How it works:
Despite having 60 different numbers, Dudley locks really only have 10 different possible positions. Each position is 4 numbers long, with a 2 number gap between them.
To find these 10 different positions, simply pull on the shackle and turn the dial. You will find that it catches on a certain number, twist it the other way and it will catch on another number, about 4 numbers away from the first one. This 4 number area is one of the 10 positions, or 'zones'.
Look at the example to the right, you can see that the green areas are the 10 different positions, and the blue areas are the two numbers that separate each position. So now, knowing that there are only 10 different positions, instead of 60, we can determine that there are 1000 (10 x 10 x 10) different three-number combinations. At this point, you could just spend some time trying all 1000 combinations, it is a manageable number, but we can cut it down further.
The first step to cutting down the number of combinations is to remove the third number. It isn't necessary, because on the third turn you can just spin the dial through each zone while pulling up on the shackle. So, after removing the third number, we are down to 100 (10 x 10) possible combinations!
Now, on most (not all) Dudley locks, the second number is lower than the first number. Using that piece of information, we can shorten the possible combinations down to just 45! Use the tool below to get your 45 possible combos. If none of them work, use the "Swap" button to see the combinations where the second number is higher, and try those.
The Tool:
This is a simple tool to figure out all your possible combinations, all you need is the first 'zone' starting on or past zero. For example, in the image above that zone would start at 2, and end at 5. So you would select '2' in the dropdown below, and click the "Get combos" button. By default it will assume your second number is lower than the first number, but you can change that with the "Swap" and "Show All" buttons.
While in most cases the second number on Dudley locks is smaller, there are a few where the second number is actually larger. This is what the 'Swap' and 'Show all' buttons are for. The 'Swap' button will switch back and forth between Large-Small combinations, and Small-Large combinations. The show all button will show all 100 possible combinations.
Remember that these are 2 number combinations. For the third number, just spin the dial around, trying the shackle in each of the 10 zones.
Video: