This is already in the archives at least a couple of times, but this
will get it into the new system.
Bubble reading to Degrees to Bearing Load conversion
for Lowell and Baldwin downbearing gauges.
Measure bubble offset difference between string segments
on both sides of the bridge. Look up angle and bearing factor
on appropriate chart. For bearing load in pounds, multiply
bearing factor times string tension.
Ron Nossaman July, 1997
Baldwin Gauge | Lowell Gauge
------------------------------|-----------------------------
Bubble Degrees Bearing | Bubble Degrees Bearing
------------------------------|-----------------------------
0.5 0.14167 0.0025 | 0.5 0.08333 0.0015
1.0 0.28333 0.005 | 1.0 0.16667 0.003
1.5 0.42499 0.0075 | 1.5 0.25 0.0045
2.0 0.56666 0.01 | 2.0 0.33333 0.006
2.5 0.70832 0.0125 | 2.5 0.41667 0.0075
3.0 0.84999 0.015 | 3.0 0.5 0.009
3.5 0.99165 0.0175 | 3.5 0.58333 0.0105
4.0 1.13332 0.02 | 4.0 0.66667 0.012
4.5 1.27499 0.0225 | 4.5 0.75 0.0135
5.0 1.41665 0.025 | 5.0 0.83333 0.015
5.5 1.55832 0.0275 | 5.5 0.91667 0.0165
6.0 1.69998 0.03 | 6.0 1. 0.018
6.5 1.84165 0.0325 | 6.5 1.08333 0.0195
7.0 1.98331 0.035 | 7.0 1.16667 0.021
7.5 2.12497 0.0375 | 7.5 1.25 0.0225
8.0 2.26664 0.04 | 8.0 1.33333 0.024
8.5 2.40831 0.0425 | 8.5 1.41667 0.0255
9.0 2.54997 0.045 | 9.0 1.5 0.027
9.5 2.69163 0.0475 | 9.5 1.58333 0.0285
10.0 2.8333 0.05 | 10.0 1.66667 0.03
10.5 2.97497 0.0525 | 10.5 1.75 0.0315
11.0 3.11663 0.055 | 11.0 1.83333 0.033
11.5 3.25829 0.0575 | 11.5 1.91667 0.0345
12.0 3.39996 0.06 | 12.0 2. 0.036
12.5 3.54163 0.0625 | 12.5 2.08333 0.0375
13.0 3.68329 0.065 | 13.0 2.16667 0.039
13.5 3.82496 0.0675 | 13.5 2.25 0.0405
14.0 3.96662 0.07 | 14.0 2.33333 0.042
14.5 4.10829 0.0725 | 14.5 2.41667 0.0435
15.0 4.24995 0.075 | 15.0 2.5 0.045
15.5 4.39162 0.0775 | 15.5 2.58333 0.0465
16.0 4.53328 0.08 | 16.0 2.66667 0.048
1-29-1997
TS039D
PROCEDURE TO ESTABLISH PROPER DOWN BEARING OF STRINGS ON BRIDGES OF
BALDWIN GRAND PIANOS DESLGNED WITH HOLLOW VERTICAL (ACU-JUST) HITCH
PINS
These conditions must exist before bearing can be established:
1.All strings associated with the treble bridge must be in place,
(Bass strings to be installed later.)
2. These strings must be tuned to A-440 pitch.
3. All strings on the treble bridge must be set at proper height on
their hitch pins to read zero (0.0) bearing at the bridge. Follow this
procedure; begin at treble end of treble bridge with note #88 and work
toward bass. Lift wire and raise tension of the strings on the first
ten (10) notes, Then raise wire and adjust tension of the next ten
(10) notes and proceed on until all wire is adjusted in this manner on
the treble bridge.
Procedure for string height adjustment.
1. Become familiar with bubble gage adjustments and application as
shown with the attached illustrations,
2. With strings at normal tension, begin with strings at the bass end
of the treble bridge and work toward the middle, Set bearing values as
shown in the following chart on specified notes only. Tap the string
down by placing the tool over the hitch pin, resting on the wire, with
the bubble gage held onto proper strings with the magnet built into its
base, tap the setting tool with a small hammer to lower the string to
achieve a proper bubble gage reading. If the string is too low, raise
the string, using a coil lifter and leather or felt to protect the
plate finish.
Scale SA(5'2") ST(5'8") SC(6'3'')
SF10(7'0") SD10(9'0'')
Notes to be set 27-44 27-43 23-40 21-39
21-35
Bubble Deflection 1 divis. 1 divis. 1 divis. 1
divis. 1 divis.
3. After strings associated with the notes which were adjusted in the
preceding operation have been set, proceed on with notes listed in the
following charts.
Scale SA(5' 2") ST(5'8") SC(6'3'')
SF10(7'0") SD10(9'0")
Notes to be set 45-53 44-53 41-53 40-53
36-53
Bubble Deflection 2 divis. 2 divis. 2 divis. 2
divis. 2 divis.
Scale SA(5'2") ST(5'8") SC(6'3")
SF10(7'0") SD10(9'0")
Notes to be set 54-88 54-88 54-88 54-88
54-88
Bubble Deflection 3 divis. 3 divis. 3 divis. 3
divis. 3 divis.
4, Install bass strings and set at zero bearing, Then adjust bearing
according to the following chart.
Scale SA(5'2") ST(5'8") SC(6'3")
SF10(7'0") SD10(9'0")
Notes to be set 1-26 1-26 1-20 1-20
1-20
Bubble Deflection 1 divis. 1 divis. 1 divis. 1
divis. 1 divis
5. Retune piano to A-440 pitch.
CONCLUSION:
1. Bearing adjustments should only be made when the piano is maintained
under proper climatic conditions. (Humidity 35% - 45% with temperature
70 - 75)
2. The procedure and bearing gage must be applied in the order
established.
3. A bearing value, previously set, cannot be rechecked because the
accumulated force of all strings on the bridges will lower the
soundboard and reduce the settings which were originally set.
4. Pianos equipped with the vertical (Acu-Just) hitch pins are designed
to function with a minimum positive bearing at the bridges, compared
with other pianos with string rests and angled hitch pins.
*Hand written note at bottom: 1 div. = .005" shim thickness with a
Baldwin Rocker Gage.
Ron N
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