Wow, that's quite an accomplishment! I can't tell for sure, but it looks like the design fails to make the inside wheel turn sharper than the outside wheel. (The inside wheel has to turn a smaller radius; so to avoid having the two front wheels fighting each other, the inside one has to turn sharper.)
I worked professionally in vehicle dynamics and suspension design.
Wow, I'd like to correspond with you about various suspension ideas for my next bike cargo trailer. The current one is at
Wilson Mines Co., road-bike trailer, with lots of pictures and description, and at the end of the page, some ideas for my next one which will be for much bigger and heavier loads. I don't know if there's an appropriate section for that on this forum, or if it should be by PM. I'm sure others would like to be involved in the conversation. I can only post sketches, not nice CAD drawings like Hodala posts. Not particularly related to bikes, but still to matters of suspension, I made a wooden sidewalk car for our kids 30+ years ago, with McPerson-strut-type suspension, including in the front. It is stable at all speeds. (I run when I push them.) Now it's in use for grandkids. You can see it at
Wilson Mines Co., kids' wooden sidewalk car .