Thanks will look thru those, integrated gearing is useful - I'm thinking of using unitised 4WD front bearings (generation 3 type) drive using the spline. NSK have design data. But they are "thicker" (75mm) than slew bearings so take up more space. I used 2 on a robot I built many years ago.... or "thin" bearings all up in the air at the moment.. But the answer will fall out soon...Peter