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How to fix incorrect, unknown angles?
m_p381
Member Posts: 3 ✭
I have been trying to find a model of this shape for a while now. Since I wasn't able to I got an Onshape account and attempted to create it. I wasn't able to get the exact angle between the pentagon and the hexagon from Wikipedia but was able to get it to a point where it is only possible to tell that the angle is off if you zoom in on the intersection of the vertexes of two pentagons. through brute force. However, now I am unable to enclose the shape. How do I find the right angle?
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Best Answer
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EvanReese
Member, Mentor Posts: 2,188 ✭✭✭✭✭
Wow! pretty impressive. I've never used the approach of just using sketch faces to enclose, but I see no reason it can't work with accurate enough angles.
You might have better luck starting with a simpler polyhedron and modifying it from there. Have you seen the polyhedron custom feature? you can make an icosahedron with it. to truncate it you can use cuts or chamfers. to excavate it you might use the Shell feature. The shape of your holes is more complex, but you could model it as a separate body just once, and use Transform (by mate connectors) and circular patterns to duplicate it everywhere else and boolean subtract. Here's a quick, not-so-precise example to get you started.
If you're looking for platonic perfection you've still got a challenge ahead of you which probably involves dimensions with lots of decimal places, or actually typing the equation that defines each angle (you can just type a formula right into the dimension and onshape will handle it). If you just want the shape and want to be pretty accurate, you could use this 3D Point feature to plot the cartesian coordinates of each point according to the formulas on Wikipedia. This would be pretty painstaking. If you want to be able to adjust the size later, I'd use the Variable feature to set a multiplier that you can add to each coordinate input.
Have fun!Evan Reese5
Answers
You might have better luck starting with a simpler polyhedron and modifying it from there. Have you seen the polyhedron custom feature? you can make an icosahedron with it. to truncate it you can use cuts or chamfers. to excavate it you might use the Shell feature. The shape of your holes is more complex, but you could model it as a separate body just once, and use Transform (by mate connectors) and circular patterns to duplicate it everywhere else and boolean subtract. Here's a quick, not-so-precise example to get you started.
If you're looking for platonic perfection you've still got a challenge ahead of you which probably involves dimensions with lots of decimal places, or actually typing the equation that defines each angle (you can just type a formula right into the dimension and onshape will handle it). If you just want the shape and want to be pretty accurate, you could use this 3D Point feature to plot the cartesian coordinates of each point according to the formulas on Wikipedia. This would be pretty painstaking. If you want to be able to adjust the size later, I'd use the Variable feature to set a multiplier that you can add to each coordinate input.
Have fun!