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© Copyright 2006, Sargent & Greenleaf, Inc.
Model 6730, 6735, 6738, 6741 Mechanical Combination Lock
Troubleshooting/Dialing Diagnostics
Dialing ten combinations is very little work compared with
the alternative – drilling. It takes so little time that virtually
nothing is lost in the attempt to open the lock in this
nondestructive manner.
Now it’s time to figure out what we can do about a lock with a
fly stuck on the 3rd wheel. This will affect all the wheels in the
lock. To keep it simple, just think about two adjacent wheels
at a time. The 3rd wheel is dialed left when entering the lock’s
combination, which means numbers get higher as we turn the
dial. When a fly is stuck, its wheel is moved by the drive pin on
the drive cam earlier than expected, or at a lower number than
what was set on the lock. Possible 3rd wheel numbers (using
our original combination of 20 • 60 • 40) are 30, 31, 32, 33,
34, 35, 36, 37, 38 and 39. Make a chart similar to the one you
drew for the stuck fly wheel on the #2 wheel, this time filling
in possible numbers for the #3 and #2 wheels.
1st Combination
1st NO. IS NOT DETERMINED 60 (60+0) 30 (40-10)
2nd Combination
1st NO. IS NOT DETERMINED 61 (60+1) 31 (40-9)
3rd Combination
1st NO. IS NOT DETERMINED 62 (60+2) 32 (40-8)
4th Combination
1st NO. IS NOT DETERMINED 63 (60+3) 33 (40-7)
5th Combination
1st NO. IS NOT DETERMINED 64 (60+4) 34 (40-6)
6th Combination
1st NO. IS NOT DETERMINED 65 (60+5) 35 (40-5)
7th Combination
1st NO. IS NOT DETERMINED 66 (60+6) 36 (40-4)
8th Combination
1st NO. IS NOT DETERMINED 67 (60+7) 37 (40-3)
9th Combination
1st NO. IS NOT DETERMINED 68 (60+8) 38 (40-2)
10th Combination
1st NO. IS NOT DETERMINED 69 (60+9) 39 (40-1)
Now that we know where to set the 2nd and 3rd wheels for the
trial combinations, we can calculate the numbers for the 1st
wheel. Since we’re only considering two adjacent wheels at a
time, and the total pair displacement is always ten (because
this is how far a freely moving fly can travel in this lock), the
1st wheel numbers are automatically determined by what we
have already written down for the #2 wheel.
1st Combination 10 (20-10) 60 (60+0) 30 (40-10)
2nd Combination 11 (20-9) 61 (60+1) 31 (40-9)
3rd Combination 12 (20-8) 62 (60+2) 32 (40-8)
4th Combination 13 (20-7) 63 (60+3) 33 (40-7)
5th Combination 14 (20-6) 64 (60+4) 34 (40-6)
6th Combination 15 (20-5) 65 (60+5) 35 (40-5)
7th Combination 16 (20-4) 66 (60+6) 36 (40-4)
8th Combination 17 (20-3) 67 (60+7) 37 (40-3)
9th Combination 18 (20-2) 68 (60+8) 38 (40-2)
10th Combination 19 (20-1) 69 (60+9) 39 (40-1)
Once again, there are only ten combinations to try. Everything
you need to know to develop these numbers is available from
the combination which is set on the safe (4 times to the left
to 20, 3 times to the right to 60, 2 times to the left to 40)
and what you can diagnose through the dialing procedures
(distance, in dial numbers, of maximum fly travel, and which
wheel contains the problem fly).
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