I was interested in seeing how folks would explain-in english-two bits of xingyi jargon. The two concepts I am wondering about are:
滾軸力
槓桿力

They come out in a modern xingyi book written by 張桐 titled「形意拳實戰技法」

He says:
探討虎形在上下旋轉中如何利用圓形滾軸力和平面槓桿力

In a sense I am not so interested in a direct translation (i.e. it says "axle power"), what I would appreciate help with is what the phrases mean in real practice.

Thanks,
Brian

Depending on the context, axle power often refers to the spine being the centre of the wheel of movement created by that practitioner's body. If the axle is stiff or broken, then the rotational power of the limbs is impeded for martial purposes. In addition, the axle seems to be relatively still when moving although the wheel itself is obviously turning at a variety of speeds,

It can also mean keeping yourself as the centre of the "action' when interacting martially with someone who tries to dominate or manipulate you. You remain the axle for their movement instead of allowing yourself to be dominating by theirs.

Maybe it's just a colourful analogy that is hard to put into words... ;-}

Hi Michael, thanks much for the input.
take care,
Brian