The main safety considerations are the tipping point of the frame and pinch points. The
wheels on the bottom of the frame are potential pinch points. A solution that does not limit
mobility is to include guards, welded or fixed to the frame to cover the wheels. An idea to
prevent the machine from tipping while it is stationary is to mount the wheels onto triangular
frames that can swing out and distribute the weight of the machine outward. The extendable legs
can then be folded back in while the device is being transported so that it can fit through
doorways. Design and testing of this concept will take place once the base frame is constructed.
The tipping point of the final frame is determined using geometric and mass properties provided
Climbing on top of the frame is another risk for tipping. To prevent children or students
from climbing on top of the machine, steel letters will be carved out on the burn table to spell out
“Department of Mechanical Engineering''. The decorative sign on top of the machine will
discourage people from climbing or hanging off the frame.
The individual components of this machine containing interfacing gears or other pinch
points must be covered to ensure user safety. The current design covers all interior pinch points
of the machine with an acrylic casing. The durability of each individual step, the connection
between steps, the frame, and the electronic components is important for the longevity of this
project. In addition to ensuring that the machine holds up, the safety of the users is also vitally
important. This design must be in compliance with engineering standards for a product being
used by children and minors.
Engineering Specifications and Engineering Standards
Due to the nature of this project, the majority of testing will occur once the machine itself
is completed. Preliminary testing has included the part materials and their compatibility with the
rest of the machine to ensure that the Rube Goldberg setup works. Since this device is being built
from the inside out, only rudimentary analyses have been completed for a few of the following
specifications that apply to the completed project and are summarized in Table 1 below. All
standards that apply thus far are listed in Appendix D.
The most significant engineering standard for our project is the ASTM F963-17 Standard
Consumer Safety Specification for Toy Safety. Within this standard comes our customers
primary concern of tipping. ASTM F963-17 states that “Stationary floor toys of... greater than 10
lbs shall not tip when placed on a 10° incline” (section 4.15.4). Once the weight of the final
device is known, we can apply this physical property to our current SolidWorks model and
perform the necessary analysis on a 10˚ incline. The Standard Safety Specification for Clothing
Storage Units (ASTM F2057-14) is also being referenced for our project. The potential to have
children climb on the machine similar to how they may climb on dressers presents another
concern for our design if they were to tip it over. Tests will be conducted once the final weight is
determined and additional weight may be added if proven necessary. The letter display on top of
the machine is a preventative design feature that will discourage any climbing that may lead to
Additionally, our project must comply with section 4.7.3 which states that “edges,
including holes and slots, shall be free of hazardous burrs and feathering…”. To ensure the
safety of all that interact with the device, our design must comply with this specification for
metal parts, specifically our frame structure. Given that we also have interactive components to
this machine that the user will be in contact with, the same specification applies to other
fabricated parts including handles, gears, and other hands-on pieces that are not metal. No
specific number was provided for the surface roughness of the parts, so once the parts have been
manufactured, our team will seek professional opinion from a professor or lab instructor.
The ASTM E2299-13 Standard Guide for Sensory Evaluation of Products by Children
and Minors is another engineering standard that applies to the Rube Goldberg machine. The
specification concerned with our project states that “it is the responsibility of the testing group to
make sure no harm or injuries occur as a result of faulty products or test facilities”. In relation to
our device, for any testing that occurs while children and minors are present, it is the senior
team’s responsibility to ensure user safety with the machine itself as well as the surrounding
areas. Once the inner workings of the project are functional and safely enclosed, it is our
intention to showcase the preliminary machine to a small group of elementary-age children and
gather thoughts, ideas, and potential areas to improve on.
Given that our design is to be transported around Samson Plaza, it has to fit through
entryways and doorways within the buildings. For a design constraint, we limited the size of our
project to fit through a doorway (7’ tall x 32” wide) and into an elevator (51” x 61”) with
dimensions specified by ADA Compliance 4.13.5 and ADA Standard 407, respectfully.
Preliminary testing with a wooden frame mockup prototype showed our design is compatible
with all the doors and elevators within the Samson Plaza buildings.
As an educational tool, it is our intention to have students with disabilities interact with
our machine as well. While no testing has been conducted for this specification, ADA
Accessibility A4.12.2 states that a user “should require no more than 5 lbf (22.2 N) to move” any
interactive cranks or gears. Testing will be completed as soon as the interactive components are
functional and force inputs by the user can be adjusted to meet this standard.
Stability and Visibility
The device will be displayed primarily in Stephenson Hall where it will remain stationary
unless being used for an event. To ensure the device does not roll while students are interacting
with it, the castors we have must comply with the ANSI Institute of Castor and Wheel
Manufacturers. Section 184.108.40.206 states that a “break must hold for 10 seconds with applied
horizontal force” that is a fraction of the total device weight. Once the final weight of the
prototype is determined, the breaks that we have can undergo testing in order to meet this
While not necessary, the final standard we want to meet for our project involves the
radiometric and photometric properties of materials (DIN 5036-3). Our team was informed that
museums use this standard which states that plastic barriers or encasings should have “greater
than 90% light transmission”. The exact section this specification comes from is unknown, but
we will use it to ensure that users have maximum visibility of our machine and are able to take
photos of it. Manufacturing data for the plastic will tell us the light transmission of the material
and whether or not it should be used as our final encasing.
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