DynaDrive Drive Train Tension Measurement Tool

Team: Jakob Gienger-Nieves, Cooper Larsen and Austin Webster

Project Description

The tension in the rope ladder drive train system utilized by the DynaDrive bioreactor for mixing working fluids in vessels is a critical parameter that remains undetermined. Customers have previously contacted Thermo Fisher to request tension calibration information when issues arose in their tests; however, only a theoretical model is currently available. The ability to isolate tension as a controlled variable will help determine drive train lifespan and simplify the troubleshooting process.

Thermo Fisher requests a tool that collects tension data of the drive train over a prolonged testing period. Experimentally quantifying the magnitude and trend of tension in the drive shaft over time will allow for more accurate diagnosing of problems compared to current theoretical models.

DynaDrive Bioreactor
Thermo Fisher DynaDrive Bioreactor
Rope Ladder Drive Train
DynaDrive Rope Ladder Drive Train

Design Description

The design implements a U-shaped 6061-T6 anodized aluminum frame with four circular cutouts for load cells. The load cells are wired to a transmitter contained within a mounting box 3D printed from PLA filament. The transmitter interacts with a computer that contains scripts for data collection and analysis. Because the hub is manually raised along two rods, 3D printed supports are placed around the rods to prevent the main hub lift from lowering.

System Setup With Hub Lift and Motor
System Setup With Hub Lift and Motor
Bottom View of Frame with Load Cells
Bottom View of Frame with Load Cells
Isometric View of Frame
Isometric View of Frame
Isolated Load Cell System and Transmitter
Isolated Load Cell System and Transmitter
Installed Device
Installed Device

Performance Review

Comparison of requirements, constraints, and goals against target, threshold, predicted, and actual performance values for the DynaDrive tension measurement tool.
Requirements, Constraints, Goals Target Threshold Predicted Performance Actual Performance
Structural Safety Factor 3 2 13 15
Measured Tension Range N/A 18–500 lbs 10–4000 lbs 440 lbs
Lifespan 5000 hours 1000 hours 40 × 106 hours 95+ hours
Measured Tension Error 1–2% 10% 1.24% 6.8%

The frame was modeled in SolidWorks and ran through a static simulation at 500 and 1500 lbf. The frame passes both tests. A machined frame was also tested in a Tinius Olsen Compression Test and withstood about 7,600 lbf before failing.

The Phidgets 50 kg button load cells have a rated load range of between 0.5–50 kg, and with 4 load cells that gets a maximum load range of 200 kg or about 440 lbs.

Three tests were conducted to quantify the decrease in tension over longer periods of time and further evaluate the performance of the design under different circumstances.

A test to quantify error was conducted by placing a 10 lb weight on the load cells and frame; the weight output from the code was compared to the known weight for accuracy.

SolidWorks Stress Simulation at 1500 lbf Load
SolidWorks Stress Simulation at 1500 lbf Load
Force–Strain Curve of Frame
Force–Strain Curve of Frame
First Long-Term Test — Calibration Problem
First Long-Term Test (Calibration Problem). An issue in the load cell offset caused a lower initial weight reading than expected, leading to a tension trend that fell into the negatives. This was fixed for subsequent tests.
Second Long-Term Test (Full Day)
Second Long-Term Test (Full Day).
Third Long-Term Test (Four Days; Zeroed at End of Second Test).
Third Long-Term Test (Four Days; Zeroed at End of Second Test).

Conclusion

Structural Safety Factor
Actual performance greatly exceeds target value due to the strength of material used for the frame.
Measured Tension Range
Phidgets load cells were initially used for testing, but shipment delays caused a pivot to use these for the final product.
Lifespan
Current design is confirmed to function for 6 days of use, with time constraints preventing testing for longer durations. No concerns exist regarding long-term testing, as the load cells are rated for millions of cycles.
Measured Tension Error
Experimental testing trendlines follow the expected trendlines provided from theoretical analysis.

Future Work

  • A new frame for heavy-duty load cells needs to be manufactured from the already existing CAD model.
  • The new load cells will need relevant hardware and software setup to work with the new transmitter.
  • The mounting frame will need to be remodeled to case the new transmitter.
  • The rod stoppers need to be perfected, or a permanent alternative needs to be implemented into the bioreactor.

Lessons Learned

  • An essential factor in project building is component delivery, and frequent communication with vendors is necessary to stay on schedule.
  • A common form of manufacturing is CNC milling and there are important methods to use while designing.
  • Using electrical components can be more than just wiring and may involve software development.

Thank You

Our group would like to thank our sponsor, Thermo Fisher Scientific, and our faculty mentor, Jackson Graham, for their support with this project.