Thanks Sluggo. Your thoughts are exactly what I was looking for in seeking out criticism.
Originally Posted by
Sluggo
Not obvious to me. The end of the cantilever arm only moves 1 mm with 1 mm of cable motion if the cable is pulling at a perpendicular (thus the sin beta term). If the arms are horizontal and the straddle cable is also horizontal, in the rigid idealized system you can't have 1 mm of cable motion because the force is parallel to the cantilever arm.
Yes. When the cantilever arm is at 90 deg and the yoke height is zero, MA will be zero. In fact, MA will be zero whenever beta is zero.
The equation accounts for this: MA = 1/sin(gamma) * sin(beta) * PA/DO
I think the best way, for me, to think about MA not changing with yoke height for a cantilever arm of 90 degrees (except when beta = 0), is that in this condition gamma = beta. Thus, the equation becomes MA = PA/DO. In other words, the anchor angle and the straddle cable angle cancel each other out, leaving just the ratio between the anchor arm and the pad (or resistance) arm.