How do I dimension the height of a parameterized segmented arch?

[redmoncoreyl]

I want to make an arch with equal sized segments. The number of segments and height of the arch are parameters:

IMPORTANT: The ArchHeight parameter needs to control the height of the apex of the segments, not the construction arc. This means if NumberOfSegments is even, the apex of the arch will be a point where two segments meet; if it is odd, the apex of the arch will be a segment. 

I am racking my brain, but I can't figure out how to do this.

[davebYYPCU]

Radius of the circle doesn't change, add a dimension.

Sketch patterns are not recommended when a Modelling Pattern will get you there.

The angle in my sketch is a calculated one, 360 / 12 for your 12 sided polygon.

Start here - happy to answer questions.

Might help...

[redmoncoreyl]

That will not work. You cannot calculate the angle between segments as 180/NumberOfSegments because the angle also depends on the height of arch: It is not necessarily a semi-circle.

[davebYYPCU]

Send your file, and requirements.

Who said anything about 180 degrees.  Currently 150 / 5 = 30.

Changing to 6, 7 or more segments, at 15 high, no trouble.

Might help...

[etfrench]

Pathagoras is your friend😁  Just solve for the center section.

[redmoncoreyl · Accepted solution]

I figured out how to do what I want. These are the steps I used:

1. Establish the three parameters.

2. Create a sketch including the base, the arc, the first segment, and the apex of the segments. Dimension only the width and the height.

3. Dimension the angles in the sketch. The entire sector angle is a driven dimension. The other two angles are calculated using the NumberOfSegments parameter.

4. Apply a circular pattern.

Note: I have had issues where updating the parameters doesn't automatically recompute the model. I have been using Ctrl + B to recompute. If someone knows why that is happening please feel free to comment.

[davebYYPCU]

... I have had issues where updating the parameters doesn't automatically recompute the model.

Are you seeing this while editing parameters,

or editing sketch,

or downstream features after the sketch?

I am not seeing that problem, with sketch only.

Might help...

[redmoncoreyl]

It happens at an point even during sketching. It seems to be most likely to occur by changes to NumberOfSegments. I think it might have to do with d9 (see above images) being a driven while also driving other dimensions d10 and d11. But I can't really say because this is the first time I have used driven dimensions.

I just tried your file and it does work as far as I have tested. My file also works most of the time, it just isn't 100% consistent.