Loose lock knob for rack - how tight.

luckas · Post by **luckas** » 24 Jul 2005, 13:32

Hi,

In seeking the source of a vibration in my Yamaha U1, I noticed that one of the two hand lock knobs that hold the rack in place (apologies for my obvious lack of technical knowledge) was quite loose. The other is very tight. In addition, the sloted mounting which fits onto the threaded rod was somewhat ajar from its fully seated position (5mm or so). I've tightened the knob in question which has reseated the 'rack'.
Is there any science to this particular mechanism ? It looks as if the two knobs are supposed to be hand tight, and do not represent an 'adjustable' mechanism, but I don't want to put any strain on the metal frame (the thing I'm calling a rack) where none should be.

I don't want to call a technician unecessarily if it is a simple issue. Any advice gratefully received.

Paul

Post by **Barrie Heaton** » 24 Jul 2005, 13:49

I am not sure what you mean by the term “Rack” please describe

Barrie,

Post by **Gill the Piano** » 24 Jul 2005, 18:11

Do you mean the bolts which hold the action (engine!) against the strings inside? If so, the action should be pushed as close to the strings as possible (so the action standards are close to the frame) and the bolts tightened hand tight. You can't overtighten them, but don't make the tuners work too hard for their living!

luckas · Post by **luckas** » 25 Jul 2005, 01:32

Barrie / Gill,

Thanks for your replies - and sorry for my lack of correct terminology. Yes, the "engine" - all the hammers, action etc. which appears to come out of the piano as one unit and is held in place by a lock knob at each end. One of mine (the right one) was loose, with a result it was somewhat ajar of the fully seated position. I've assumed, and I think Gill has confirmed, that it just needs to be tightened back into place.

Where can I find a nice exploded view diagram of a piano with all of the insides labelled ?

Paul

Post by **Barrie Heaton** » 25 Jul 2005, 17:38

luckas wrote:Barrie / Gill,
Where can I find a nice exploded view diagram of a piano with all of the insides labelled ?

Paul

You have
http://www.fletcher-newman.co.uk/flash/index.html

Barrie,

Post by **Gill the Piano** » 25 Jul 2005, 18:09

There are a couple of 'coffee table' tomes with nice diagrams in; The Book of the Piano (ed. Dominic Gill); Piano by Jeremy Siepman, and Piano by David Crombie. Your local library will probably have it or get it for you.
Barrie may know about websites; I think the American Piano Technician's Guild had one diagram on it if I remember rightly...but it being a Monday and my having tuned three pianos, I probably don't...

!