I thought this would be simple but I can't get it to work.
I'm trying to draw an arc that's tangent to a line at a specific point and tangent to an arc. I drew the line, started the arc command, hit enter to force the arc tangent to the line at the endpont and then tried to use a Tangent OSnap to hit tangent to the arc. This is what I got. Note the Tangent snap at the midpoint of the arc.
If I accept the Tangent snap it does draw the new arc to the midpoint of the existing arc. Definitely not tangent. Does this mean there is no solution? I think I'm missing something. I'm usually aiming for a set radius and have no trouble. This is kind of a Best Fit situation. The only criteria are that the new arc be tangent to the red line at the intersection with the yellow line and tangent to the red arc.
Allen
Allen Jessup
CAD Manager - Designer
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That's sort of the problem. The only thing controlling where I'll hit the red arc is wherever a tangent curve will hit it. I've got a "close enough for government work" solution. But with $6 grand of computer and software I thought I might be able to do a little better.
Thanks.
Allen
Allen Jessup
CAD Manager - Designer
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I have tried to no avail to get this to work using arc, curve and even alignment 'curve' functions. In this instance I would recreate it the old fashioned way with trimming, cutting, etc....until you get the curve data you want.
I never use the 'tan' snap so the process you've described is new to me.
By using Circle by TTR (Tangent, Tangent, Radius) and taking a couple of guesses on the radius. I've gotten it to withing 0.000091m of where I want to hit. No problem with construction. Just an annoyance!
Allen
Allen Jessup
CAD Manager - Designer
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Allen,
Yup, definitely time for an Iterative Government Solution.
Dave
Dave Stoll
Las Vegas, Nevada
Assuming you are using plain cad elements you should be able to solve it by applying parametric constraints. Will that work for you?
Joe Bouza
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@Anonymous wrote:
Assuming you are using plain cad elements you should be able to solve it by applying parametric constraints. Will that work for you?
Doesn't seem to. If I constrain the proposed arc to the existing arc it move the other end. If I then constrain the other end to the tangent line the line is offset to be tangent to the arc. So that doesn't seem to help.
@Anonymous wrote:
BTW it might be simpler to create some construction elements to establish the tangent points
Yes. I usually would. But without knowing the tangent point on the arc I haven't figured out how to do that.
Allen
Wait a Minute! I think I may have gotten the constraints to work by applying them in a different order. I'll do some testing and post back.
Allen Jessup
CAD Manager - Designer
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@Joe-Bouza wrote:
What happens if you temporarily extend the larger arc beyond the extension of the tangent? does the osnap give better results?
No. I tried that. No luck.
Allen
Allen Jessup
CAD Manager - Designer
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No. It changes the tangent point along the line by. 0.055 m. I'm sort of disappointed.
Allen
Allen Jessup
CAD Manager - Designer
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All these things consider leads me to believe the starting PC creates a non-solution to the reverse curve.
filleting the tangent to the reverse curve should yield the correct PC and tangent length, no?
Joe Bouza
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This is actually a pretty easy thing to accomplish.
See my screencast recording
Matt.
Looks good Matt. I just got out of a meeting and have an hour to clean up a few things. Then off until Monday or Tuesday. I'll give this a try then. I had tried with an alignment but didn't think to pull the snap back to the point line you show. I think that will do it!
I'm attaching a drawing with a copy of my entities in case anyone wants to try in the meantime.
Allen
Allen Jessup
CAD Manager - Designer
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John Mayo
Very good Matt
Looks like it worked for me
Joe Bouza
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