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Weight reduction for drilling one hole all the way thru two 3mm plates with 3mm holes already in it:

Code
5,0mm	0,59g
5,5mm	0,79g
6,0mm	1,00g
6,5mm	1,23g
7,0mm	1,48g
7,5mm	1,75g
8,0mm	2,04g
8,5mm	2,34g
9,0mm	2,67g
9,5mm	3,01g
10mm	3,37g 

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Originally Posted by ambrozy
You didn't measure it like that? You just measured the weight of the whole hammer? if so, you have to tell which hammer weighed the 23.8g with the correct measurement method and subtract the difference from all the hammers

I did weigh the actual weight of the complete hammers, not the strike weight. Here are the corrected measurements for strikeweight:

----White-------------Black---(*gram)

1 - 26.1
2 ---------------------22.5
3 - 26.1
4 - 26.2
5 ---------------------22.5
6 - 25.9
7 ---------------------22.5
8 - 26.1
9 - 26.1
10 --------------------22.5
11 - 26.1
12 --------------------22.5
13 - 26.1
14 --------------------22.5
15 - 25.9
###################
16 - 24.8
17 --------------------21.3
18 - 24.8
19 --------------------21.3
20 - 24.8
21 - 24.7
22 --------------------21.3
23 - 24.8
24 --------------------21.3
25 - 24.9
26 --------------------21.3
27 - 24.7
28 - 24.9
29 --------------------21.2
30 - 24.8
31 --------------------21.4
32 - 24.8
###################
33 - 23.9
34 --------------------19.9
35 - 23.9
36 --------------------20.0
37 - 23.8
38 --------------------19.9
39 - 24.0
40 - 23.8
41 --------------------20.0
42 - 23.8
43 --------------------19.9
44 - 23.8
45 - 23.9
46 --------------------20.0
47 - 23.9
48 --------------------20.1
49 - 24.2
50 --------------------20.1
51 - 23.8
52 - 23.9
53 --------------------20.0
54 - 23.9
55 --------------------20.0
56 - 23.8
57 - 23.8
58 --------------------20.1
59 - 23.8
60 --------------------20.0
61 - 23.8
62 --------------------20.0
63 - 23.8
###################
64 - 21.3
65 --------------------17.5
66 - 21.2
67 --------------------17.5
68 - 21.2
69 - 21.2
70 --------------------17.6
71 - 21.2
72 --------------------17.5
73 - 21.2
74 --------------------17.6
75 - 21.3
76 - 21.1
77 --------------------17.6
78 - 21.3
79 --------------------17.5
80 - 21.2
81 - 21.2
82 --------------------17.5
83 - 21.2
84 --------------------17.5
85 - 21.3
86 --------------------17.5
87 - 21.2
88 - 21.4

Quote
And I suspect that that difference between white and black hammer weights are mostly to compensate for black keys being lighter on the front portion than white keys, so they have similar downweight on the end, if so, it's not technically correct way to do it

Do you mean the way Kawai made this is not technically correct, or the way we are planning to lighten the hammers would not be technically correct because of this?

Quote
Can you measure downweight and upweight of couple adjacent black and white keys to confirm that? and when you do this make sure that you measure in a spot that has the same keydip for black and whites

This seems not entirely possible as the keydip of the black keys is 11mm and the white keys is 12 mm.

But I measured 6 adjecent black and white keys (from middle c and up) and the down and upweight of the black and white keys seems to be exactly the same. Measuring untill the hammer reaches the let-off simulation rubber notch I get 65g downweight for both black and white keys. (If i take off a couple of grams it just results in the keys going down a tad less far) I get 50g upweight for both black and white keys.


Originally Posted by ambrozy
Those weight irregularities are negligibly small, I'd rather smooth those 4 sections but it also would be overkill in this case, so I think that making one additional section inbetween middle and treble section would be sufficient.

Your right. I made a mistake when I worried about the irregularities. I was thinking in grams, but of course the irregularites are just tenth of grams.


Originally Posted by ambrozy
so I think that making one additional section inbetween middle and treble section would be sufficient.
I see why you say that. The gap in weight between these sections is larger than the others. Probably not a bad idea!

Originally Posted by ambrozy
Weight reduction for drilling one hole all the way thru two 3mm plates with 3mm holes already in it:

Code
5,0mm	0,59g
5,5mm	0,79g
6,0mm	1,00g
6,5mm	1,23g
7,0mm	1,48g
7,5mm	1,75g
8,0mm	2,04g
8,5mm	2,34g
9,0mm	2,67g
9,5mm	3,01g
10mm	3,37g 

Great, thanks!

It seems doable to get the right ammount of weight off, especially since there also is space to drill a couple of extra holes in the plates if necessary.

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Originally Posted by U3piano
Do you mean the way Kawai made this is not technically correct, or the way we are planning to lighten the hammers would not be technically correct because of this?

They did this incorrectly, front of black key is lighter than white key, so for the same hammer weight you'll get higher downweight on black key. They reduced hammer weight of black keys so that downweight is the same for black and white and this is ok, but side effect of this is that moment of inertia is not the same for black and white, it should be done by weights in fronts of black keys. I'm not saying they have bad engineers, this decision was probably forced by some accountant who decided that installing weights in all black keys would be too expensive, so engineers had to find some other solution.

I put your data on chart so it's easier to see what's going on

[Linked Image]

Black hammers are on average 3.7 g lighter than white hammers, which is as much as we would like to take off. I see two solutions, leave it as it is and take off the same amount of weight from all hammers or take off 3,7g from only white hammers, and reduce downweight of black keys by weighting their fronts. We concluded earlier that weighting those keys would be hard without using standard lead weights, but I have one more idea, do something like they do in bass keys by screwing nuts under the keys with wood screws, one m6 nut weights 2,5g and small wood screw 1-2g, so two sets of two m6 nuts and wood screw screwed as close to front as possible should give 10g reduction of downweight for blacks. In the end you have to make decision what to do.

Quote
This seems not entirely possible as the keydip of the black keys is 11mm and the white keys is 12 mm.

There is a point on white key where key dip is 11mm, it's just not on the end of key but closer to pivot right? smile but I don't need any other measurements, I now understand situation well, the fact that they made different keydip in fronts of blacks and whites is understandable, they compensated short pivot length, I would design it similarly.

Last edited by ambrozy; 02/19/21 02:16 PM.
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Quote
They did this incorrectly, front of black key is lighter than white key, so for the same hammer weight you'll get higher downweight on black key. They reduced hammer weight of black keys so that downweight is the same for black and white and this is ok, but side effect of this is that moment of inertia is not the same for black and white, it should be done by weights in fronts of black keys. I'm not saying they have bad engineers, this decision was probably forced by some accountant who decided that installing weights in all black keys would be too expensive, so engineers had to find some other solution.

I see. learning alot here! smile

Quote
There is a point on white key where key dip is 11mm, it's just not on the end of key but closer to pivot right?

Ah yes, I understand it now.

Quote
Black hammers are on average 3.7 g lighter than white hammers, which is as much as we would like to take off. I see two solutions, leave it as it is and take off the same amount of weight from all hammers or take off 3,7g from only white hammers, and reduce downweight of black keys by weighting their fronts. We concluded earlier that weighting those keys would be hard without using standard lead weights, but I have one more idea, do something like they do in bass keys by screwing nuts under the keys with wood screws, one m6 nut weights 2,5g and small wood screw 1-2g, so two sets of two m6 nuts and wood screw screwed as close to front as possible should give 10g reduction of downweight for blacks. In the end you have to make decision what to do.

Interesting idea. While I would probably be happy with either option, I take it this would be the most ideal situation, so I will look into it and see if I think there's enough space underneath the black keys etc. Would this also mean adjusting the capstans to adjust the rest position of the black key hammers? Or should they stay the way they are? (which is not level with white key hammers)

What do you think is the reason these are higher in resting position anyway?

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What do you think is the reason these are higher in resting position anyway?
It looks like they reduced black keys keydip that way, it should rather be done by altering black keys leverage ratio. I'm guessing now, but blacks keydip was probably changed after production started and this was only way to do that. You can't correct this without altering key leverage ratio, so we have to leave it as is.

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You have to try that drilling because if I see correctly, these existing holes are there to keep the metal plates from rotating around, so you can probably only drill one hole.

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Originally Posted by ambrozy
Quote
What do you think is the reason these are higher in resting position anyway?
It looks like they reduced black keys keydip that way, it should rather be done by altering black keys leverage ratio. I'm guessing now, but blacks keydip was probably changed after production started and this was only way to do that. You can't correct this without altering key leverage ratio, so we have to leave it as is.

Aha. Well, leaving that as it is sounds good to me. That was the answer i was hoping for.

Originally Posted by ambrozy
You have to try that drilling because if I see correctly, these existing holes are there to keep the metal plates from rotating around, so you can probably only drill one hole.

I hate to say it, but your're absolutely right again. I didn't see it before, and I wondered why these holes were there, but I just noticed these holes are actually filled halfway by plastic notches designed to keep the metal plates from rotating around.

Anyway.. not touching these original "holes", I think I could get at least 4 extra holes per plate in, so that shouldn't be a problem.

I have asked a Kawai dealer what these hammers cost for the possiblity that things would go wrong. The answer was €16 per hammer. So all hammers would cost me about a new vpc-1, but as I try, of course I will see how it goes, and Ill only risk having to buy one or 2 new hammers. That said I don't really expect problems drilling a couple of small holes in them.

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