S & S 'A' parts, geometry -- shanks and flanges

[Avery Todd]

Hi Ric,

   What's the matter? Have a slow day today? :-) Kind of interesting, though.

Regards,
Avery

>List Newton
>	I came up with 1/7 ratio for rise of knuckle to rise of hammer.
>	So.....Increasing the knuckle diameter by .05 " (.1.25mm) will cause an
>increase in hammer height of almost .350 " ca 11/64 +.    Or 1 mm increase
>results in a 7 mm increase. If the knuckle flattens out by 1mm subrtract
>7mm.
>
>For calculations see below. If there are incorrections or errors please
>post and or email. For drawings send sase and $100 per hour for engineer
>consulting fee. Since I am not an engineer nor a student make that $10 an
>hour.  What a bargain.
>
>Ric Inthe Bar'gain
>
>
>Increasing the diameter of the knuckle by .05"  (five hundreths of an
>inch)  (1.27mm)....thats about the equivialnt of the thinnest felt or
>thickest cardboard balance punching. (btw 1 mm is close'nuf to .4 in.)
>(1mm = .03937 in)
>	The first effect would be to raise the hammer....... um how long is the
>shank from knuckle and how far from the pivot point is the knuckle?
>	From actual size drawings from an Asian supplier, (for their Steinway
>flange and shank) it looks like 17 mm from center line of knuckle to
>center of flange center pin.   The knuckles measure 10 mm. (.393).  From
>center line of knuckle to center line of hammer I guess (they don't show a
>hammer on the shank) 123 make it 120 to be conservative. So we have a
>17/120  ratio.  or 1 to 7 plus a  hair.    So my guess... increasing the
>knuckle diameter by 1 mm would raise the hammer 7 mm.  Increasing to 1.25
>would give 8.75mm.   Egads, that's a lot.
>	Well the knuckle isn't raised straight up, it is actually going in a
>circle. But I will leave that to a college undergrad engineer student to
>figure out, and assume it won't matter more than a whopping one mm.
>	I did try to confirm with a hammer shank flange assembly and
>washer, and
>came out close enough to get into the Astro Dome.  rm
>
>an interpolation reference....
>
>Knuckle 17mm from C pin  hammer center 125 from knuckle = 1/ 7.35
>
>Knuckle 17   hammer 120 =1/ 7.05
>
>Knuckle 17  hammer  115 =  1/ 6.76
>
>Knuckle 17.5  hammer 120 = 1/ 6.86
>
>----------
>> From: Newton Hunt <nhunt@jagat.com>
>> To: pianotech@ptg.org
>> Subject: Re: S & S 'A' parts
>> Date: Monday, October 05, 1998 9:39 AM
>>
>> OK, just for fun think what would happen, throughout the action, if the
>> diameter of the knuckle changed from .360 to .420 or more.
>>
>> Then think what would happen, just for the fun of it, if the knuckle,
>> engorged, moves toward the center pin 2mm or so.
>>
>> The knack serves as the lift point of a lever.
>>
>> Let me know when you have some results of your thinking since this is a
>> physics examination and you are expected to hand in your drawings and
>> calculations.
>>
>>         Newton
>>