Any good resources, case studies about bootstrapped Hardware startups?

May not be exactly what your looking for but bolt VC posts some really interesting content around starting hardware companies. https://blog.bolt.io

Theres a whole series on the hardware process: https://blog.bolt.io/ideation/ https://blog.bolt.io/design/ https://blog.bolt.io/engineering/ https://blog.bolt.io/validation/

They also have a bunch of great posts on strategy and business models.

Hewlett Packard[0] is interesting. I'm sure one could find companies for which the place was called Silicon Valley.

You could also check out Shenzhen and ask Andrew Huang.[1] Apparently, hardware startups there move really, really fast.[2]

He also has a book entitled "The Essential Guide to Shenzhen", here's a thread about it.[3]

[0]: https://en.wikipedia.org/wiki/Hewlett-Packard#History

[1]: https://en.wikipedia.org/wiki/Andrew_Huang_(hacker)

[2]: https://www.youtube.com/watch?v=SGJ5cZnoodY [Vice report with Andrew Huang]

[3]: https://news.ycombinator.com/item?id=21817656

Depends on what experience you have in the field you target, and more importantly how large (in physical dimensions and technical complexity) the hardware product you want to develop is?