Rotary motors ?

[Inkslingers]

To my knowledge, nobody uses brushless motors for tattoo machines because you need a special speed control wired in. It'd be nice for performance and longevity, but it isn't very viable.
I agree though, most builders don't want to make their motor specs public as it makes it that much easier to have your designs ripped off by douchebags.

Actually, there is a rotary on the market that uses a brushless motor....