Adaptive springs and cam following

[Anonymous]

GDay All,

I have a few questions that are sort of related, but the first question is of more concern at this point.

I am trying to create a moving valve train in my engine model. So far, I have the crank, pistons, cam, lifters, pushrods, rocker arms and valves moving more or less as they should (see Question 2). So I thought I would add an adaptive spring to the mix. I followed this tutorial on Youtube to make the adaptive spring:  

http://www.youtube.com/watch?v=TaKX68LjhUo

But, when I add a second spring to the assembly, I am not able to make it adaptive. The option for 'adaptive' is greyed out and cannot be selected.

Question 1.
Why can I not make the second spring adaptive?

Question 1a.
Why can't I drive a constraint to move the spring that IS adaptive? (there is only one spring in the assembly at present 😉

Question 2.
In Inventor 200x I was able to add a tangent constraint between the cam lobe and the lifter, and the lifter would follow the cam lobe profile as it was rotated, but in 20xx onwards you can no longer do this, why not?

I managed to fudge a connection between the cam lobe and lifter so that it sort of works, but I would like to make it work the way it used to (IE: the lifter follows the profile of the cam lobe). Anyone got any ideas on making it work in 2013 Pro?

Any help, hints, ideas welcome 🙂

[lis_wang]

I created a cam shaft which the cam motion function is the same as yours. However why my acceleration profile has sharp change at 90degree? Please see the screen shot here. I also attached my file here. Please check for me what wrong with my file

[WHolzwarth]

IMO that's ok. Your cam has no symmetry, therefore you have a steeper change of diameter, and a slighter change. At the connection of both, there's a sudden change of the velocity curve tangent, which means a  jump in acceleration (red curve), too.

Walter

[lis_wang]

How to make the cam symmetry? I use the same motion as yours.

[JDMather]

If you set the second segment to Double Harmonic-Part 2 motion law rather than Harmonic (sinusiodal) the acceleration curve would be smooth.

[lis_wang]

HI, JD. I got it. What is "Actual Segment"?

[JDMather]

You can create any number of segments dividing up the 360°.

The Actual Segment is the active segment that you are editing and that the parameters are shown in the dialog box.

Each segment has a number, and also, when you click within the segment in the dislacement diagram it highlights the boundary with dashed line and shows the "Actual Segment" number.  I think they should have named this "Active Segment" rather than Actual Segment.  I would be surprised if it wasn't a translation error from some other language (like maybe French?).

[lis_wang]

Thanks. I got it.