How to Set Up and Cam Rocker and Valve for Motion in Fusion 360

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In this video we will do a follow up to the Tangent Relationship video and focus specifically on the trouble area of analyzing mechanical motion of a valve relative to a cam lobe. Since we know that Tangent Relationships and Contact sets are struggling with this a little we want to learn how we can use Motion Links to potentially overcome this.
You can follow along with this dataset: a360.co/3Gao9vL

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Опубликовано:

30 янв 2022

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Комментарии : 7

@HonorNecris 6 дней назад

I found you can get a lot closer of a simulation by first capturing the cam orientation when the rocker is fully off the lobe, then capture the position of the valve at its point of contact with the rocker. Sketch a circle from the center of the rocker pivot to the approximate point of contact between the valve/rocker and note the diameter, then in your motion link keep the angle value at 360 and use ( D * Pi ) for the distance value, where D is the diameter of the circle sketched. This way you're using the circumference of the arc made by the rocker as it pivots to drive the valve - the only caveat is because the contact surface of the rocker where it meets the valve stem is a curve, the rate at which the valve translates is non-linear, so there still is a tiny bit of 'float' when the valve is fully open. There is probably a way to account for the curved contact surface in the distance formula, but I didn't find one while messing around. If the tappet was a flat surface, the motion achieved with the above method should theoretically be near perfect, fwiw.

@LearnEverythingAboutDesign 5 дней назад

Thanks for taking the time to write that! Great tip! A solution to this problem would be for Fusion to have a joint that allowed for point contact one on component and a sketch path on another component like other CAD programs. The tangent relationship seems to have gotten a little better since this video but could be better still. Ill pin your comment to the top in case someone is looking. thanks

@martinquirk3466 2 года назад

If you split Rocker Arm into 2 pieces then join with rigid joint before Tangent Relationship then you can get the mechanism to work without locking. You can animate manually but it doesn't keep rotating when you animate model for Cam Lobe revolve.

@LearnEverythingAboutDesign 2 года назад

Martin, I tried that before posting this video and it didn't work for me. Are you saying that the tangent relationship worked for you on both the valve and the cam with a 2 piece rocker???

@martinquirk3466 2 года назад

@@LearnEverythingAboutDesignYes. I could rotate lobe using mouse and valve followed rocker. Using Animate Model lobe rotated partially and then froze.

@martinquirk3466 2 года назад

Actually I had to supress the sweep at the end of the time line to get it to work. Even then it is very unstable.

@LearnEverythingAboutDesign 2 года назад

That is very interesting! So one note is that before the sweep I had attempted this with multiple selections and found that it worked a bit but then it didn't. I ended up with the most consistent result being selecting the follower first, then the cam lobe face. Unfortunately most consistent meant "mechanically locked" each time. I did try duplicating the follower and making a rigid group as well. I was banking on the fact that I was doing something wrong. The sweep was put in place to reduce the point of contact with the cam itself in hopes that it would help, but seemed to make no difference. If I figure anything out further I will post an updated video. I appreciate your comment and playing around with this as well!!