Constraints problem with Inventor 2011

[Hopinc]

Hi Guys,

 

I have got a problem that is driving me insane! I have almost finished constructing a V-8 engine assembly within Inventor 2011, I am just 6 push rods away from final completion.

 

My problem is that when I try to apply tangential constraints to the domed ends of the remaining push rods and their corresponding mating sockets nothing happens. The parts refuse to snap together.

 

Whilst I have not counted the total number of parts there must be well over 250 and I have checked each an everyone to see if there are any conflicting constraints - there are none! I have suppressed all bar the 18 parts required to place these last components and that has made no difference.

 

No errors are reported by the "health" Cross at the top of the main toolbar so nothing should cause the problems I am having.

 

Anyone experienced this? Anyone have a solution?

 

Thanks for your help.

 

Regards all.

Dave

[kencaz]

Do the rods constrain to one socket and not the other? If so, cam or rocker side?

 

Are the cams and the rocker arms free to move? If one is grounded it probably allow the second constraint...

 

Are any of the parts part of a contact set and is the contact solver turned on?

 

Are your constraint conflict warnings turned on. Do you get an audio confirmation that the constraint took?

 

really hard to say it could be many things. Probably something small you missed.

 

KC

[Hopinc]

Hi KC,

 

Answers to your questions in order:

 

1) No, the remaining six pushrods will not constrain to either socket. None of the parts involved with these rods are grounded. Although because of the camshaft, followers, pushrods, rocker arms and valves the constraints are fairly complex.

2) Yes. No the contact solver was not turned on. Since I read your post I tried it with it on and it made no difference.

3) Yes they are. Yes I have been getting an audio "Ping" confirmation when a contraint is good. However, these last six items will not give that, yet the selections turn from red to green to say everything is OK.

4) Possibly, but I have checked EVERY component's constraints (a tiresome job) and there are no conflicts showing in the history tree.

 

Obviously there is something the program does not like but I cannot see what it is. I have actually had all these rods in place before I decided I wanted to modify the carburettors to have 'O' ring seals.

 

When I tried these mods a conflict appeared between the pushrods and the carbs yet there was no constraint connection between them at all (most strange). I removed the rods, modified the carbs, reattached 10 out of the 16 pushrods and then ran into trouble.

 

Dave

[JD Mather]

Can you share the files?

[kencaz]

When I tried these mods a conflict appeared between the pushrods and the carbs yet there was no constraint connection between them at all (most strange). I removed the rods, modified the carbs, reattached 10 out of the 16 pushrods and then ran into trouble.

Dave

 

Well, it seems you have identified at least some of the problems...

 

Confilcts? You mean when you updated the assembly after the carb mods?

 

Also, you say you removed the rods then modified the carbs... Did you Delete or only suppress the previous rod constraints?

 

I am just throwing out ideas as I only have 2009 and I could not open the assembly anyway....

 

Have you tried suppressing the carb assemblies and then applying the rod constraints? At least that would confirm the initial error message.

 

Good Luck...

 

KC

[Hopinc]

Hi Guys,

 

Yes, that is when I first got an error message, the conflicts appeared to be connected to the tangential constraints placed on the pushrod ends. Two things about this irritated me, the first is that the constraints applied to the carbs and rods are totally unconnected and secondly that no errors were shown anywhere until this point.

 

If these errors existed before the mods to the carbs Inventor should have reported them.

 

I did not suppress the rods, rather I deleted all of them from the assembly to totally remove any and all constraints. The carbs were also deleted and re positioned with new constraints prior to the fitting of the 6 push rods in question.

 

As I said ALL components except the necessary 18 - the 6 push rods and 12 cups - were suppressed when I was trying to apply these final tangential constraints.

 

Thanks for your help.

 

Dave

[Hopinc]

Hi Guys,

 

I have finally sorted the constraint problems, although I think the way I had to do it was somewhat less than satisfactory.

 

I had saved two versions of the assembly, one that I experimented with that would not allow me to constrain the last 6 pushrods and another that had all the pushrods in place before I made the mods to the carbs.

 

I won't go into a blow by blow account but I ended up with supressing all the constraints on the carburettors and that produced a complete model with no errors showing.

 

I still cannot figure out how Inventor made a constraint connection between these items and the pushrods, nor was I impressed by the way the contraint relationships were reported/handled. This needs work AutoDesk. I was particularly underwhelmed by the way 2011 handled transitional constraints on the camshaft and followers as it seemed to get confused about them, and of course these tangential constraints - I think you already know my feelings about these.

 

This is my first real project using 2011 since I discovered the rendering crashing problem I posted about some months back, and it has highlighted some pretty quirky and strange errors using various aspects of the program. All in all I personally think that this release was short of some proper field testing.

 

I am hoping that SP.1 will cure some of these issues, it can't come too soon. Has anyone got a definite release date yet?

 

Regards.

 

Dave