We built this bike cart out of EMT conduit for our Kickstarter video, and in the time since we have received a lot of questions about how it was done. Specifically people ask about how the wheels attached to the conduit and how the whole thing attaches to the bike.
We used mountain bike wheels that had a quick detach axle. The blocks that mounted the wheels were 3D printed and worked pretty well for short term use. I think if you were going to use it long term, I would try and machine something similar or used a threaded rod for an axle. I have attached the STL files of the wheel block to this post if anyone would like to make their own.
The attachment to the bike was done with solid rubber. This worked really well and I would do it again the same way. It allowed the cart to turn and flex independently of the bike without feeling out of control. You might even be able to use a garden hose as a substitute. The rubber was bolted into the conduit of the cart, and then attached to the bike with a special bracket.
I hope that helps with your bike cart project and feel free to post/comment with your ideas.
