Geoffrey Crabb Posted April 9, 2007 Share Posted April 9, 2007 Recent and ongoing discussion about one piece reed plates in other threads has prompted me to comment about my own venture into their use. Some thirty years ago, with a view to producing a cheaper instrument using techniques that were less time consuming in the making, one thought was about the use of a single plate to which the reed tongues were attached instead of the usual separate reed assemblies. Against advice from my father who, in his usual words, exclaimed “it’s all been tried before and if it was a success it would be in use”. However, I was given time to carry out some practical experiments and thought I would share the results. I do not claim any originality for the design etc. but if any one does make a fortune from this information, please remember me. I have dragged out a model that I constructed at the time and have included the following pictures. The single reed plate The reed plate in situ in the bellows frame The action/chamber unit upper side The action/chamber unit under side The action/chamber unit in situ The end box in place It will be seen that this consists of the right end of a 40 key English Treble, something that I thought would be suitable as a trial and that would produce a result. The model also included some change in construction of the action pivots (which I have described although not strictly topic) and radical change from the usual traditional construction. It will also be seen that the usual fretwork has been replaced by a machined simple design. Basically each end of an instrument made to this design would consist of four units, the bellows frame, the reed plate, an action/chamber unit and an end box. The Bellows Frame is formed with a ledge on its inner sides to support the reed plate. This ledge is faced on its upper surface with chamois to provide an airtight seal. The Reed Plate is shaped to closely fit into the bellows frame and rest on the formed ledge. With possible eventual machining techniques in mind, the reed slots are arranged radially. On this model, the slots were hand pierced and finish filed. It will also be seen that the tongues are fixed using standard screwed blocks (clamps). The Action/Chamber Unit. This again is shaped to sit closely and partially within the bellows frame and in contact with the reed plate. The unit has a 6mm base board to the upper face of which is installed the action and to the under face, the divisions or chambers. The outer ends of the chambers are closed with a peripheral rail. All surfaces that contact the reed plate are chamois covered to provide a seal. Note. The action incorporates a pivot post (upright) that passes through a hole in a flattened portion of each round lever. This flattened area is orientated at 90 degrees to that normally seen with riveted actions. A pivot post is round in section, spread at it’s upper end to retain and provide a pivot for the lever and threaded at its lower end to allow it to be screwed into a pilot hole in the action unit baseboard. This unit does not require a separate desk (disk) due to the thickness of this baseboard. Normal springs are fitted which also keep the lever up against the spread portion of the upright. Because the upright is round, it is imperative that the levers are kept absolutely straight in all aspects to avoid any tilting. The use of the threaded upright allows the key height to be adjusted by screwing the upright further in or out of the baseboard avoiding any requirement to bend the levers. It may be noticed that no pills (beads) are used on the ends of the levers, the pads being glued to the flattened ends. The End Box. Consisting of an end plate and six attached sides, it is drilled to support the upper ends of the keys (buttons) ensuring the alignment of the action levers. Blocks located around the inner side edges are made to ensure that the action/chamber unit and the reed plate are firmly held against the bellows frame ledge providing air tightness between the relevant parts. The end box is secured to the bellows frame by six round head wood screws. The model was fitted with a thumb strap only and the whole assembly fitted to a test rig comprising a bellows for test purposes.(See below) The model did produce a working result and whilst the single reed plate does reduce the need for the repetitive work of producing separate reed frames and the fixing of these onto a reed pan, the biggest problem encountered was in the fine tuning both in the physical execution and in the time taken to achieve acceptable accuracy. The reed tongues fixed to the plate prevent the application of a file correctly due to obstruction by any adjacent tongue fixings resulting in the reed tongues having to be ‘scratch’ tuned, personally not preferred. Whilst I can see that production of the raw reed plate could be easily done now using, what I am assured, modern controlled cutting techniques and the carcass construction fairly simple, I believe that tongue production, fitting and tuning are major obstacles to be overcome. Conclusion. The tuning issues encountered and the pressure of fulfilling orders for conventional instruments at that time prevented me from pursuing this venture further, in other words it was easier to make a conventional instrument. An issue that was raised elsewhere was how the reeds were sounded for tuning purposes. By fixing the bellows frame temporarily to the upper surface of a perforated board, attached to overhang the bench, and a bellows which can be operated by hand beneath , the reed plate, action unit and end box can be installed and held in place by one hand whilst a button is operated, the other hand operating the bellows to sound the appropriate reed. One final word I would make to any considering this method of construction is the use of chamois as a sealing material. Upon opening the model after thirty years I found that the leather had reacted with the duralium reed plate causing some corrosion of the surface that may be evident in the pictures. Geoff Quote Link to comment Share on other sites More sharing options...
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