Using a lenker rod for a level run

[Wheelin]

I am with an employer who, instead of using a Philly rod over long distances for a level run, prefers to use a Lenker rod. While I conceptually understand that Lenker rods are useful for quickly obtaining direct elevations a in a relatively flat area, I have never used a Lenker rod to run a level circuit over long distances up-and-down hills. As such, I am unfamiliar with all the shifts of the rod levers, and the math. I am hoping somebody can point me to some material that might show me how to use a lenker rod in this fashion, particularly when the instrumentman has to move and I as the rodman am occupying the turning point.

Frankly, I’m a bit embarrassed that I don’t know how to use a Lenker rod in this manner. I guess part of me is still rebelling and wanting to use a Philly rod, because that’s what I know how to use. Any help is appreciated.

[SPMPLS]

Lenker, or Direct Reading rods, are not designed for differential leveling. I wouldn't even attempt to use one for a leveling run. You would have to invent a way to keep the notes, but it makes my head hurt just thinking about it. Legend has it that one of largest firms in the Sacramento area back in "the day" threw all of their Lenker rods out (or burned them) after a 10' bust on an undulating construction site.

I can see nothing good happening from attempting to run a leveling circuit with a Lenker rod.

[bruce hall]

I ran "level circuits" with a lenker rod many times. This is not an appropriate tool for level runs. the tape can slide, I can read a wrong number, and there is not check on the work.

This is flat out wrong. would be better to just go buy a twenty five foot extendable plastic rod (for dipping sewer manholes) and use that for the pluses and minuses. the numbers or values that I can get will be more than close enough for most work and I have a check on my work, cause the pluses gotta equal the minuses. With a lenker, I don't have that.

I use a lovely 13 foot rod for my level circuits, and if I screw up, ill find it. Not so with a lenker.

Using a lenker for level circuits is stupid. Stupid, Stupid, unknowing, un seeing, a bunch of things except correct.

[Peter Ehlert]

@Wheelin
I agree with the others, wrong tool for the job.

I Love lenker rods, but just for what they are designed for... large volume of sideshots, no math to run, instant answers.

sorry, I don't have a tutorial on how to use one, but I bet there are dozens on Google and Youtube.
Yes, do learn to use one, a valuable skill.... and You Need The Job... make your boss happy!

and in your spare time look for another job, something tells me your "new company" is not going to survive the next downturn.
a Lenker is not only an inaccurate tool for differential levels, it is a Damned Slow way to do it

[Scott]

I agree, Lenker rods are not for differential levels.

When I was a rod person there was one of my Party Chiefs who was from out of state and refused to use a Lenker rod at all.
We did a 100' topo grid of a large relatively flat row crop field and when we got back to the office, he had to reduce the notes to elevations.
Didn't seem very efficient to me and our manager told him to learn how to use the Lenker rod.
He couldn't grasp the idea of the upside down Lenker rod tape and he did not last long with us.

[Wheelin]

Thanks, folks. I agree, wrong tool for the job, but as Peter mentioned, got to keep the boss happy. I’m glad that I’m not the only one whose head is spinning and wishing that they would limit the Lenker to its proper usage.

[Jim Frame]

I started as an apprentice in the late '70s at a firm that didn't use Lenker rods. Rumor had it that someone had once busted a foot with one and cost the company a bunch of money, after which management banned them from use. We used Philly rods, and later 25' fiberglass rods, for everything.

During the recession of 1980 I got laid off, but soon got dispatched from the hall to another firm that used only Lenker rods. I understood the basic concept from book-learning, but had never actually handled one. The first time I went out with a party chief to run levels, I took the rod to the BM, and as the chief walked past he said "54.37" or something similar. I assumed that was the BM elevation, and thought it considerate of him to share it with me. The chief set up the level, read the rod and then hollered "5.82" of some such. I laid my finger across the 5.82 mark as he looked through the level, but he didn't seem to find that useful. He hollered "5.82" and looked again, but was clearly not getting the response he wanted. He calmly walked back to me and asked, "Have you ever used a Lenker rod before?" When I told him "No," he very patiently explained the procedure, and things flowed smoothly after that.

[Wheelin]

He calmly walked back to me and asked, "Have you ever used a Lenker rod before?" When I told him "No," he very patiently explained the procedure, and things flowed smoothly after that.

You were fortunate that he was patient. Many party chiefs aren’t, which is a shame, as screaming and yelling undermines productivity in the field...and office.

[-Dave Ryan-]

When I was pretty new, I thought I'd do the crew a favor and during lunch or in the evening, can't remember, decided to lube our seemingly tight Lenker rod with some WD40. Next day we were setting grades for forms on a concrete spillway and nothing was checking, and curiously by varying amounts. Good thing we were incorporating check shots on previously set work. Someone with more experience came over to take a look at the rod when my "well intended deed" was revealed. The lesson; never, ever lube a Lenker rod. Things were slipping and sliding all over the place. I always liked the concept of the Lenker, and still do, but you have to be aware there are more than a few ways things can quickly go south if you're not careful.

Dave Ryan,
Arcata, Ca.

[Peter Ehlert]

"jack the rod" was shouted frequently

[SPMPLS]

I am pretty sure that Jim is referring to the same firm that I did with regards to banning the use of Lenker rods. I moved to the area in 1983 and heard about it shortly thereafter even thought it had happened years before.

Honestly, it is hard for me to conceptually grasp how one would keep notes trying to use a Lenker for differential leveling? I guess it would just be the difference between the numbers you read on backsite and foresite, which would give you the difference in elevation between the two. Keeping track of that without error (applying the change in the correct direction using an inverted rod) or the rod slipping through several turns and back seems like inviting problems just for the sake of saying "because I told you to."

I guess if all you have is a hammer everything looks like a nail.

[E_Page]

First off, I agree with all the opinions given here about Lenker rods. Great tool for grading stakes over a flat area and even analog topo where lots of shots are taken from a single setup, but a very poor choice for a level run.

Where you are making turns and there is more than minor relief in the ground surface, 10' busts are not difficult to make and can be difficult to find the location of. It's also not uncommon for a blunder of reading the wrong direction from the foot mark, creating a 1' bust, also being difficult to detect or to locate after the fact. If there is a bust due to tape slippage, it is virtually impossible to find.

If you must use a Lenker, either because it's all you have or a boss who hasn't properly considered the potential problems insists on it, you need to build in a check at each turn. Near each turning point, establish a secondary turning point that is a bit more than 1' different in elevation from your turning point. Take shots on the secondary turn and the primary turn before moving the level ahead. Your next setup needs to be such that you can read from both turn points just established. Set the rod face at your primary turn, then check the secondary turn to ensure you don't have that easy to make 1' bust in setting the rod face. If you're good, continue on with your level run. If not, do a double check on your primary turn to determine if your bust occurred at the beginning of this setup or in the previous setup.

Adding this system of checks to your procedure will add a minute or so to each setup, but that's less time and less problem than if you find that a bust exists only upon closing into a known BM. Having that check at each turn makes it much more likely to find a bust right after it occurs and require you to correct it there, or at worst, go back to repeat just one previous setup. Without the checks built in, when you find a bust, you have no choice but to re-run the entire level run from start to finish.

To use the Lenker, taking off from Jim's example, the rodman is told that the BM elevation is 54.37. The chief's 1st reading is 5.82.

As the rodman, brace your left thumb on the wood edge (not on the tape face of the rod) next to the rod face with your thumb nail right at 5.82. That's 0.82 BELOW the 5' mark, NOT 0.82 above it as on a Philly Rod. Do not let your thumb slip from its position until the setting process is done.

Loosen the clamp knob of the locking pin (right side of rod as you look at face, near top). Slide the pin toward you so that the pin tip comes out of the brass lined hole in the edge of the tape. Use your right thumb to slide the movable face tape until 4.37 (0.37 BELOW the 4' mark) is at your left thumbnail. Don't try to slide the face unless the locking pin is fully out of the hole. You can damage the locking hole in the tape face.

The locking pin will not be lined up with the nearest brass hole, but that pin slides up and down a little more than a tenth, so slide it so that the pin is lined up with the nearest hole. If you can't quite reach it, slide in the other direction to the next nearest hole.

Push the pin forward into the hole and tighten the pin locking knob. Test that the face is adequately locked into place by trying to slide the face with your right thumb. If it slips at all, completely loosen the locking pin, reset so that 4.37 is lined up with your left thumbnail, re-lock and retest for slippage.

With no slippage, you can now remove your left thumb from being a marking tool. Place the rod back on the BM (or turn point) to allow I-man to check reading.

If the I-man calls out another reading (i.e. 4.35), repeat the process just described. It's all the same except that you need to move the tape only a very short amount. If the I'man calls out "Good", then move to the secondary turn point for the check shot.

When getting used to using/setting a Lenker, it is not uncommon that the 2nd reading will be off a hundredth or two. Generally, that means that the rodman needs to pay a bit better attention to ensuring his left thumbnail does not move and/or that there is no minor slippage of the face as he locks it down. With some practice, it's common to still need to adjust the setting by half a hundredth. It might be tempting to call a setting that's half a hundredth off as being good enough, but don't do it. Although minor errors are supposed to randomly cancel each other out, Murphy is often the invisible extra man on all survey crews and Murphy's law says that all errors, regardless of type or cause, will tend to compound. Besides, with a bit more practice, minor 2nd adjustments of 0.005' to 0.01' will only be needed occasionally.

Notes for a level run with a Lenker would be pretty clean. No columns for BS, HI, and FS. Just a column for Elev and the respective TP identifier together with a good description next to each respective elevation. No math to check.

Hope this helps.

[land butcher]

Wrong tool for the job.
When setting the lenker after adjusting the tape and locking it I vigorously move the sliding part of the rod up and down then have the IM read it. Another safety method is to "read the brass" read the sliding tape where the stationary brass clamp is that way you can occasionally check for slippage.

I'm not sure what the level notes would look like with a lenker if you didn't set the tape to the new elev at each new set up, and that in itself is too time consuming to not be using a fixed tape rod.

I too have come across surveyors that refused to use a lenker, but then I also worked with a IM that after wrapping up a set of angles would unwind the instrument.
I had a friend move to another State and they ran a long traverse for a sewer project and didn't check in for a tenth or two and reran the traverse. When they started rerunning the traverse my friend suggested they invert the inst and double the angles to reduce angular error. The look he got told him to just keep quiet and do your job.

[Wheelin]

First off, I agree with all the opinions given here about Lenker rods. Great tool for grading stakes over a flat area and even analog topo where lots of shots are taken from a single setup, but a very poor choice for a level run.

Where you are making turns and there is more than minor relief in the ground surface, 10' busts are not difficult to make and can be difficult to find the location of. It's also not uncommon for a blunder of reading the wrong direction from the foot mark, creating a 1' bust, also being difficult to detect or to locate after the fact. If there is a bust due to tape slippage, it is virtually impossible to find.

If you must use a Lenker, either because it's all you have or a boss who hasn't properly considered the potential problems insists on it, you need to build in a check at each turn. Near each turning point, establish a secondary turning point that is a bit more than 1' different in elevation from your turning point. Take shots on the secondary turn and the primary turn before moving the level ahead. Your next setup needs to be such that you can read from both turn points just established. Set the rod face at your primary turn, then check the secondary turn to ensure you don't have that easy to make 1' bust in setting the rod face. If you're good, continue on with your level run. If not, do a double check on your primary turn to determine if your bust occurred at the beginning of this setup or in the previous setup.

Adding this system of checks to your procedure will add a minute or so to each setup, but that's less time and less problem than if you find that a bust exists only upon closing into a known BM. Having that check at each turn makes it much more likely to find a bust right after it occurs and require you to correct it there, or at worst, go back to repeat just one previous setup. Without the checks built in, when you find a bust, you have no choice but to re-run the entire level run from start to finish.

To use the Lenker, taking off from Jim's example, the rodman is told that the BM elevation is 54.37. The chief's 1st reading is 5.82.

As the rodman, brace your left thumb on the wood edge (not on the tape face of the rod) next to the rod face with your thumb nail right at 5.82. That's 0.82 BELOW the 5' mark, NOT 0.82 above it as on a Philly Rod. Do not let your thumb slip from its position until the setting process is done.

Loosen the clamp knob of the locking pin (right side of rod as you look at face, near top). Slide the pin toward you so that the pin tip comes out of the brass lined hole in the edge of the tape. Use your right thumb to slide the movable face tape until 4.37 (0.37 BELOW the 4' mark) is at your left thumbnail. Don't try to slide the face unless the locking pin is fully out of the hole. You can damage the locking hole in the tape face.

The locking pin will not be lined up with the nearest brass hole, but that pin slides up and down a little more than a tenth, so slide it so that the pin is lined up with the nearest hole. If you can't quite reach it, slide in the other direction to the next nearest hole.

Push the pin forward into the hole and tighten the pin locking knob. Test that the face is adequately locked into place by trying to slide the face with your right thumb. If it slips at all, completely loosen the locking pin, reset so that 4.37 is lined up with your left thumbnail, re-lock and retest for slippage.

With no slippage, you can now remove your left thumb from being a marking tool. Place the rod back on the BM (or turn point) to allow I-man to check reading.

If the I-man calls out another reading (i.e. 4.35), repeat the process just described. It's all the same except that you need to move the tape only a very short amount. If the I'man calls out "Good", then move to the secondary turn point for the check shot.

When getting used to using/setting a Lenker, it is not uncommon that the 2nd reading will be off a hundredth or two. Generally, that means that the rodman needs to pay a bit better attention to ensuring his left thumbnail does not move and/or that there is no minor slippage of the face as he locks it down. With some practice, it's common to still need to adjust the setting by half a hundredth. It might be tempting to call a setting that's half a hundredth off as being good enough, but don't do it. Although minor errors are supposed to randomly cancel each other out, Murphy is often the invisible extra man on all survey crews and Murphy's law says that all errors, regardless of type or cause, will tend to compound. Besides, with a bit more practice, minor 2nd adjustments of 0.005' to 0.01' will only be needed occasionally.

Notes for a level run with a Lenker would be pretty clean. No columns for BS, HI, and FS. Just a column for Elev and the respective TP identifier together with a good description next to each respective elevation. No math to check.

Hope this helps.

Great info, thank you. I hope that a scenario never develops right actually have to use a Lenker in this capacity, but I appreciate the feedback.