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Kearny Fallout Meter
© 2006 RogueTurtle.com
A Home-made Radiation Meter that Requires No Batteries

A scientist named Cresson H. Kearney, at the Oak Ridge Laboratory, designed this meter. It's simple to make and may save your life.

Range of Meter Readings:

Low: 0.03 R/Hour
High: 43 R/Hour



A Kearney Fallout Meter (KFM) is a simple electroscope-ionization chamber with which fallout radiation can be measured with reasonable accuracy. To use a KFM, an electrostatic charge must first be placed on its two separate aluminum foil leaves. These leaves are insulated by being suspended on clean, dry insulating threads.

To take accurate readings, the air inside the KFM must be kept very dry by means of a drying agent such as dehydrated gypsum (easily made by heating gypsum wallboard or "sheetrock"), or using a silica gel. (Do not use calcium chloride or other salts.) Pieces of drying agent are placed on the bottom of the ionization chamber (the housing can) of a KFM.

An electrostatic charge is transferred from a homemade electrostatic charging device to the two aluminum foil leaves of a KFM by means of a charging wire. The charging wire extends through the transparent cover of the KFM.

When the two KFM leaves are charged electro-statically, their like charges (both positive and negative) cause them to be forced apart. When fallout gamma radiation strikes the air inside the ionization chamber of a KFM, it produces charged ions in the enclosed air. These charged ions cause part or all of the electrostatic charge on the aluminum foil to be discharged. As a result of losing charge, the two KFM leaves move closer together. This is a measurable amount indicating the amount of gamma radiation present at the time of the reading of the KFM.

To read the separation of the LOWER edges of the two KFM leaves with one eye, look straight down on the leaves and on the scale on the clear plastic cover.

Keep the reading eye 12 inches above the SEAT. The KFM should be resting on a horizontal surface. To be sure the reading eye is always at the exact distance; place the lower end of a 12 inch ruler on the SEAT, while the upper end of the ruler touches the eyebrow above the reading eye. It is best to hold the KFM can with one hand, and the ruler with the other hand. Using a flashlight makes the readings more accurate.

If a KFM is made and maintained with the specified dimensions and of the specified materials, ITS ACCURACY IS AUTOMATICALLY AND PERMANENTLY ESTABLISHED BY UNCHANGING LAWS OF NATURE. Unlike factory-made radiation measuring instruments, A KFM NEVER NEEDS TO BE CALIBRATED OR TESTED WITH A RADIATION SOURCE. A KFM is used with a watch and the following table that is based on numerous calculations made at Oak Ridge National Laboratory.

The millimeter scale is cut out and attached (see photo illustrations below) to the plastic cover of the KFM so that its zero mark is directly above the two leaves in their discharged position (when on a horizontal surface). A reading of the separation of the leaves is taken by noting the number of millimeters that the LOWER EDGE of one leaf appears to be on, on one side of the zero mark on the scale; and almost at the same time noting the number of millimeters the LOWER EDGE of the other leaf appears to be on, on the other side of the zero mark. The sum of these two apparent positions of the two leaves is called the KFM reading.


As will be fully explained later, the radiation dose rate is determined by:
  1. Charging and reading the KFM before exposure to radiation.
  2. Exposing the KFM to radiation for a specified time in the location where measurement of the dose is needed when outdoors, position the KFM about 3 feet above the ground to avoid accumulated particles on the ground.
  3. Reading the KFM after exposure.
  4. Calculating, by subtraction, the difference between the reading taken before and after exposure to radiation.
  5. Using the following table, find the dose rate during the above exposure time. More on this later
DIFFERENCE
IN
READINGS
TIME INTERVAL OF AN EXPOSURE
REM per Hour of Exposure (R/Hr)
Difference between the reading before exposure and reading after exposure. (8-ply leaves)
15 Seconds1 Minute4 Minutes16 Minutes1 Hour
2 mm6.2 R/Hr1.6 R/Hr0.4 R/Hr0.1 R/Hr0.03 R/Hr
4 mm123.10.8.020.06
6 mm194.61.20.30.8
8 mm266.21.60.40.10
10 mm317.72.00.60.13
12 mm379.22.30.60.15
14 mm4311.02.70.70.18


Fig. A. An uncharged KFM. The charging wire has been pulled to one side by its adjustment thread. This photo was taken straight down at the upper edges of the two flat, 8-ply aluminum leaves.

At this angle, the leaves are barely visible, hanging vertically side by side directly under the zero mark, touching each other and with their ends even. Their suspension threads insulate the leaves.

These two threads are almost parallel to each other and touch (but do not cross) each other where they are extended over the top of the rim of the can.

Fig. B: Charging a KFM by a Spark-gap Discharge from a piece of plastic rubbed with paper. (The plastic is outlined in green.) Note that the plastic is moved so that its surface is perpendicular to the charging wire. The high-voltage electrostatic charge on the plastic jumps the gap between the plastic and the upper end of the charging wire. This charge then travels down the charge wire and jumps to the insulated aluminum foil leaves suspended inside the KFM.

Since the upper edges of the two leaves are " below the scale, and this photo is taken at a high angle, both leaves appear to be under the right side of the scale. They are actually separated and equally spaced on either side of the zero line.

Fig. C: A charged KFM. Note the separation of the upper edges of the two leaves. The charging wire has been raised to an almost horizontal position so that its lower end is too far above the aluminum leaves to permit electrical leakage from the leaves back up the charging wire and into the outside air.

Also note the SEAT. This is a piece of pencil taped to the side of the can, opposite to the charging wire.

In both Fig. B and Fig. C, you can make out the small pieces of drying agent laying in the bottom of the can to keep the air dry.

Fig. D: Reading a KFM. A 12 inch ruler rests on the SEAT and is held vertical, while the reader's eyebrow touches the upper end of the ruler. The lower edge of the right leaf is under "8" on the scale and the lower edge of the left leaf is under "6" on the scale. This gives a KFM reading of "14".

For accurate radiation measurements, a KFM should be placed on an approximately horizontal surface. This lets gravity hang the two leaves equally. However, it is NOT necessary that the two leaves be charged equally. It is OK if one reads higher or lower than the other when you start the measurements. It is the "before" and "after" readings that count here. For example, if you started the measurements with a KFM reading of 20, and after the reading you read 14, the change in measurements is "6".

Note: In these photos the paper scale is taped to the top of the transparent plastic film over the meter. It is better (but not easier) to tape the scale under the cover, where it is less likely to get wet or damaged.


 
Franco American "SpaghettiOs 7 1/2" Ounce can with Flip-Top Lid, is the PERFECT Size for the KFM Meter Can.

KFM - List of Materials Needed

Best Materials to use are listed first, followed by alternative materials
  1. Any Type Can: Size: 2-9/16" (inside diameter), 2-7/8" (inside height). Franco American SpaghettiOs 7 1/2 Ounce Pop Top Can is PERFECT without alterations. Almost any standard 8-ounce soup can has an inside diameter of 2-9/16", but the inside height may be too tall. Bee cans and soda cans can be used. The can may be cut down by marking a line 2-9/16" from the bottom, around the top of the can. To keep the can from bending while cutting off the top, wrap newspapers tightly around a round dowel or stick so that the wood is covered with 20 to 30 layers of paper. The diameter of the paper/dowel should be only slightly less than the inside of the can. Hold the paper covered dowel firmly (a vice helps here) and place the can over the paper covered end of the dowel. Wear leather gloves if you have them. To cut the can smoothly, use a file or a hacksaw drawn backwards along the cutting line. Or, you can use a sharp, short-bladed knife (like a box knife) and cut the can slowly along the marked line. When completed with the cut, use a fine file to round off the sharpened edges of the can. Cover the top edge with small pieces of flexible tape.
  2. Standard Aluminum Foil: Approximately 2 feet square. This foil is to construct the 8-ply leaves of the meter. If you can only get "Heavy Duty" or "Extra Heavy Duty" foil, then you will use only a 5-ply leaf. Instructions for making the leaves come later in this chapter. There is little difference in accuracy between the 8-ply and the 5-ply leaf, but the 8-ply is preferred.
  3. Doorbell Wire: A lightly insulated wire, with only one solid copper wire inside the insulation. You need about 6" of wire.
  4. Thread for suspending leaves: Must be a NON-CONDUCTING thread and NOT anti-static treated. Very thin monofilament fishing line or leader is an excellent insulator. A Human Hair (my daughter's) is on my meter. Du Pont's "Stren" monofilament fishing line is best. "Trilene" 2 pound "nylon leader", a monofilament manufactured by Berkley and Co., is also excellent. Any line heavier than 2-pound strength will work but may be a little too stiff for accurate readings. Some un-waxed dental flosses may be used for stop threads but may not work for the suspension threads. However, Johnson & Johnson's Extra Fine Unwaxed dental floss used without splitting makes a quite satisfactory leaf-suspending thread. If using leader line or dental floss from an exposed spool, discard the outer layers that may be contaminated with finger-print oils or other dirt and oils during storage. Store clean stock inside sealed plastic bags. Human hair cleaned with shampoo and alcohol wipes is excellent provided it is strong enough to support the weight of the aluminum leaves. Only trial-and-error will tell you about hair strength. The hair needs to be at least 6" long. If no dental floss or nylon leader is available, you can use very thin polyethylene film cut into 1/16" strips. To cut this thin film, mark 1/16" lines on a piece of heavy paper and tape a piece of film (about 6" x 10") over the paper and lines. Using a very sharp, clean knife or razor blade, and a ruler as a guide, cut off a bunch of thin strips. Use the best 2 strips of the bunch and hang the leaves. If you are using thin polyethylene, it is critical that you have no sharp edges inside the can, and that you handle it with extreme care. It won't stand up to much abuse. Regardless of the type material used, NEVER TOUCH THE MIDDLE PART OF ANY THREAD WITH YOUR BARE FINGERS. The oil from your skin will be conductive to electricity and ruin the insulating capability of the thread.
  5. DUCT TAPE, Masking Tape, or Freezer Tape: Scotch tape is also OK. Save 1 roll of Scotch Magic Transparent Tape to use to charge the KFM later on in the project.
  6. Band-Aid Tape, because of it's non-conductive nature, can be used on the leaves to hold them together and for suspension purposes. Some plastic electrical tape can also be used.
  7. Clear Plastic Film: 6" x 6" Square. Clear vinyl (4 mils thick) used for storm-proofing windows is best, but any reasonably stout and clear plastic can be used. This is for the top cover of the meter and you must be able to clearly read the scale and the position of the leaves through the film. If it's even slightly cloudy, it will be very difficult to see inside the can. Plastic film made from cellulose (such as Flex-O-Pane) and oven roasting bags are too permeable to water vapor and will allow moist air into the chamber. I used clear plastic laminating material for my meter. I used the type that has no sticky mastic on it.
  8. Drying Agents: Gypsum Wallboard (Sheetrock). About 1/2 square foot, 1/2" thick. Remove the paper backing with a sharp knife and cut up into 1/2" squares. Silica Gel, dark blue in color is an even better drying agent, but is not readily available in most communities. It can be obtained from chemical supply houses.
  9. Miscellaneous:
    • Glue: 1-Hour epoxy for leaves is best. Model airplane glue is OK. Use Rubber Cement for the label.
    • 2 Strong rubber bands.
    • Zip-lock storage bags: These store the KFM when it is exposed where fallout particles may get on it and contaminate the inside of the meter. Any thin plastic bag can be used as long as there are no leaks.

OTHER MATERIALS NEEDED FOR KFM

FOR CHARGING DEVICES:

Most hard plastics rubbed on dry paper. This is the best method. You can use Plexiglas and most hard plastic such as draftsmen's triangles, common smooth plastic rulers (6" or longer), etc. Dry paper must be tough, such as grocery bags or typing paper. Softer papers can be used but will fall apart shortly due to the hard pressure needed to charge the plastic.

Scotch Magic Transparent Tape (" is best). This tape, or other PVC tapes (such as insulating electrical tapes) and some other brands of "Scotch-type" tape may also work. This method is used inside a dry bucket. Some plastic tapes do not develop sufficient charge when unrolled quickly. Scotch Magic Transparent Tape does.

FOR DETERMINING DOSE RATES AND RECORDING DOSE RATES:

A good watch with a second hand. Also, a flashlight to read the KFM in low-light conditions. A pencil and paper, preferably if you use the "Individual Radiation Exposure Card" shown in this article (coming up).

FOR THE DRY BUCKET:

A KFM must be charged inside a dry bucket if the air (inside or outside the shelter) is very humid. A crowded shelter will be very humid from the exhaled air from the people jammed into a crowded shelter.

  • 1 large bucket, pot, or can: Preferably with a top diameter of at least 11 inches.
  • Clear Plastic: The storm window covering works well here. The piece used should be at least 5" larger than the bucket diameter.
  • Cloth Duct Tape: 1" wide strips, at least 8 feet long, or 4-foot long if 2" tape is used. Freezer tape can also be used.
  • Two Plastic Bags: 14" to 16" in circumference, such as ordinary plastic bread bags. The length of these bags has to be at least 5" longer than the height of the bucket.
  • Drying Agent: Use the same stuff you use for the KFM. Keep extra dried quantities stored tightly in sealed quart jars to speed up reloading the bucket when the agent in the bucket needs to be replaced. Dry out the "wet" agent in the oven and store while hot.
  • Large rubber bands or string: Strong enough to loop around the bucket and seal the plastic top.


USEFUL BUT NOT ESSENTIAL MATERIALS

- Which Could be Obtained BEFORE a Crisis -
  • Airtight Container for the KFM: A large peanut butter jar with at least a 4" wide mouth; A bucket with a sealing-type lid. Keeping the KFM dry greatly extends the time the drying agent inside the KFM itself remains effective.
  • Commercial Drying Agents: Commercial anhydrite with a color indicator, such as the drying agent Drierite. This granular form of anhydrite remains light blue as long as it is effective. It turns pink when ineffective. Silica gel can be obtained with a color indicator that is dark blue but turns pink when ineffective. Heating the anhydrite in a hot oven (over 400° F) or over a fire reactivates the drying agent and restores their blue colors. Use enough to cover the bottom of the KFM but not more than 1/2" deep.
  • Four square feet of aluminum foil: Used to cover the top of the dry bucket when not in use.

TOOLS NEEDED

  • Small nail, sharpened
  • Stick, round dowel, or tool handle, 2 to 21/2" diameter and 12" long
  • Hammer
  • Pliers
  • Large Needle and a small straight pin
  • Very sharp knives or razor blades
  • 12" ruler with inches AND millimeters (mm) marked
  • File and/or fine-toothed hacksaw
  • Scissors and tweezers

MAKE YOUR OWN DRYING AGENT

This is the easiest part to make but is time consuming. Make more than you think you will need.

For a KFM to measure radiation accurately, the air inside the ionization chamber (the can) must be kept VERY DRY. An excellent drying agent (anhydrite) can be made by heating gypsum from ordinary gypsum wallboard (drywall or sheetrock). DO NOT USE CALCIUM CHLORIDE. Do NOT use the "Green Board" used in wet areas of houses as it will be water resistant, and we don't want that...we want it to ATTRACT water. Gypsum is not technically a drying agent but it readily absorbs water and that keeps the air dry. When it stops working (the gypsum gets saturated) and the agent must be removed and replaced with dry material. Any contractor building a new home will be glad to let you rummage around in the junk pile for small scraps of drywall. If you take it, he doesn't have to pay someone to haul it off for him. Take more than you think you can use.

Carefully cut off all the paper covering the gypsum, front and back. The paper loosens up if you wet the paper slightly. Carefully break up the gypsum into pieces about 1/2" square. Scoring the surface with a razor knife before breaking it helps keep sizes uniform. Use pliers to break up the drywall and keep finger oils off the gypsum. Throw away the small stuff. You need to be able to easily get the gypsum into and out of the KFM without leaving small, wet pieces behind.

The useful life of the drying agent inside a KFM can be greatly lengthened by keeping the KFM inside an airtight container with some drying agent inside. Extra, pre-dried anhydrite can be easily stored inside a 1-quart mason jar with a good sealing lid.

To drive the water out of the gypsum molecules and produce an anhydrite drying agent, heat the gypsum in an oven at temperatures over 400° F for ONE HOUR. Heat the gypsum by putting the small pieces no more than 2-deep inside a pan. An aluminum foil packet will do fine. Or, if there is no oven available, heat the pieces over a fire for 20 minutes or more inside a pan or can that is heated to a dull red color.

Another technique is to make up a set of smaller foil packets that will hold sufficient gypsum for at least one reload of the KFM. If you make them small enough, they can be stored individually inside mason jars while they are still hot from the oven. This reduces the possibility of water absorption from the air of the jar itself. It also gives you an easy method of putting the gypsum into the jar, as well as taking it out quickly and resealing the jar. Pieces have to go into the KFM one at a time, without the foil.

Anhydrite is best placed into, and taken out of the can using tweezers. Cover the bottom of the can with a single layer of gypsum squares, with no overlapping pieces. Quickly reseal the top of the meter with tape and rubber bands. Place the newly dried meter inside the airtight dry bucket until it is needed.

DO NOT USE ANY ANHYDRITE THAT CONTAINS SALT (NaCl) OR SALT PRODUCTS. These cause the can to rust.

CUTOUT VIEW OF IONIZATION CHAMBER



MAKING THE IONIZATION CHAMBER OF THE KFM

1. THE CAN: Select a suitable can that has an outside diameter of 2-9/16", and an inside height of about 2-7/8". An ordinary 8-ounce can will probably do. I STRONGLY recommend using the Franco American SpaghettiOs 71/2 Ounce, Pop-Top can. It has a thin plastic lining that helps protect the inside of the can from rust and makes it easy to clean. Whatever can you use, wash it in hot, soapy water and remove the can label completely. If the glue from the original label will not come off in the soapy water, use mineral spirits to remove the factory glue. Let the can dry thoroughly.

a. For cans that are too tall: Find a can with the inside diameter of 2-9/16". Soup cans, most pop cans, and beer cans are this size. The height of the can may be cut down by measuring and marking a line that is 2-7/8" up from the bottom of the can. Then, to keep the can from bending while cutting, wrap newspapers tightly around a round stick or dowel (a tool handle will do) until the wood is covered with a diameter only slightly smaller than the inside of the can.

1. One person should hold the can over the paper-covered stick while a second person cuts the can little-by-little along the marked line. Wear leather gloves, if available. To cut the can smoothly, use a file, or use a fine-bladed hacksaw drawn backwards along the cutting line. Another option is to cut the can with a sharp, short blade knife either by stabbing downward vertically into the paper; or by repeatedly making a cut about " long by moving the knife into a sloping position (keeping the point pressed into the paper) and moving the can around until the cut is completed. Care must be taken not to distort or bend the can.

2. Smooth the cut edge with a file, and cover it with small pieces of flexible tape.

b. Cut out the paper pattern marked "Construction Label Only", provided in patterns. Wrap the pattern securely around the can using either rubber bands or scotch tape. Sharpen a nail, either by filing or rubbing on the concrete, for use as a punch to make four holes needed to install the stop-threads in the can. The stop threads are insulators that stop the charged aluminum leaves from touching the sides of the can and being discharged accidentally.

Using the same round tool used to cut a can (1.a., above) firmly hold the can in place and punch 4 holes at the marks indicated with the arrows. Then, using a large needle, move the needle point around to bend back any sharp protruding metal that could cut the stop-threads.

c. Next, using a thin-toothed hack saw (or a small flat file) notch the upper rim of the can exactly on top of the opposite centerline marks on the construction label. It may help if you use the edge of the file to mark the start of the cuts. If using a hacksaw, only pull backwards on the saw teeth. Pushing the blade forward will cut too deep and probably bend the lip of the can. The depth of the saw/file cut is only as deep as the thickness of the thread hanging the aluminum leaves. No deeper.

d. Once the holes are set and smoothed, and the two top grooves are cut, take off the construction label and set it aside. You won't need it again for this can. I recommend that you keep it to make other meters, if you desire.

e. Cut out and laminate the outside of the finished label for the can. Coat the can and the back of the label with a thin coat of rubber cement. When the glue is dry to the touch, carefully place the finished label around the can, keeping the label close to the upper rim of the can. Where the two ends of the label meet, use a small piece of Scotch Tape to keep the ends firmly in place. Wrap rubber bands around the can until the glue completely dries (about 10-15 minutes).

f. Take a small straight pin and, using pliers, punch 4 holes from the inside of the can through the finished laminated label. Install the stop-threads according to the diagram below:



Left: Photo of Turtle's KFM under construction. My daughter ate the SpaghettiOs.

Note the Construction Label held in place with two rubber bands (red on top, blue at the bottom). You can also hod it in place with tape. Punch the holes at the arrow marks.

The white arrow shows the location for the two notches to be cut to hold the thread for the aluminum leaves. This groove prevents the threads from slipping off the sides of the can.

Since this particular can is a "Pop-Top" type can, there is a small inner ridge of metal left over when the lid was peeled off. This rib is very sharp and gets in the way during construction. It will also get in the way when hanging the two leaves. To get rid of it, take a pair of pliers and slowly bend the rim back down inside the can until it is almost flush with the sides of the can. To finish the job, take a round wooden dowel or metal bar and roll out the edges flush on a table top. (Don't do it on a new marble counter-top or you'll get yelled at by your wife.)

Left: Photo of the Turtle KFM with:

A. Holes already punched and smoothed over with the needle shown.

B. Notches cut into the top edge along the centerline of the can.

C. Finished label trimmed and glued to can.

D. Stop thread tied to toggles.

E. Stop thread installed in can but not yet pulled tight.

F. Excess thread still attached to a large sail needle used to install thread and round out the holes in the can.

I used red plastic olive picks for toggles because they were available and photogenic. You can use anything that works. The notch on the front lip of the can is just barely visible. It doesn't have to be very big at all. The thread used here is dark colored string that is there only for photo purposes. It is too heavy and electrically conductive (it's a waxed thread) to use in the finished can. It replaced it with 2-pound monofilament line as per instructions. The STOP is not yet attached to the can.

To punch the holes in the can, I sharpened a 3" galvanized deck screw. Screws are make of harder metal than nails. After 4 holes were punched, the screw was just as sharp as when I started. I feel a nail would have dulled the point somewhere along the process, requiring me to re-sharpen the nail to complete the project. I used a scrap 2" x 3" board with the edges rounded off as the "anvil" to punch the holes. I screwed this board down to a sawhorse for support. I had no problems punching the holes without assistance.

CHARGING WIRE

Left: A sample charging wire. This one is from a piece of 12-2 electrical wire and is approximately 3 times too large for actual use. Refer to the diagram below, in the upper left corner for the correct dimensions of this wire. The thread shown here is the same heavy black thread as above and will be replaced with monofilament line. The sticky pads will be added last to prevent the sticky part from getting dirty (and getting in the way during construction). The location of the top threads is not critically important, but should be no closer to the lower end than shown in the photo.

This part is INSIDE the ionizing chamber. The lower part is stuck through a hole punched in the plastic cover to the can.

Use "bell wire" or a very light (22 gauge) solid core wire (Radio Shack # 278-1221) to make the wire for use in the KFM. The diagram below is NOT TO SCALE.

MAKING THE 8-PLY ALUMINUM LEAVES

A. Cut out a piece of standard weight aluminum foil approximately 4" x 8" and lay it out flat on a table. Smooth out wrinkles.

B. (FOLD #1) Fold the aluminum foil in half to make a 2-ply (2 thickness') sheet that will be approximately 4" x 4".

C. (FOLD #2) Fold the 2-ply sheet in half again to make a 4-ply sheet approximately 2" x 4". All folds have to be EVEN.

D. (FOLD #3) Fold the 4-ply sheet in half one more time making a 8-ply sheet that is approximately 2" x 2" square. Be sure that the two halves of the second fold are EXACTLY TOGETHER. This third fold makes an 8-ply aluminum foil sheet with one corner exactly square.

E. Cut out one of the full-sized templates for the finished leaf found in LAYOUT SHEET & TEMPLATE FOR MOUNTING LEAVES. Go ahead, I'll wait..Note that the template is a rectangle, not a square. It is smaller than the 2" x 2" packet of aluminum foil you just made for the 8-ply aluminum leaf.

F. Flatten the 8 thickness' of aluminum foil with your fingers until they appear to be a single, thin, flat sheet of foil.

G. Refer to the diagram, below, right. Hold the FINISHED-LEAF TEMPLATE (PATTERN) on top of the 8-ply foil sheet. The bottom of the template should line up with the Third-Fold Edge and the Square Corner of the 8-ply sheet.

H. While holding a straight edge along the THREAD LINE of the pattern (still in place atop the 8-ply sheet), press with a sharp pencil to make a shallow groove for the Thread Line on the 8-ply sheet. Also, using a sharp pencil, trace around the top and right side of the pattern to mark the finished size of the leaf. The top and side grooves from the pencil are your cutting marks.

I. Remove the template and cut out the finished size of the leaf. In order to prevent possible excessive electrical discharge from the overly-sharp points on the lower corners of the leave, cut about 1/16" off of each corner (a small triangle). This will "round-off" the corners.

J. While holding a straight edge along the indented THREAD LINE, lift up on the OPEN EDGE (top) of the 8-ply sheet, keeping all 8-plies together. Raise the edge up until the open edge is vertical, as illustrated, below, right.

K. Carefully remove the straight edge and continue folding the top part of the leaf (now called the "HEM") and fold it flat to the leaf.

L. Open up the folded hem of the finished leaf until the 8-ply leaf is almost open again...don't fold it back flat. The leaf is now ready to attach to its supporting line, shown in the next section.

M. Make at least 2 of these leaves. Make extra leaves in case one gets damaged during use, or if you plan on making more than one meter.

Now is the time to select and gather the hanging threads for the meter leaves. A thick human hair, over 6" in length is ideal. You do NOT have to pluck the hair out by the roots...and you only need TWO hairs for a set of leaves. Going "bald" is NOT AN OPTION. Katie's hair should be great. My hair can't support anything...it's too old.

Whatever you pick, keep it clean and free of skin oil.

MAKING THE 8-PLY ALUMINUM LEAVES, with TAPE - Continued...

N. IF THERE IS NO EPOXY GLUE AVAILABLE, FOLLOW THIS STEP TO ATTACH LEAF TO LINE:
Cut a Band-Aid adhesive section into 1/8" x 1" strips. Peel off the paper backing. Attach two of these strips in the location shown with the yellow arrows on the ASSEMBLY TEMPLATE. Fold each end back under as seen on the left, about 1/8". Attach one end of the tape at the upper end of the yellow arrow on the assembly template, and the other end of the tape at the lower end of the yellow arrow. The tape will slant from the corners in towards the middle of the leaf. The tape should NOT touch the sides of the leaf itself. Using tweezers helps with this step. Alternate Tape: Masking tape, Freezer Tape, Scotch Tape (in descending order of preference).

1. Be very careful not to touch the two 1-inch lengths of line/thread/hair coming out of the leaf. This has to remain spotlessly clean and free of skin oil. Any oil will reduce the insulating value of the line/thread/hair between the leaf and the rim of the can. If the electrical charge from the leaf "shorts out" to the sides of the can, the meter will NOT work at all.

2. Tape the piece of line/thread/hair you will be using to support the leaf to the spots marked "Tape Here" on the Assembly Template. Stretch the material out without touching the center of the material at all.

3. Slip one finished leaf under the line/thread/hair by lifting up on the material with the point of a sharp knife. Line the leaf up with the pattern on the template for the Finished Aluminum Leaf (in blue). Lower the line/thread/hair so it sticks to the two strips of tape along the line marked "Thread Line" on the template. Press the line/thread/hair into the tape strips.

4. Using the point of a sharp knife, hold down the thread in the middle of the leaf, and start lifting the hem up to fold it over the line/thread/hair. Carefully fold it back over the thread and press it almost flat. Remove the knife point and press the hem down completely flat against the leaf. This is now called the "Hem". The line/thread/hair must come out exactly at the corner of the leaf. If it has slipped down slightly from the fold, start over until it comes out exactly correct. The leaf will not hang correctly if the thread is not placed properly. This will make all your meter reading slightly "off".

5. Mark the line/thread/hair at the 1-inch point out from the leaf, on both sides of the leaf. This mark is where the line/thread/hair passes over the rim of the can (in the notch).

6. Cut 5 pieces of Band-Aid tape, each approximately 1/8" by 1/4". They are very small.

7. Attach the 5 pieces of tape as shown on the diagram on the far left.

8. Mark the bottom edges of the leaf with black ink if the anhydrite used is a light color. Use "White Out" if the anhydrite is a dark color.

The purpose of the coloration is to provide contrast inside the can so that the bottom of the leaves can be seen in low-light conditions. Avoid red colors. They fade with time.

You should make at least two of the leaves above. Make more leaves while you have all the tools and equipment out, including attaching them to line/thread/hair supports. Store the extras in a secure, dry container, like an old peanut butter jar (with lid). If any leaf gets damaged later on, you can easily change them out with new ones, instead of having to repair an old one. Extra leaves also gives you an option of making more than one meter. Working with curly human hair is an interesting and challenging experience.

MAKING THE 8-PLY ALUMINUM LEAVES with GLUE - Continued...

O. IF YOU DO HAVE GLUE AVAILABLE: One-hour epoxy glue is first choice; Model Airplane Glue is next choice. Most of the same steps above, paragraph N, still apply. The exceptions are in the use of glue instead of Band-Aid Tape.

1. Aligning the Finished Aluminum Leaf on the Assembly Template. Follow the same steps as for the "Taped" leaves, but place one small drop of epoxy on the thread where the 2 yellow arrows cross the line. You will see a small "o" at this point. Place the glue on this spot on the leaf. Follow the remaining steps up to and including folding the hem over and flattening it out. PLACE NO GLUE WITHIN " OF A POINT WHERE THE THREAD GOES OUT FROM UNDER THE FOLDED HEM. This prevents any excess glue from making the supporting line too stiff.

2. Use a toothpick and apply epoxy at the same 5 points that the tiny pieces of tape are shown on the diagram. Gently pry open the 8 ply leaves and dab a little epoxy between each sheet. When finished, press the sheets flat again. Epoxy glue will harden within 1 hour; Model Airplane Glue will take hours to dry between the flat sheets. If you use airplane glue, let them dry overnight.

MAKING OPTIONAL 5-PLY ALUMINUM LEAVES

P. If only heavy-duty aluminum foil (or extra heavy duty foil) is available, make 5-ply leaves the same size. The tables for using the 8-ply leaves can also be used for the 5-ply leaves to determine radiation dose rates. To make the 5-ply leaves, start by cutting out a piece of 4" x 4" heavy foil. Fold it into a 2-ply leaf, and then again into a 4-ply leaf. Keep one corner square. You should now have a piece of 4-ply foil approximately 2" x 2" square, with one corner perfectly square. Next, from a single thickness of foil, cut a square approximately 2" x 2". Slip this extra leaf into the 4-ply pack, making it a 5-ply stack of foil. Then, using the same template for the 8-ply leaf, cut the leaf into its final size. Installation and assembly are the same for all leaves from this point on.

INSTALLING THE ALUMINUM FOIL LEAVES

The can you will be installing the leaves in should be completed to the following point

a. Can properly trimmed to size and the top edges covered with tape (for those cans that were cut down).

b. The inner lip of the can folded down and smoothed flat (Franco American SpaghettiOs Can).

c. The notch on the can centerline cut in the rim of the can, and 4 holes punched for the Stop Threads.

d. The finished label glued and secured to the outside of the can.

e. The stop threads and toggles tied to thread, loosely installed in the can.

Q. Take one of the two leaves to be installed and make sure that there is tape secured to the suspension line/thread/hair to secure it to the outside of the can. The tape should be at least 1/2" or more out past the 1" mark on the thread. (Refer to KFM-13, N-5.)

a. Without touching the thread on either side of the leaf (within 1" of the leaf), align the mark exactly on the rim of the can. This mark and the thread should pass through the small groove cut in the rim of the can.

b. Firmly tape the line/thread/hair to the outside of the can.

c. Align the mark on the opposite side of the leaf, passing through the other groove in the edge of the can. Tape firmly in place. The leaf should be centered and level inside the can, hanging about 3/4" below the top of the can.

d. Take the second leaf and tape it just as you did the first leaf. Make sure the threads do not cross each other and the leaves hang side-by-side and level with each other inside the can. THE HEMS MUST FACE AWAY FROM EACH OTHER, AND FACE THE OUTSIDE OF THE CAN, NOT THE CENTER OF THE CAN. THE FLAT SIDES OF THE LEAF MUST FACE EACH OTHER IN THE CENTER OF THE CAN.

e. Make sure the tops of both leaves are level with each other. If not, adjust the lengths of the support threads until they are exactly level in the center of the can. When uncharged, these leaves will touch each other inside the can. When charged, the leaves move away from each other, limited only by the stop threads.

f. Using tape or epoxy glue, firmly fix the leaves in their final position in the can. This is important so that when the lid is taken off the can, the threads do not get accidentally pulled out or loosened in the can. Do NOT epoxy the threads INSIDE the can.

R. Take a piece of Scotch Tape and by carefully pulling the stop thread, tighten the stop thread until it is tight inside the can. Tape the toggles in place. Later, if the stop threads start to droop, retighten the thread and re-tape the loose end. One toggle is taped in place directly over the hole for the stop thread, and the other end (the loose end) is pulled out to adjust tension.

INSTALLING THE SEAT

The SEAT is a 1" piece of a common #2 pencil or a piece of wood or plastic approximately the same size and diameter of a pencil. It is taped in place on the outside of the can 3/4" from the rim of the can. This marks the same location as the top of the leaves INSIDE the can. Try not to place the SEAT over any of the information on the label, if possible.

The SEAT is used by the person reading the KFM. A 12" ruler is set on top of the seat, and then the forehead (or an area around the eye) sits on the ruler. This ensures that the same readings are taken from the same angle and distance above the leaves in the can. The person reading the KFM should insure that the ruler is placed on the same part of the head every time the meter is read. Having your head too far off to one side, or too high or too low, will significantly change the readings from the scale. Never have two people read the meter, particularly one "before", and then another "after" exposure to radiation. The readings will be unreliable. Remember, when taking meter readings, one reading is measured "before" placing the meter into the radiation area; and then another taken after a designated time period. It's the DIFFERENCE between the two readings that gives you the fallout dosage rate. Consistency is very important when using this meter.

Left: Photo of Turtle's KFM with the SEAT installed 3/4" below the rim of the can. I used GOOP Outdoor Contact Adhesive & Sealant to glue it into place. I used a wide rubber band to hold it secure while the glue set up (approximately l hour). However, it took all night to completely dry. I should have used 1-hour epoxy glue instead.

Inside the can you can just see the tops of two leaves I have installed in my KFM. They are suspended by 2 very long blonde hairs stolen from my daughter's hairbrush. The hair was a LOT stronger than I thought it would be, but it is a LOT harder to work with than I thought. I had a hard time just seeing it, let alone holding and taping it to a flat surface. A long BLACK hair would be better. Katie, where are you?

Left: Inside the can you can see the two Stop Threads on either side of the two 8-ply Aluminum Leaves. Tension is maintained on the Stop Threads using the toggle seen on the left side of the can. Pull it tight, and tape it down.

The stop thread is seen from above, just slightly up from the centerline because I wanted to be able to clearly read the label.

The small red Charge Wire is the one I will use in the finished KFM. The large wire was the one I used for photo purposes only.

MAKING THE CHARGING WIRE

1. The Charging Wire is simply a 2 5/8 " piece of solid core copper 22 gauge (bell size) wire. Its purpose is to transfer a static electrical charge from outside the can to the two 8-ply aluminum foil leaves sealed inside the can. The drawing below shows how it is constructed.



2. Only 1/4" of bare wire is exposed at each end of the wire. The 2.5" adjustment threads are installed 3/4" from the top end of the wire. These will be used to set the bottom tip of the Charge Wire exactly on top of the two leaves inside the can, maintaining about a 1/8" gap above the foil leaves. The wires never actually touch either the charging mechanism or the leaves themselves. The electrical charge "jumps" from the charger to the Charge Wire, and again from the Charge Wire to the Aluminum Leaves.

3. The "Band-Aid" Stop is set 1.25" above the bottom tip of the wire. This acts like a pivot-stop at the point where the wire passes through the clear plastic cover to the meter. Band-Aid tape (or any type tape that will not conduct electricity) is used in 1/4" wide strips to wrap around the wire and form the pivot point.

4. Two Sticky-Ended Adjustment Pads are attached to the two adjustment threads. This is probably the most difficult part of the job because the sticky tape sticks to everything, including things you don't want it to stick to. Any kind of tape will actually work. Using Band-Aid Dots "as is" also works. Tape finger holds to the top of the sticky pads so that you can adjust the wire to the exact location inside of the can. If you are careful, you won't have to adjust the location of the wire more than once. However, every time the lid comes off to reload the anhydrite, they must be removed and relocated when putting the lid back on.

MAKING THE CLEAR PLASTIC COVER

1. This is the hardest part of making the KFM. The plastic used has to be as close to "perfectly clear" as possible. A good selection is the clear plastic film used for making storm windows. However, in Florida, they don't sell it. Usually it's available from Home Depot. Another good choice (which is the one I used for my KFM) is 3M Gloss Finish Laminating Sheets for Photos and Documents. This heavy, clear plastic film is Ultra-clear, and comes with 25 sheets per package. It is a two-page "sandwich" with only one sheet in the package covered with adhesive. The two sheets are separated by a protective sheet between the two pages. You only want to use the non-adhesive sheet for the plastic cover. You will find one of these sheets included in this book. If used carefully, you can cut two tops from one sheet.

2. Cut out the full-sized template from PATTERN FOR CLEAR-PLASTIC COVER FOR KFM CAN.

3. Cut out a piece of plastic for the cover and make sure you have enough for the circle from the pattern to be superimposed on top. Tape the full sized template to the plastic to prevent it from moving around while you cut it out. Make sure the printing on the template faces the plastic and you can read the directions through the plastic.

4. The original directions for constructing this cover called for taking this cut-out plastic , centering it over the can, and folding it over the can, holding it in place with a rubber band. This is OK but the "skirt" of the plastic will have to be folded neatly so there are no wrinkles in the top. I couldn't do it without excessive wrinkles in the top, so I changed the rules.

The sheet of 3M plastic I chose was too heavy to fold, so I took a sharp pair of scissors and cut slices out starting at the outer edge of the circle and stopping about 1/16" short of the dashed line labeled "APPROXIMATE RIM OF CAN". I cut these strips so that when I got the to rim edge, the cuts were about 1/4" apart, all around the rim.

With the cuts made, fold the strips 90° up until you have a roughly round circle formed. Turn it over and slip it over the can. As you push the strips over the edge of the can, the small sections will overlap and form-fit themselves to the can. Use a 1/4" wide rubber band and hold the plastic top around the rim of the can. The rubber band must be on the RIM of the can, not below the rim. Now comes the tedious part:

5. Using very small pieces of tape (I used Scotch Tape), carefully tape the cut sections of the lid together flush to the sides of the can. Here's the rub: You must tape the lid pieces together so that they are snug, but not too tight so the lid won't come off over the rim of the can. You have to be able to remove the lid to take out and put in anhydrite drying agent. You will find that the plastic pieces that go over the lip near the STOP will have to be trimmed off to pass over the STOP and still be flush with the side of the can.

Carefully trim 2, 3 or 4 sections so that they are slightly less than 3/4" from the rim of the can. Now they will fold over and can be taped down like the rest of the can. Periodically throughout the taping, make sure the lid is re-centered because it will tend to slip around on the can while you work on it. The cover will also tend to "pucker" around the edges. Smooth out distortions as you get to them.

6. Once all the pieces are taped in place, you can finish and trim the top to whatever length you want. Constantly refit the lid to the can so you don't tape it up either too loose or too tight. You may want to use more tape on the inside of the lid so that the cuts are held in place both inside and outside of the skirt. This will make taking it off, and putting it back on, a lot easier. Once you have a final fit and everything taped firmly in place, run a strip of 1/4" clear Scotch Tape around the rim of the lid, sealing up the potential holes where the cuts meet the flat top. When finished and without the rubber band, the top should be snug to the rim of the can and the skirt should flare out slightly from the can.

7. Using clear Scotch Tape again, tape the skirt so that the inside, outside and bottom edge of the skirt are covered with a continuous covering of tape. This makes the lid as air-tight as possible. When finished, the only seal you need is the 1/4" rubber band.

8. Next, with the lid in its final position on the can, sight down over the can and measure a spot 1/2" from the rim of the can, on the opposite side of the seat. Take a small pin (such as a sewing pin) and hold it in a pair of pliers. Take a cigarette lighter and heat the tip of the needle until it is red hot. Quickly take the hot needle and "melt" a small hole in the plastic lid, 1/2" from the rim of the can and over the centerline of the two leaves. The charging wire will pass through this hole. DO NOT USE A KNIFE to cut a hole as it will tear later on during use.

Test fit the charging wire. It should be snug but not too loose. It it's too tight, re-heat the pin and make the hole slightly larger. Since this wire is very light, if you try to force it through the hole it will bend the wire. The charging wire must be free to move around in the hole without any pressure on it one way or another. If the wire bends, the hole is too small.

9. Center a cut-out of the mm scale, center it over the centerline of the leaves. Tape the "0" mark over the centerline. Tape it down.

MAKING THE CLEAR-PLASTIC COVER - PHOTOS

Left: Clear plastic sheet laid out and taped down to the template.

As you cut out the circular pattern, re-tape the plastic to the pattern paper. This will prevent the slippery paper from moving out of alignments when you cut the skirt strips.

Right: The completed circle cut out and re-taped to the pattern. The inside cuts end just before touching the circle of the rim of the can.

Carefully peel the plastic off the pattern, taking all the excess tape off of the plastic.

Left: Set the plastic on a flat table and bend up the sides so they will fit over the top of the can. Set this piece over the can and hold it down with a 1/4" rubber band. This forces the skirt pieces down almost flush with the can

Tape the skirt pieces in place, but not so tight that the lid cannot be eventually removed from the can.

Right: The finished KFM. The lid cover is trimmed to clear the SEAT, and a 1/4" strip of tape added around the lip of the can. Completely tape the inner and outer portions of the skirt to hold them in place and seal the lid. Use the rubber band again just under the (red) taped edge of the lid to secure it in place.

Shown at the bottom, use pliers and a straight pin (heated cherry red with a lighter) to melt a hole in the lid. This hole must be on the centerline of the KFM; and must be large enough for the charging wire to easily pass through the lid without bending the charging wire. You will probably have to heat the pin several times since it loses heat quickly.

CHARGING THE KFM

It's a cold, dry night, and you are wearing leather-soled shoes on a nylon carpet. Unconsciously, you scuffle your feet and, without meaning to, you touch your younger sister on the tip of her ear. A large spark jumps off your finger and with a loud "Snap" your sister grabs her ear and starts screaming "MOOOOOOM"! You like it so much that later on you do it again. Life is good.

I digress. We're talking about a static electrical charge built up by friction and released to another conductive element. It's still a valid scientific principle with other uses besides torturing your sister. In this case, we will use this built-up current to charge our KFM. The two 8-ply leaves inside the KFM have to be charged so that they swing away from each other. Inside the KFM, the ionization chamber is filled with a drying agent (anhydrite) that keeps the moisture out of the meter. There is a charging wire that pokes through the lid of the can and is supported by two thin, non-conductive threads. All you have to do is : 1. Build up a static electrical charge using hand tools; 2. Line up the charge wire so that it sits 1/16" above both leaves of the discharged KFM; and 3. Hold the built-up electrical charge close enough to the charge wire so that it "jumps" to the wire...which then "jumps" to the leaves.

There are two main method of charging the KFM, but before you can use either one of them, you need to set up the meter to be ready to take the charge.

a. The meter should be filled (one layer thick only) with anhydrite, or your own drying agent. It should be no more than 1/2" deep on the bottom of the can. Pink anhydrite is too wet, and should be replaced.

Removing and replacing anhydrite: Remove the lid to the can and, using tweezers, carefully pull out all the 1/2" squares of anhydrite. Replace them all, not just the "pink" ones. Use the same tweezers to replace the anhydrite with stuff that has been dried in a 400° oven, or pre-dried and stored inside a sealed mason jar.

b. The charge wire must be carefully set up on the lid to the sealed and dried meter, using the two strings on the end of the wire to hold it in the proper spot over the leaves. This is necessary because the "snap" of the charge jumping the wire may have enough force to move an unsecured wire. The inside tip of the wire must be placed 1/16" over the top of the two discharged aluminum leaves that will hang together inside the can. Once you fix the charging wire, unless something else happens, the charge wire will return to the same spot over and over again when the meter is discharged. The charge wire should NOT touch either of the two leaves. The spark should jump evenly between both leaves. Recharging the anhydrite will require you to re-position the charge wire threads since the lid has to be take off for recharging.

A note about the DRY BUCKET: In those areas where high humidity (Florida) is a problem, the use of the dry bucket filled with extra anhydrite will help keep the KFM from getting too moist between readings. We'll cover how to make one later in this article.

CHARGING METHOD #1 (Dry Paper & Plastic)

1-A: Select a piece of Plexiglas, such as a draftsman's plastic triangle or a smooth plastic ruler, or any other piece of hard, smooth plastic. The plastic must be kept dry.

1-B: For charging a KFM (especially in a Dry Bucket), cut a rectangular piece of plastic into a stick about 11/2" wide and about 6" long. All sharp corners and edges should be smoothed off. To avoid contaminating the charging end with sweaty, oily finger oils, it is best to wrap one end with electrical tape and only hold the plastic by the taped end. Even when using gloves.

1-C: Fold DRY paper (a piece of clean paper bag, or other smooth, clean paper) to make an approximate square about 5 inches per side and about 15 to 20 layers thick. This many sheets of paper lessens leakage of the electrostatic high-voltage charge generated to the finders holding the paper.

1-D: Right: Fold the dry paper in half as shown and vigorously rub the plastic piece. Hold on tight to the plastic and keep your hand away from the paper pack. With practice, you'll be able to tell how hard to rub, and for how long.

1-E: Lightly "bump" the plastic piece to remove any unstable part of the charge. Move the now electrically-charged piece of plastic and hold it perpendicular to the charging wire (at a 90° angle to the wire). The charge will jump from the plastic to the charging wire, and immediately jump to the aluminum leaves. The leaves should swing away from each other. Do NOT touch the charging wire with your fingers.

1-F: Fully charged leaves will read 15 mm or higher, but do not touch the stop threads.

1-G: If the initial reading on the KFM is MORE THAN 20 mm, (to get the most accurate reading possible, carefully partially discharge the leaves by touching them with the charging wire with you fingers on the wire insulation only. Some of the electrical charge will bleed through the poorly insulated wire into your fingers (it won't hurt). Or, completely discharge both leaves by touching the bare charging wire with your fingers. If you hold on to the can, the electrical charge will pass through you (harmlessly) into the can, discharging the aluminum leaves. Re-charge the leaves again, but this time vary either the number of strokes on the plastic or pressure on the plastic while rubbing. Always try to start readings with the leaves between 15 and 20 mm on the scale. When the KFM readings are within 15-20 mm, move the charge wire up and out of the way of the leaves. Gently pull one of the charge wire support threads and move the wire up towards the top of the can. This avoids the possibility of bleed over from the leaves back through the charge wire (which is poorly insulated).

1-H: Store all components of the KFM, including the charging plastic and paper, inside a sealed jar with drying agent inside. If possible (and time permitting) store all the components, including the KFM, inside a dry bucket.

1-I: The only test you can do on the capabilities of this meter is to let it set, fully charged, for 3 hours. If it holds the charge, or only drops 1 mm, then the meter is well made and the leaves are sufficiently insulated by the hanging threads to give accurate readings on the radiation dosage rates printed on the Finished Label. This test will only work in a RADIATION FREE area.

If the meter fails to hold charge, or drops more than 1 mm in 3 hours, replace the leaves with newer, cleaner hanging threads. The only way electric charges can be discharged is through the hanging threads. Even oil from your fingers can conduct very small electrical charges to the can that may spoil the readings from the KFM.

CHARGING METHOD #2, (Unwinding Tape)

2-A: It sounds funny, but when you rapidly unwind a section of clear Scotch Transparent Tape, you create an electrical charge in the tape. Make sure BEFORE you begin the charge that the meter has been prepared as explained previously. Almost any other type of PVC tape, electrical tape, or other brands of "Scotch-type" tape will probably also work.

2-B: Left: GET SET With the charge wire centered over the leaves with a 1/16" gap, rapidly unroll about two to three inches of tape as shown. The tape should NOT be in the dispenser for this to work. You will soon be pulling out another 10 to 12 inches off the tape roll with only the left hand, keeping the right hand in place. Note that when you start this procedure, you are only about 2" away from the Charge Wire, so be careful you don't knock the charge wire out of position as you unwind the tape.

2-C: Left: QUICKLY pull out 10" to 12" of tape by pulling the end with your left hand, while the right hand allows the roll to unwind and at the same time remaining in the same "Get Set" position as 2-B, above.

2-D: Left: While holding the unwound tape tightly, about perpendicular to the charging wire and about 1/4" from the end of the charging wire, promptly move BOTH hands and the stretched-out tape to the left. Moving slowly, move the tape to the right, taking about 2 seconds to move the 8" of the tape along the end of the charge wire. The electrostatic charge from the unwound tape will "jump" the 1/4" gap from the tape and charge the two aluminum leaves. This system will take a little practice to get right.

2-E: Make sure that neither leaf is touching a Stop Thread.

THE OPTIMUM CHARGE IS FROM 15 mm TO 20 mm. Gently bump or shake the KFM to remove any unstable part of the charge.

2-F: Move the charging wire up and away from the leaves using the adjustment threads. Do not touch the charging wire with you bare hands. Bring the bare end of the wire up close to the underside of the can lid.

TROUBLE-SHOOTING THE KFM

IF CHARGING DOES NOT SEPARATE THE TWO LEAVES SUFFICIENTLY, TAKE THESE CORRECTIVE ACTIONS:

1. Be sure the pieces of anhydrite in the bottom of the ionization chamber (the can) are in a single layer, with no pieces on top of another and the top of no piece is higher than 1/2" above the bottom of the can. If it's too high, it will hit the bottom of the leaves.

2. Check to be sure that the threads suspending the leaves are not crossed; Then try charging the KFM again.

3. If the KFM still cannot be charged, replace the used anhydrite with fresh, dry anhydrite. Moisture will stop the charging process.

4. If you cannot charge a KFM when the air is very humid, charge it inside a dry-bucket.

5. If you cannot charge the KFM while in an area of heavy fallout, take it to a place affording the best protection against radiation and try to charge it there. A dose rate of several hundred R/Hr will neutralize the charges on both the charging device and the instrument so rapidly that a KFM cannot be charged. TAKE SHELTER IMMEDIATELY...THIS DOSE LEVEL WILL KILL YOU.

6. If a KFM or other radiation measuring instrument gives unexpectedly high readings inside a good shelter, wipe all the dust off the outside of the instrument and repeat the radiation measurements. When exposing a fallout meter outdoors where there is fresh fallout, keep the instrument in a lidded pot, plastic bag, or other covering to avoid the possibility of having it contaminated with fallout particles and afterwards getting erroneously high radiation measurement...and tracking contamination inside the shelter.

MAKE AND USE A DRY BUCKET

A dry bucket is a sealed plastic container with a transparent top that contains a drying agent in the bottom. It has openings in the sides of the can (with plastic bags or gloves sealed to the can) so the KFM can be charged inside the bucket without opening the bucket to the ambient air.

About a cupful of anhydrite will keep the inside of the bucket very dry. The size of the pieces of anhydrite (dehydrated gypsum drywall) doesn't matter in the bucket, but do not use powdered anhydrite. It will take about an hour (or two) to make a dry bucket.

See Rogue Turtle's Dry Bucket Photos

1. Use a plastic bucket with a top diameter of at least 11 inches, and a height of at least 9 inches. A 4-gallon bucket having a top diameter of 14 inches and a depth of 9 inches is ideal. A plastic tub approximately this same size is satisfactory. If the handle supports interfere with sealing the top, remove both the handle and the supports with a sharp knife. (Home Depot and other painting supply stores sell self-sealing paint buckets of the approximate size suitable for dry buckets. Their major advantage is that they are new and don't need to be thoroughly cleaned prior to use.)

2. SEALED LID: Cut out a circular piece of clear plastic with a diameter of about 5 inches larger than the diameter of the top of the bucket. Clear vinyl 4 mils thick, used for storm windows, works best. Stretch the plastic smooth across the top of the bucket and tie it in place, preferably with strong rubber bands looped together to form a circle. Strong rubber bands can also be cut out of bicycle or automotive tire inner tubes. Cut them about 3/4" wide and cut slowly in a continuous circle around the tube.

3. DUST COVER: Make a second, plastic top out of any type material that fits snugly but is easily removable. Cover the bucket with plastic and tape over and around the top of the bucket. Do not let the edges of the cover snug up to the sides so that it is too tight to easily be taken off. Use one-inch cloth duct tape, or one-inch wide glass reinforced strapping tape for the edges. Tape the inside of the edges to the cover with the same tape to make it easy to get back on. This cover is for dust protection when the bucket is not in use. Setting the whole bucket inside a large garbage bag also works.

The original plans for this bucket called for holes to be cut into the sides of the bucket and plastic "bread bags" sealed in the can to make an airtight method of working inside the sealed can. I don't like that method, but you can do it if you want to. I like my method better, to follow:

4. Cut out the oval shaped holes found on the template DRY-BUCKET HOLE TEMPLATES. Test fit the hole to make sure your forearms can pass through without binding. If the hole is too large, you can make the hole smaller if you desire. If the hole is too small, enlarge the hole. The marked spots for screws are recommended spots, but can be adjusted as needed for the particular bucket you are using. You will be cutting 3 holes in the sides of the bucket. A rectangular hole will be cut near the bottom of the bucket, about 1 inch above the bottom. The KFM and anhydrite are put in and taken out through this hole. The two arm holes are cut out, one on each side of the rectangular hole, about 3" to 4" above the bottom of the bucket. The idea is to be able to work with the KFM without exposing it to the outside air which could contaminate the bucket with fallout particles, making the KFM readings unreliable.

5. The Rectangular Hole Pattern is 6" wide and 3" tall. It is large enough for the KFM to pass through and to empty and refill the dry bucket with anhydrite as needed. The hole should be located 1" above the bottom of the bucket as shown below.

Tape the Template into position at the location of the rectangular hole. Use magic marker to clearly mark the hole . Remove the Template and save it for the next dry-bucket you need to make.

To cut out the hole, drill a 1/4" hole in each corner of the rectangular hole. Using a sharp knife or saber-saw, cut out the hole along the lines marked. SAVE THE CUT OUT PIECE TO USE LATER ON.

This extra cut-out piece will be used, along with a lot of duct tape, to re-seal the bucket.

6. Left: Tape the Oval Pattern in the appropriate location as shown on the left. To mark the location comfortable for you, rest your forearms on top of the bucket, with your hands inside the circular area of the bucket. Mark this spot as the "Left and Right" side axis for your holes. Center the oval pattern over the lines down from the top where your forearms were resting, with the lowest point about 3" to 4" above the bottom of the bucket.

Drill 1/4" holes for a starting point for a sharp knife of hand-held electric saber-saw. Cut out the holes SLOWLY, and throw away the oval cut-out pieces. Save the Pattern for reference when attaching the screws, and to make another bucket.

7. Shop around at the local grocery store and find a pair of extra-large latex gloves that have fairly long sleeves. Use the extra-large size to make it easy to get your hands in and out of the bucket. Most good gloves have a fabric liner that are easier to get on and off than the solid vinyl gloves. The next step is to put them on your own arms and extend both arms into the bucket. Part of the sleeves must be outside the bucket. Make sure that you have enough of the gloves inside of the bucket to reach all the parts of the sealed bucket, both top and bottom. Have a friend take the Magic Marker and make dotted lines where the gloves pass through the outside of the bucket. Also, mark a spot on the TOP of the gloves that matches up with the red "TOP" mark on the pattern. This is the line that will be glued to the outside rim of the oval cutout. If needed, used scissors to trim off the gloves, leaving about 1" to 11/2" for the gluing surface of the gloves, outside of the bucket.

Make sure you glue the right-hand glove into the right-hand hole. This can be an embarrassing mistake.

8. GLUE: The glue used to secure the latex gloves to the plastic bucket must be capable of holding on plastic surfaces. Model airplane glue, Rubber Cement, or fast-drying epoxy (for plastic) all work. The construction adhesive called "Liquid Nails" also works very well, but takes a long time to dry. If possible, experiment with a piece of the trimmed off sleeve material and the oval cut-out pieces to see how well the glue holds. Do not use Hot Glue as it will get brittle and fall off eventually.

9. Use a small 1/16" drill and drill holes in all the spots marked for screw holes. You can adjust the pattern as needed. We'll come back to this later.

10. Coat the outside rim of the hole evenly with glue, making sure there is at least 3/4" of coverage back away from the edge of the hole, and completely around the rim. Coat the sleeve of the glove with a stripe of glue starting from the dotted line and working back away from the fingers of the glove. If the glue calls for it, let is set-up for the appropriate length of time.

Starting at the two top-marks (#1 on the pattern), carefully fold the sleeve open and press the sleeve to the rim of the hole. Hold it in place and carefully put in one flat-topped screw (with a flat washer) through the glove and into the hole drilled in the bucket. Next, evenly fold the sleeve to find the exact bottom of the sleeve. Press this spot over the bottom hole of the cutout and secure the sleeve the same way as above. Work around the edge of the hole, following the numbering system on the template. Attach all the screws (with washers) until the entire sleeve is glued and screwed to cover the arm hole. Do not tug or pull on the glove sleeve until all the glue has dried, probably overnight. Use extra glue to fill any voids that may appear while stretching the gloves around the holes.

11. Attach the other glove in exactly the same manner as #10, above.

12. Extra sealant can be used inside the can, around the arm-holes, if needed. Silicon sealer works well. Clean out debris in the can.

13. Clean out the dry bucket and dry it as best as possible. Put in about 1 cup of anhydrite on the bottom of the bucket.

14. Place the KFM and the charging system selected inside the dry bucket.

15. Take the 6" x 3" piece of the bucket you cut out in step 5 and cover it on the outside of the piece with duct tape. Press the duct tape all around the edges to seal up the bucket. Do NOT put tape on the inside of the bucket. If you need a better seal around this "door", use more duct tape. Your gloved fingers cannot add or remove tape from the inside of a sealed bucket. This door is used to add or change anhydrite when the KFM is in use. You can also take out the KFM through this door, if you want to work on it later.

PUTTING IT ALL TOGETHER

Now you have finished the Kearney Fallout Meter (KFM) and a Dry-Bucket to store and/or charge the meter. A few final words are in order:

  • Store the anhydrite for both the meter and the dry-bucket in quart-sized, sealed containers. If you make up and store sufficient dry anhydrite, you may be able to get through a fallout "incident" without needing to re-heat any anhydrite.
  • Store the charging mechanism (plastic and paper, or rolled tape) inside the dry-bucket with the KFM. Store any replacement parts you have made inside a small zip-lock bag inside there too. Store extra tape in the bucket. It is recommended that the plastic and paper system be used if you plan to charge the KFM while still inside the dry bucket. It's easier to handle than unrolling the tape with gloves on.
  • At night, you will need a small flashlight to read the meter, no matter where you are.
  • Taking fallout meter readings out-of-doors may be done best while still inside the dry bucket. This bucket is completely sealed from the outside atmosphere and can also be put into another plastic bag before setting it outside in a known fallout condition. When you bring the dry-bucket back inside the shelter, either remove and clean the plastic bag, or throw it away. If you use a bag, make sure to wipe off all the contaminated dust that will hold contaminated particles of radiation.
  • The weakest link in the KFM is the thread holding the two suspended 8-ply aluminum leaves. Handle with care.
  • Having a KFM or any other dependable fallout meter, and knowing how to use it, will enable you to minimize radiation injuries and possible fatalities. This is especially true by skillfully using a high-protection factor fallout shelter to control and limit exposure to radiation. By studying the first section of this book you learned how to measure and calculate radiation dose rates at different time intervals and how to predict dosage rates for future outdoor (unprotected) exposure to ever-decreasing radiation levels. This last section gives you a "MacGiver" type radiation meter that really works. It's cheap and dependable.
  • With the cold-war threat of all-out nuclear war becoming less and less, the threat now (as I see it) is from localized disasters involving intentional harmful activities or human error. Our 103 nuclear power plants remain vulnerable. My family and I, as well as our loyal readers, travel a great deal. There are many more nuclear power plants all over the world, and I won't even try to list all of them. Other governments aren't as "open" about their plants as the United States is. You can still find out about them on the internet, if you try hard enough. If you plan to go overseas, look up the countries you will be traveling in and locate exactly where they are. Having at least a general idea of their location sure beats the heck out of driving INTO a disaster, instead of driving AWAY FROM a disaster.
  • Tin cans, aluminum foil, drywall, and plastic are available overseas too. You don't have to take a KFM with you. Just keep a copy of the finished label with you...use it as a bookmark. Once you've made one, you will feel confident to make another one. Teach a friend how to do it. At first, it sounds complicated. But, when you're done you'll say, "Hey, that wasn't too bad". Mr Kearney, inventor of the KFM, has had his children building these meters for sale for years.
  • The chances for an "accidental" nuclear melt-down are very, very low. The chances for an intentional attack on our nuclear plants is much higher. If you at least have a KFM prepared ahead of time, you can store it away in a zip-lock bag and make fun of your favorite author for being paranoid. I don't care. At least you're prepared. Need a quick source of drywall? Chop a hole in the wall in a closet or in the garage. Fix it later. Call me if you have problems during construction. Live long and prosper.

    "Forewarned is Forearmed"

    Rogue Turtle's Finished KFM



    KFM and Dry Bucket Patterns

    These links provide you scaled templates for many of the important cuts and pieces for the KFM and the dry bucket. These images are provided at 96 dpi (dots per inch). To ensure the scale is preserved, you should download the images and open them in a photo editor or desktop publishing application. Opening the images in a browser window will not guarantee the proper scale.