to the installation of back checks

[themaximillyan]

https://afmforum.ru/static.php?p=klopov22
В.А. Клопов.
Переходим к установке фенгеров (back chek). Желательно сначала проверить отсутствие засаленности в зоне контакта фенгеров с контрфенгерами (catcher), если она есть - почистить полоской относительно крупнозернистой шкурки (примерно 180) кожу контрфенгера и, возможно, фильц фенгера. При собственно регулировке здесь важны два момента. Во-первых, для надежности захвата контрфенгера фенгером необходимо чтобы их соприкасающиеся плоскости в стандартном положении захвата - 10-15 мм от струн до вершины головки молотка — были параллельными. Параллельность достигается креповкой проволоки фенгера вверху, у его головки. Но такая креповка неизбежно изменит дистанцию подхвата. Дистанция регулируется креповкой проволоки внизу, у самого ее основания. Но эта операция нарушит параллельность соприкасающихся плоскостей. Таким образом, правильная регулировка должна производиться методом последовательного приближения к идеалу с попеременным осторожным подгибанием проволоки вверху и внизу. В известной мере это аналогично ранее описанной креповке демпферов при установке атаки.

Параллельность плоскостей фенгера и контрфенгера обеспечивает сразу три важных момента в подхвате молотков: надежную их остановку, стабильность величины дистанции подхвата и минимальный износ контактирующих поверхностей. Поэтому есть смысл установить эту параллельность как можно более тщательно.

Последнее замечание по фенгерам. В тех случаях, когда следующее обслуживание данного пианино ожидается скоро, по желанию его владельца можно установить дистанцию подхвата на фенгеры немного короче стандартных 15 мм - это обеспечит чуть более резвую репетицию и более надежное отсутствие «дреббеля». Однако сокращать эту дистанцию до величины менее 10 мм уже не стоит из-за риска прижатия молотков фенгерами к струнам при тихой игре.

V.A. Klopov.

We move on to the installation of back checks. It is advisable to first check for any greasiness in the contact area of the back checks with the catchers. If there is any, clean the leather of the catcher with a strip of relatively coarse sandpaper (approximately 180 grit) and possibly the felt of the back check.
In the actual adjustment, two important points must be considered. First, for the reliable capture of the catcher by the back check, it is necessary that their contacting planes in the standard capture position—10-15 mm from the strings to the top of the hammer head—are parallel. This parallelism is achieved by securing the wire of the back check at the top, near its head. However, such securing will inevitably change the pickup distance. The distance is adjusted by securing the wire at the bottom, at its base. But this operation will disrupt the parallelism of the contacting planes. Thus, the correct adjustment should be made by a method of sequentially approaching the ideal, with alternating careful bending of the wire at the top and bottom. To some extent, this is analogous to the previously described securing of dampers during attack installation.
The parallelism of the planes of the back check and the catcher ensures three important aspects in the pickup of hammers: reliable stopping, stability of the pickup distance, and minimal wear of the contacting surfaces. Therefore, it makes sense to establish this parallelism as carefully as possible.
A final note on back checks. In cases where the next servicing of this piano is expected soon, at the owner's request, the pickup distance on the back checks can be set slightly shorter than the standard 15 mm—this will provide a slightly more lively repetition and a more reliable absence of "bobbling." However, reducing this distance to less than 10 mm is not advisable due to the risk of the hammers being pressed against the strings by the back checks during quiet playing.

'Methodology of Vladimir Sukhopyatkin'. By bending 'the backcheck wire' of an upright piano.

The purpose of regulating the double strike of the upright piano hammer on the string is to understand how the upright piano mechanism (the action) works. When a key is pressed, it activates a rod with 'the capstan' at the end, which contacts 'the whippen'. 'The whippen' has 'the jack', a movable stick on a spring that activates 'the hammer'. The hammer has a part called 'the catcher', and the whippen has a part called 'the backcheck'. The ability to increase the number of strikes the hammer makes on the string depends on how 'the catcher and backcheck are adjusted relative to each other.
In the video, Mr. Vladimir Sukhopyatkin demonstrates how he achieves an increase in these strikes on the string by bending 'the backcheck wire'. When the mechanism is not functioning correctly, 'the jack' slips out from under the hammer after striking the string, causing 'the catcher' of the hammer to fall deeply onto 'the backcheck'. This prevents a double repetition because 'the jack' has slipped.
Sukhopyatkin adjusted the mechanism so that 'the backcheck' immediately "catches" the balance, allowing the jack to repeatedly activate move the hammer. The operation is simple: you push the backcheck wire (lightly bend off it) away from you, creating the possibility of a double repetition.
However, it is important to note that if the author demonstrates bending 'the backcheck wire' on a simple piano, he is "forcing" the jack to rest against in 'the hammer butt' immediately after the first strike of the hammer on the string. This is the essence of Sukhopyatkin's methodology: the jack always remains on 'the hammer butt', without slipping off.
One limitation is that the force of the hammer's strike on the strings is restricted because the key is partially depressed, allowing for double repetition only at a softer sound level (p or mf). Additionally, to follow this methodology, it is advisable to add extra weight to 'the hammer head', which can improve results by ensuring a sharper return to the hammer to 'the hammer rail rest'. However, this also requires precise regulation of the mechanism.

Summary: The main difference in Mr. Klopov's adjustment method is the emphasis on maintaining the 10-15 mm distance for reliable capture of the catcher by the fenger, ensuring that their contacting planes are parallel. In contrast, Mr. Sukhopiatkin's[ Invalid YouTube link ] approach disregards this measurement in favor of achieving quicker hammer repetitions.[/center]