What’s the expansion limit for the 24 x 24 x 24 robot and 15 x 15 x 15 robot in VEX U? I’ve read that the designated x24 can expand upto 24 inch but what about the x15 robot?
Read the Game Manual VEXU appendix. All the standard rules apply if not explicitly modified in that section.
So, the 15x15x15 robot has the same expansion constraints of 22x22x22.
The 24x24x24 gets the exception concerning expansion constraints.
All V5 rules apply as long as a VEXU rule doesn’t contradict it. SG2/3 say that it can expand to be 22"x22"x22".