Removable Bike Milk Crate for Yepp Rear Rack With 3D Printed Bracket

I wanted to add more hauling capacity to my bike and was looking for something compatible with my Yepp rear rack that I use with a removable child seat for my daughter. The child seat (Yepp Maxi) has this ingenious mechanism that allows it to slide into my rear rack quickly and securely, and be removed just as easily. I was thinking it'd be great to have a similar compatible rear basket that also quickly attach/detach from my rear rack. I couldn't this anywhere on the Internet so I decided to make my own.

I designed a removable Yepp-rack-compatible rear basket that consists of a milk crate, some plywood for stability and a 3D printed bracket threaded for M6 bolts which hold the whole thing together. It can be attached and removed in seconds and is extremely secure.

1. Milk Crate (this one is 13x13x11 inches)
2. 3D Printer and UV/heat resistant filament (PETG or ASA)
3. 5x M6 threaded inserts (I used 4x 10mm inserts for the top, 1x 12mm insert for rear locking bolt)
4. 5x M6 hex bolts (I used 4x20mm for top, 1x 40mm for rear locking bolt)
5. 1/2 inch plywood (cut to roughly 12x12inch)
6. 4x M5 nuts and bolts to attach plywood to Milk Crate

I didn't want to reinvent the wheel so I took a picture of the mounting bracket on my Yepp Maxi child seat and imported it into Fusion as a canvas. I right clicked the canvas in the sidebar, used the calibrate tool and entered in the the length of the bottom of the bracket to size the canvas appropriately. I then sketched on top of the canvas to create the profile of my bracket.

After I was happy with my profile of the mounting bracket, I extruded the sketch into a 3D shape. I then created four 7.8mm diameter holes on the top for mounting it to the milk crate. I made them 9.5mm deep so the threaded insert would sink into the bottom of them slightly. I also created a single 11.5mm deep hole (same diameter) on the rear of the bracket that I would use to thread in my rear locking bolt. Lastly, I created a handle that fit around the 40mm M6 hex bolt that made it easier to grip and turn with my hand.

I printed both the parts in PETG filament as I wanted them to be at least somewhat UV and heat resistant (ASA would be a better choice but I didn't have it on hand). After printing, I used my soldering iron to heat up the brass threaded inserts on the top and rear of the bracket and sunk them in.

After some initial testing I noticed that the crate would flex and wobble as the bike moved around. I discovered this was because the bracket was only attached to a narrow middle section of the milk crate and I decided to solve it but adding a layer of plywood inside the crate to add rigidity. This way the bolts would sandwich the milk crate between the plywood and bracket and the plywood's rigidity would prevent the milk crate from wobbling.

I just rough cut a piece of 1/2 inch scrap plywood to size, set it inside the milk crate, drilled holes through the plywood/milk crate and inserted M5 bolts and nuts.

I 3D printed a template to make sure I drilled the holes in exactly the right position. I flipped the milk crate upside down, measured carefully, and taped the template to the bottom of the milk crate trying to make the bracket as absolutely centered as possible. I also importantly didn't want to make any more holes in the milk crate so I confirmed my template was lined up to miss the plastic crate and only go through plywood. After drilling the holes I threaded in my M6 hex bolts using my ratchet making sure they threaded properly into the inserts of the 3D printed bracket.

After attaching the bracket to the milk crate I had a very hard time sliding the whole thing into my rear rack. I discovered it was due to two issues. The first issue was the the milk crate itself was rubbing against my rear rack when trying to angle the bracket in. I used my dremel to cut away a bit of the front of the milk crate in the two places they were rubbing against my rack. The second issue was the friction of the back of the bracket rubbing against the mounting post of my rack. To address this I simply used my orbital sander to smooth down the back of the 3D print.

After addressing these two issues I was super happy with the end result. The milk crate slides easily into my rear rack and all I need to do is hand tighten a single M6 bolt to secure it to my bike.