Christina Holman | Design Blog

We finally made it to the end! After the preliminary design report, it was time to finalize our actual design (since we were given enough materials to make one truss to test). After doing a few more draft sketches and analysis, I was able to pick up on patterns on which types of designs produced the maximum strength (all within the parameters we were given). Finally, I came up with the sketch at the bottom-right, and the MATLAB analysis produced the highest load we were able to reach. We theorized that: two members would buckle first instead of just one (Members 3 and 4); the maximum load is 11.62 ± 0.063N; and the total cost of the truss is $290 (under the budget limit). From there, we moved to prototyping: we cut the straws as close as possible to the lengths specified in our final design. To create uniform gusset plates, our "joints," we used the circular cap of an individual Tropicana Orange Juice bottle. It met the area requirements and acted as a stamp aga

Planetary Carrier Somehow I was able to use Creo to create all of the components of the gearbox in one day (not recommended). After destructing the B&D Li2000, opening up the gearbox (which took a bit of strength), and calculating the measurements of each component, I was finally able to re-create all of the parts. Ring Gear Then, with each individual design, attach the components to one another in assembly (left) so that the kinematics or the motion of the CAD-assembled gear train resembled that in the gearbox. Planet Gear Additionally, I was able to use the motion analysis feature in Creo to model the pitch diameters and gear ratios for the cylinders representing each gear. (We did not go into depth on how to actually create the teeth on the gear since it requires manufacturing details we did not have.) Sun Gear Below is a video demonstrating the mechanism analysis for a multi-stage epicyclic gear train like the one used in the B&D Li2000 Screwdriver.

Motor and Case So, in the most recent lectures, we've talked a lot about what is called " Design for Manufacturing and  Assembly (DFMA) " -- or the combination of designing for the ease of manufacture and designing for the ease of assembly. Even the best assembly process in the world can fail under human errors like fatigue, time pressure, and plain carelessness. (We've all accidentally dived into an Ikea furniture assembly without fulling reading the instructions beforehand.) Hence, wisely, product designers tend to use 'mistake-proofing' features in order to make those kinds of careless mistakes obvious within seconds. Like a puzzle, either a piece fits or it doesn't. Otherwise, you'll end up with a deformed piece and an unclear final product. Honestly, those small DFMA pieces like a raised section of plastic can make or break how well-connected a handle is -- or even how easy it is to replicate the same level of quality that the company is promi

So ME359 has been great but it has been an exercise in stamina . For a 2-credit class, where weekly homework is 70% of your grade, this is a lot of time and energy -- but, still, exciting. Like I said before, I do really well when it comes to project-based learning and real-world applications. And this course's final project has really been wonderful for that. The final project is to reverse engineer the Black and Decker Li2000 Screwdriver and then use the computer-aided design (CAD) software Creo to re-create the gearbox. This is an interesting task since the B&D Li2000 uses a planetary gearbox, which consists of three types of a gears that all lie on the same horizontal axis. My task is to create the ring gear (the outermost gear), the three pinion gears that rotate around that inner radius of that ring, the sun ring around which the pinion gears rotate, and, then, the planetary gear connected to the central axis of the screwdriver. Ultimately, I need to create all of

The second part of the final project for EK301 (Mechanics) consists of a preliminary design -- or, rather, several preliminary designs and one identified draft. Having the data from the straw lab test and the resultant code to determine the approximate load that a straw can hold based on its length, it took quite a bit of creativity to find the perfect combination of straws. However, to simplify this process, the class was instructed to use a MATLAB code that would take a design and then indicate which member of the truss would fail first. It is important to note that all designs were given the same parameters: Figure: One of two designs selected The truss must be a single, planar, simple truss.  Members must be joined concurrently at joints using the provided pins and double pinned to the guest plates.  Gusset plates may be any geometry but must have an area of less than 16 sq. cm. All joint-to-joint distances must be at least 10 cm and no longer than 16 cm. The truss mus

Testing Apparatus for Straw Lab Fall 2018 has been off to a very strong start. Being back in an academic environment is both really challenging and very inspiring. It has been tough to balance a full-time course load with a part-time job, but, so far, being able to still do classes like EK301 (Mechanics) has been rewarding. I missed creating designs and prototypes more -- much more -- than I realized. The truss design project that I just started has really switched on the engineering light bulb. I am not a huge fan of the traditional, exam-based learning that most engineering classes use, but these little peaks into applications and projects (which is how I fell in love with engineering) makes it all worthwhile. The final project started off with a lab test on the straws my group will use to design a sturdy bridge or 'truss.' The straw lab required lots of attention to detail and control, and, fortunately, I was able to stay later to complete the remaining tests and

So, hey... I'm in grad school! Life is going great. Last year -- the year after graduating from Wellesley College -- was a whirlwind, and settling into the world as a post-graduate is much more difficult than I had thought. My sincere apologies to anyone following this blog, only for it to be really left behind. Long story, short: "Christina made into an amazing program at Boston University College of Engineering as a MechE (Mechanical Engineer) -- and she is living her best life!" Yet, if you still want to know what has happened in my life. Let me give you all a short recap of 2017-2018. Last Semester of College (Winter - Spring 2017) I was accepted into the Madeleine Korbel Albright Institute for January 2017. And, it was absolutely phenomenal. Every day was a new topic of contemporary politics and high-profile policies. On top of that, we were also pushed to conduct a rigorous case study in those four weeks. (Take a peek here . ) The administrators (righ