://www.tractorbynet.com/forums/build-yourself/148164-device-emptying-backhoe-bucket.html
is getting side tracked as we begin to talk about how to maintain an even slope for a drainage trench. This topic really deserves a thread of its own. I've copied a bit of that thread here. Please add your methods and comments.
Thanks, Ray

Volp 9-20-09

RedDirt your digging is impressing!
Any tips on how to get the right leveling of the trench bottom so that the water will flow easily?

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RedDirt 9-22-09

I shoot for 1/4" per foot slope for my minimum slopes. I use a tilting transit. I set it up at the far end of the trench and measure the length from hoe to transit. With transit set level I measure the depth of my trench at the hoe then calculate the drop for the hoe to transit distance. Then I tilt the transit down (or up) that distance and clip a target on my height pole at that spot. The transit is now set to the slope I want to dig. Before I move the tractor down the trench to the next grab length I'll get off, set the pole w/target in the trench, check my progress, and fine tune the slope concentrating on flattening the trench bottom before moving down the trench.

At first you'll get on and off a lot but this decreases as your skill increases and you are more able to judge your progress and trench depth. A helper is very handy especially if your dig is in soft ground and progress along the trench is fairly quick. The helper can set the pole in the trench, walk back to the transit, shoot the target and give you a progress report. You just stay on the tractor and dig .

Ebay is a great place to shop for a cheep transit and tripod. You don't need anything fancy. I bought mine, a Craftsman, many, many years ago but I recently picked up a $700 Leica auto level for $60 on ebay. An older, four leveling screw, tilting transit should be in the $20-$50 range, a tripod $15-$30. My leveling rod is a broken tape measure taped to a stick and I use two more sticks pinch clamped to the rod to hold it upright. You can see the rod in the first picture of my trenching photos above.

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J_J 9-22-09

Just thinking out loud here. I have one of Dewalts rotating laser level, and I believe some of the laser receivers beep when level. If that receiver were on the BH dipper, you would know if you were above level or below level, and flatten the bottom of the trench based on an audible, or visual indication. If one knew how to set up the level for a gradient, you could dig the trench keeping the receiver on the beam. Pretty much the same way they level a field with a set grade. They do some amazing work with those laser graders/box-blades.

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RedDirt 9-22-09

Your idea would work regarding knowing if you were above or below level but working a grade would require more sophisticated equipment. Most laser levels I am familiar with will not function out-of-level. I do know they make laser levels that you can program a gradient into at set up but they are special units. In any case, if you had the receiver/target attached to the dipper it seems you'd need to "probe" the trench with the bucket and dipper in the identical position for each reading. Like bucket fully curled and dipper as vertical as possible.

I think gradient laser levels are fairly spendy units although I've never researched them specifically. The excavators on our job sites have some of that stuff and they spend thousands, even tens of thousands on them. Over the years I have bought six digital theodolites for our company and trained field crews to run highly accurate site and building layout. I can set or read a gradient with them but they are optical instruments. At 17K a piece they are certainly out of my range; I paid less for my tractor! A professional gradient laser may be near the same price or at least 6k-8K. But maybe there are affordable homeowner models that will read grade and someone can tell us about them. I'd like to know. In the meantime my reasonable (cheep) optical tilting transit with or without a helper works fine.

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Brad_Blazer 9-24-09

Here's an EL Cheapo laser with with manual leveling that would presumably be able to function while adjusted to follow a slope.
- Harbor Freight Tools - Quality Tools at the Lowest Prices
Otherwise some reflective tape with graduations might be a simple alternative to the receiver and sloped laser.

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RedDirt 9-24-09

I don't mean to hijack this thread off original topic yet OP asked and this is where it is leading. This should be a thread of its own since there is probably some interest with varying opinions and methods for digging a sloped trench. Anyway...

I went and looked at the HF instruction manual. Now they don't specifically say that you can set the level "out-of-level" but their precautions warn you to "level carefully because just having the bubble off the thickness of the scribed vial line can give a variance of 3" in 100ft". And it does not mention an auto off feature if out-of-level.

So maybe you could set this unit out-of level. If you could you could proceed as I describe above with an optical transit with a couple of twists.

This appears to be a visible laser without a receiver/beeper. Therefore you'd need to see the laser and if the target was attached to the dipper you'd need to place the laser behind you, ie the FEL end of the tractor. You'd still need another rod and tape to calculate the slope and set the laser out-of level but that's easy.

Say you want to dig a 2% trench. That's 1/4" per foot drop. Set the tractor on the trench and dig to the desired depth. Set the level at the FEL end but a bit off to the side so the laser strikes the dipper. Level the laser. Now measure out say 20 feet on the ground from the instrument along your trench line and set up your height rod. 20ft x 1/4" = 5" vertical drop so wherever the laser, (when level) is hitting the rod, adjust the leveling screws until the laser hits the rod 5" down (or up) from the original level reading. The laser should now be set to the 2% slope. Now set the dipper plumb in the trench, bucket hitting the bottom of the trench. For a standard reading I'd have the bucket either fully curled or fully open so you are always measuring the same depth. Place a target (a card with a horizontal line on it) on the dipper where the laser strikes the dipper. Now as you move down the trench, when you want to check your slope, put the dipper in the "measure depth mode" and read on the card to see if you are high or low.

What remains to be seen is if the laser beam is strong enough to read outside. Some cheap (and even some expensive) lasers lack the brightness to be effective in the sunshine. Maybe one could devise a target shade to help out in this regard.

I don't have any drainage projects on my to-do list but the next one that comes up I might just buy one of these cheepo lasers and give it a try. The $50 is certainly reasonable and it would save an awful lot on and off the tractor that's needed with an optical instrument.

Your reflective tape idea would also work if you owned a rotating visible laser that would not tilt out-of-level. You'd need to lay out distances along the trench and relate the required depth at those distances to the target/card on the dipper. EG. the laser is shooting level so the target would have one inch divisions for every four feet traveled along the trench for a 2% slope.

 

[DraftHorse]

I have just finished laser leveling one of my small turn-outs for my horses, 135' x 165', using a Dewalt rotating lased and a Porter-Cable Robotoolz detector. I had no problems with detection in bright sunlight.

The laser is one of the non-self leveling units and can be set to create a grade to a certain degree. (have not tested the grade feature yet.)

The detector has a 270 deg detection and is designed to work with a rotating laser and not a straight continues type.

Now the fun part. You can make a continues unit work with this detector by putting a slowly rotating disc with a slot in it in front of the laser, so instead of the beam rotating, you are pulsing the beam.

 

[RedDirt]

Drafthorse,
Could you post the model numbers of your Dewalt Laser and Robotoolz detector?

How did you deploy your leveling equipment? Did you use it conventionally, ie laser on tripod and use a leveling rod, or did you have any of the equipment tractor mounted, ie the detector? Please explain your method.

BTw - The HF rotating laser that Brad_Blazer mentions above, [FONT=arial, sans-serif]ITEM 92801-3VGA[/FONT]

- Harbor Freight Tools - Quality Tools at the Lowest Prices

is on sale in my current sale flyer for $39. The sale ends 10/12. Reg price is $59 and current web price is $49. If I can get to HF before the sale ends I'll get one. It is worth the $40 to me for experimenting to see if I can devise a cheep tractor mount leveling/grading system. Besides it could be useful for other projects. I don't expect much from it or any high degree of accuracy but as a rough grading guide or for other rough leveling it would be handy. I have my Leica optical level for precision work.

 

[jcaron2]

How about stretching a mason's line parallel to the trench (at the appropriate grade) then mounting one of those $20 wall-mountable rotating laser levels used for hanging pictures and shelves to the dipper. Since the line would always be only a few feet off to the side of the tractor, I think you'd be able to see the spot where the laser intersects the string even in the sunlight. If the intersection is uphill from your current position, the trench is too shallow; if it's downhill, the trench is too deep.

Josh

 

[tommu56]

If the trench is straight I put my laser level in trench on a 4' level with a shim to get the pitch right level the 4' at the offset for were the target will be on my bucket.
I keep laser beam focused on the hook on the back of my bucket to set the depth.

I have a regular transit but working it by your self is a pain!
One of the'se days I'll get a laser one

tom

 

[RedDirt]

How about stretching a mason's line parallel to the trench (at the appropriate grade) then mounting one of those $20 wall-mountable rotating laser levels used for hanging pictures and shelves to the dipper. Since the line would always be only a few feet off to the side of the tractor, I think you'd be able to see the spot where the laser intersects the string even in the sunlight. If the intersection is uphill from your current position, the trench is too shallow; if it's downhill, the trench is too deep.

Josh

Josh,
I like your thinking but I don't know if a rotating laser will continue to rotate for the 99% if the time the dipper is not plumb; often way out of plumb. It would also need to be self leveling or the laser beam would just give you a line perpendicular to the mount. Then too there is the question if a low end rotating laser, intended to be set on a stable platform, could stand up to the abuse of being dipper mounted, constantly in motion and jarred on occasion.

I don't have one of these lasers and have never used one. If someone here has could you put it through a range of motion test and tell us if it functions like Josh suggests? If you report remember to tell us the make & model. There are so many like, but different products out there.

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[If the trench is straight I put my laser level in trench on a 4' level with a shim to get the pitch right level the 4' at the offset for were the target will be on my bucket.
I keep laser beam focused on the hook on the back of my bucket to set the depth.

I have a regular transit but working it by your self is a pain!
One of the'se days I'll get a laser one

tom]

Tom,
Great method. I like it. simple, cheep, effective. A simple straight edged HF laser level would work too.

 

[tommu56]

Tom,
Great method. I like it. simple, cheep, effective. A simple straight edged HF laser level would work too.

I thought of it after seeing the contractor laying sewer pipe in our township The have a fitting that go's in the pipe at a manhole and the laser go's in it and they have a target at the working end,
They put too much stome in the trench and work pipe back and forth till its on target.

tom

 

[DraftHorse]

Drafthorse,
Could you post the model numbers of your Dewalt Laser and Robotoolz detector?

How did you deploy your leveling equipment? Did you use it conventionally, ie laser on tripod and use a leveling rod, or did you have any of the equipment tractor mounted, ie the detector? Please explain your method.

QUOTE]

The laser is a Dewalt DW071 manual leveling and the detecor is RT-A1650.

I built a simple mount out of 2 6" c-clamps, and misc angle and pipe. The main pipe is sch 40 so that when I tighten the bolts i will not warp or dimple it. I then used a section of square tube and a piece of pipe that slides over the mast.

The detector is mounted on the square tube using the mount clamp supplied with the detector.

I first set the laser in the center of my field and leveled it.

I then used the detector mounted to a leveling rod and took a reading right by the laser. This became my 0 point. I then walked the field and found that 80% of the field was +8" to -6" and the remaining 20% being a corner that was -16".

The 20% section was eliminated for leveling right now because I will be bringing in dirt to build it up.

With the deviation being 14", I knew that I had to set the laser for a +1 reading.

Next, mounted the detector on the square tube and adjusted it so that the center mark of the detector was at the 0 reading measurement. I then lowered the detector 1" which would give me the +1" that I needed.

I then locked the detector in place with the 2 bolts. Then I butted up to the bottom of the square tube the round ring and tightened it.

This lower ring allows me to change the angle of the detector without having to remeasure it again.

The detector has a fine and course visual modes and allows for audio tones. The tones are loud enough to be heard over the tractor with the window open.

If you are high, the unit emits a rapid beeping, low a slow beeping and a continous tone at level.

All one does is drive in circles so that the detector is facing the laser and listen for the tones, adjusting the 3pt as required.

It does not take long to get the hang of the tones and it almost becomes automatic.

The one modification that I will be making to this setup is putting a microphone, either wired or wireless and feeding the audio to the cab so I can leave the dust outside and the ac inside.

Hope this helps

Peter

(I reread my previous post and the detector angle is 170 deg, not 270)

 

[RedDirt]

Peter,
Thanks for the reply and follow up. Great post and pictures not to mention the very excellent set up. Well done on all counts!

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.

If anyone is interested I'll dig up and post a simple method to check the accuracy of your instrument.

Ray

 

[SpringHollow]

Some very good deals on Ebay. Managed to pick up a David White self leveling one with x and y incline and extreme range for a very good price. Then bought a cheap electronic detector.

Ken

 

[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