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Kromer 14a

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MartinHewitt

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Post Sat Aug 03, 2019 12:57 pm

Kromer 14a

Now first to increase the diversity Oldfast's most anticipated to him unknown lock, the Kromer 14a. I will post the Mosler probably on Monday.

The Kromer 14a is in the catalog of 1918. In some generic pages the name was inserted via corrections. Perhaps this was the catalog introducing this lock model or maybe it is a few years older. In 1925/26 a manipulation protection was introduced, which this lock doesn't have. (Edit: The patent is actually from 1921/22. So the lock was probably made between 1918 and 1921.) The dial has 25 big and 25 small upper case letters. "I" is missing.

One of the special features of this lock is that the bolt work is locked like in a time lock, i.e. a bar is blocked entering the case.

One of the special features of this lock is that W2 (in standard manipulation notation) can be turned only clockwise. This is achieved by a springy pin on the spindle and a spiral inner opening of the wheel to form a single step. Turning right the pin pushes against the step. Turning left the pin is pushed in without moving the wheel.

One of the special features of this lock is that ALL wheels are directly driven by the spindle. To drive three wheels with one spindle the spindle can be pushed and pulled and it depends on the direction of rotation. W2 is the wheel nearest to the dial. It is only and always turned, when the dial is turned right. W1 is the wheel most far away from the dial. It is only and always turned, when the dial is pushed in. W3 is in the middle. It is always turned.

So the opening sequence is:
1) Pushed in 2xR to first letter. (All wheels to first letter. 2x to collect W2.)
2) Pulled out 1xR to second letter. (That is indeed a "continue to turn right". W1 at first letter, W2+W3 at second letter.)
3) Pulled out 1xL to third letter.

One of the special features of this lock is that a full relocking after opening is enforced by the double gravity fence. The main fence is longer. It is open when the lock is open. The secondary fence is a bit shorter. It is open when the lock is closed. So after the lock is opened like described above, the bolt work can be moved inwards a little bit. Then the dial needs to be turned and pushed in to scramble W1 (and thereby automatically at least W3 and possibly W2) to lift the secondary fence. Then the bolt work can be opened fully. When the safe is locked again the main fence is moving up automatically. It is nowhere mentioned and it was probably never intended, but the secondary fence can act as a relocker, when the wheels are punched. (No wheels, no pushing up secondary fence, no opening)

Changing the combination is done with a change pin quite normally. Enter old combination, put change pin in, enter new combination, remove change pin.
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Last edited by MartinHewitt on Sat Aug 03, 2019 10:13 pm, edited 1 time in total.
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MartinHewitt

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Post Sat Aug 03, 2019 12:59 pm

Re: Kromer 14a

And the second batch of photos.

Btw. all fotos from the back.
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Oldfast

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Post Sat Aug 03, 2019 10:48 pm

Re: Kromer 14a

That is really somethin' there Martin. Wow.

What a fascinating lock! And really quite a
piece of history you've gotten your hands on.

What a treat you've shown here.
" Enjoy the journey AS MUCH as the destination."
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MartinHewitt

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Post Mon Mar 09, 2020 11:42 pm

Re: Kromer 14a

Over the weekend I finally made a mount for this lock with three pieces of wood. The former safe door had been 24cm (over 9") thick. That gave me the opportunity to attempt a manipulation after I got my CCG to set a combination. I manipulated this lock in 19 minutes. With the right strategy it is really quite easy.

I could identify four possible variants of this lock:
1) Mine is the first/oldest one. Lots of false gates. I haven't found any patents for it (and the previous model 14), even so I would think that these locks have probably patentable stuff. I haven't seen any other lock with the coupling mechanism between center and outer ring of a wheel. And I haven't seen any other lock with this double lever construct to enforce the clearing of the combination.
2) For the second variant there is patent DE361110 from 1922. I know that this lock exists too. Here only W3 has a large number of false gates and a spring-loaded pin which operates shifted by a halve phase from the fence. I don't know if this is really helping against manipulation. I will try to get my hands on one to check. The construction of more variants is not a sign that the mechanism was that good.
3) Third variant is shown in patent DE435883 from 1925. I have never seen such a lock, but considering how many lock patents were really implemented, it is IMHO likely that such a lock existed. On this lock W1/2/3 have no false gates, but there is another wheel with a few false gates to hide the true code wheels. It would indeed make manipulation more complex, but I really don't believe it would stop it.
4) And the final version is described in patent CH131763 from 1928. Again I haven't seen such a lock, but there is a model 14b lock, which has exactly this mechanism against manipulation. So unless the 14a has been discontinued until then it is very likely that such locks exist. In it all three wheels don't have any false gates, but a gear wheel that has 50 teeth (same number as the letters on the dial) is attached to W3. A spring loaded pin is pushing this gear wheel and hence W3 to fixed positions. If this is really done well I don't see a chance to manipulate it in a classical way.
In case you wonder ... Martin Hewitt is a fictional detective in stories by Arthur Morrison:
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MartinHewitt

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Post Wed Mar 10, 2021 4:08 pm

Re: Kromer 14a

A little video showing the opening.

https://vimeo.com/520705162
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MHM

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Post Wed Mar 10, 2021 8:14 pm

Re: Kromer 14a

MartinHewitt wrote:A little video showing the opening.

https://vimeo.com/520705162


Wow, that's lovely. Baroque as all hell, but lovely none the less.
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edocdab

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Post Fri Mar 12, 2021 10:18 pm

Re: Kromer 14a

That is a very interesting lock Martin! Thanks for sharing the write up and clear video of the opening. It's a really nice mechanism and a beautiful piece of history!
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