This arrangement is sketched in Fig. 38. The roller-board, g, is above the key-tails, which act by stickers on arms brought through openings in the board. The opposite arms, h h, in front as usual, act on the pull-downs by trackers. We have adopted this plan in a very small organ, and under the necessity of economising space as much as possible, with complete success, although every pallet had its roller, the fan-frame being entirely absent.
Rollers are often made of iron, especially in the case of pedal movements, where space is not abundant. It will easily be understood that iron tubes of small calibre, plugged with wood at the ends to receive the pivots, and having iron arms screwed into drilled holes, would present no serious difficulties to the workman, and might be arranged upon a board little more than half the size of that required by a set of rollers in wood.
We must not close this chapter without explaining that the plantations of pipes sketched or indicated in Figs. 8 and 9 may be contrived without grooving by an arrangement involving no serious difficulty or complication.
Fig. 39.
In Fig. 39, a b c is a sound-board shown in section, divided internally into two unequal parts by a longitudinal bar at b. The front part, b c, nearest to the player, has 42 channels, and carries all the pipes from Tenor C upwards. The hinder part has 12 channels only, and supplies the bass octave. These two separate internal divisions will have their pallets and springs as usual, and a single wind-chest may include both sets of pallets, or two wind-chests may be united by a short trunk, or separate trunks may be fitted to each, at the discretion and convenience of the builder. We have now only to adapt a set of backfalls in a fan-frame to the front pallets, and a roller-board acting on twelve parallel backfalls to the pallets of the bass octave, and we have a very compact and sightly arrangement of pipes without a single groove, every pipe standing on its wind. If the back pipes were these—Stopped Diapason, Bass, 4-feet tone, and open Flute, wood, 4 feet; while the front pipes comprised a Dulciana, Stopped Diapason, and Principal, or some equivalent—this little instrument might be entirely satisfactory in all respects.
We may add that this arrangement of a double sound-board and wind-chest has been successfully applied by the writer to an organ with two manuals. The sound-board was about 5 feet 3 inches in length. The front division had 84 channels, viz. 42 for each of the two manuals from Tenor C to top F; the hinder division had 24 channels, viz. 12 for each manual bass octave. There were practically eight stops, two of them grooved to each other in the bass. Of this grooving, when there are two manuals, we shall have something to say in a subsequent page. It is not quite so simple an affair as the grooving already described.
When the key-board is in its place, the stickers adjusted, and the keys levelled by attention to the buttons on the tapped pull-downs, a heavy damper or "thumping-board" should be laid across the key-board. In modern organs this is generally a solid bar of lead, about ½ inch thick, and about 1½ inch in width; it is covered with baize on its under side, and a guide-pin, moving loosely in a little vertical groove cut in the key-frame at each end, keeps it in position. Our damper may be of oak or mahogany, very straight and true, and loaded with lead, run when fluid into cavities made with a large centre-bit. The damper, lying upon the keys, and supported by them, helps to keep them level, and by receiving the blow or shock of each key, as the finger leaves it, it prevents a tapping noise which might be heard if the rising keys were stopped only by the board of the key-frame.
The descent or fall of the keys when pressed by the fingers should not exceed ⅓ inch.