The beauty of LEGO is that there is a little bit of tolerance and flex in pieces. The other beauty is that everything works with everything. EVERYTHING! So it should be no surprise that a Hero Factory torso can be the basis for an otherwise completely system build. Sure, you could pull in pieces like modified bricks with balls or cups. But then there would be no blog post for me to write.
The balls on the Hero Factory joints are listed by LEGO as being 10.2mm in diameter. There's not much going on here for being within system. You can subtract either 3.2mm, 4mm, 6.4mm, 8mm or 9.6mm and never get a result that is within our 0.8mm expectations. The closest dimension is 10.4 and maybe that's where they intended to land, then cut the tolerance by the 1mm on each side. This would be two plates of height (6.4mm) plus half a brick width (4mm). Or a brick height (9.6mm) plus a quarter plate height (0.8mm) Whatever.
But the thing about spheres is that a ring can be placed over it at some point. Place two rings on opposing sides and the distance between the rings will be less than the sphere diameter. Lost yet? Perhaps an example:
Imagine the bottom of two plates. The 4.85mm anti-studs will slip over the ball joint and reduce the total distance. What is the distance between these plates (assuming they are parallel)? A little SketchUp render tells me it is just under 9.0mm which is a little more than a brick width (8.0mm). But remember the tolerance and flex that I opened up with?
And since the spacer is a typical brick width, it works for other parts with holey relief too, like technic liftarms and bricks.
By the way, these are all the Hero Factory type pieces that I own. See why the need for more system connections?
Yeah, last finds post for the year! A decent one too. Yes, I took the busted pieces including a black motorcycle, two plates, and an empty sprue. It's all LEGO! Better finds were the Tiny Turbos road/case, several Hero Factory joints and the Pearl Gold C3P0 (missing an arm). He'll be a great addition to my R2-D2.