DMU Kinematics joint issue.

[Lambent32]

Hi, I have been working on a v12 engine and have my entire crankshaft assembly assembled as i would like it to be but in kinematics im having issues. This crankshaft assembly consist of the crankshaft which is mounted just temporarily to a mount with a triangular block for alligning the pistons to their correct angles and a piston sub-assembly that consist of the piston, gudgeon pin, circlips, conrods(upper and lower), and conrod bearings. In DMU kinematics i have the issue of keeping the pistons aligned to the triangular block. When i use the command to automaticly create joints it make the connecting from the conrods to the crankshaft revolute joints (which im not sure is correct for what i want. It also doesnt add any joints to anything else. When i rotate the crankshaft it takes the entire assembly with it. I have tried and tried to keep the pistons alligned to the fixed block but nothing works, when i try to make the connections from the conrods to the crankshaft cylindrical joints i cant get past two without it giving me an error saying that the assembly is over constrained. Can someone tell me what im doing wrong or if it is even possible to make this work without an engine block to allign the pistons to. Sorry if this is a little confusing or unclear, im not very good at describing things.

If needed a can post some pictures.

Thank you.

 

[itsmyjob]

yes i like pictures!

Eric N.
indocti discant et ament meminisse periti ​

 

[Lambent32]

Here are the pics

 

[Lambent32]

alignment block

 

[Lambent32]

The auto revolute joint that i keep getting for the connecting from the gudgeon pin to the conrods

 

[itsmyjob]

ok I think i got it.

It looks like you are working with sublevel (flexible) product instances for the piston, gudgeon pin, circlips, conrods(upper and lower), and conrod bearings.

Kinematics is not able to define JOIN within the same sub assembly (flexible or not). A join between the piston and the gudgeon pin for instance can not be defined in a Mechanism at a higher level in the Product structure.

I have the feeling we cannot combine a sublevel mechanisme with a current level mechanisme in order to define complexe kinematics from several lower level simplified kinematics. Something like a sub mechanism with the piston fix and the conrod moving around its axis combine with higher level mechanism and add piston / engine bloc and cranckshaft / conrod JOINS would not be possible from my understanding.

Solution : bring everything in a flat tree structure (with copy/past) and voila !

I try not to use the automatic join creation as I'd rather have to think about my join and make sure I am actually doing the right stuff.

Eric N.
indocti discant et ament meminisse periti ​