20 Dec 2015 20:47
Bent metal tabs offer perhaps the ultimate in versatility, effectiveness, and economy for holding cameras straight on a stereo rig-even a simple Z-bar. No need to find a camera with an anti-rotation pin hole, deal with such cameras' typically larger size, painstakingly install a pin such as a "dog tip" setscrew into a rig, or overstress the tripod hole trying to snug a camera without one against the slightest twisting.
Just make the Z-bar (or other support) wide enough to extend a quarter-inch or so forward of the flat and mostly-flat bottom of the camera, and bend little tabs up to bear against the two sides of the front of the camera to prevent twisting. A silicone skin or rubber padding can take up small imprecisions in fit and protect the cameras' surface finish - plan for its thickness as you design. As usual, make the bar's main bends before you drill, notch, or otherwise weaken points along its length which could misdirect the bending force's effect. Choose the bar's width and place tripod-screw holes and other features with spare material for the front tabs in mind. (You could also put tabs on the back, but material extending behind the cameras is more likely to cause discomfort and scratch bags, glasses or even your face in use.)
Form the tabs as follows. Cut a line along the side of each tab to a depth about where the bend is to begin. A good tab width is…however wide your compound locking pliers to hold and bend it with is (or a little narrower, but the pliers shouldn't catch on the outsides of the notches.) Simply clamp the rest of the bar in a vise and swing the pliers to form the bend. Don't worry about bending the tab to a completely right angle, especially if the camera has a rounded lower edge or will be cushioned against the bar: super-sharp bends in cold metal often break.
For best results, practice and measure the relation of the notch depth to the point at which the bend begins, and the point at which the tab assumes its greatest angle, on scrap material before proceeding with your carefully mostly-made bar. Basic hot-rolled steel works great for tabbed bars: it's about as stiff as other steel until it begins to bend, it can take plenty of stress from normal camera handling before bending to the point at which it'll stay bent, and when it does bend it bends fairly easily and far without breaking..