Chiming Grandfather Clocks

Implementing a grandfather clock puzzle.

The participants enter the room, and the row of large grandfather clocks immediately grab their attention. As shown in our storyboard, participants will have to place chimes in the correct clocks in order to play the correct melody and advance to the next room. For further detail, please see our Sketch Models Storyboard.

This activity allows for a variety number of people to participate actively. Being able to physically move around chimes makes particpants feel more invovled. The incorproation of grandfather clocks fits easily into the mystery manor theme and is versatile to fit many story lines.

Clock Body Design and Implementation

The grandfather clock assembly was intended to be simple and easy to assemble and maintain. To this end, the clock has a modular design. An outer clock shell houses a module for chimes and a module for the clock face/hands. Not only must the clock be easy to put together (screw access, room to fit tools), it must also be easy to take apart (maitenance, transportation from shop to final venue).

The materials to make the physical clock are common: 1/2" Plywood, 1/8" Plexiglass, wood stain, and molding. To facilitate easy cuts and wasting little material, the dimensions were chosen so that pieces fit on standard 4'x8' plywood sheets.

Easy assembly and maintenance were the guiding intentions in designing the clock body. A number of measures were taken to meet this goal. First, the pieces of the clock body are made of straight, flat pieces of plywood - pieces that can be easily cut on a tablesaw out of common 4'x8' stock. Other smaller pieces are dimensioned to fit inside of a laser cutter; likewise, other decorative pieces are easily found at hardware stores like Home Depot.

Another factor in making the assembly easy to put together (and take apart) is the use of slots. Each module, rather than being fastened in, is simply placed in slots. This way, a maintainer can conveniently access a part for servicing without taking apart the entire structure. In other words, each module is separate from the others.

There are also features to make the clock more friendly for users. To simplify user interaction, users can only touch/access the parts of the clock that they need to - namely the chime in the chime module. Other moving elements that are either decorative or need not be touched are behind a layer of plexiglass, as shown above. Below is a picture of the actual assembled clock body.

Chime Design and Implementation

In our gameplay, the clock needed to be able to detect when a chime is hung on the clock, hit the chime with a hammer, and respond by moving its gears, pendulum, and clock hands when the correct chime was put in place. To be able to detect different chimes, we hid different resistors within the chimes such that when each chime was put in place, a circuit would be completed. The circuit contained a voltage divider that would output a different voltage to our arduino for each chime that was put in place, allowing us to control when the "success" response initiated.

To keep our design modular, all chime elements are contained in a separate box that could be easily slid into slots on the main frame of the clock. The picture below shows an assembly and exploded view of a CAD model of the chime box. The chime box includes the box and attachement points (1/2" mdf), a chime mallet (wood handle, plastic mallet), VS-2 servo, two screw hooks, and a chime.

Because large chimes are expensive and are typically sold in sets, we used 3/4" conduit pipes to make our own chimes. Two electrical conduit pipes were cut to different resononant lengths to produce two different pitches. The chime consisted of conduit pipe, a steel bar, foam, copper tape, and a resistor. The steel bar was bent and welded to the chime so that it could be attached to the clock. Different resistors were attached to the handle, the ends held in place using conductive copper tape so that the resistor could be inserted into the circuit. The rest of the handle was covered in a thin layer of foam to hide the resistor.

In order to attach the chime to the clock and complete the circuit, the user places a chime onto two screw hooks attached to the chime box. The screw hooks are soldered to wires, and the copper areas on the handle conduct such that the hidden resistor on the inside is now part of the circuit and the clock can sense which chime is in the clock.

The hammer is attached to the servo using the servo horn and mini wood-screws. The servo sits on a shelf in the chime box with an empty space where the hammer sticks through.

Electronics Design and Implementation

To detect when the correct chime was placed in the clock, we embedded a different resistor into the handle of the chimes. The hooks that the chime were placed in were wired into a voltage divider . A microprocessor then reads the voltage drop to determine when the correct chime was placed. There is one motor and three servos connected to the microprocessor. To power the accessories for our clock we used a SpringRC Continuous Rotation Servo for the gears and Vigor VS-2A Analog Servos for the clock hands, hammer, and pendulum. For a picture of how the resistor was embedded in the chime, see the section above on Chime Design and Implementation.

Photo of final chime with resistor embedded in the handle

When users walk into the room they will find a clock that reads a time that is not midnight. When the correct chime is placed, the servo attached to the clock face will turn to midnight and the servo attached to the hammer will engage and strike the chime . Then, the motor attached to the gears in the clock will begin spinning and the servo attached to the pendulum will begin swinging to indicate that the clock is now properly functioning.

Unfortunately, during transportation to Endicott house for presentaitons the motors for everything besides the hamer stopped working for an unknown reason so we have a video below showing the process of what happens when an incorrect (1st chime) and correct (2nd chime) are placed in the clock.

Video of functioning clock with all features including what happens when an incorrect chime is placed.


Our concept implementation allowed us to gain key insights into how our gag would work in real life. The size of our model was a good size for the puzzle. Even though it was larger than the average grandfather clock, our clock made it easy for people of varying heights to comfortably replace chimes. Participants of our user testing appreciated the antique look and feel of the clock, and the chimes were intresting enough that they didn't mind the other parts behind Plexiglass. They enjoyed trying the different chimes and seeing which one "worked." They also thought it was clear when the correct chime was place - the effect of the gears, pendulum, and clock hands going crazy was a fun indicator. The modularity of the model made it relatively easy to build, but more importantly easy to troubleshoot a certain part of the clock without needing to take the entire clock apart.

Of course, there are lots of improvements we can make after this iteration of concept refinement. The chimes we created didn't make the most pleasant or loud sound, so we need to experiment with more materials for a more robust sound. In addition, for our model we haphazardly taped the electronics to the back of the clock, so in the future we need to create a safe space in the clock for the electonics to house in so that they are out of sight but also won't break after being moved. More things for us to implement would be to add a button or lever that will activitate all the chimes, try different indicators for wrong chime replacement, and create clues on the clocks for partipicants to realize what the task is. After those improvements it's important for more user testing, and this time with more than just one clock and few chimes. It's important to test with multiple clocks to understand how users will be able to interact with each other while completing the full puzzle.