# yade-users team mailing list archive

## Re: hello? -help with a spinning bucket!

```I now have a theory on how to do this..  I am going to try implementing several rotation engines sequentially, computing myself what the new location of each zero point should be.  so what would need to happe is, each iteration, all the points would have to be shifted about the central axis, then the new zero point of the minor axis would have to be computed, and then the points undergoing the secondary rotation would have to be shifted around their minor axis.  it seems to me that this would work, the only thing missing is how to define the time-step and step number within the RotationEngine.

one hope is that instead of saying O.run(1000), you say O.iter, then calculate the new location of the zero point of the minor axis, then iterate again.  the calculations of the new zero point location would take place outside the definitions/declarations of the engines, but the engines would never-the-less have access to, and make reference to, the new calculated zero point of the minor axis.

I will test this theory..

--- On Thu, 7/15/10, Michael Jensen <jenmichael2000@xxxxxxxx> wrote:

From: Michael Jensen <jenmichael2000@xxxxxxxx>
Subject: Re: [Yade-users] hello? -help with a spinning bucket!
Received: Thursday, July 15, 2010, 1:05 PM

salutations once more :-D

I have another question for you, very interested to know what the answer will be..

one of the partial engines is the RotationEngine.  This engine takes several variables, notably a bolean, a point, and an axis.  so far so good.  with a point and axis defined, everybody is happy.

what if I want my point itself to move?  for example, I want my thing to rotate around an axis whose direction is fixed in time, but I want the location of that axis, defined by the point, to itself rotate around another point and axis, a second point/axis pair.  this is the situation that occurs when you have one object rotating, attached to another one that is also rotating.

that is the most direct way to approach what I want to do.  the other way is to introduce the manually the forces that result
when my bucket spinns, so that I don't have to make it spinn at all, and I can go ahead and add my second spinning device.

I will have to implement one of these two solutions, or something equivalent, if my simulations are ever to completely represent my device.

it seems to me like the first option should be relatively easy to code, if it does not yet exist, and that it could be a powerful way to extend yade, in that a user would not be limited to two such spinning things, but could in theory simulate much more complex motion.

-mike

```