Problem Statement
After purchasing a Yamaha Crosscore RC e Bike, I needed a place to hold my large chain lock while riding. I had a few solutions at the time, including keeping it in a backpack and fixing it to the rear rack, but none of them were satisfactory for riding the bike longer distances. To fix this, I wanted to design a box that could attach to the factory fittings on the bike without impeding normal operation while keeping the chain safe and secure. Parts for this project will be 3D printed on my Anycubic Kobra 3 v2.
Design
The design for this part was conducted in SolidWorks and slicing for my printer was done in the Anycubic slicer. Initial designs were made to fit in the bottom part of the bike frame, where the two tubes meet. The basket should be attached to the factory screws in the frame. The first design is shown in the figure below.
Figure 1: Initial SolidWorks Design
This initial design did not fit the bike to my liking, so I tweaked and printed the design until it met the criteria I set for it. Printing the part only took a few hours in PLA filament, so I could make several of them within a few days to dial in the design. After the first few designs, I decided to add holes so that the small u-lock could sit near the top of the box, rather than inside the box with the chain. Below are the prints of the different designs.
Figure 2: 3D Prints of Several Lock Box Designs
After the design fit the bike how I had envisioned, I printed it again in PETG filament for increased toughness and durability. The printed part on the bike with the chain lock is shown in the figure below.
Figure 3: Lock Box Mounted on Bike
Next Steps
This lock box has functioned quite well as I have been riding around with it on my bike, however it could use some improvements. The first issue is that the box has broken near the bottom, as shown in the figure below.
Figure 4: Lock Box Failure Point
Along with this, the box currently has sharp edges which can cause discomfort if hit while riding. Based on these considerations, I have created an updated design in SolidWorks, and will print and test this box to create something that will be able to function ideally, and be able to withstand long rides for several years. This design increased the wall thickness, filleted the sharp edges, and added a chamfer to the bottom of the basket, as shown in the figure below.
Figure 5: Updated Lock Box Design
Figure 6: Updated Lock Box Print
I plan to test this part over the next few weeks and see where any improvements could be made as well as making an annealed version of this part to see how that changes the geometry and strength of the design. While I see this design improving as I continue to test it, I hope to get it to a point where my design meets my all of my needs within the next few months.