# Combined motions

Hey guys, I'm trying to define a combined motion on a gear that rotates around its own axis while rotating around another axis, like in the picture below. Is that possible somehow? Thanks in advance!

• Yes, it is ;)

• Haha great thank you :D can you maybe give me an example how to do it?

• Have a look in: Examples_motion.pdf

Find the relevant xml file

Play a bit around

Kind regards

• I already played around with the rotational motion and I figured out how to do the omega1 rotation like in the picture. But my problem is that the axis for omega2 is rotating, so I'm kinda clueless how to define that axis :/

<objreal ref="1">

<begin mov="1" start="0" />

<mvrot id="1" duration="1000" anglesunits="degrees">

<vel ang="600" units_comment="degrees/s" />

<axisp1 x="0" y="0" z="1" />

<axisp2 x="0" y="0.1" z="1" />

</mvrot>

</objreal>

• I would be interested in this kind of setting too.

To make it work there should be a way to define different coordinate systems: a fixed first one, and a second rotating around the first one.

I tried to work around some examples, but I also couldn't make it work.

The usually referred example is Motion03, which is about hierarchy of motions.

In 2015, Ephytech runned this simulation, in which they must have set a moving axis for the wheel. But still I don't have any clue.

• Hi,

To reproduce the epytecch configuration, you must use "hierarchy of motion"... see example given by Alex and Asalih !

Try it and play with it on a simple configuration !

best regards

• Hey you all,

I finally found a solution for the epytecch configuration and also for my described problem. Thanks for showing me to the right direction.

In this case object ref=2 is the spinning wheel and object ref=3 is a drawline that basically represents the moving axis. That's why ref=3 is defined as a uniform rectilinear movement in the x-direction and object ref=2 has a rotational motion depending on the movement of object ref=3. You can draw a line like this:

For the solution of the configuration that I described in the beginning of this discussion, you just change the uniform rectilinear movement of object ref=3 to a rotational motion and you get a combined rotational motion.

@lormal

• Hi,

Happy for you ! and thanks for posting your solution.

Best regards

• Really well done!

If I have to do it some time I will make sure to ask you if I cannot do it 😅

Kind regards

• Sure you are very welcome to do that 😀

• That's great! Thank you, Zwulch, for sharing your findings!

• I shall have another question linked to this topic.

Normally (i.e. for to non moving axis) I use the ComputeForces.exe to obtain forces and torque, with this code, by giving it the gear's axis.

In this case of a moving axis, would it still be possible to calculate the torque in some way?

• Have you tried to see if results make sense?

If it is a moving object it is not far fetched to imagine that it would move the moment axis with it in the post-processing too. But you can easily double check

Kind regards

• edited 10:47AM

Sorry Asalih, I forgot to answer.

I did checked:

As my motion is linear and I'm getting a torque increasing linearly with an almost constant force applied, as expected it must be the moment arm the one which is linearly increasing.

So yes, the double check checked what was initially expected