CAMERA BELLOWS CONSTRUCTION

My personal technique


bellows photo

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        The fabrication of the camera bellows begins by obtaining the correct materials and cutting the individual parts to the desired size. For this particular bellows the required list of materials is as follows:

4 pieces wood stock 3/4 x 3/4-inches square and 14-inches long.

2 pieces of plywood (or equivalent) 11-3/4 inches long x 6-1/2 inches wide x 1/2-inch thick.

2 pieces of plywood (or equivalent) 11-3/4 inches long x 5-1/2 inches wide x 1/2-inch thick.

2 pieces of plywood (or equivalent) 5-1/2 inches long x 5-1/2 inches wide x 1/2-inch thick.

2 pieces of blackout cloth, AT LEAST, 28-inches long x 13-3/4-inches wide.

3 pieces of paper card stock 14-inches long x 11-3/4-inches wide.

1-16oz can of spray adhesive (or adhesive of your choice).

2-liquid ounces of 5-minute epoxy adhesive (or adhesive of your choice).

Hot glue gun and glue sticks (or adhesive of your choice) to assemble the form box.

10 linear feet of REPOSITIONABLE double sided tape in an appropriate applier.

1 roll of CLING type plastic wrap (name brand= Glad or Saran wrap)

End Ring Fabrication

        Lets begin the bellows project with the item that you must construct first, the "End Rings". First cut some strips of stock that are equal dimension on both sides, lets use 3/4 x 3/4 inch and at least 14 inches long to allow for the area lost to the saw when cutting to specific length. Four (4) strips 14 inches long will be required. From these, cut four pieces that are 6 1/2 inches long and four pieces that are 5 inches long. For custom sizes make sure that the side spreaders are shorter than the top and bottom by exactly twice the material dimension. So in this case that is how we arrived at 5 inches long for the side spreaders.

        Next on a smooth, flat, non-adhesive surface glue two of the 6 1/2 inch pieces to an equal number of 5-inch spreaders to make two complete frames that are 6 1/2 inches square. I prefer to use five minute epoxy(ref: photo1) available at model aircraft suppliers because it rapidly wets out the stock for good penetration and sets rapidly so that you can move on to the next part of the project without delay. After the adhesive has set, sand the excess adhesive from the frames. (ref: photo2)

        Drilling the mounting holes for attachment to the end frames is the next procedure. Place the completed frames on a flat surface with the 5-inch wide spreader facing away from you. Draw a tranverse line from one side of the frame to the other across the two (2) 3/4-inch wide x 5-inch long spreaders, that are located at the top and bottom of each end ring assembly, taking care to center the line from SIDE to SIDE on the 3/4-inch width of each spreader. Measure along these line 1-1/2-inches, toward the center, from each side and place a mark at these points on the line. Drill a perpendicular 3/16-inch diameter hole straight through the frame at these eight (8) points. Counter bore each 3/16-inch diameter hole to a depth of 1/2-inch utilizing a 3/8-inch diameter bit. Care must be taken when counter boring to prevent the drill from grabbing the stock and drilling all the way through! If this happens, plug the hole with a piece of wood that is glued in position. Allow the adhesive to set and then re drill the 3/16-inch hole and the 3/8-inch x 1/2-inch deep counter bore.

        Double check the frames for true square to make sure nothing has shifted during glue setup and if you need to make corrections, now is the time, because these simple items control the fit of the bellows to forward and back camera frames, as well as the overall outside end dimensions of the form itself. (ref: photo3)


Form Construction

        The form can be made from any rigid material that you can obtain and have the tools to cut. I prefer to use an inexpensive grade of plywood because of the precision cut that can be obtained. Foam core board (1/2 inch or thicker), or a urethane insulation board will work just fine if you want to use a knife to cut the pieces to size.

        Two items control the size of the form. The size of the end rings you utilize and the overall finished length that is required for the format that you wish to utilize in your project. The INSIDE square dimensions of the end ring should allow for clearance of the bellows itself when it is folded. Be AWARE that even though the initial form is square when the creases and folds are placed and the bellows are collapsed, the INSIDE dimension takes on the shape of a RECTANGLE that can infringe on the aperture size that is required.

        The end rings can be fabricated from sheet metal if you have the skill or are reusing rings from a factory-fabricated camera, but for the rest of this instruction we will assume you will be using wood stock that is cut from the same thickness material that you utilize in the rest of the camera components.

        The overall dimension of the form that we will construct will be 11-3/4 inches long and 6-1/2 inches square at the ends, assembled from two pieces of plywood 11-3/4 inches long x 6-1/2 inches wide x 1/2-inch thick and two pieces 11-3/4 long x 5-1/2 inches wide x 1/2-inch thick. The thickness of the individual panels will depend on the material that you select for your form and will control the dimension of your spacers that you will insert INSIDE the box to maintain square shape of the form. After cutting the pieces of stock to size assemble them into a rectangular box. I prefer using a hot glue gun because of how rapidly the adhesive sets and how easily it can be collapsed and disposed of after construction.

        You will then need to stabilize the box by inserting end caps that fit snugly into each end of the form to keep it from distorting when pressure is applied to the side. If you must use a material that is less stiff than is desired just add more spacers inside that are the same dimension as the spacers that you cut for the ends. The idea of placing the spacers INSIDE the form is to make them easier to remove if you must collapse the form to get the skin of the bellows off after the glue dries. So don't go wild with the glue, use just enough to keep it from falling apart with handling.(ref: photo4)

        Now that you have finished your form, double check the size to make sure that the end dimensions exactly match the end rings and the LENGTH includes The THICKNESS of the end rings that you have chosen to utililize(ref: photo5). If you are making a replacement bellows for a camera that is already constructed, just use the dimensions that the fabricator used on the bellows that you are replacing for the overall length and end dimension.


Layout Pattern for Bellows and Side Stiffeners

        The cutting of the side stiffeners for the bellows is best accomplished using a drop knife type paper cutter, but with care can be done with a single edge razor blade or x-acto knife. Begin by cutting 48 pieces of poster board or card stock 3/4 inch wide by 6-7/16 inch long. The overall length of the stiffener is 1/16 inch shorter than the HEIGHT of the side to allow for material displacement during the folding and creasing procedure. Cut extras, because some will be distorted or totally lost in the glue-up process and will have to be replaced as necessary. You will not want to interrupt the glue up process to cut extra stiffeners so a little extra time at this point is worth the effort involved.

        Trim the ends of 20 stiffeners at a 45-degree angle so that the angles are OPPOSING each other at opposite ends. These 20 individual stiffeners will now have a flat top triangle shape. Again be sure to make extras to allow for waste. Leave all the remaining stiffeners (28) as rectangles 3/4 x 6-7/16 long.

        To draw the layout, you will need a stiff piece of poster board or Formica that is large enough to draw out the entire lengthwise dimensions of one side and one top or bottom, SIDE-by-SIDE, leaving a space between the side rectangles to allow for material displacment when folding. In this case a board of 12 x 14 inches will be required.

        To begin the layout draw two (2) rectangles SIDE by SIDE, with the ends aligned, that are 11-3/4 inches long by 6-1/2 wide (be sure to leave a space between the rectangles to allow for material displacement). Next divide the rectangles into 12 spaces 3/4 inch wide with a 1/4-inch space between them. Start with a dividing line at 3/4 inch from one end and then a 1/4-inch space followed by another 3/4-inch space. When you are finished the pattern should break even at the end (ref: photo6), using 12 spaces 3/4-inch wide separated by 11 spaces 1/4-inch wide, with a 3/4-inch space at the beginning and a 3/4 inch space at the end. (ref: photo7)

       (For custom applications it is ESSENTIAL that the number of stiffeners is always EVEN or you will not be able to complete the fold pattern properly! Also be AWARE that the bellows will not be stretched out tightly when it is at its full focal distance so be sure to add an additional full set of stiffener strips at one end to compensate for this. These will be added to the pattern just before the end ring collar, and must incorporate an entire fold (two stiffeners) into the pattern of each panel. So when laying out the pattern remember to add these extras to the overall length of the FORM BOX! )


Parts Assembly

        At this point you should have two (2) end frames that are 6-1/2 inches square, a form box that is equal to the overall length and width of the bellows, 48 card stock stiffeners, 20 of which have tapered ends (Just a reminder, The angles on the end of each tapered stiffener must have the slope opposing each other so that you have one short side and one long side.) and a stiffener layout board with correct SIDE-by- SIDE pattern layout drawn on it using a contrasting color ink or pencil to allow you to rapidly place the individual stiffeners with the precision required.

        Begin by placing your darkroom cloth, or any blackout material on a flat surface to trim it roughly to size. You should have, at least, 1-inch overlap at the ends and also at the point where the cloth meets after wrapping it around the form. To check it, lay the form box on the cloth and temporarily tack the edge of the cloth to the form at a point midway between the two lengthwise edges (ref: photo8). Next roll up the box in the cloth until you have completely covered all four (4) sides and are back to the starting point. Now add the extra 1- inch and trim cloth in a straight line from one end to the other lengthwise. Cut one more piece to the same dimension and then set them aside.

        Wrap the form box in Saran wrap, or any other self-adhesive food wrap, taking care to avoid bubbles or puckers in the wrap(ref: photo9). I usually wrap the form in at least two complete layers of plastic wrap because it makes removing the form from the cloth skin much easier at the end of the glue up procedure. Trim the excess plastic wrap off and set the form aside.

        You will now apply a 1-inch wide stripe of adhesive to the, approximately 13-3/4-inch edge of one piece of your blackout covering material and with the glue side facing OUT, firmly thumbtack the overlapping ends to your form block maintaining lengthwise alignment of the glued edge at the approximate longitudinal centerline of the top side of the form. Carefully continue to wrap the block in the material until you are back to the edge just before you will lap over the start glue line (ref: photo10). Now apply another stripe of glue to the UNDERSIDE of the area that will overlap and allow glue to dry to a lightly tacky surface, Then continue to wrap the block over until the glued edges come into contact with each other and then press them firmly together along the entire gluing area creating a flat, overlapped fully glued seam (ref: photo11). At this time trim the covering material FLUSH to the ends of the form box. (ref: photo12)

        If you intend to utilize flat metal end rings from an existing camera, ensure that you leave AMPLE material extending past the form to fold over the ring and glue into place to prevent it coming loose during installation and use! Also I prefer 3M brand Super77 spray adhesive for glue up, because the results are predictable and the excess is easily rubbed off the overlap area. The downside to this adhesive is that you may have to go back and re-apply pressure to the glued areas at regular intervals until the solvents totally evaporate thru the covering material. (Just check it once in awhile to make sure every edge is still tight).

        Proceed by next placing the layout board on a flat surface that has been covered with a disposable drape, such as old newspaper or wrapping paper. Apply a strip of double back REPOSITIONABLE tape lengthwise across both sides of each individual, layout rectangle starting about 1-1/2-inch in toward the center from each longitudinal side so that you end up with two (2) strips about 3-1/2 inches apart that extend from one end collar to the other on the stiffener layout (ref: photo13). These strips of tape will allow you to pre-position the individual stiffeners in the proper place on the board without the worry of misalignment when applying the form to the pattern.

        The use of REPOSITIONABLE grade tape is MANDITORY to this procedure or you will end up with a form attached firmly to the layout board and you will have to start over from the beginning. This tape is available from most craft and hobby outlets or your local drafting supply. It is possible to temporarily apply the stiffeners to the layout with two very fine drops of rubber cement placed at opposite ends of each piece, but you still run the risk of not being able to remove the form, with the stiffeners attached, without destroying your work.

        The next part of the procedure gets a little sticky in more ways than one! Begin by covering a flat work area with disposable drop sheets. (Be SURE to place your pre-taped layout board on a SOLID, FLAT surface.) Next place half, 10 tapered and 14 rectangular, of your pre-cut stiffeners on a flat surface and apply an even coat of adhesive on the side facing up, which side up does not matter because each item can be rotated on use to the correct orientation. After the adhesive dries to a lightly tacky finish, position one rectangular strip, glue side up, upon each of the four (4) 3/4 x 6-7/16-inch areas located at the end of each 11-3/4 x 6-1/2-inch SIDE-by-SIDE rectangle. Press the stiffeners lightly onto the tape tacking care to avoid misalignment. Double check each stiffener as you apply it to assure even spacing in the pre defined area. Remember you can reposition the stiffeners as needed. (ref: photo14)

        Decide which layout board rectangle you will use for the TOP and BOTTOM panel, and apply a pre-glued RECTANGULAR stiffener to each remaining 3/4 x 6-7/16-inch open area remaining, on the chosen panel only! The SIDE panels will be set up slightly differently.

        The next panel will, at this point, have a rectangular stiffener applied to the opposing end spaces. The next stiffener in the line will be TAPERED, apply it on the following 3/4x 6-7/16-inch empty space so that the long side is aligned with the initial rectangular stiffener and the short side is facing the opposite end. Now apply the rest of the TAPERED stiffeners to the remaining 3/4x 6-7/16-inch open spaces, on the layout board, with the SHORT SIDE aligned next to a SHORT SIDE and a LONG SIDE aligned next to a LONG SIDE.

        The completed pattern should now look like a row of rectangles with a 1/4" inch space between horizontally aligned segments, laid out next to a matching pattern of stiffeners with a saw tooth lengthwise adjoining edge that has a rectangular stiffener at each end (ref: photo15). Be sure to maintain a space between the longitudinal panel layouts to allow for material displacment.


Final Assembly

        Before we proceed please take a moment to collect your equipment and to prepare for the final glue up process. At this point you should have before you a layout board with 24 stiffeners temporarily applied in the required positions as described in the preceding text, suitable adhesive (3m Super77 in a spray can.) and a form box covered in a single layer of blackout material.

        An even coat of adhesive is now applied to two (2) adjoining panels of the form box being sure to avoid drips and runs that will prevent even drying of the adhesive and prevent the stiffeners from adhering to the form surface in a uniform manner. Now that the adhesive has dried to a lightly tacky surface you may place the form box in position on the layout board, aligning one panel of the form, with adhesive applied, with one (1) panel of the board that has the stiffeners applied as required. Take your time and slowly lower the form into position taking the care required to align all portions of the panels with each other before allowing contact between the form and stiffeners. If for any reason alignment is not accurate, stop and correct it at this time to prevent total loss of the bellows (ref: photo16). Remember that you produced sufficient extra stiffeners to account for errors at this point!

        Carefully remove the form box from the layout board. The individual stiffeners should now be free from their position on the board and adhered to the material on the form box in a pattern that is the same as it was on the layout board (ref: photo17). If any of the stiffeners have become misaligned reposition them and proceed to the next step in the process. Align the next portion of the form, which has adhesive applied, over the remaining unused panel of the form board and repeat the procedure performed on the first panel.

        Now the form box will have stiffeners applied on two adjacent panels with all stiffeners aligned at the intersecting corner of the form (ref: photo18). Apply adhesive to the next two adjoining panels of the form box and allow the adhesive to dry to a tacky surface while you re-apply the remaining stiffeners to the layout board using the same procedure that was presented for the first two (2) panels.

        Caution! The remaining panels on the form box must MATCH on OPPOSITE sides of the form so that you have two (2) panels with rectangular stiffeners applied that are on opposite sides of the form, and two (2) panels that have a saw tooth pattern of stiffeners applied.

        Now that all sides of the form have stiffeners applied and all stiffeners are aligned properly at the intersecting form corners, the final covering of blackout material may be applied. Spread out the remaining blackout material on a flat surface and apply an even coat of adhesive to one side only. Now apply adhesive to the entire surface of the form box and allow the adhesive on the form box and the blackout material to dry to a lightly tacky surface.

        Carefully align the edge of the blackout material with the longitudinal position on the form box (BOTTOM) that you wish to incorporate the overlapping seam (ref: photo19).(The seams of the blackout material should be located on OPPOSITE sides of the bellows to avoid excessive material buildup which will prevent full collapse of the bellows!) Firmly press the material onto the adhesive at this line and begin to wrap the rest of the form in the blackout material until you have reached the overlap area. Mark the end of the overlap area on the underlying material and apply an even coat of adhesive to this area only and allow adhesive to dry to a light tack before pressing the overlying blackout material onto the overlap area underneath. Apply pressure to the entire outside of the form box at this time to remove any air pockets and to ensure that the outer covering is firmly adhered to the underlying structure. Trim off all excess material that extends past the open ends of the form and set the completed assembly aside to dry (ref: photo20).Check often to ensure that separation of the layers does not occur. If separation is noticed just apply firm pressure to these areas until they adhere.


End Ring Placement

        After the assembly has sufficiently dried carefully slide the covering material off one end of the form until 3/4 of an inch of it is projecting from the end of the form. Place one of the end rings, that you have obtained or fabricated INSIDE the material that is projecting from the form (ref: photo21).NOTE! always insert end rings into the bellows with the mounting hole pattern at the right and left sides of the bellows! If the holes are on the top and bottom they will be partially covered by the fold of the bellows making installation very difficult, also be sure that the COUNTERBORED side of the end ring is facing the interior of the bellows)Gently lift the cover, ONE side of the frame at a time, and apply adhesive to the intersecting areas between the frame and covering material using a small disposable artist brush and place a plastic separator between the two (2) areas until they have dried to a light tack (ref: photo22) and then remove the separator and press the cover onto the end ring to achieve a tight bond. Go slowly at this point to avoid misplacement of the end ring and glue ONE side of the end ring at a time to allow for easy correction of alignment .

        After the entire end ring is glued in position and has sufficient time to dry, gently slide the entire cover off of the form taking care to not dislodge the end ring from its position (ref: photo23). Clamp the end of the bellows that has the end ring installed, onto the edge of a table or board so that the frame projects upward from the clamping surface at a 90-degree angle. The bellows will now resemble an open ended square tube with a square end ring glued in position at one end. Follow the procedure that was utilized to install the previous end ring ensuring that the end ring that is now being installed is set EVENLY at the remaining open end of the bellows and sets flat on one edge upon the clamping surface that retains the entire bellows assembly.(ref: photo24)


Creasing and Folding

        Before the creasing and folding is performed on the bellows, remove all excess adhesive from areas that will contact each other by gently rubbing the exposed glue with your finger to ball up the adhesive. This is necessary because contact adhesive will adhere to itself even after it is totally dry. If the adhesive cannot be removed you can apply a small amount of body powder or cornstarch on the area and then remove excess powder with a light puff of air.

        Start the creasing on the bellows panels that have the rectangular stiffeners applied. Begin by placing the fingers of one hand inside the bellows and then press the area between the first and second stiffener INWARD into the gap formed by the thumb and forefinger of the hand inserted into the open end of the bellows. Work carefully from one corner to the other until the fold is fairly deep, then turn the bellows over 180-degrees to expose the opposite side and repeat the above procedure. Now repeat this procedure on the opposite end of the bellows.

        As you crease the panel you will notice a tendency for the panels that have the tapered stiffeners applied to bulge out. Gently press outward on the area of these panels that is INLINE with the previously creased fold on the adjacent panel and crease it between the thumb and forefinger of the hand that is outside the bellows so that it rises OUTWARD. Repeat this procedure on the opposite panel and then on the opposite end of the bellows. The bellows has at this point begun to take on its characteristic shape and it is now apparent why keeping an even number of stiffeners between end rings is ESSENTIAL! You always incorporate two (2) stiffeners into every fold and you cannot end the pattern with 1/2 of a fold! Now complete the creasing and folding of the remaining sets being sure to copy the adjacent folds exactly.(ref: photo25)

        After all folds are performed place the bellows, ring down, onto a flat surface and apply pressure to the end to fully collapse it into a neatly layered stack. Check the sides of the stack as you compress it for any misalignment and correct it with gentle pressure. At its fully collapsed length the end rings should be lined up squarely over one another with no twist. If there are more than a few degrees of twist between them one of the end rings will have to be removed and refitted to achieve proper alignment. Place a weight on the stack that is heavy enough to keep it compressed and allow drying for several hours before carefully extending your new bellows into the light of DAY!



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