[jon@harrison.ne]

As a PhD in Mechanical Engineering I can't resist commenting on this statement by Old Dog, who otherwise made a lot of correct statements. HP is simply one commonly used unit of power and has nothing to do with whether it is produced in linear or rotational motion. For example, a solid rocket engine has no rotational parts, in fact it has no moving parts of any kind, but it sure can have a lot of power, which we can express in HP, watts, Btu/min.,....