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  • ot dumpy level

    I was given a dumpy level called an autobuild 24 Probably chineese.
    My mate gave it to me because he bought a new one . He could not get the bubble to sit in the middle of the bulls eye. Does anyone know what would cause this to happen? When I adjust the three legs it just does not want to stay in the bulls eye.

  • #2
    If it is an auto-matic self-levelling level it will automatically level itself - as it will if the level and the "bulls-eye" are not aligned.

    So set the level to level itself - that it is betwwen its limits (no red lines in the telescope) - and then set the bulls-eye to its centre.

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    • #3
      You don't have a dumpy level, you have an automatic level. A real dumpy is a 4 screw, long tube level with a spirit vial that is fairly long. Adjusting a dumpy isn't hard, it takes some time.

      Your level does it's thing by some sort of pendulum. The circle vial is there to get it close, and the mechanism does the rest. Don't be concerned about that. To test it, set it up, center the bubble and sight a stable object. Then, while watching your object, slowly turn one of the screws which will take it "out" of level. If it's working right, it will adjust itself back to the original object. It has a much broader range then what that little circle shows.

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      • #4
        plunger --

        As oldtiffie and rws say, your level is an "automatic level" (aka "autolevel"). Without examining it in person, it's hard to diagnose its problem, but the first two items on the list of usual culprits would be 1) the mounting of the bullseye vial is compromised, or 2) the bullseye vial is severely out of adjustment.

        Generally, the bullseye vial glass is mounted in a metal carrier with plaster, and the carrier is screwed to the instrument body. The screws work against springs -- often a leaf spring shaped like a cupped Y -- to allow the vial to be adjusted relative to the instrument spindle axis. Occasionally, the bullseye vial will pivot on a ball rather than be spring-loaded, and if on a ball pivot, there are often four screws holding the vial carrier in place.

        The adjustment of the bullseye vial is pretty straightforward, but it can be persnicketly. For a three-screw mounting, you adjust the footscrews until the bubble is centered in the vial, and then rotate the telescope a half turn. The bubble changes position by twice its adjustment error, so adjustment is iterative. You can either adjust the footscrews to bring the bubble half way to center before adjusting the vial mounting screws to center the bubble, or adjust the vial mounting screws to bring the bubble half way to center and then adjust the footscrews to center the bubble. Repeat as necessary until the bubble stays centered after rotating the telescope a half turn. Remember that the bubble moves away from the adjustment screw being tightened.

        If the vial mounting is a four-screw and ball pivot version, follow the same general process, but adjust the vial by loosening one screw and tightening the diametrically-opposite screw the same amount. The bubble will move toward the loosened screw. Four-screw mounts are tricky to deal with because all four screws need to be under a tiny bit of tension, but NOT tight enough to distort anything.

        If the instrument has a mechanical problem, you'll need to find and fix that before adjusting the bullseye vial as described above. So, going through the list . . . are all of the vial mounting screws present? Are the screws screwed in far enough that the spring between the vial housing and instrument body is loaded? Is a pivot ball missing? Is the plaster holding the glass vial in its housing cracked or separated?

        John

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        • #5
          Originally posted by John Garner View Post
          plunger --

          As oldtiffie and rws say, your level is an "automatic level" (aka "autolevel"). Without examining it in person, it's hard to diagnose its problem, but the first two items on the list of usual culprits would be 1) the mounting of the bullseye vial is compromised, or 2) the bullseye vial is severely out of adjustment.

          Generally, the bullseye vial glass is mounted in a metal carrier with plaster, and the carrier is screwed to the instrument body. The screws work against springs -- often a leaf spring shaped like a cupped Y -- to allow the vial to be adjusted relative to the instrument spindle axis. Occasionally, the bullseye vial will pivot on a ball rather than be spring-loaded, and if on a ball pivot, there are often four screws holding the vial carrier in place.

          The adjustment of the bullseye vial is pretty straightforward, but it can be persnicketly. For a three-screw mounting, you adjust the footscrews until the bubble is centered in the vial, and then rotate the telescope a half turn. The bubble changes position by twice its adjustment error, so adjustment is iterative. You can either adjust the footscrews to bring the bubble half way to center before adjusting the vial mounting screws to center the bubble, or adjust the vial mounting screws to bring the bubble half way to center and then adjust the footscrews to center the bubble. Repeat as necessary until the bubble stays centered after rotating the telescope a half turn. Remember that the bubble moves away from the adjustment screw being tightened.

          If the vial mounting is a four-screw and ball pivot version, follow the same general process, but adjust the vial by loosening one screw and tightening the diametrically-opposite screw the same amount. The bubble will move toward the loosened screw. Four-screw mounts are tricky to deal with because all four screws need to be under a tiny bit of tension, but NOT tight enough to distort anything.

          If the instrument has a mechanical problem, you'll need to find and fix that before adjusting the bullseye vial as described above. So, going through the list . . . are all of the vial mounting screws present? Are the screws screwed in far enough that the spring between the vial housing and instrument body is loaded? Is a pivot ball missing? Is the plaster holding the glass vial in its housing cracked or separated?

          John
          I have used but never owned my own dumpy before > have never taken more than a minute to get the bubble centered to the bulls eye. On this one I cant and that is why my friend bought a new one. It has two small jacking screws next to the bubble and comes with a mini pry bar to adjust the screws I have played with them and it moves the bubble but I still cant get it level. Is there possibly something wrong with the bubble that makes it impossible to get right?

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          • #6
            I normally can get the bubble centered in less than a minute but not on this one. Thats why my friend gave it to me. It has two minute jacking screws next to the bubble and when I play with them they move the bubble but I still cant get it right. Is it possible the bubble is faulty?

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            • #7
              the table underneath is the tribrach, it has 3 levelling screw jacks, allign sight on 0 degrees, level with the three jack so bullseye centered.
              rotate 90 degrees repeat.
              the level is now within the levelling range of the self levelling
              nearly all levels use the same guts so read this;
              http://216.128.21.110/docs/manual/O10001.pdf
              mark

              Comment


              • #8
                Dunno about the instrument you have, but my 1940s-era K&E transit is totally field-adjustable and field-verifiable for any sort of misalignment of anything. It's designed so a surveyor can fix it when he's stuck on a mountaintop in the Andes. I would imagine that same philosophy went into the design of what you have. You just have to figure out the alignment sequence to use. Maybe.
                ----------
                Try to make a living, not a killing. -- Utah Phillips
                Don't believe everything you know. -- Bumper sticker
                Everybody is ignorant, only on different subjects. -- Will Rogers
                There are lots of people who mistake their imagination for their memory. - Josh Billings
                Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                Don't own anything you have to feed or paint. - Hood River Blackie

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                • #9
                  Look at the directions that boslab linked to, page 11, I think it is. DO NOT rotate the level while adjusting, you'll drive yourself crazy. Put the eyepiece over one of the adjusting screws, move the other 2 to center the bubble above or below the circle, then adjust the 3rd screw to put the bubble in the center of the circle.

                  Unless it is truly broken, but it's hard to imagine that.

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                  • #10
                    Originally posted by jdunmyer View Post
                    Look at the directions that boslab linked to, page 11, I think it is. DO NOT rotate the level while adjusting, you'll drive yourself crazy. Put the eyepiece over one of the adjusting screws, move the other 2 to center the bubble above or below the circle, then adjust the 3rd screw to put the bubble in the center of the circle.

                    Unless it is truly broken, but it's hard to imagine that.
                    They can be a bit amusing to watch the uninitiated setting up, best place to learn is the kitchen table, plant it on the table and do first alignment,rotate 90, do second, the whole process is about 1 1/2 mins or less, 1 1/2 hours without practice, as you have said set 2 level 1, don't move any more than 1 jack at a time unless your showing off!, its just like a 4 jaw chuck, once you get the knack its relatively easy, once you upwardly migrate to a full blown theodolite, then it gets tricky, unless you bypass and go straight to a total station with EDM, [dis measuring not spark eroding!]
                    And remember Presidents 1, 3 and 16 were surveyors so your in good company!
                    All you have to do now is persuade SWMBO to hold the staff vertical, that's harder than using the thing
                    regards
                    mark

                    Comment


                    • #11
                      Mark,
                      Actually, with a self-leveling instrument, you do not rotate the instrument during setup. Simply follow the directions on that link you sent, it'll take less than a minute. What confuses things is when someone is familiar with the older instruments where you level it, turn it 90 degrees, level it, turn & check, fine tune, etc. I've watched folks chase their tails for 5 minutes or more, when it should take a half minute or less.

                      I have a Lietz/Sokisha self-leveler that I bought 30+ years ago. Although it was well over $1000.00 at the time, it was so fast to use and very accurate that it was worth every penny.

                      Again, the O.P.'s instrument may be broken, I just can't see how a simple bubble level could go that badly out of whack.

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                      • #12
                        Im old fashioned, i still do it the old way on my Leica and sokisha, the only one i have that works without is a pentax EDM total station that does its own thing, i suppose its a matter of personal preference, i cant see that its wrong as thats what they taught in school, all be it the Swansea Institute of Mining 35 years ago! so the method may be defunct, still works for me though as i spin round the bullseye sits in its ring and most things end up level [ish] but nothing a few shims wont fix!
                        Its not difficult to recal a level if the bubble is out and worth knowing how to check, this is what i use;
                        http://www.cmiindustries.com.au/trou...alibration.pdf
                        Again practice makes it quicker
                        regards
                        mark

                        Comment


                        • #13
                          Originally posted by rws View Post
                          You don't have a dumpy level, you have an automatic level. A real dumpy is a 4 screw, long tube level with a spirit vial that is fairly long. Adjusting a dumpy isn't hard, it takes some time.
                          A real dumpy is a 3 screw level outside the US. Never could understand the point of 4 screws.
                          "Patriotism is the last refuge of a scoundrel"

                          Comment


                          • #14
                            Originally posted by boslab View Post
                            And remember Presidents 1, 3 and 16 were surveyors so your in good company!

                            mark
                            I knew that about number 1. I was running a transit when I was 14 and thought I was doing pretty well until my father told me George was running a survey party at 13.

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                            • #15
                              The term "dumpy" level has been around and used for decades before ANY 3 screw automatic level was ever born. The long tubes and spirit vial are classics. Most were made with all brass, very heavy.

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