Corkscrew - Fatigue Torsion Test Jig
Designed, developed and validated for Halter
Background
Nicknamed the Corkscrew, this fixture was designed, built, and validated for A|B fatigue testing for collar material and geometry changes.
This jig assisted in validating the changes that were implemented in the design for verification build, which included an increase in the thickness of the TPU band connecting both sides of the Halter collar tubs, and material changes. The goal was to ensure that these changes did not reduce the working lifespan of the collar, or introduce any additional failure points. This testing was conducted using the HASS test procedure, within thermal chambers, which introduced interesting challenges, as the cyclic temperature operating range was -10 to 70*C, with 95% humidity. This, while fatiguing the collars, also fatigues the jig at the same rate, this required rapid prototyping with different materials for the construction of the jig, including stainless steel hardware, moisture-protected stepper motors, adding additional heatsinks to the servo motors to get them under their max operating temperature, designing the required electronics to be water resistant and be placed outside the chambers as much as possible.
Besides all of these efforts, the time to repair the jig once broken was long and the availability between these periods was small. The jig was successful in achieving its task, however, allowed me to learn the importance of looking further ahead at points of failure, designing for harsh environments, the importance of safety considerations early in the design process, and implementing redundancy.
This experience underlined the significance of these lessons in engineering projects of this nature, where precision, reliability, and robustness are important. The lessons from this were utilized to build the next fatigue chamber.
Learnings:
Nicknamed the Corkscrew, this fixture was designed, built, and validated for A|B fatigue testing for collar material and geometry changes.
This jig assisted in validating the changes that were implemented in the design for verification build, which included an increase in the thickness of the TPU band connecting both sides of the Halter collar tubs, and material changes. The goal was to ensure that these changes did not reduce the working lifespan of the collar, or introduce any additional failure points. This testing was conducted using the HASS test procedure, within thermal chambers, which introduced interesting challenges, as the cyclic temperature operating range was -10 to 70*C, with 95% humidity. This, while fatiguing the collars, also fatigues the jig at the same rate, this required rapid prototyping with different materials for the construction of the jig, including stainless steel hardware, moisture-protected stepper motors, adding additional heatsinks to the servo motors to get them under their max operating temperature, designing the required electronics to be water resistant and be placed outside the chambers as much as possible.
Besides all of these efforts, the time to repair the jig once broken was long and the availability between these periods was small. The jig was successful in achieving its task, however, allowed me to learn the importance of looking further ahead at points of failure, designing for harsh environments, the importance of safety considerations early in the design process, and implementing redundancy.
This experience underlined the significance of these lessons in engineering projects of this nature, where precision, reliability, and robustness are important. The lessons from this were utilized to build the next fatigue chamber.
Learnings:
- The importance of designing parts and equipment with parts that are rated for well outside their operantining conditions.
- Creep Failure is highly understated, and the importance redundancy and emergency cutoffs.
- Testing your assumptions, a lot of design decisions are based on certain assumptions about a problem or an issue, validate these to ensure the success of the project, otherwise you can end up in a long feedback loophole.
- Avoid Custom parts as much as possible, Especially in an R&D, where rapid results are important. When the goal is to drive results for a certain test, the pathway to getting those results is important, anything that will extend that timeline, isn't critical to the success of the project.
