Unexpected movements

Here is a base with 3 cylinders controlled by a point “Cylinders top”.
It is an IK chain. They are all telescopic and have limits defined.
The type of tweening is linear.
There is just one movement set: down by 8310.
Why do the cylinders twist at the end ?
CLP 1250 cylinder.MP4 (1.5 MB)
Here is the Rhino file:
CLP 1250 cylinder.3dm (1.2 MB)

I have noticed that
if I uncheck 3D tweening, I still have strange movements at the end
if I uncheck limits (joint properties), then it works.
But without these limits, each cylinders does obviously not stop at its right position.

To walkover this problem, I have tried to use expressions for z position but I did not succeed.

The setup isn’t ideal and there are too many different solutions, that’s why it jumps.
I’d recommend using another approach for making that kind of animation. Please see attached models. 001 is without Ik and 002 is using Ik.
CLP 1250 cylinder 001.3dm (1.5 MB) CLP 1250 cylinder 002.3dm (1.6 MB)

Thanks for your examples.
In my file, I used only one ‘control point’, the ‘Cylinders top’ point. This file will be included as a block in a gantry crane file and the gantry crane file will be a block in the real animation file of the harbour. A lot of animated objects, so I want to control each part with the minimum of ‘Bongo control object’, just the ‘Cylinders top’ point for the cylinders that will be constrained by the ‘Gantry crane top’ in the Gantry file.
Is my way of work compatible with Bongo ?

Hi Alan,
This version CLP 1250 cylinder 003.3dm (1.5 MB) uses expressions based upon the movement of ‘cylinder mechanic’, your so-called ‘control object’. From my own experience a rather simple straightforward mechanical structure can often be made operative through a right set of expressions. Apparently for Bongo the handling of expressions is far, far, far less complex than IK-solving.

Thanks for your cooperation. I have indeed introduced expressions where it was possible to lighten the work for Bongo.

This solution is limited :
If in an expression, you refer to an object, e.g. Position Z = #cylinder mechanic/3.PositionZ#
then when you copy the cylinders into an other file, objects are renamed 'Object nnn" but names in the expressions are not updated.


Thank you for pointing this out. I’ll ask the developer to have a look at the problem.