GEEN 2851 - Truss Project
GEEN 2851 - Truss Project
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In GEEN-2851 my group, the Moment Makers, designed and tested a small truss.
In GEEN-2851 my group, the Moment Makers, designed and tested a small truss.
Our team, the Moment Makers, built a truss designed to withstand at least eight hundred pounds of force. The design constraints were a maximum height of 9 inches tall, a width between 22 and 23 inches, and a gusset coverage of 30% of the total beam surface area. In addition, the beams could not touch, and the strength to weight ratio had to be between 800 and 3000 lbf/lb. We used a four-point bending test and a tension test to determine the strength of our material, and ultimately designed a Howe truss to maximize the load the truss could withstand, while remaining within the design requirements.
(Fig.1) The Moment Makers' truss, before testing it with the universal testing machine
MATERIALS TESTING
Before we could begin designing the truss, we had to test the strength of the pine wood and the wood glue. We used a four-point bending test to determine how much bending stress the wood could bear before it failed. We placed a wood sample of known dimensions between four rollers in the universal testing machine, and applied force until the beam failed. We centered our 12” sample along its long edge on two support rollers 11” apart, which left a 0.5” overhang on each end. We then placed two load-applying rollers on the upper part of the wood 4” inside of their respective lower rollers
(Fig.4) Initial prototypes, arranged earliest to latest from top to bottom
(Fig.5) Initial CAD drawing of the box with the colored lights and red fall button
TRUSS DESIGN PROCESS
Left: Final CAD drawing of the TPU shell, the PLA box with the divider separating the batteries from the other electronics, and the TPU button covers (Fig.6)
Above: Circuit diagram for the climber device, which is identical to the belayer circuit except with an accelerometer (Fig.7)
FINAL PRODUCT
FINAL PRODUCT
The final version of the Belay Buddy featured three buttons that each triggered a different light and haptic vibration pattern. We placed a large hole in the side of the TPU shell so that the light from the neo-pixels would shine through the side, since a climber or belayer would not necessarily be able to see the light from the top of the box all the time. We added a curved base to the TPU shell for the belayer device so that they could wear it on their arm and a flat base to the climber device so that the velcro could go around and lie flush with a harness. The TPU shell had a lip on two sides and a tight tolerance to the PLA case, so it would not slip out of the shell while it was being used. The CAD files for the TPU shell and PLA case can be found at the bottom of this page.
The final electronics (Fig.3) were all from Adafruit: a motor and driver, Feather M0, accelerometer (for climber device), and neo-pixel strip. These fit snugly inside the PLA case with no room to move around inside. The electronics were programmed to light up a certain color and produce a certain vibration pattern when the corresponding button was pressed. This code can be found in the appendix at the bottom of this page.
(Fig.8) Poster with summary of what the Belay Buddy is, what electronics we used, results from testing, design constraints, plans for future work, and the bill of materials for the project
(Fig.9) Image from Fall 2024 Design Expo
My Role on the Team
My Role on the Team
(Fig.10) CAD drawing of climber TPU shell
(Fig.11) CAD drawing of belayer TPU shell
Once I had a good enough design for the climber and belayer TPU shells (Fig.10 and Fig.11), the rest of the team had completed most of their work as well. The devices were functional except for a few small kinks in the ele
(Fig.12) CAD of mountain desgin in side of climber device
(Fig.13) Belay Buddy with lights showing through mountain design
TESTING AND ANALYSIS
To ensure our design met the requirements we conducted extensive testing and analysis. We tested the durability of the PLA case with and without the TPU shell, as well as the IP rating of the PLA case, and the battery life of the electronics.
Electronics
Runtime: 28 hours of use
Range: 230 m
Charge time: 45 minutes
Power draw at rest: 0.18 W
Power draw (during transmission and alert): 0.775 W
Case
Expected waterproofing performance - IP52
Case withstands falls of up to 65 feet without damage
The full details of our testing and analysis can be found in the paper directly below.
Testing and Analysis.pdfPage updated
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