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Spring forces - some research

h4yn0nnym0u5e

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Hi folks

I've been doing a bit of measuring on key forces on various saxophones we have about the place, as listed below.

Whilst referring to Stephen Howard's excellent chapter in his highly-recommended Haynes manual, I did use a somewhat different method: I borrowed a force gauge from work, and pressed the keys (or touches, where keys are the opening type) while the instrument was near-vertical, so as to get an idea of how much work the fingers actually have to do. As a result I'd expect my figures to be a little higher than Stephen's, as I didn't have the weight of the keys helping the "blob of Blu-tack" to close them. It's also quite hard to get a decent measurement, as the force varies by ±5 to 10g as you push inwards or release the keys, and also of course as the spring force increases until the key closes.

Here are the numbers (forces in grams), low notes at the bottom except for the side keys which I put in the top 3 rows:
Code:
             |    YAS62    |     YAS275  |   BW tenor  |    YBS62
             |  key  touch |  key  touch |  key  touch |  key  touch
      Side C |         130 |         140 |         340 |         525
     Side Bb |         180 |         140 |         280 |         580
     Side F# |         155 |         155 |         360 |         250
   (Side) F# |         170 |         200 |         370 |         240
           F |         310 |         190 |         270 |         270
    (Side) E |         190 |         190 |         300 |         415
        E(b) |         190 |         170 |         200 |         230
           D |         170 |         200 |         180 |         250
       Aux B |   35        |   65        |   30        |   65       
           B |   45        |   85        |  130        |  165       
      Bis Bb |   42        |   45        |   60        |   95       
           A |   45        |   50        |  100        |            
          G# |   35    120 |   35    140 |   45        |   90       
           G |  170    100 |  170        |  250        |            
       Aux F |   65        |   65        |   60        |  105       
           F |   55        |   75        |   60        |  150       
        E(b) |   60        |   95        |   90        |  200       
          Eb |         320 |         160 |         230 |         420
           D |   65        |   75        |  120        |  150       
          C# |         220 |   40    220 |   35        |            
           C |   60    250 |   45    170 |   52    190 |   85    325
           B |   65    250 |   50    180 |   80        |   45       
          Bb |   60        |   50    160 |   80        |   60       
           A |             |             |             |   60
(I couldn't get to the G or A on the bari, and also forgot to do its low C#.)

And here's a chart, with the forces scaled to those recommended for each type, so we can compare properly. I looked at the numbers, and decided that as my YAS62 feels very nicely set up, it was "right", and hence that the touches (palm keys etc.) should be counted as correctly set if their force was about 4x that for a key:

Apart from a couple of keys, the YAS62 looks (and feels!) good; the YBS62 on the other hand looks like it's a bit heavy, especially some of the side keys (though Stephen has no advice on those, and I suspect they can be set quite heavy because of how you actuate them).

The unevenness of the 275 and BW may be lack of servicing, though the YAS62 has remained unserviced for even longer. Thinking about it, I should probably now repeat this exercise having consulted Chapter 10 - Lubrication...

I think we can call the G keys "reasonably strong", at about 3-3.5x the others - though this is mitigated by the longer lever to the pearl, so it only feels like 2x.

Comments?

Cheers

Jonathan
 

kevgermany

ex Landrover Nut
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21,947
That's (for me) really interesting. I guess G is high because of the octave mechanism link & the G# closing with it.

I've adjusted springs on my saxes to get even, light key pressures. But it's a tricky to get right cos if you're not careful you end up with too little pressure (and leaks) on the keys which are held closed by springs. And also if you go too far, the keys are sluggish to open afterwards.

Good work! Will be interesting to see how it changes after you've oiled it.
 
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