Engine Assembly Constraint Conflict- Please Help!

[fsascaddy]

Apparently I bit off more than I could chew when I decided to build a small scale engine block for my Inventor Class. I have a connecting rod and piston assembly, a crankshaft assembly, and a block ipt. I have a free range of rotation with my crankshaft assembly. The crankshaft assebly is constrained to the block assembly so that the bearing journals sit in the the correct position. The piston also has a full free range of motion around the crankshaft assembly.

However; I am unable to get my piston/connecting rod assembly to remain inside the cylinder of the block. When I rotate the crankshaft, the piston remains in the current position. thus, the piston does not ride inside the cylinder wall. If I constrain the the piston to the inside of the cylinder wall (insert constraint) it no longer allows me to rotate the crankshaft? Thank you for your help. I have to turn this project in a few days from now and I am struggling to finish it up!

[JDMather]

---

@fsascaddy wrote:

 If I constrain the the piston to the inside of the cylinder wall (insert constraint) ... 

---

Wrong constraint - it does not allow any translational degrees of freedom

Mate axis of piston to axis of cylinder.

And

An assembly file (*.iam) is only a list of hyperlinks to the part files (*.ipt) and a record of assembly constraints (and a bit more).

You must include the part files.

[fsascaddy]

Ok,. I used both the axis already associated to my Complete Connecting Rod and piston assembly, and the block cylinder, as well as creating an axis specifically for the cylinder and the piston, both giving the same result as using the mated work planes. I still have no motion ( rotation of the crankshaft. is this a constraint I need to drive? I don't believe I can upload all of the parts ( too many files)

[fsascaddy]

Since my Main assembly is a component of sub assemblies, I have three of them uploaded here,. followed by the remainder of them in order.

[fsascaddy]

here are a few more of them

[fsascaddy]

And here are some more;

[fsascaddy]

More.....

[fsascaddy]

still more...

[fsascaddy]

I think this is the last of the part and sub-assembly files.

Do you see what I am talking about now?

[JDMather]

Whoa...

You have done an astonishing amount of unecessary extra work.

and you don't need to create axis for cylindrical features.

See the attached image to get your piston/crank working.

You would then go on and add an angle constraint to drive.

I will not be at a 2013 machine until Monday to post Inventor example.

In general -

assembly the same way you would in the real world.

You cannot possibly attach the rod end in a sub assembly and then place it in the main assembly.

I recommend you go through these to reduce the amount of work (and therefore time) spent on something like this.

http://home.pct.edu/~jmather/SkillsUSA%20University.pdf
http://inventortrenches.blogspot.com/p/inventor-tutorials.html
http://wikihelp.autodesk.com/enu?adskContextId=HELP_TUTORIALS&language=ENU&release=2014&product=Inve...

[fsascaddy]

I know I did do alot of extra Uneccesary work. That was my second attempt because my first attemt was not working properly so I was trying a bunch of different things and adding extra work to try and solve it.  Thank you very much for your help! I actually had those assemblies of assemblies to try different approaches. (I also know that I had several extraneuos items in the part sketches as well, but I am a beginner and this is my first time trying to build anything complex using Inventor (I've only been using it for a few months. I will try your suggestions today and hopefully be able to respond with " accept as solution.)

[fsascaddy]

One more Quick Question for you,.

In the Attachment you sent me with the constraints listed that I need to have. the screen cut off what the Mate:3 constraint is constrained to? I am sure it sounds rediculous to ask but I am humble to your expertise.  The symbol in front of the mate constraint:3 is different from the other mate constraints. What am I missing? I apologize for my insufficience. 😞

[JDMather]

Can you wait till tomorrow when I am at my r2013 machine?

I can try to explain in words, but it would be easier to show you with your actual files.

You had two Mate constraints for the crank to the block, one to mate axis and the other to mate faces for position.

These two could be replaced with one Insert constraint.

Then all you need is one Mate between the axis of the piston to the block and one Mate between the axis of the connecting rod and the crank.

I am curious about how much instruction (or not) you have had.  I would expect my students to have significant experience in creating parts before moving on to an assembly such as this.  Its all about building a strong foundation....

[fsascaddy]

That Makes perfect sense to Simplify the 2 mate constraints with an insert constraint. My alignment was perfect once I did that.

And as you said, I mating the cylindrical piston axis to the cylinder axis and it worked great too. then I created the mate constraint between the crank and the connecting rod planes.

am I correct in  assuming I would have no motion until I set the angle constraint to drive, correct?

I can most certainly wait until tomorrow, but I like to try and figure it out based on some guidance.

[JDMather]

---

@fsascaddy wrote:

... then I created the mate constraint between the crank and the connecting rod planes.

---

No, no, no.  Do not mate any planes (yet).

Then large end of the connecting rod is a (negative) cylinder, therefore has an axis.

The journal on the crankshaft is a cylinder, therefore has an axis.

Mate these two axis by selecting the two cylinders.  (we'll worry about placing the rod cap later)

You should now be able to drag-rotate the crank with the mouse and the piston should move as expected.

Once you get that motion I can explain how to get it to drive itself in rotation.

[fsascaddy]

Sorry,.

I did not mean plane. (that was a poor choice of wording on my behalf.)

what I meant was exactly what you just told me to do.

I mated the negative cylindrical axis of the connecting rod to the positive cylindrical axis of the crankshaft ( carefully because the connecting rods do not fit if they are connected backwards and cause a ton of interference problems)

However. Once I attach that constraint. it locks down and i cannot rotate the crank nor can i move the piston by dragging it either.

Now,. if I return to the constraints list and I supress the constraint of the piston axis/cylinder, the crankshaft will rotate just like it is supposed to, with the connecting rod attached to it.

but once i have both constraints ( the two mate constraints)  it locks down and doesnt allow any movement. is this possible because of a constraint that was placed on the piston/connecting rod assembly?

[JDMather]

Post screen shot of your browser.

Did you set the piston sub-assembly to Flexible?

[fsascaddy]

Yes, the PIston assembly is set to flexible. It is also Set to enabled. Adaptive is greyed out.

[JDMather]

A 2 meg screenshot?

I'm connected by a G4 hotspot with limited montly download.

Go to the little Windows Globe icon in lower left of screen.

In the search box start typing Snipping

start the windows snipping tool and capture the browser area (similar to the screen capture I posted in earlier response).

Save as *.png and attach here.