The angle of a keyboard

[the romantic]

Hello,

If you place a marble or spirit level onto the keys of a piano, sometimes the surface is perfectly flat, often the marble rolls back towards the strings, and rarely it rolls off the keys towards the player.

Is there a standard for the angle of the keyboard?  Is it supposed to have a small incline towards the performer for example?  Is there a reason for this?

Thanks for any info!

[jimbo320]

As far as I know the level of the piano surface, or case, is not that important but having level keys are. The marble should not roll away or towards the player when on the keyboard...

[richard black]

Yes, I've noticed that the keys often slope very gently away from the player. No idea what the arguments are for and against, and I can't honestly say I've ever been aware of it while playing!

[silverwoodpianos]

The key set is levelled horizontally at the front edge so that each key travels the same amount of distance down and up.

In a properly regulated grand action when the key lever is at full stroke(down as if played) the key should show level with a spirit level as should the hammer stem of the corresponding key. Therefore it would be impossible for the key set to be level front to back when at rest.

In this photo album for example one can see that the geometry of this particular action is not perfect. Some of this is due to the fact that this instrument still retains the original key set but has had a modern double escapement action installed a long time back. If I changed the knuckles out for new ones of a larger diameter the stroke geometry would be correctable.

Photos #21 & 22
 
https://picasaweb.google.com/silverwoodpianos/CollardCollard7ftGrand116091829#

[the romantic]

Thanks a lot for that explanation Dan - the mystery is solved!

Now that you mention it, it makes sense that the keys should be level when fully depressed, which obviously explains why they must be tilted away from the performer when they are untouched.

Thanks again!

[jimbo320]

Wow! Good full explanation there Silverwood. I am always happy to learn things. That's probably why I come here a lot...

Jimbo

[silverwoodpianos]

Well, thanks for the replies, but not quite the whole story on key set angles. I could get into a long technical discussion about action/keyboard geometry, but that would make most readers glaze over in less than a few sentences.

Think if the key as a lever; one has to have a certain amount of leverage to drive the weight of the action up to the strings (or forward in an upright.) So the key lever acts much like a see-saw in a playground.

If the see-saw has one person too close to the center pivot then the other person on the other side has more leverage right? The ratio of a grand key set is 2:1(or is it 3:1? Maybe that is the upright…..I can never remember all this stuff any longer……… I just do it…) I would have to look that up in my research library to be sure of the ratios…

So if the pivot point is off-set to one side of the length, then the key will not sit level at rest, correct? The geometry calculations are for the key to be level at full stroke……and the action at full strike…..the grand action is almost perfect in its motion….almost …..