Ceiling mini-rail system
Introduction: ceiling rail systems for photographic studios
Ceiling rail systems are a standard fixture in photographic studios. A ceiling rail system allows the unrestricted positioning of light sources (typically, studio flash units or continuous light sources) in three dimensions without cluttering the floor. The simplest rail system typically consists of two parallel rails attached at fixed positions on the ceiling, and a third, mobile rail connected to the fixed rail with a set of double rollers.
The above figure shows a typical double roller used to connect a fixed rail (topmost) to a moving rail (bottom). Double rollers allow a considerable freedom in the placement of the mobile rail. They are composed of a pair of single rollers connected by a rotating bolt.
The mobile rail, in the simplest case, has an H-profile with the two sides of the H placed topmost and bottom, respectively (above).
Most rails designed for photography studios, however, have a more complex profile similar to the one above. This rail accept a top and a bottom roller. For stiffness reasons, the same type of rail is normally used also for the fixed ceiling rails, which use no top roller.
A simple roller rides along the bottom of the mobile rail and connects to further accessories. In the simplest case, this type of roller carries a "baby" stud with a diameter of 5/8", like in the above picture. A light source can be directly connected to the stud, or via a rigid pipe of fixed length (both alternatives prevent the height of the source above the floor to be adjusted) or via a system that allows the height to be changed. Such a system may include a telescopic rod of variable length, similar in construction to a monopod, or a pantograph.
A spring-loaded pantograph is typically used to regulate the height of light source across a broadly variable height above the floor. The spring is dimensioned to carry a specific range of weight. Sometimes, the spring can be tightened or loosened to adapt to the weight of a light source. Professional pantographs may be equipped with interchangeable springs to accept a broad range of loads. The above pantograph is a simple and relatively cheap Walimex model designed to carry weights from 0 to 6 kg. It extends from 30 to 200 cm.
At least in principle, a cable and pulley system could also be used to change the hight of a light source. I have never seen this used in practice, because it involves a high risk of uncontrolled swinging of the load. An articulated arm can also be used to connect a light source to a roller and allow a change in height, but this solution may force the roller to assume a skewed or inclined orientation of the roller on the rail (which should be avoided for obvious reasons).
A mini-rail system
I don't do ordinary studio photography, Instead, I am doing almost exclusively small-subject photography (which I like to define as ranging from close-up photography through macrophotography and into photomacrography). In close-up photography, the entire photographic studio has the approximate area of a tabletop. Therefore, my purpose was not of building an ordinary rail system for a full-size photographic studio. Instead, I needed a much smaller system attached to a low ceiling above a work table. In practice, the purpose of this system is similar to the one of a traditional rail system (i.e., allowing an unrestricted placement of light sources without using the table surface), but its size and range of travel is much smaller.
My first attempt used an aluminium angle profile attached to the system by two L-shaped iron brackets. This is not a true rail, but it allows a pair of Manfrotto Super Clamps and Manfrotto Friction Arms to carry a modest load at a height variable within a range of approximately half a meter. The arms also allow a small range of lateral adjustment, but cannot carry heavy loads while locked in an oblique, off-center position with respect to their attachment to the ceiling. Multiple profiles could be attached to the ceiling, but the arm must be detached and reattached at a different position whenever the light source needs to move around. This is when I realized that a rail system was becoming unavoidable.
A full-size rail system would be overkill, let alone the facts that this system would not fit on the ceiling of my small studio/lab/office, and that I did not find a full-size rail system that could be delivered to my location for a reasonable expense. I did find the relatively cheap Walimex components (rollers and pantographs), but I had to resort to my own devices for the rails. Suitable iron T-profile is available, but unnecessarily heavy (especially since it would have to be attached to a reasonably solid, but not extremely so, wood ceiling). Instead, I decided to use aluminium T-profile. The types I found were a bit too thin to be reassuring, but aluminium flat profiles could be used as reinforcements at critical positions.
Two 90 cm rails were the first to be attached to the ceiling. The bottom of each rail was strengthened with aluminium flats of the same width (30 mm). Since this portion of the ceiling is slightly inclined, the attachments are asymmetric in order to make the rails horizontal (which is necessary because I was building a rail system, not a roller coaster). The placement of these rails was constrained by the position of underlying wood ceiling studs.
I added one more fixed rail perpendicular to the first set and located as close as possible to the ceiling. Its purpose is to carry equipment even higher than the mobile rail. Since the ceiling is quite low - I can almost touch it - even a difference of 10 cm is significant, especially with large flash units and a large diffusing cube placed atop the table. Of course, the placement of the lower rails does somewhat interfere with positioning any equipment attached to the high rail, but this additional rail is nonetheless better than nothing.
With a higher ceiling, two fixed rails and one or two mobile rails are probably all that is needed. If the ceiling cannot carry loads, or if the position of the work table may change in the future, in principle it is possible to build a frame of wood studs or metal profiles surrounding the table and supporting the fixed rails. This solution might even be more acceptable to your better half than a fixed system attached to the ceiling, because it does not involve "permanent" and "ugly" modifications of the room.
For a while, I contemplated an even more minimalist rail system, with only one fixed rail and one end of the mobile rail pivoting around an axle instead of riding along a second rail. This restricts the surface accessible to light sources riding on the mobile arm, but not by much, and cuts the amount of needed materials. The idea is yours to try if you are interested.
The mobile rail was built with two T profiles joined together by 3 mm thick flats. I did not reinforce the top and bottom of the mobile rail since it seemed quite stiff enough. It has now been in use for a few years, with a Bowens 1500 Pro hanging permanently from it via a pantograph, and shows no deformation or wear. The short angle profiles at either end of the rail are end stops for the rollers. Note that the mobile rail can ride perpendicular to the fixed rails, or oblique with respect to them. This allows some freedom of placement for a second light source riding on the same mobile rail. This may avoid the need of a second, independent mobile rail. The latter, however, would provide a higher versatility.