Modified Dial Lock- Security Enhanced

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EGR 120 Final Project Report
Combination Lock
Section 14, Fall 2015
Combination Lock
Jorge Figueroa Nicole Drevlow Alex Herrera
Submitted to:
Professor Cassandra Gribbins
12/4/2015

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Table of Contents
Project Overview .................................................................................................................................... 1
Original Assembly.............................................................................................................................1-2
Modified Assembly...........................................................................................................................2-3
Team Dynamics ................................................................................................................................3-4
Conclusion and Evaluation................................................................................................................... 4
Original Assembly .................................................................................................................................. 5
Original Assembly Drawings................................................................................................................. 5
Assembled.................................................................................................................................. 5
Exploded Front Section .............................................................................................................. 5
Exploded Back Section ............................................................................................................... 5
Nicole Drevlow .................................................................................................................................... 6
Dial............................................................................................................................................. 6
Dial Dimensioned Drawing.......................................................................................................... 6
Spring ......................................................................................................................................... 7
Spring Dimensioned Drawing ...................................................................................................... 7
Back Cover.................................................................................................................................. 8
Back Cover Dimensioned Drawing............................................................................................... 8
Shackle ....................................................................................................................................... 9
Shackle Dimensioned Drawing .................................................................................................... 9
Shackle Pin................................................................................................................................ 10
Shackle Pin Dimensioned Drawing ............................................................................................ 10
Jorge Figueroa ................................................................................................................................... 11
Steel Back Plate ........................................................................................................................ 11
Steel Back Plate Dimensioned Drawing ..................................................................................... 11
Red Circle.................................................................................................................................. 12
Red Circle Dimensioned Drawing .............................................................................................. 12
Inner Shell................................................................................................................................. 13
Inner Shell Dimensioned Drawing ............................................................................................. 13
Inner Cylinder ........................................................................................................................... 14
Inner Cylinder Dimensioned Drawing........................................................................................ 14
Steel Circle................................................................................................................................ 15
Steel Circle Dimensioned Drawing............................................................................................. 15

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Yellow Circle ............................................................................................................................. 16
Yellow Circle Dimensioned Drawing .......................................................................................... 16
Inner Circle ............................................................................................................................... 17
Inner Circle Dimensioned Drawing ............................................................................................ 17
Alex Herrera ...................................................................................................................................... 18
Outer Shell................................................................................................................................ 18
Outer Shell Dimensioned Drawing............................................................................................. 18
Rod........................................................................................................................................... 19
Rod Dimensioned Drawing........................................................................................................ 19
Bow .......................................................................................................................................... 20
Bow Dimensioned Drawing....................................................................................................... 20
Lever......................................................................................................................................... 21
Lever Dimensioned Drawing ..................................................................................................... 21
Block......................................................................................................................................... 22
Block Dimensioned Drawing...................................................................................................... 22
Modified Assembly .............................................................................................................................. 23
Modified Assembly Drawings............................................................................................................. 23
Assembled ............................................................................................................................... 23
Exploded Front Section ............................................................................................................ 23
Exploded Back Section .............................................................................................................. 23
Jorge Figueroa .................................................................................................................................. 24
Modified Steel Circle................................................................................................................. 24
Part Title Dimensioned Drawing................................................................................................ 24
Modified Red Circle................................................................................................................... 25
Part Title Dimensioned Drawing................................................................................................ 25
Alex Herrera ...................................................................................................................................... 26
Outer Shell................................................................................................................................ 26
Outer Shell Dimensioned Drawing............................................................................................. 26

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Project Overview
Figure 1 Original Assembly Rendered Image
Original Assembly
The inside of a combination lock is comprised of a few key pieces besides the structural
components. There is the shackle, the curved piece seen from the outside that latches onto items. The
shackle pin on the inside is used to keep the shackle from exiting the lock. An obvious piece is the
locking mechanism that interacts with the shackle to keep the lock secure until the combination is
entered. The internal back plate of the lock is the base for the steel circle cams that are responsible for
the numerical unlocking; these cams are separated by red and yellow plastic spacers. Besides providing
proper spacing, they are designed to keep the cams from falling off of the back plate.
The pieces that comprise the lock’s structure are susceptible to easy breaking. A common way
these locks are broken is by using tools to puncture the weak back plate to remove it. The lock can easily
be opened once it is exposed.

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There are multiple methods of breaking into a Master lock without using any tools. One
common way of cracking a Master lock is by applying force to the dial while turning in order to pinpoint
the location of the internal knobs on the steel circles. Using mathematical formulas you can get fairly
close to the correct combination. Another similar, easier solution is to pull on the shackle while applying
pressure to the turning dial. When the shackle is released and the dial turned, it will cause the dial to
catch near the point where the first number is. This can be repeated several times to gain all three
numbers.
Figure 2 Modified Assembly Rendered Image
Modified Assembly
A major modification we made to the design was changing the lock’s structure. Since a common
way of breaking open this type of lock is to take advantage of the slim metal on the back by prying it
open with hand tools, we decided to make the outer body a singular part. This uniform piece would be
much more difficult to break open by hand or using hand tools. This would make it much harder and
time consuming to break open the lock.

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A second major modification was the addition of small offsets on the inner steel dials in order to
make it more difficult for those cracking the lock using pressure methods. As pressure is applied to the
dial, the location of the knobs can be pinpointed. Adding false knobs increases the chance of the person
cracking it mistaking a false knob for a real one. This increases the amount of time needed to open the
lock, decreasing the odds of a successful break-in. A cosmetic modification was the removal of gaps in
the inner shell in order to make the inside of the lock less complex and manufacturing easier.
Team Dynamics
The project was completed with the goals of efficiency and time management in mind. We did
not want to have set weekly meetings due to conflicts with scheduling. We would meet after or before
class and work in the College of Business computer lab. We met between one and two times a week to
discuss progress and work on the project. Although these meetings were always timed well, it caused
some friction by not having a set date and time every week. Often it would be two group members
working during a meeting instead of the whole group. We utilized SMS messaging and email through
ERNIE for communication.
A great method we used was created subassemblies that were imported into the final assembly.
This made constraining parts significantly easier when sections were already fully constrained. These
four subassemblies were divided into two sections for the assembly drawings: front and back. The front
started at the dial and included every piece up to the locking mechanism. The back part started with the
red circle spacer and extended to the back cover.
Jorge Figueroa was in charge of the Inner Shell, Inner Shell Cylinder, Back Plate, Red Circle,
Yellow Circle, and the Steel Circle. He helped with organizing meetings, writing the report, keeping team
members in communication, and coming up with ideas for modifications.

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Nicole Drevlow was in charge of creating the Back Plate, Shackle, Shackle Pin, Spring, and the
Dial. She was involved with planning, dimensioning, report writing, rendering images, and compiling the
assemblies. She helped come up with modifications to the assembly.
Alex Herrera was in charge of the Outer shell, and the four components in the locking
mechanism: Block, Lever, Bow, and Rod. He was involved with creating parts and dimensioning.
Conclusion and Evaluation
The end result is a simplified and more secure version of a standard Master lock. The completed
modified assembly features added degrees of protection from obstruction. While not absolutely
unbreakable, individuals will experience significant difficulty trying to break the lock quickly. The
negative about this increased break-in time is that it leads to an increase in manufacturing time; the
modified assembly would take more time to assemble due to the outer shell being a singular piece and
not several as in the original. This modification could be removed if possible in order for manufacturing
time to be reduced; the steel circle cams with their false knobs are a step up from the basic lock of
today.
The file syncing could have been managed better, but the constant emailing and sharing of flash
drives was satisfactory for our purposes since all members worked on separate parts. A singular flash
drive was designated as the master copy for the most up to date files.
Possible future improvements would include a way to make the lock sturdier while also keeping
it relatively easy to assemble. Right now the singular body piece is a good option, but not the most cost
and time effective one. Also, adding an additional steel circle cam or two would aid in increasing
security. More of these mean more combination numbers, which leads to more time needed for
individuals to break into the lock. However, this would also require the user to memorize extra digits, so
a balance must be found between safety and usability.

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Dial by N.D.
Figure 3 Dial
To create the top portion of the dial, whose surface is a rounded knob, I used multi-sectioned
solid using three different circles on four different sketches. The two “base” circles have a radius of 7.6
mm and were spaced 1mm apart. The next circle was of a 6 mm radius and spaced .5 mm above the
second sketch. The final circle was an immensely small circle spaced .5 mm above the third sketch, as
using a point to represent the end of the surface was impossible. I then used the shell command on the
bottom half of the dial to create a universal thickness.
A challenging part was creating the triangle shaped notch on the top portion where the existing
circular pattern of pocketed ridges were. I created three sketches of rectangles on three separate planes
spaced .875 mm apart starting at the top face and used the removed section solid feature.
Figure 4 Removed Section Solid

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Spring by N.D.
Figure 5 Spring
For this part I created a base sketch of a circle with diameter 5.3 mm on the xy plane. I then
created an extremum and center point from Generative Shape Design. I created a plane perpendicular
to the sketch on the extremum point. I generated a line from the center point to the spring’s length of 8
mm. I created three helix structures based off of the pitch measurements from the spring itself. The rib
feature was applied to the three helixes after creating corresponding planes at the endpoints.

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Back Cover by N.D.
Figure 6 Back Cover
This part was created by mirroring a half-circle in order to minimize the amount of work done as
well as for easier visualization. Three half-circles were padded one on top of the other starting on the xy
plane. The corresponding fillets were added. To create the indentation on the back side, several
pocketed circles were created and more fillets were added. The shell feature was originally used to
create this, but the part was deemed too complex by CATIA.
The “Master Lock” text was created in the drafting workbench, saved as a dxf file, and imported
into the part. It was positioned using a construction circle and using the fix constraint.
Figure 7 Back of Cover Figure 8 Master Lock text

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Shackle by N.D.
Figure 9 Shackle
This part was created with a base sketch on the xy plane to represent the “centerline” running
through the part in order to utilize the rib feature. Below you can see the base sketch. The longer side
was made slightly shorter in the base sketch in order to create the indented section near the end. This
was after I discovered that creating a revolved cut around a certain section was more difficult than it
need be. The angled cut out sections on the left side were created by drawing sketches on the xy plane
and pocketing them “up to last” using both directions.

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Shackle Pin by N.D.
Figure 10 Shackle Pin
This part was created using a base sketch on the xy plane to get as many details as possible by
utilizing the top view. An angled plane of 21.01 degrees was created on the rightmost edge to create the
angled feature. After the angled feature was padded, the excess material protruding from the bottom
face of the part was removed. The pockets on the base object and angled piece were created in
separate sketches. Fillets were added last. The non-filleted edges pictured were intentionally left out for
accuracy.
You can see below how the angled feature generates a small section of the base part that is
extended.
Figure 11 Front view of Shackle Pin

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Steel Back Plate by J.F.
Figure 12 Steel Back Plate
The back plate is located inside the lock under the back cover. This unique part has a purpose to
hold certain parts together on the middle rod. The rod holds crucial parts, such as the inner steel circles,
which are the parts that make the locking mechanism possible. In addition, the rod synchronizes the
dial’s movements because the rod is imbedded into the hole of the dial and making it possible to be
unlocked.
Figure 13 Steel Back Plate Figure 14 Steel Back Plate

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Red Circle by J.F.
Figure 15 Red Circle
Two red circles are used in the original and modified product. When assembled, the circles are
located on the rod of the back plate between the steel circles. The circle has two purposes. The first
function is to keep all the underneath parts from moving off the rod, keeping everything tight, using the
extended bar to push on the extended block from the rod as shown in figure 16. The second function is
to keep the two steel circles from touching and this is important because this separation makes the
locking function possible.
Figure 16 Red Circle

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Inner Shell by J.F.
Figure 17 Inner Shell
This is one of most essential parts. The inner shell is where everything is
located. It has the function to hold everything together in their place, as shown in
figure 18. In addition, the inner shell contains the first piece that assists in
connecting the inner and outer shell together using the cylindrical extended piece
that is found on front of the inner shell as shown in figure 19.

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Inner Cylinder by J.F
Figure 20 Inner Cylinder
The inner cylinder is used for two purposes. The first purpose is to hold tight the block in a
specific location. The second function is to support the connection of the inner shell and outer shell. The
inner cylinder assist the cylindrical extended piece found on front of the inner shell. Figure 22 shows
how the cylindrical and the inner cylinder connect the two shells.
Figure 21 Inner Shell Figure 22 Inner Shell

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Steel Circle by J.F.
Figure 23 Steel Circle
Two of these are used in the product. It is located on the back plate’s rod and it has the function
of locking. The steel circles have the purpose of representing a number in the lock’s combination. There
are three numbers in a lock’s combination; the first number is represented by the “inner circle”, which is
a separate circle from a different location. These tow steel circles represent the last numbers of the
combination. If one circle is missing, the lock will never be able to be unlocked.
Figure 24 Steel Circle

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Yellow Circle by J.F.
Figure 25 Yellow Circle
There is only one yellow circle in the whole product and it is located on the back plate’s rod
between a steel circle and a spring. This yellow circle only has one function and it is to separate one of
the steel circles with a spring as shown in figure 26.
Figure 26 Yellow Circle

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Inner Circle by J.F.
Figure 27 Inner Circle
The inner circle has the same function as the steel circles. The function of this circle is to
represent a number of the combination lock. Without this circle or any of the other two steel circles, the
unlocking mechanism will be impossible. This is a very crucial piece. This unique part is set between the
dial and the inner shell. The dial contains a metal ring that holds the ring in place and it moves along
with the dial’s movement. This piece represents the lock’s first combination number.
Figure 28 Inner Circle Figure 29 Inner Circle

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Outer Shell by A.H.
Figure 30 Outer Shell
For the outer shell, the overall diameter and thickness were measured as well as the diameter of
each of the holes on the back face. When modeling the rear casing, the overall shape of a cylinder was
made first by sketching a circle and then padding the appropriate distance. The cylinder was then
hollowed out using the shell tool to a thickness of 0.4 inches. The hole and pocket tools were then used
to create the three circular holes and one square hole.

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Rod by A.H.
Figure 31 Rod
The design for modeling the rod was fairly simple. The diameter and length of the rod was
measured and a corresponding circular sketch was padded the length of it and the edges on either face
were filleted. This rod is inserted into one of the holes on the front face of the block part that was also
modeled.

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Bow by A.H.
Figure 32 Bow
For the bow the height and width of the part were measured and used to create a simple sketch
that was padded out the overall height of the bow. This bow is inserted into the slot on the rear face of
the block that was modeled.

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Lever by A.H.
Figure 33 Bow
The lever is the part that connects with the shackle in order to keep the lock closed. One of the
challenges was getting all of the parts in their precise locations since this part was small and complex.

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Block by A.H.
Figure 34 Block
For the internal block of the locking mechanism, the overall height and width were measured as
well as the diameters of all of the holes on the part. The length and width of the top cavity were
measured and the varying thicknesses of the left side of the part. A base sketch was drawn and then
padded out the appropriate length and the edges were filleted. The holes and pockets on the front of
the block were created using the hole and pocket commands. Then the slot on the side was created with
the pocket command followed by the rear slot for the bow piece to be inserted. The top cavity and holes
were created last with the pocket tool. Both the rod and bow are connected to this part.

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Modified Steel Circle by J.F.
Figure 35 Modified Steel Circle
The modifications to this part included the reduction in height of the real knobs and the addition
of several false knobs. The height of the false knobs was calculated in order to keep their ability to be
felt by the pressure cracking method, but not tall enough to interfere with normal operation. It was
challenging to find a balance between tall enough to still work correctly and provide enough of an offset
to make an impact on thieves.
Below you can see the comparison between the original sub-assembly and the modified one.
Figure 36 Original Back Plate Subassembly Figure 36 Modified back Plate Subassembly

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Modified Red Circle by J.F.
Figure 37 Modified Red Circle
The modification to this part was solely the height increase in order to compensate for the
heights of the knobs on the steel circle changing. The height was changed from 1.21 mm to 1.33 mm.

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Outer Shell by A.H.
Figure 38 Outer Shell
This modified piece is a replacement of the outer shell and the back cover. Even though there is not a
huge difference in visuals, security-wise, this modification has an important function. The created part
consists of one single solid part, instead of 2 individual parts. The purpose of this is to lower the
possibility of cracking open the back cover and removing all the parts. In the original product it is very
easy to destroy the outer shell and to remove the inner parts by just using pliers. With the new
modification, the possibility of opening the lock with pliers is decreased because instead of having an
assembly of a few separate parts held together by a thin wall, now it is one complete solid shell with no
edges. As show in figure 39 and figure 40 the solid is one complete part, and the edges are replaced with
curved fillets, making it nearly impossible to crack open.
Figure 39 Modified Shell Figure 40 Modified Shell

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