brooke.benfield wrote:The only part of a crescendo/swell pedal that needs to conduct electricity is the potentiometer. All the rest of the unit can be of any suitable material.
Just so, though the friction strip at the bottom, and to a lesser extent the potentiometer linkage from the top corner of the pedal, will at times be under compression as well as tension.
The drawing above gives some more detail, as well as a sense of scale.
The only important mechanical part is the hinge (in black on the drawing) which should be of really good quality. I happened to have one lying about which, I think, was intended for use on a fire door. It is very solidly made, smooth in operation, and has very little (if any) 'play' in its movement.
The potentiometer is a 10k Ohms linear, with an overall length of 60mm. Not all the travel is used, but I wouldn't use a shorter one unless absolutely necessary since the geometry of the linkage might become rather difficult to determine.
The 'buffers' where the pedal hits the frame are self-adhesive felt pads, and there are also two providing friction against the strip at the bottom. The geometry of the arrangement isn't critical, I seem to recall trying to find out if there were RCO/AGO recommendations for the limits of the pedal travel but couldn't find any. On mine the pedal varies from between 30 (closed) and 60 (open) degrees from the vertical. The width of the pedal is about 12 cm (4 1/2 inches) which might be a bit narrow I suppose.
The whole assembly is bolted to the back edge of the pedal board through the bottom plate.
Good luck,
Nick