You will probably find that the FMs here have a sufficiently rounded knowledge of electronics in general that they would help you with robotics questions.
I go to DelphiForums. I use the RFL (Robot fighting league) the most.
Create a new forum!
Northeast Robotics Club & Robot Conflict
Robot Fighting League
SouthEastern Combat Robotics
Western Allied Robotics
All on Delphiforums. Northeast does a lot with autonomous and smaller robots with brains, translational drift and such.
RFL Has it all including the ROBO1 type robots.
SECR is just about dead but used to be one of the livelier forums.
WAR is always busy with big bots that are pretty much combat only....