5th Axis head rotation questions.

[whiteriver]

Got my motors and drives up and running today. No limit on rotation for B or C. Just keeps on going round and round. No Stops. Nice. 2000+ ipm Fast.
I do have one problem. Well several. One right now. I might be labeling these axis's wrong I don't know. See picture below. The B axis Rotates around by its self like it supposed to. When I move the C axis it moves the B axis. Not the B motor or timing belt. Just the head. Designed that way by Fanuc. If the C travels 1 full rev 360 degs then the B axis makes a full turn, I can make the C go in one direction and the B go in another but the B goes very slowly that way when the C is moving. Has to double travel I guess to get where it needs to be cause of the gears are linked together.
Wonder how I write a post for this head. The B would have to have two settings. One for by itself and one for how C affects it.
I can't think of a way to tell Mach2 where the B is if the C moves. Bummer.
After more thought:
(B = B - (Delta C)ie. if C moves + 1 degree then B should move minus 1 degree ) <<<-- From CNC Toolkit Forum

The head will flip 90degs in the picture. So it will point out from the Z axis horizontal. I think how I'm mounting the spindle on it will allow it to point down or horizontal. Depends on how the head is rotated at the time. That way I can cut something on the table or on the rotary 4th axis.

After even more thinking:
I was thinking of mounting the spindle to the vertical surface in the picture. B axis. When I lay it on its side like it would be mounted on the machine I can position the cutter vertical or horizontal by rotating the axis's. It was hard to see till I taped a straight rod on it and moved it around.
With no power to the motors I can rotate the C and the B does not rotate. But with power and rotating C I can't hold B from rotating. Wish I had a exploded drawing of how that thing was put together.
With B going around in circles as C moves could be a nightmare to figure out.
If I had more gantry clearance I would love to mount it vertical but with only 8" I couldn't do much with it.

Any ideas how to figure out a post to dictate to the software where the bit is. Since B move backwards as C moves and mach2 does not know about the movement i'm lost.Can't put a encoder on the B motor since it doesn't move when C moves. Just the head not the motor moves.
I also need to understand how to figure offsets.

Donny

www.whiterivermfg.com