A discussion about folding bikes would not be complete without mentioning Helix. Helix folds almost as small as a Brompton but has 24” wheels and standard bicycle components such as disc brakes, Shimano/SRAM drivetrain etc.

Also the fold is the most compact possible, even more compact than Brompton in terms of maximizing the use of space. It also fits in a standard airline luggage without any disassembly which few other folding bikes can claim.

The frame is full titanium including the locking mechanisms. It’s made in Canada and is the lowest cost complete titanium bike on the market, folding or not.

https://www.helix.ca

Full disclosure, I’m the owner/founder of Helix. Happy to answer any questions related to it or folding bikes in general.

>> This looks super exciting, particularly the idea of building a new Open-source B-Rep CAD Kernel.

Yes, I think he's being rather naive about that. Starting with flat surfaces and straight lines is really ignoring the hard problems and will likely require a complete rewrite later. IMHO support for NURBS surfaces is a requirement for CAD and export/import of STEP files as well. Having said that, if he keeps going it will be a good thing. Some related efforts:

Another (stalled?) CAD kernel in Rust: https://github.com/ervanalb/arcade

Another one in Rust that can also read STEP: https://github.com/ricosjp/truck

That one reads STEP by using: https://github.com/ricosjp/ruststep

There is a geometric constraint solver written in Rust: https://github.com/Michael-F-Bryan/constraints to be used in another CAD: https://github.com/Michael-F-Bryan/arcs If I recall he moved all his work to gitlab. Here is arcs: https://gitlab.com/Michael-F-Bryan/arcs

All of this is very ambitious and I look forward to a day when a good CAD system written in Rust is readily available.

In the mean time I shall keep plugging away at the Solvespace C++ code: https://solvespace.com/index.pl