# Sign convention for angular velocities in 3D gear train Consider a Humpage gear train shown above. We are viewing the gear train from right and gear B is rotating in clockwise direction. If we consider clockwise direction as positive what will be the sign conventions of gears D and C. Can you provide a reference for the same. This is the question for your reference. They have considered the angular velocity of gears D and C positive here.

• I’m voting to close this question because the phrasing looks like a homework exercise. Sep 6 at 9:18
• Oh. Actual question is quite different. I will give the image of the question in case you need to refer it. Sep 6 at 9:26
• I think you're reading more into the question than it's asking for. I don't know of any way you can define CW or CCW as being positive or negative. The question just says "200 RPM" without a direction of rotation and asks for an output speed. The answer would be an RPM and whether H is rotating in the same direction as G or opposite. Sep 6 at 13:14
• Consider the axis gear B is rotating around is the "global axis", on which the CW and CCW are defined. Now, C & D are moving on a different axis which should be considered a "local axis", then the sign convention can be related out by looking at the motions on both sides of the interception point of the global and local axes - they shall agree for simplicity.
– r13
Sep 6 at 19:42
• My rule is to always assume rotation is mathematically positive defined for math like problems such as this…if it‘s something other than that, it should be specifically mentioned. Sep 7 at 15:01