4 Replies Latest reply on May 10, 2017 11:09 AM by Dennis Dohogne

    Cam Mates ????

    Dave Bear

      Hi Guys,

      The scenario is this :-

      I have a V12 cylinder head. Both the Intake and exhaust sides of the head are twin valve. Therefore I have 12 valve stem tops to 'cam-mate' to the respective camshaft lobes. My question is, is it better to finalise each and every 'cam-mate' (per lobe that is) or is it better to mate all of the valves stems to respective lobes for the entire camshaft and then finalise it? Or............. does it make no difference either way? In my way of thinking I end up with the same amount of mates either way but I want to keep rebuild times to a minimum and therefore wondered if one process might be better than the other.

       

      Regards,

      Dave.

        • Re: Cam Mates ????
          John Stoltzfus

          Tough one to answer correctly without that experience, but just thinking that I would do each one separately, but, in the past Cam Mates were erratic and sometimes would flip, so I would suggest that since you have the cam path, create a sketch in the Cam at the center of the Valve and adding a point or use the roller center point and make those two coincident rather than using the cam mate. 

           

          The only way you will be able to use a sketch as a Cam "Path" is the sketch needs to be a spline not individual sketches, so take the original Cam Path sketch and sketch over it with the Spline Sketch tool, that way it's a complete path and will follow correctly without selecting all the cam and cam follower faces, much easier and more robust in my book, see the sample attached....

           

          Sample Sketch

           

           

          I added additional points and then used the spline sketch tool

           

           

          I used the center point of the Valve profile

           

           

          Now it has free movement within the sketch area with one mate

           

           

          • Re: Cam Mates ????
            Dennis Dohogne

            Dave Bear,

            John's and Peter's comments will serve you well.  John's point-to-path technique is a little more work than a standard cam mate, but it is far more robust.  Cam mates, and other mechanical mates such as gear mates, require SWX to calculate as things move.  So the more of these you have the more calculations SWX has to do.  The problem with that is that it is easy to move the system faster than the calculations can be performed and these mates are then subject to get jumped.

             

            When you do get all this put together and moving the way you want I suggest you use the Motion Study with a slow motor turning your system.  Start it out with a bunch of mates that put items in their starting position and would effectively overconstrain the system.  This is okay and you might have to temporarily suppress other mates, such as gear mates, to allow this starting alignment.  Then, at the start of the motion study, suppress those starting condition mates and unsuppress the other mates and let the motor turn the system.  In this way if the system gets "overrun" you can reset it by going to the starting position mates.  You can speed up the motor until the system overruns and explodes (don't worry, you won't throw a rod), then just bring the motor speed down a tad and you should be good.

             

            In order to simplify things you could do a couple of things.  Copy with mates might be a help, but perhaps you could create some sort of subassembly and use it multiple times and leaving it flexible.

             

            I hope this helps.