Basic Action Design/Performance Question

[John Delacour]

At 23:26 25/09/01 +1000, Ron Overs wrote:


>> The only significant improvement in the geometry of the intermediate lever was made by Herrburger of Paris about 1900 and was adopted by very few makers.
>
>Where is there an illustration of this action? Does anybody have a jpeg to post to the list? JD?

I thought from a previous posting you were familiar with it.  I'll get a gif done in the next day or two.  

>As long as the repetition lever center is located in the correct position (to minimise friction - and it isn't in the Renner/Steinway style of action), it matters little which wood is used.

                 
               J

         L R    C
             H

In the Herrburger lever JL is 70, LC is 69, LR is 9.5 and R is almost in line with LC.  JC is 50.  LH is 47, CH is 30.  The jack tender makes contact 26 mm from C, 4 mm above the line LC produced.


>>Reduced to essentials, the action consists of nothing but points, each of which consists of contacting surfaces.
>
>Sure, but in the case of the majority of contemporary actions, little attention has been given to friction control. The roller/knuckle contact scrubs badly since the contact is around 8 mm below the line of centers at the rest position.

Yes.  The actual figure will vary according to the rest angle of LC, but supposing it is 8, then reducing LC to 75, as you have done, will diminish this figure and reducing it to 69 as Herrburger did will diminish it further and other advantages also ensue.

>>and it in these two respects that makers and/or grand finishers . .
>
>. . . .  generally give little or no consideration to good design. It's 'carry on marketing' as usual, while 'ignorance is bliss'.

Of course!  Broadwood was even better at it!

>We've replaced split tubular action rails with milled rails of solid brass, tapped for machine screws. It seems to work quite well, but its a lot of trouble. At least it won't split open in response to moisture exposure.

I have used on a prototype a 12 mm stainless square hollow section, loosely dowelled with virtually any wood (maple, beech, or walnut) and with 6 mm o/d "riv-nuts" (4mm thread) pressed in from the bottom.  Even if some ham-fisted repairer should strip a thread, the riv-nut can be pushed out and replaced.  

>For those who played our piano in Reno (with a new action design JD),...

Yep, gottit :-)

> ...we are getting very favourable reviews with our 225 piano no. 003, on trial at the Sydney Conservatorium of Music this week (we're delighted that it is being tested against a Yamaha CF3 and a Steinway D).

That's the only way. Immediate comparison in the same environment is essential.  I am about to start work building my "new" action to a Steinway D in the old concert hall here where there are two Model Ds cheek by jowl, one of them supposedly kept in concert condition.  This is a relatively expensive step in the process of building a whole piano using this action, but I consider it an important step since it will prove the idea conclusively, not least to myself -- you know how fond and blinkered we can become if we're not careful!  I shall have to be prepared for some yet unseen and insuperable flaw in the design and luckily I have the old Herrburger action above to fall back on.  In fact, until quite recently this was going to be the basis of the action, but more radical ideas suggested themselves.

JD