Mainspring sizes for Big Ben, Baby Ben and other old Westclox alarm clocks.
|
America (ca. 1927)
|
Time spring |
Same as Big Ben Loud alarm |
| America (ca. 1927) |
Alarm spring |
Same as Ironclad |
| Bunkie and Sleep-Meter Intermittent
|
Time spring |
Same as Big Ben Loud Alarm |
| Bunkie and Sleep-Meter Intermittent
|
Alarm spring |
5/16" x .013" x 48" |
| Baby Ben (mov't. 1, 1912 to mid-1914)
|
Time spring |
6.2 mm (just under 1/4") x .0102" x 29" hole end
New replacement: 1/4" x .010" x 26" loop end, convert
to hole end.
|
| Baby Ben (mov't 2 - 4, mid-1914 to 1960)
|
Time spring |
5/16" x .0087" x 30" hole end (measured in type 2
& 3 movements)
5/16" x .009" x 30" hole end (SPR-3414 factory material)
New replacement: 5/16" x .009" x 36" loop end, cut
off 6" and make hole in end. (CMH-80.2 or 80.3)
|
| Baby Ben (all two key wind) |
Alarm spring |
7/32" x .0082" x 27" hole end (measured in type 2
movement)
7/32" x .0087" x 27" hole end (SPR-3246 factory material)
New replacement: 7/32" x .008" x 26" hole end (CMH-56.1)
|
| Baby Ben single key wind (mov't. 5)
|
|
9/32" x .0085" x 41"
hole end |
| Big Ben Loud Alarm (mov't. 1 - 2, 1908
to 1956) |
Time spring |
5/16" x .015" x 40" hole
end (CMH-80.13) |
| Big Ben Loud Alarm (mov't. 1 - 2, 1908
to 1956) |
Alarm spring |
1/2" x .0138" x 40" loop end (style 1 & 2 cases)
1/2" x .0138" x 32 1/2" loop end (style 4, 5 and 6 cases)
|
| Big Ben Chime Alarm (mov't 3, 1931 -
1956) |
Time spring |
Same as Baby Ben mov't 2 - 4
5/16" x .0088" x 30" (SPR-3418 factory material)
|
| Big Ben Chime Alarm (mov't 3, 1931 -
1956) |
Alarm spring |
9/32" x .0105" x 20"
loop end (measurement of factory original spring) (CML-70.6 is close)
|
| Clock of Tomorrow |
|
5/16" x .010" x 72" (CMH-80.10)
|
| Ironclad |
Time spring |
Same as Big Ben Loud Alarm |
| Ironclad |
Alarm spring |
3/16" x .0155" x 25 3/4" hole end (measured in clock)
New replacement: 3/16" x .012" x 31" loop end (CML-48.4),
cut off loop and make a hole
|
| Model 66 (Bingo, Raven, Waralarm, etc.)
|
Time spring |
5/16" x .0125" x 24"
loop end |
| Model 66 |
Alarm spring |
Type one: 1/4" x .008" x 18 1/2" loop end
Type two: 1/4" x .0085" x 14" open loop end. SPR-3254,
model 66AH. This type of spring may be installed without dismantling
the movement.
|
| Sleep-Meter (also fits Black Bird, Blue Bird, Ironclad,
Jack o'Lantern) ca. 1924 |
Alarm Spring |
7/32" x .01" x 40" loop end (measured
in Black Bird dated 1924 on movement.) |
| Travalarm |
|
5/32" x .0093" x 35" (measured in
12-65 example). Can use CML40.3 (5/32" x .009" x 38 1/4")
from S. LaRose and shorten it by 3". |
| Two-inch movement (time only) |
|
7/32" x .012" x 29.5" loop end (measured in clock)
New replacement: 3/16" x .012" x 31" loop end (R &
M and Timesavers)
|
|
Compute the correct length of the time spring for the Big Ben Loud
Alarm:
Length = Pi(B squared - A squared)/2t
| where Pi = 3.1416 |
B = barrel radius |
A = arbor radius |
t = mainspring thickness |
| In this case: |
B = 18 mm |
A = 4.65 mm |
t = .015" |
Doing the computation, Length = 49.2". If a spring
this long were used, the clock would run longer on a winding than
with the standard 40" spring.
|
