The two instruments shown in here are more advanced ones, intended to be kept as part of the tool box.

A Permanent Self- Adjusting Dumpy Level. is a floating model small enough to fit in a toolbox. If the screw feet and bubble indicator are added, it can be used either manually or self levelling (floating); each method has advantages and disadvantages The recommended float diameter, 187 mm., allows the level to pack upside down in a Yates 250 mm. Tuscan flower pot saucer, which becomes the water container.

Manual Mode. The level will stand on any firm, flat and reasonably level surface (see ‘Stands and Tripods’ under ‘Accessories’ ) and the screw feet can be adjusted until the bubble indicators show level. Then look at the target and crosshair through the backsight slit.
Check the bubble indicators when the level is turned or moved; small errors occur if the stand isn’t fairly level to start with. However the level has a large field of view and only needs turning occasionally. It is very stable in manual mode if a weight is placed on top, or it can be bolted to a tripod (see ‘Accessories’).

Automatic Mode. Float the level in a container of water - a paint drum, bucket, or the recommended flower pot saucer, which can be held from underneath by a 6 mm.(1/4 in.) bolt.Fill the container and roughly level it, using the water surface as a guide. Gently lower the level into the water; some will spill. The level should spin freely without touching the container sides.

Description. The main parts of the level are:-
1.The circular float, made from pine board or plywood at least 20 mm. thick.
2. Two side strips, holding a crosshair at one end, and the backsight plates at the other.
3. Upper and lower backsight plates, with a slit between. This slit increases the eye’s depth of field so that both the crosshair and the field of view are in focus, and also reduces parallax error to near zero; the crosshair stays stationary against the field of view even if you move your eye.
4. A crosshair of nylon sewing thread or fine fishing line, stretched in grooves across the fronts of the side strips, and tied off each side under reversed cup washers and screws. A third washer and screw on one side holds spare crosshair thread.
5. A balance weight(s) to make it float level in water. A single balance weight can’t be placed between the side strips, so one each side may be needed.
Optional extras. The basic model will be improved by adding the following :-
6. A centre hole and tee nut in the float, for bolting the level to a tripod, and one fixed and two screw feet, for setting the level in manual mode.
7. A bubble level indicator - either the round type, or the preferred type, with two straight capsules at right angles. Both types come in different sensitivies; to check this, place the indicator and an ordinary spirit level on a flat board, and tilt it; the indicator bubble(s) should move as far as the spirit level bubbles. Round ones may not have a mounting flange; if not, make one from light gauge sheet metal, like this:-

DO NOT drill a large hole in the float to take the bubble housing - this would upset the buoyancy of the float. Mount the housing on the deck of the float.
8. A cover plate, to shield the backsight from direct sunlight, and protect the crosshair. A weight can be placed on the cover to unbalance the float for drain gradient setting, or to hold the level down in manual mode.
Construction This description includes all extras. First mark out the float outline, and the centre and sight lines, which must be across the grain of the float; so the side strips stop the float warping. Cut and sand the float to shape and scribe the centre line. Drill all holes. Since it works in water, give it a coat of paint or varnish before assembly. Make sure the holes are painted or varnished inside.
Cut the side strips from dressed hardwood, and mount them with brass or plated screws from below, along the sight lines as in Fig. 4-1. Cut and drill the cover from 4 mm. (5/32”) 3-ply , and screw it temporarily in place. File or sand a flat on the back ends of the side strips, and the back edges of the cover and float, to take the backsight.

Make the backsight plates as in Fig.4-3. from thin sheet metal - gal. iron, tinplate from a can, or aluminium. (to saw or file thin sheet metal, clamp scrap wood pieces each side and cut or file all three). Sand the edges smooth and straight.

Screw the upper plate in place, with its bottom edge parallel to, and 10 mm. from, the float deck; if necessary, put thin packing material under the top flange to achieve this.
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Slot the holes in the lower plate with a rat-tail file, or drill the holes oversize and use washers under the mounting screws. Make sure the top edge is smooth and straight; use an oilstone if necessary. Hold the lower plate in place, with the edges of the plates touching, and position the screws so this plate can slide up and down a little, to allow a slit height of from zero to 1 millimetre between the plates

Check that the slit edges are straight and parallel. Then screw the plate in place, leaving a slit of about 1/2 mm. Cut two small grooves in the front ends of the side strips, exactly 10 mm. above the float deck, to take the crosshair. Put small screws in the outer face of each side strip about 10 mm. from the front, to tie off the crosshair; to store spare thread, put another screw half way along one side. Tying off is easier if you put no. 4 or 6 cup washers, upside down, on each screw.

Make the crosshair from sewing thread or fine fishing line; the best is no.24 (0.1 mm. diameter) nylon sewing thread. White or clear nylon will be visible in most light, but for white targets with black markings, black thread may be better.
If the recommended flower pot saucer is used, try putting the assembly upside down in the saucer; if it doesn’t pack neatly it may be necessary to shave a little off the front edge of the cover.

Now take the cover and backsight plates off, and coat the plates, the float deck area between the side strips, the insides of the side strips, and the under side of the cover, flat black. Re-assemble when dry, and screw the feet, crosshair screws, and bubble indicator in place. Paint (any colour) or varnish all external surfaces.
Attach the crosshair, making sure it is in the grooves, pulling it tight to keep it straight, and loop the extra length between the side screws. Put a black mark, 5 to 10 mm. long, on the centre of the crosshair; sometimes this mark is more visible than the crosshair.

Set the backsight slit with feeler gauges; if these are not available, use trial and error. Set the slit height to about 20 thous. of an inch (1/2 mm.) at each end. Look through the slit at an object 5 - 10 M. away; both the crosshair, right across, and the object, should be clear and sharp. If not, try narrowing the slit about 1 thou. at each end, or simply tap the lower plate closer to the top, until the crosshair and object are both in focus.

Too wide a slit makes the crosshair appear fuzzy; if the slit is too narrow the whole view will look hazy and dark. Without feeler gauges, make a rough one from a double layer of tinplate cut from a can; it will be about 16 thous. thick. Then start narrowing. or widening the gap as above.













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TOP:- Dumpy level, floating in water in its saucer mounted on a tripod.
LOWER:- Packed upside down in its saucer, ready for transport.




Aligning the Sights. Slit and crosshair sights can’t be easily lined up with an end for end check Here’s another method.
1. Find an open space between two posts,trees or walls, from 6 to 12 M. apart. Any combination of posts, trees, or walls, will do. Call these points A and B.
2. Put the water container on a stand or tripod, at eye height, and float the level with the balance weight and screw loose on deck. Leave the screw feet in place, even though they are not needed for this test.
3. Tie a line between the posts, at the same height as the crosshair. If possible, use nylon fishing line; it has a high strength to weight ratio and no discernible sag if tensioned almost to breaking point (See ‘Line Strainers’ in ‘Accessories’). If possible, roughly level the line with a line level
4. Place the instrument exactly midway between the posts, and close to one side of the line. Measure this mid point accurately - the final adjustment depends on it. Like this:-

5. Set the instrument level, as shown by the bubble indicator(s), by moving the balance weight forward or back. Look at post A through the sights, keeping the post in line with the centre of the crosshair; from here on,each time the instrument is turned, the bubble indicator(s) should be checked, and the balance weight moved to again bring the bubble indicators level.
6. Move the line up or down the post, until the line end is at the sight line.
7.. Turn the instrument 1/2 turn , and repeat steps 5 & 6 with post B.Tension the line as tight as possible, sighting along the line to detect any sag. Like this:-

At first, the sights will probably aim too high or too low; although the sights are not yet level, the line will now be level.
8. Turn the instrument 1/4 turn, until the crosshair is facing the middle of the line, and look at the line through the sights If the line is at a different height than the crosshair, raise or lower the line at both posts by the same amount, to bring the line and crosshair to the same height (If the stand or tripod has height adjustment, the instrument may be raised or lowered instead). The setup will now look like this:-

9. First check the side to side alignment; the crosshair and line should be parallel. If not, bring the crosshair parallel by moving the balance weight from side to side.
10. Turn the instrument to again look at post A, and move the balance weight forward or back, to bring both ends of the crosshair in line with the end of the string line at A. Repeat steps 8 and 9 until the crosshair is both porallel and level with the string line.
11. Turn the instrument to post B; the crosshair should now also be level with the string line at B, without further adjustment.
12. But if not, repeat all steps, until the line of sight matches the line at both ends and in the middle, and the line and crosshair are parallel. Like this:-


13. Once the sights are set correctly, screw the balance weight(s) in place. If the bubble indicator isn’t showing level, loosen the mounting screws and slide a piece of thin packing under the flange and move it round until the bubble shows level with the screws tight.
Using the Level.
Manual Mode was briefly described above.
Automatic Mode. The inside diameter of the water container should be only 5-7 mm. larger than the float. Fill the container, and level it, using the water surface as a guide. Gently lower the float in - it should spin smoothly without scraping on the container.
With the level floating, nothing must be taken off or added to it; this upsets the balance. (leave the screw feet in place). If using the level for more than a day, use it to put a level reference mark on a nearby fixed object, and check the level each morning, to guard against spillage, evaporation, etc..
If wind may causes the level to drift round, throw a little fine sawdust in the water. It may also pitch -normally only for seconds; if it persists, steady it with one finger, but let go just before taking a sight. For persistent pitching go to manual operation. .

The level may be used with a staff and target in the usual way; the reference height to be marked on the staff is the height of the crosshair (See ‘Levelling, Gradient & Height Measurement’, above.)

If both manual and auto. modes are to be used with a tripod, the tee nut in the centre of the float must be counterbored 5 -8 mm., so that a bolt can be screwed equally into either the float for manual mode, or the saucer baseboard for auto mode, a locknut on the holding bolt being set to stop the bolt screwing in too far. For other mounting suggestions, see ‘Accessories’

Drainage Gradient. The bubble indicator has marks which give a rough idea of the drain gradient (50:1).The float can be unbalanced enough by placing a weight on the cover and sliding it along until the bubble gives the right indication. In manual mode, just reset the screw feet.
Mounting the water container. To anchor a flower pot saucer to a tripod, a baseboard is attached to the underside of the saucer (Fig. 4-3). It may be stuck to the underside, or drill three small screw holes in the bottom of the saucer at 120º intervals, and attach the board with three round head wood screws and washers, sealed with silicon. To make the baseplate sit firm on any surface, put three small plastic feet on its undreside at 120º intervals.

The Wide Angle Dumpy Level has a field of view of 90º, allowing it to stand close enough to the work to read the numbers on a steel tape. Standing it about 1M. from the corner of a small house (6 M. x 6 M.) gives an artificial horizon line across the whole site. It can be used to lay out lines at right angles (90º), and can measure approximate distances with a stadium rod.

It is set by adjusting screw legs until the circular bubble indicator shows level.
Fig.4 -6 shows the assembly - a base plate with straight side and back edges and a curved front edge, on which is mounted two side strips; two aluminium plates for the backsight slit are screwed to the back ends of the side strips. A crosshair is stretched across the front of the level, held by the shafts of three 4 mm. (5/32 inch) screws, which can be turned to adjust the crosshair alignment.
The crosshair ends are wound under reversed cup washers screwed to the side strips - a single screw and washer on one side, and two screws and washers to store spare line on the other. A top plate encloses the area between the side strips.
The base plate stands on one fixed and two screwed legs, for level adjustment. All three legs pass through 6 mm. (1/4 inch) tee nuts under the base, then through holes in an adaptor plate, and are held in position in this plate by 6 mm. fibre locknuts and 8 mm. (5/16 “) washers. The washers need to be this size to allow the locknuts to swivel slightly as the screws are turned, giving smooth level adjustment.
The screwed legs are two 6 mm. x 63 mm. (2 1/2 “) hex. head bolts.If the legs are too hard to turn using the bolt heads, the heads can be cut off and replaced by 6 mm. shaft control knobs obtainable from electronics stores.The knobs are recommended; they make adjustment easier.
A 6 mm. tee nut is let into a centre hole in the adaptor plate, to allow mounting the level on either a camera tripod or the permanent tripod described in ’Accessories’.
A round bubble level indicator is either screwed to the base plate deck if it has a mounting flange, or let into a hole in the base plate if not.
Construction. Start by marking out the base plate as in Fig. 4-4; the best material is dressed hardwood, but pine or M.D.F. can be used provided they are sealed against moisture Work from one straight edge, and make it the back. Draw in the side lines square with the back, then the centre and 45º lines from the same point; the front arc can be drawn by taping a scrap of thin lath to the base plate back edge. Then the point of a compass can be placed in the crack between the two. Like this:-

If a compass of the size required isn’t available, make one by drilling two small holes 200 mm. apart in a strip of wood, and putting a drawing pin in one end and a pencil point in the other.
Draw in the side strip guide lines, with the end of each line intersecting a 45º line at 145 mm. from the back edge, as in Fig.4 - 5. Cut out the plate and drill all base plate holes. Make and drill the adapter plate (Fig.4 - 4); its external dimensions are not critical, provided its leg holes match those in the base plate, and the holding bolt hole is located as shown. Give the plates a coat of estapol or similar before assembly.
Screw the bubble indicator and the feet into the base, but don’t attach the adapter plate yet. Level checks should be made several times during assembly; they save alignment problems later.
Stand the assembly on the bench and adjust the screw feet until the bubble shows level, and check the base plate surface with another spirit level, from front to back and side to side. If the plate isn't level, adjust the feet until it is, then. pack the bubble indicator flange with a sliver of thin plastic or sheet metal ( shim brass or tinplate from a can) until it shows level.
Cut the side strips from dressed hardwood (Fig 4 - 5), making sure that the 20 mm. dimension is correct. Screw them to the base plate, making sure the inside front corner of each strip is on the 145 mm. point of its 45º line. The back ends of each strip will extend over the base plate; and must be cut flush with the back edge.

Use the assembly as a template. to mark out and cut the cover plate slightly oversize. Drill all cover holes, making sure the crosshair screw holes match the corresponding holes in the base. Screw the cover temporarily in place. File or sand the back edge, and the side strip ends, flush with the base plate, and sand the side edges flush with the side strips. Check that the height between base and cover at each side strip is exactly 20 mm; if not pack or sand the side strips as required. Finally screw the cover on.












Make and drill the backsight plates (Fig 4-5), making sure the lower edge of the top plate, and the upper edge of the lower plate, are filed straight - finish with an oilstone if necessary. Level the assembly on the bench as above, hold the top backsight plate in position, and check that the lower edge of this plate is level from side to side. This step is important for final accuracy.
If not, pack the low end of this plate, between the flange and the top of the cover, and screw in place. The lower plate can now be positioned by butting its top edge against the upper plate, and placing the screws to allow it to slide up and down to adjust slit height.
The pinhole shutter is only needed if the level is used for measuring distances and/or setting out right angles. Before mounting the lower plate, scribe a centre line on the upper plate. Mount the lower plate, then position the shutter plate like this:-
Drill a pivot hole in the shutter, hold the shutter with the notch on the centre line, and mark the hole position on the lower plate. Drill this hole for a self tapping screw, and screw the shutter in place..

Next, put in the crosshair adjusting screws - 4 mm. (5/32”) screws and locknuts; the left and right hand screws are 38 mm. (1 1/2”) long, and the centre screw must be 50 mm. (2”) long, or counter bore the underside of the base plate to let in the lower lock nut. Like this:-




Attach the adapter plate to the feet, like this:-



The adapter plate holes and washers are oversize, with the curved face of each lock nut sitting neatly in its washer hole. Adjust the tightness of the locknuts to give smooth screw adjustment without any slop.
Winding the crosshair is best left till last, to avoid breakage. Make it from a length of No. 20 nylon sewing thread or fine (2 kgm.. breaking strain) fishing line. The sewing thread gives a finer crosshair, but is easier to break. Wind it like this:-



Fasten one end of the crosshair under the left hand cup washer, then wind it once anti-clockwise around the left hand adjusting screw, across the face of the centre adjusting screw, and once around the right hand adjusting screw; finally pull it moderately tight across the face of the centre screw, and wind off a few turns - sufficient to supply a spare thread if the crosshair is broken - around the right hand cup washers. Make sure the crosshair is roughly in the centre of the gap, parallel to the base, and only engaging one turn of each screw thread.
Your level is ready for varnishing and final alignment.

Adjusting the Backsight Slit

 The easiest way to do this is with feeler gauges, but if they aren’t available, it can be done by trial and error. Start by setting the slit height to 20 thous. of an inch (0.508 mm.) at both ends. Look through the backsight at any object about 5 - 10 M. away; both the crosshair and the background should be clear and sharp right across. If not, set the backsight gap to 19 thous.., and try again, narrowing the slot 1 thous.. at a time until the crosshair and background are both in focus. Without feeler gauges, make a rough one from tinplate cut from a can - a double layer is about 16 thous. - then start narrowing the gap as above. Ensure the slit height is the same at both ends.

Aligning the Sights.

The method is almost exactly the same as for the floating dumpy level, except that the base is brought roughly level first, then the crosshair adjusting screws are turned to bring the crosshair level.
1. Find an open space between two posts, trees or walls, from 6 to 12 M, apart. Any combination of posts, trees, or walls will do.The following description assumes posts, but any combination of posts, trees or walls may be used.
2.. Put the level on a stand or tripod, at eye height.
3 &4. Follow steps 3 and 4 for the floating level.
5. With a separate bubble level placed on the cover, adjust the screw feet until the instrument is level, both front to back and side to side. If the instrument indicator doesn’t show level, put a thin piece of packing - tinplate from a can, thin plastic, or even cardboard - under the bubble housing and move it around until the bubble shows level with its mounting screws tight. Look through the sights at post A, keeping the post in line with the centre of the crosshair.
6. Move the line up or down the post, until the line end is at the sight line.
7. Turn the instrument 1/2 turn, and adjust the screw feet to again bring the bubble indicator level (Do this each time the level is turned). Repeat steps 5 & 6 with post B.
Steps 8 - 12. Follow steps 8 - 12 for the floating level, except that instead of balancing the float, turn the crosshair screws to bring the crosshair into line. Adjust each screw, to bring the middle and BOTH ends of the crosshair into line.
13. When everything is in line, dab a little varnish or adhesive on the heads of the crosshair screws, and on the points where the crosshair touches the screws, to stop the screws or crosshair from moving.

Using the Wide Angle Level

The level is set by standing it on any firm, flat and reasonably level surface, or screwing it on a tripod (see ‘Stands for the Level ‘ in ‘Accessories’). Adjust the two screwed feet until the bubble in the level indicator is central. Looking through the backsight slit will show the crosshair forming a horizontal line across the viewed area
The bubble indicator must be checked when the level is turned or moved, and minor errors can occur if the stand isn’t fairly level to start with. However the dumpy has such a wide field of view that it seldom needs moving. It is very stable if a weight - e.g. a stone or heavy tool - is placed on top, or a locking bolt is used as described in ‘Stands for the Level’.
The level may be used with a staff and target in the usual way; the reference height to be marked on the staff is the height of the crosshair or backsight slot.
Note to experienced operators:- Do not expect this level to act like a commercial instrument with lenses. e.g. There is no vertical crosshair, and no focussing. Stand the dumpy as close to the work as possible, and use large brightly coloured targets.
Drain Gradient Indication
The bubble indicator has an outer circle to give an approximate idea of the drain gradient (50:1). The level adjustment can be offset to this extent by turning the screwed feet until the bubble gives the right indication. Like this:-

This level can also show the drain gradient by standing the level side on to the work and adjusting the levelling screws to tilt the level sideways. The bubble indicator will look like this:-
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Range Finding
The level may be used for rough length measurements. The height between the bottom plate and top cover is 20 mm., and the distance from backsight to the front edges of the plate and cover is 200 mm. - a ratio of 10/1. Sighting two height measurements on a staff or stadium rod and multiplying by 10 gives the distance between level and target. Like this:-


Example:- If H = 1.6 M., D = 1.6 x 10 = 16 M..
A suitable stadium rod was described above for the self - levelling dumpy.

Setting Out Angles

This level can be used to set out lines at right angles (square), or 45º, to each other. Start by moving the small shutter plate over the backsight slot to form a pinhole, then sight each end of the side strips, like this:-

The angle between sight lines 1 & 2 (i.e. between either side strip and the centre crosshair post) is 45º; the angle between sight lines 1 & 3 is 90º (square). A target for use with a plumb line can be used here; one is shown in fig. <<<.
This method can also be used for range finding over rough ground such as a gully, like this :-

If pegs are put in the ground on the far side of the gully, the length L1 = D, the distance across the gully; or the distance between pegs A & C is twice D.


Stands for the Level
Because this level doesn’t float in water, and is larger than the floating level , it has fewer mounting options. A firm, flat, and level surface, large enough to support the adaptor plate when it is facing in any direction, is needed.
The top of a short stepladder, or a stile with a top board just below eye height (provided it is quite firm) are two options. The tripods described in these notes will hold it.

Target Patterns.
For measuring gradients, a staff and target will be needed; the target need only be a short length of wood. See ‘Accessories’ for different target patterns which may be downloaded and printed on A4 paper.

Have fun with these levels, but remember - you wouldn’t treat an expensive transit level or theodolite roughly, so treat these with respect, too - they will perform better. Part 5 covers measuring and laying out.

   


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