Can someone clarify purpose of "movable flys" on the wheel?

[Nitrous]

Hi folks,

Can someone clarify the purpose of the movable flys on wheel packs?

If I understand correctly, the fly moves over a range. I recognize the role of the fly is to drive the next wheel, but why the range? It seems that a stuck or sticking fly can be a problem in terms of altering a set combination by effectively changing the point where the next wheel is picked up making opening difficult/impossible.

Doesn't a movable fly introduce dead zones in combination selection?

Any thoughts from you safe guys would be appreciated.
Thanks

Notrous

[mh]

http://www.sargentandgreenleaf.com/pdf/ ... _locks.pdf mentions an "optimum amount of fly travel which will allow use of every number on the dial in selecting a combination". So that's one purpose.
Another purpose could be to allow dialing both LRL and RLR using the same numbers.

[Lockules]

<<what mh said.

You might be confusing the role of the flys with dead or 'forbidden' zones when setting combinations: forbidden zones are created by the mechanical limitation imposed by the geometry of the drop lever as it rides along the drive cam. The cam needs to rotate far enough to lift the fence out of the wheel gates before the lock bolt can be extended.
If you crowd that last number, you may not give the lever a chance to clear the wheels before it tries to move the bolt, and you end up "locked in," unable to re-lock the lock after it's been opened.

[Nitrous]

Thanks guys,

I had read the S&G PDF section title "The Fly in the Ointment".

I guess I was looking for some insights into "how" the movable flys do this.
I know the "key" likely lies in the statement that the optimum range is "twice the width of the fly plus the diameter of the pin".

It strikes me that if the flies are fixed, you have to accept that the dial range contained by the width of the pin PLUS the fly width is forbidden. Is this correct?

I still haven't sorted it out completely in my mind's eye, but I'll get there!

Thanks
Nitrous

[Raymond]

Imagine or use a common Master combo padlock. Turn the dial several times to the right and stop at the first number. Now turn the dial left and carefully note that the dial, (your drive wheel) will touch the second wheel 3-4 numbers before it actually reaches the first combo number. This touch is where the fixed pin on the drive wheel first contacts the second wheel to start moving it. If that lock actually had moveable flys, the touch would be almost exactly on the first number. There are several numbers that cannot be accessed due to the thickness of the pin. As you continue dialing on a multiple wheel safe lock, the error adds some for each wheel.

[Nitrous]

Thanks,

That was what I was thinking, except now you've introduced a new variable.

I would have thought that since the width of the pin is considered in the size of the milled out fly recess, that ALL numbers were available, at least in terms of setting the combination for all but the final wheel. In that case, as previously stated by someone eleses post, there are mechanical limitations in the last numbers chosen. S&G seems to suggest 90-20 is out for the final number, at least in the instructions in the 6730 combo lock. I wonder how a fixed fly differs (practically anyway) from a drive pin....

With these "forbidden zones" known, it's no wonder that computer scientists and mathematicians/physicists like Richard Feynman could open the "secure locks" at Los Alamos so easily! Of course, he limited the possibilities only knowing math and human nature!

Thanks again,
Nitrous

[Raymond]

The example I hinted at with the Master padlock is applicable only to non-moveable flys. (safes such as Sentry, Brinks, Harbor Freight, Tractor Supply, etc., etc.) You are correct in presuming that the manufacturer creates the milled out section on moveable flys to eliminate almost all of the problem. Safe locks with moveable flys theoretically should be able to be dialed starting from either direction. But, the last few times I tried it did not work. I know they used to work very well. I just have not taken the time to see why they don't work any more. If you dial one the 'wrong' direction, after setting the last number you have to move back to let the nose drop into the drive wheel gate. When you dial the correct direction, the nose automatically slides into the drive wheel gate and then continues to draw back the bolt in the same direction. Much smoother!

S&G established 90-20 as the forbidden zone to eliminate most problems with all of their normal locks. In application some locksmiths spline the lock at different locations: 25, 50, 75, or 0. So now, the forbidden zone has moved to a different area and you have to notice this or you will set it up to fail. An example of the need to change the splining would be an in floor safe where the original dial is upsidedown. Fo ease of reading you would take everything off and rotate the dial ring and just set the spline at '0' instead of '50'. Sometimes a dial can come off and be pressed back on at not quite the original number. Often banks and stores want to daylock the safe using only the locking dial.

In reality, the forbidden zone is much smaller, about 15 numbers. If you look at the inside of an S&G lock and turn the drive wheel until it just touches the nose of the lever, note the dial number. Then turn it the opposite direction to touch and note the dial number. Your actual forbidden zone is between those dial numbers. As a safety factor I would use those actual numbers plus and minus at least 3 additional numbers on both sides.

Since you never know exactly what number the spline key groove is set at, you might use this procedure as the rule instead of 90-20.

[tomasfuk]

... Safe locks with moveable flys theoretically should be able to be dialed starting from either direction. But, the last few times I tried it did not work. I know they used to work very well. I just have not taken the time to see why they don't work any more...

I have made a small investigation how it works with my LaGard 1947 4-wheel combo.
The result is, the fly travel in this lock (expressed in dial numbers) is:

(twice width of the fly) + (width of the drive pin) + 0.5.

Thus, the first number must be incremented by 2 if dialed in the opposite direction than usual, i.e., L instead of R,
the second number must be decremented by 1.5 if dialed in the opposite direction than usual,
the third number must be incremented by 1 if dialed in the opposite direction than usual,
the fourth number must be decremented by 0.5 if dialed in the opposite direction than usual.
Obviously, there is some dialing tolerance which may cause that the corrections of the 3.rd and 4.th numbers are not necessary.

P.S. it was funny to dial all four numbers in the same direction during the investigation

[GWiens2001]

So you are saying that if you want to figure out the rotational conversion, all you need to do is take the lock apart, grab your micrometer, and do some math. Simple!

Unless, of course, you do not have the safe open.

Also keep in mind that while the rotational conversion is likely close between the same type of lock, it will have some differences. Especially when the lock has some wear from use.

There are a few threads that cover an easier way to figure out rotational conversion.

Gordon

[tomasfuk]

So you are saying that if you want to figure out the rotational conversion, all you need to do is take the lock apart, grab your micrometer, and do some math. Simple!
Unless, of course, you do not have the safe open.

Sure I did it with the safe open - it's a good measure if playing with the lock. Things may happen.
And I did it without any micrometer, without any (dis)mounting, without using any tool and without any math (except 2:4=0.5), simply by dialing
It took something like 10 minutes.

There are a few threads that cover an easier way to figure out rotational conversion

Thanks, I'll look for them. It's always nice to learn something new.

[tomasfuk]

There are a few threads that cover an easier way to figure out rotational conversion

Some clue would be appreciated, I haven't found any

[femurat]

If you set a wheel at a number, let's say left 50, and you reach the wheel from the opposite direction, you'll notice where it's picked up. This is the easy way to convert. Hope this makes sense.
But you already know this. Don't you?

Cheers

[tomasfuk]

If you set a wheel at a number, let's say left 50, and you reach the wheel from the opposite direction, you'll notice where it's picked up. This is the easy way to convert. Hope this makes sense.
But you already know this. Don't you?

Cheers

It makes sense and I know this. Unfortunately with my combo I can detect it unfailingly for the first wheel only. For the second wheel very insurely. For the 3rd and 4th wheels I hear/feel nothing if I move it enough slowly to be able to register the dial position. I tried to use a stethoscope but with no avail of that.
Maybe it's due to protective measures against manipulation in this G1 lock. Or I'm not skillfull enough for it.

[mh]

I would have thought that the result from the 1st wheel applies to the other wheels, too?

[tomasfuk]

I would have thought that the result from the 1st wheel applies to the other wheels, too?

If you mean that for the second wheel it's twice, for the 3rd wheel it's 3 times and for the 4th wheel four times that offset, then yes. (Supposing that all wheels are identical. If not, some unsteadiness may occur.)