You are welcome. Yep, haven't even exhausted the classics yet, which I'm loosely saying is anything pre-1980. But we maybe getting close. And I will move onward after that.
There are some types, as a category, that for myself I will not post more of (maybe), but feel welcome for anything you find interesting.
Very glad David B is doing so, having the story back ground to go with it, very cool indeed.
My own previous interest was for inspiration to research design and not history. But history is definitely in scope for the purposes of this thread.
One requirement for my own design work, it must represent a 'useable' and realistic engineered vehicle. Not all conceptual automotive 'art work', sticks to that. You often get the unusable windshield, impossible seating, dysfunctional entry path or non-dimensional engine. Illegal headlights are frequent.
I think I want to 'rant' on one engineering point. If the purpose of a vehicle is to 'make sense', you design to purpose. And you use a design for what it is best at. Sociable seating vs Tandem falls into scope when you discuss three wheelers for commuting.
Specific to commuter vehicles for freeway use,
Except for the purpose of reducing frontal area with tandem seating, there is very little use from an engineering standpoint to use a three wheeler. True it's slightly cheaper, and slightly lighter. But this makes a significant difference only if the vehicle is light with few occupants, up to 3. But Tandem only works well for 1 or two. And one is inherently tandem. Using seating for 3, the vehicle becomes heavier or longer or wider, often all three.
If a design is not 1 seat or tandem, the choice for three wheels is most likely not a logical engineering one. In older eras, or when you are stuck to low production methods, the cost and weight of a fourth wheel is much more significant. But this is the modern manufacturing times, the extra wheel itself can be engineered as less impact, with big benefits elsewhere. This is of course, always a choice of trade-offs.
Yet the combination of few occupants, fewer parts(&wheels), less weight, less cost, less aerodynamic penalties, smaller vehicle, in a high production volume, all that combine to make the perfect storm of very economic commuter product. This isn't just opinion. It's engineering reality.