平底直动从动件盘形凸轮机构的压力角永远为零。( )
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滚子从动件盘形凸轮的实际轮廓曲线是理论轮廓曲线的等距曲线。( )
A. 对
B. 错
凸轮的基圆半径越小,则机构尺寸(),但过小的基圆半径会导致压力角(),使凸轮机构发生( )。
We couldn't have passed the final examination ______ your help.
A. but for
B. without
C. if it had not been for
D. all of the above