How to draw Cam lobe

[neophoible]

This is a valid lesson. The only logical course of action by the student, however, is to return the assignment with a statement “Ambiguous description: Corrections or more information required.”

 

Many CAD operators will run into poorly laid out projects, and it is important to quickly determine it as such. They should strive to not make assumptions. Get clarification.

I really have to agree here. The main reason is that, without knowing the requirements of the cam, one could propagate some huge mistakes by simply following the other geometric constraints. If the R45 is meant to be concentric, as cams often have such for dwell time, then simply forcing this to the constraints will significantly distort the displacement as the shaft and profile will be way out of alignment. If one is going to insist on holding the constraints as is, then at least be sure not to make more than one before testing it. Don't make a hundred, or a thousand, or a hundred thousand and then say OOPS!

[neophoible]

If this works, here's a shot of JD's AutoCAD solution superimposed on a copy of the OP's pic. I tried to line up the angle lines and the camshaft centers. It's not perfect, but it's good enough for a basic visual comparison. Hope this comes out. Sometimes I'm locked out for a day or so after uploading; haven't figured out why yet.

[neophoible]

Overlaying Bill T's solution and rotating the profile 7deg CW about the center of the camshaft, you get a pretty close fit, but it's still not right on the money. Of course, neither is my overlaying. I did not rotate the angle lines with the profile, so obviously, they are no longer aligned. As stated earlier, the two that were not right angle, were off anyway once the R47.3 was blended.

[eldon]

Knowing how AutoCAD defaults to the angle precision set at the nearest degree, I was wondering whether being able to set a plus or minus half a degree to the angles would lead to other solutions.

 

I do not have the ability to check this out, but it might lead to interesting results.

[neophoible]

Knowing how AutoCAD defaults to the angle precision set at the nearest degree, I was wondering whether being able to set a plus or minus half a degree to the angles would lead to other solutions.

Yes, the solution is unique when you hold each of the values exactly. You will certainly get a range of results if allowed to vary the angles. However, I am not sure how much of a range of results there would be. The same holds true if you can vary the radial values. That's one of the reasons I mentioned a possible rounding or conversion factor error. If it was originally done in inches and converted to mm, that might account for some of the difference. But, again, I don't know what would be required to bring it into exact alignment.

[ReMark]

It doesn't look like there is a smooth transition where the arcs meet in the image shown above. Why is that?

[neophoible]

It doesn't look like there is a smooth transition where the arcs meet in the image shown above. Why is that?

It also doesn't appear to have the same shape as the other solutions JD created. Are the same criteria actually being applied here?

[ReMark]

The cam looks "pinched" (for lack of a better word) at each location where one arc is supposed to blend with the next. If that is the math solution then I prefer a couple of the non-math ( CAD ) solutions better.

[Guest AARi]

... FUNCTION not scale x & y grid

 

.. i did not put this restriction in a line

 

just check center points & redraw it

 

 

.... *If that is the math solution then I prefer a couple of the non-math ( CAD ) solutions better.

 

CAM EQ MATH

 

 

just maths

SHALOM

[JD Mather]

What are the coordinates of your center points (they don't look correct).

[neophoible]

... FUNCTION not scale x & y grid

 

.. i did not put this restriction in a line

 

just check center points & redraw it

Yeah, I didn't pay attention to the squashed grid--rectangles, not squares. How hard is it to put that restriction in your code. I'm not clear on what centers you actually ended up with either. Why is "bs" used for the equation? Does it stand for something? In some cultural circles, it could be misconstrued. Just saying.

Peace.

[Cad64]

AARi, your last post has been deleted due to foul language. I have also deleted all of the posts that you edited to remove your comments. I'm not really sure what happened in this thread, but please try to use more appropriate language in the future. This is a professional CAD forum, not a locker room.