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There are several types of cranks used in point rodding systems with 90 degree Standard Cranks, Accomodating Cranks and Adjustable Cranks being the most commonly used in point rodding runs in Britain. The standard variety is fortunately the easiest to make as they are required in larger numbers than any other type. Special accommodating cranks with curved arms will be needed where the rodding splits outside the signalbox and space is limited. The curved arms allow the cranks to be placed closer together than is possible with standard or raised cranks. Adjustable cranks are used at the end of a rodding run to provide a means of matching control rod travel with the mechanism to be controlled, these are fitted at the end of the rodding run ensuring that adjustments do not upset the balance of the rodding run.

The crank bases are made from short lengths of brass strip. A strip of brass has sets of four holes marked out for each base plate with enough space between each plate to allow for losses during cutting without leaving too much to file down. The holes are then drilled, this is easily achieved by clamping a steel rule or parallel block to a small drill press, This guide is set to allign the drill with the holes on one side of the brass strip, the strip is then clamped down and the hole drilled, the clamp is released, the strip is moved along to the next mark, re-clamped and drilled. This proceedure is repeated until all the marked holes are drilled along one side of the brass strip. The strip is then turned round, checking the allignment of the marks at the other edge of the strip before clamping and drilling in the same way as the first side. Once the holes are all drilled, the pivot pin has to be fixed centrally onto each base plate. This can be done with epoxy resin but due to the fine nature of the parts and the relatively high stresses on this component a soldered joint is preferred for strength. On smaller scale models a stronger joint is needed as a simple butt joint is not likely to last. A fifth hole may be drilled through the center of the baseplate, this enables a long pivot pin to be fitted through the hole, the extra length of pin below the base plate can be used to make a strong joint with solder or epoxy resin. This strong but ugly joint will be hidden beneath the plate giving a much improved look to the visible side of the plate with only a very small amount of solder or resin to fill round the base of the pivot pin. The bases must be fitted in the correct orientation as shown above, this ensures the stresses from the rodding are transmitted to the ground whilst retaining stability of the crank base and pivot pin which is crucial to safe, effective operation of the rodding. Crank bases may be bolted down with no fewer than two bolts, if using only two bolts these must be fitted diagonally opposite each other, IE; one at top left, other at bottom right. In model form I would choose to fit the baseplates (made with long pivot pin method) into holes in the baseboard with epoxy resin. In larger scales (7mm O gauge or larger) I would use flat baseplates with pivot pin butt jointed to top face, the flat underside would be fixed to the baseboard with epoxy resin using large track pins or small brass screws through the fixing bolt holes. Proper screw-bolts could be used on larger scales if you wanted your model to be closer to prototype practice.

I have used various thicknesses of brass strip to make 90 degree standard and raised cranks. The brass strip has 0.85 and 0.55mm holes drilled in groups of three in an `L' shape. It is then simply a case of marking out the basic crank arm shape and removing the metal that does not look like a crank! :-) (grin). This is probably easier to do than to describe, I file down the brass roughly to the shape of the crank with a file, then carefully bring the crank down to its final size with fine needle files and a 600 grit sanding block.

The cranks I have made so far on Stoneybridge West are not 2mm scale models as the minimum size of the cranks is limited by the diameter of the brass rodding available. The rodding runs are made from 0.8mm and 0.5mm brass rod which work out at approximately 5in and 3in respectively in 2mm scale. Due to these material limitations the minimum dimentions of rodding and cranks are actually closer to 4mm scale. Sourcing finer rodding would allow the cranks to be made smaller, the physical strength of the rodding material would then be the limitation.

I am researching an alternative design solution that uses single strands of 0.25mm wire and 2mm scale etched brass 90 degree standard cranks (2mm scale versions of the 4mm scale D&S etches). Each signal wire or rodding run will be held in constant tension with a spring acting on one end of the run. In the case of a signal operated by wire from the signalbox. The signal wire will be held in constant tension by a spring, the spring can be fitted at either end of the run, where numerous wire and rodding runs arrive at a busy signalbox it is best to fit the springs at the signal or point end of the run making the mechanics below the signalbox less cluttered. With the signal in the ON position the wire will be held in a slight tension by the spring, The signal is cleared by pulling the signal wire which will pull the signal arm to the OFF position. The signal will drop back to the ON position as soon as the pull on the wire is released. All that is then required is a form of mechanical latch or brake mechanism to allow the signal to be held in the OFF position without having to hold it there manually, this is easily accomplished by using a lever frame that allows the levers to be held in Normal or Reversed positions. Most working model leverframes have a small notch cut on one side of each lever slot to allow the lever to be shifted into the cutaway and effectively locked in normal or reversed positions whilst holding a cable run in tension. (or a rodding run in tension or compression).