PVC Bicycle Trailer
SUMMARY:
The bike trailer was a lab project in Design for Strength and Stiffness (ME 328), where my lab partners and I were tasked with designing and building a bicycle trailer from PVC pipe to tow a 50 lb. duffel bag behind a bicycle. We needed to research load cases, go through an iterative design process, model the trailer in SolidWorks, conduct FEA analysis, and iterate until we were happy with the safety factors. Finally, we built and tested the trailer.
OBJECTIVE:
The “customer” needs a bike trailer built out of PVC pipe that can be easily attached to a bike. The trailer must accommodate a 33 in. long and 16 in. wide bag with an unevenly distributed load of 50 pounds. The trailer needs to be strong enough for general road travel on a bike, and rigid enough that any deflection does not damage the trailer or its contents.
My team and I with our finished trailer, load in place. As mentioned later, our deflection predictions were more exaggerated than what we measured.
DESIGN PROCESS:
Due to the elastic nature of PVC pipe, our design was driven by stiffness. Our main objective was preventing any part of the frame from contacting the ground during loaded use. We created a design tool using Matlab to iterate for the least expensive pipe size with acceptable deflection. Once that was finalized, I modeled the trailer in SolidWorks and executed the FEA model shown in Figure 1. I first modeled one piece of pipe with an applied load to confirm the FEA results, then modeled the whole trailer using beam elements.
SolidWorks FEA screenshot set to measure critical deflection. Predicted deflection was 1.34 inches, measured deflection was less than 0.5 inches.
CONCLUSION:
This project was my first experience going from ideas to prototype on an engineering project, and I learned a lot. Every time we needed to make an estimate for lack of information (quantifying loads, material property discrepancies, load distribution, etc.), we took the conservative choice. Our trailer ended up tremendously overbuilt, and since we sourced the building materials ourselves, I would have been less conservative were I to iterate the design again. This project was an eye opener to the design process and I’m excited to see more projects come to fruition.