Renner shanks and flanges are “dimensionally correct” ensuring that the original action dimensions and relationships are maintained when the part is installed. Recent entries into our business have borrowed this term to describe dimensions, that are not authentic, and will fundamentally change the original design. Extreme examples include moving the hammer shank knuckle to a distance of 18mm from the center pin in order to reduce action weight at the front of the key. Reducing the leverage ratio at the hammer shank will certainly result in making the key easier to press down, as piano makers have known for 300 years. Doing so, however will have detrimental consequences in other areas of the mechanism including:
- A reduced amount of available hammer blow distance with the same touch depth
- Greater touch depth with the same hammer blow distance
- Slower acceleration of the hammer towards the string, resulting in lower contact velocity
- Greater hammer weight required to reach equivalent ability to displace the struck string
One of the little known secrets of every Renner action part is the use of a special wood called Weissbuche which is naturally air-dried and aged over several years. The use of only the finest quality materials, including the famous Renner bushing cloth, are among the many reasons why genuine Renner parts are preferred by the world’s finest quality piano makers and rebuilders.