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  1. #171
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    Here in the States, with a few exceptions, rectangular bolts gave way to round bolts much earlier than than in the UK, during 1850's- 60's. While there may be certain advantages with rectangular bolts such as increased contact area, I think when it comes to shear or bending strengths in bars of equal area, they are not so much different. In fact, depending on the shape of the rectangle and the type of attack, probably not as secure. For example. take a 16" tall door where the weakest point is the locking bolt itself. A single 2" round bolt has roughly the same area compared to a 12+" X 1/4" flat bar. Mosler actually made a safe like this not that long ago. Using one of the specialized pry bar devices, seen on Safeman's website, attached at the top of the door, what will happen? With the centrally located round bar, the door will start to bow out at the top, but remember in this scenario, the locking bolts are the weakest point, meaning the door is strongly enough built that the flexing is small and will focus energy of the attack on the locking bolt itself. With the flat bolt, bending and/or tearing will begin at the top of the 1/4" thick flat bar long before any thing happens on the 2" round. Only as the rectangular shape increases in thickness closer to the thickness of the 2" round do you see an increase in strength against this type of attack. I find it a bit hard to believe, that back in day the when construction costs were not the main concern in building the best burglary safes possible, rounds would be favored over flats purely for their economy. Granted I am not a safe engineer, just throwing out how I see it. Doug

  2. #172
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    I don't pretend to understand the physics of it all. When classifying safes for the government, square bolts put the safe at least one classification lower than an equivalent safe with round unless the square ones were huge

    On boltwork one thing that I thought of as a DIY improvement would be on safes where the bolts engage behind a flange- no individual bolt pockets. Wouldn't it improve the design to weld some solid into the flange between the bolts so as to create individual pockets? It would strengthen the whole of a very vulnerable part of the frame and would be a simple enough job.

  3. #173
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    Quote Originally Posted by Doug MacQueen View Post
    Here in the States, with a few exceptions, rectangular bolts gave way to round bolts much earlier than than in the UK, during 1850's- 60's. While there may be certain advantages with rectangular bolts such as increased contact area, I think when it comes to shear or bending strengths in bars of equal area, they are not so much different. In fact, depending on the shape of the rectangle and the type of attack, probably not as secure. For example. take a 16" tall door where the weakest point is the locking bolt itself. A single 2" round bolt has roughly the same area compared to a 12+" X 1/4" flat bar. Mosler actually made a safe like this not that long ago. Using one of the specialized pry bar devices, seen on Safeman's website, attached at the top of the door, what will happen? With the centrally located round bar, the door will start to bow out at the top, but remember in this scenario, the locking bolts are the weakest point, meaning the door is strongly enough built that the flexing is small and will focus energy of the attack on the locking bolt itself. With the flat bolt, bending and/or tearing will begin at the top of the 1/4" thick flat bar long before any thing happens on the 2" round. Only as the rectangular shape increases in thickness closer to the thickness of the 2" round do you see an increase in strength against this type of attack. I find it a bit hard to believe, that back in day the when construction costs were not the main concern in building the best burglary safes possible, rounds would be favored over flats purely for their economy. Granted I am not a safe engineer, just throwing out how I see it. Doug

    Hello again Doug. It's been so long since I was 'with the tools' that I realise I'm now on unsteady ground. When I see images like the Stacke and Robur high quality safes with their extensive use of flat boltwork my first assumption is that with the current requirements of test and certification their in-house research has taken them down this path.

    Where I believe the round bolt design's main weakness lies in the lower catagories where brawn is applied before brain. The problem lies not with the actual bolt which in itself will not deform, but in the rebates and recesses into which they pass and the deformation of the attachment between bolt and tail straps.

    Like a stiletto heel, the point loading on a small section of circumference in contact will surely be greater than the larger area of contact of a rectangular bolt resulting in such failure of pocket and frame as was illustrated. Not that this is in the slightest way relevant to anything!

  4. #174
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    The ground is not so unsteady Safeman. You are definitely correct on the point loading causing greater localized forces. However, I don't think I have seen a safe forced or blown open where the bolts, round or rectangular, have forced their way straight through the jamb facing. There was always some failure of the internal bolt carry bar and /or bolt attachment to the bar, and/or disconnection of the door bolt frame as well as some possible side wall deformation. Anyway, I find this all very interesting and truly appreciate your input. Doug

  5. #175
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    "Like a stiletto heel"......oh no ! Who knows where this thread might go to now !!!

  6. #176
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    Quote :

    "I find it a bit hard to believe, that back in day the when construction costs were not the main concern in building the best burglary safes possible, rounds would be favored over flats purely for their economy"

    I also admit to not being a safe engineer or having a physics degree etc but thinking about it have to agree with the above quote.

    Surely Tann & Chubb r & d departments exhausted all options before opting for & staying with round bolts ?

  7. #177
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    Quote Originally Posted by Safeone View Post
    Quote :

    "I find it a bit hard to believe, that back in day the when construction costs were not the main concern in building the best burglary safes possible, rounds would be favored over flats purely for their economy"

    I also admit to not being a safe engineer or having a physics degree etc but thinking about it have to agree with the above quote.

    Surely Tann & Chubb r & d departments exhausted all options before opting for & staying with round bolts ?


    Safeone, I now wish to retract the following earlier statement :

    "I cannot understand your scorn for rectangular bolts. They were only discarded at the turn of the century in favour of cheaper to assemble and less secure round bolts".

    It always pays to sleep on a post before pressing send in which case I might have said "they were discarded unanimously by the trade with Milner leading the way in 1919 with their List 2 (Impoved Patent) with Ratner, Chubb and Tann following suit through the 1920's" Why, firstly I would guess for purely aesthetic reasons with the bonus of easier manufacturing and assembly.

    As Chubby comments, this, along with square compared to bent bodies, led to an assumption that flat bolts were old fashioned and inferior.

    All this coincided with the post-war increase in violence against safes in the form of high explosives and the developments in the non-hazardous use of acetylene gas which in turn led to the anti-explosive and anti-thermal relocking devices which operated with equal efficiency on both types of boltwork.

    Now, 90 years later and with the judgement of a safes potential more or less solely in the hands of CEN and UL and their 'unusual' failures criteria which have a doubtful relevance to actual criminal attack, it looks as if the rectangular boltwork might be making a comeback.

    Now for a little shut-eye.

  8. #178
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    Quote Originally Posted by Chubby View Post
    On boltwork one thing that I thought of as a DIY improvement would be on safes where the bolts engage behind a flange- no individual bolt pockets. Wouldn't it improve the design to weld some solid into the flange between the bolts so as to create individual pockets? It would strengthen the whole of a very vulnerable part of the frame and would be a simple enough job.
    Your statement brings to mind the expanding frame bolt on my Martin C. Briggs safe (circa 1870).

    tarbc6 1


    2rwm2q1 1

    When the frame work expands it makes contact all around the door into a groove in the door jamb. That gives a lot of surface area and could act as a secure bolt work. Unfortunately, it is only made out of 1/4 inch steel and is held in place with bolts that are about 1/4 inch (actually a non standard size and thread). They also have small diameter heads that would easily pull through the slots that slide over them.

    ja9nc2 1

    The door front, frame and the door jamb are very stout and tight fitting so they would probably withstand a prying attack fairly well. Explosives, probably not so much. I love this safe and use it regularly. While not as entertaining as my cannonball the quality fit of the door makes me smile every time I close it. The fit and feel of the action is amazing even after all these years.

    1hxysz 1

    Perhaps if the expanding framework was beefed up and supported better it would be quite secure. Obviously not a superior design or it would have prevailed. It does create interesting conversation along with the story of the demise of the company.

  9. #179
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    There used to be (possibly still is) a round door floorsafe which had a similar idea. In the door was a circle of steel. This circle was self centring so that it was clear of the body. The lock simply pushed this off centre. Then with the circle off centre it made contact almost all the way round and, of course, was freely rotating so was difficult to counter as is anything which offers no resistance.

  10. #180
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    Quote Originally Posted by Chubby View Post
    There used to be (possibly still is) a round door floorsafe which had a similar idea. In the door was a circle of steel. This circle was self centring so that it was clear of the body. The lock simply pushed this off centre. Then with the circle off centre it made contact almost all the way round and, of course, was freely rotating so was difficult to counter as is anything which offers no resistance.
    Probably the Churchill Banker, although the ring was in the top of the body and not in the door.

    From memory I think Churchills just referred to it as their 'patented locking ring', which despite being made of phosphor bronze, actually used to seize up quite frequently causing lockouts.

    The Banker was the only model ASAIR that featured the bronze ring and was basically their answer to Dreadnought's infamous but similar Defender ABP.

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