A measuring device for measuring the uplift and downweight of a piano- or grand action.
In the picture below is shown the measuring device.
An axis A1 is by means of two ball bearings connected to support (1). On the axis a A1 are fitted two weights W1 and W2.The weight W2 is for adjustment of the measuring device and must be locked after the adjustment procedure. By shifting the weight W1, the pressure, which the ball bearing (2) exercises on the piano key, can be varied. On the scale above the weight W1 can be read the amount of pressure. The ball bearing (2) is mounted to bring the friction between the measuring device and the key to a minimum. To achieve a scale calibration where a displacement of the weight W1 of 1 mm. corresponds with a change of 1 gram of the pressure on the key, the weight of W1 in grams must equal the distance D1 in mm.
Place the end with ball bearing (2) on a scale and shift the weight in such a way that the mark of W1 is opposite the mark of 20 gr. Shift the weight W2 in such a way that on the scale 20 gram is read. After that lock weight W2.
The device is exceptional useful for measuring the up- and down-weight of piano- and grand actions. The friction can than be calculated with the following formula:
In this formula is DW the down-weight in grams, UL the uplift in grams en FR the friction in grams.