How do you constrain two cylinders that are a press fit?

[siggy]

How do you constrain two cylinders that are a press fit?

I'm trying to do an assembly that models a cam that is press fit onto a shaft. I can mate planar surfaces and align the cylindrical surfaces just fine such that the cam is in the right location on the shaft. Problem is that if I try to rotate the shaft, the cam doesn't rotate with the shaft.

How would one go about ensuring that rotational motion on the shaft transfers to the cam as well? I've tried orienting, angling and everything else I can think of. The only success I've had was to essentially design in a flat to both the cam and the shaft and angle constrain them. Surely, there is a way to do this withough modifying my parts. Any thoughts?

How about if I were trying to model transferred motion between two gears?

 

[rbrian]

Press Fit, Nitrogen Press Fit - Whatever -

Siggy / Robert - here is the deal -

There would be no way for Alibre Design to know it is a press fit in real life - since - it does not do collision detection - yet! And - in real life (Aircraft press fit experience) - it is usually called - an interference fit - meaning one part is forced onto or into another of a size that it would not normally go - because of the interference - hence the force.

Now - the normal way I know about such things being made - so that the cam lobe rotates with the shaft - would be a keyway - and a key (square or rectangular cuts and bar) that lock the two items together - and - if you did it this way - you could set up constraints that would serve you just fine!

And - Gear - to - Gear, or Gear to Chain - it's the same thing - you again still need Collision Detection!

For some linkage animations - see my web site - under the Alibre index! Robert

 

[siggy]

Thanks. Unfortunately, I can't put a keyway in because the cam needs to be adjustable - I need several degrees of advance or retard cam timing adjustment. I guess I'm not really expecting Alibre to know there is an interferance fit, I just thought there might be some technique I'm not aware of to constrain the geometry.

 

[Anonymous]

Simply align the reference planes of the two parts.

 

[siggy]

Bingo! That is the hint I needed! I didn't realize that option was available until you suggested it. Thanks.

You know, I've just converted to Alibre from AutoCAD about 2 weeks ago and am still learning the software, but I get more and more impressed with this package every day. What a great piece of SW at an unbelievable price. My hat is off to Alibre!

Robert