Stretch an arcs height without moving end points

[norm77]

Hello,
I'm trying to make a dynamic block that will stretch the height of an arc while not moving the end points; similar to using the arc's midpoint grip. Can this be done? If so could that height have a distance multiplier of 0.5 when chained to another stretch action?

-Norm

Using AutoCAD 2008.

[Charles_Shade]

See if any of these do what you are needing.
Regards, Charles Shade

[kvnbrn]

That's Awesome. Very inventive,

[Charles_Shade]

Just a collection of the bright minds that I have culled info from here.
(And one of my own.)
Regards, Charles Shade

[norm77]

> {quote:title=Charles_Shade wrote:}{quote}
> See if any of these do what you are needing.

> Regards, Charles Shade


Thanks. That isn't quite what I'm looking for. Here is a drawing of what I'm working with. I want to be able to stretch/increase the radius size (midpoint) of the arc.

-Norm

[Charles_Shade]

I believe you need 2010 and Parametric Constraints to make that happen.
Of course Juris is going to come along and prove me wrong...
Regards, Charles Shade

[strawberry12]

Here's my attempt at it (I know, it's not a dynamic block at all, pathetic really, sorry.)

[Anonymous]

I wonder if (just TOL here), somehow moving the grip that represents the middle of the arc segment....well that arc really represents a portion of a circle (the center of which is the crossing point of two identical circles with their centers at the intersections of arc and line segment). So, moving the grip would move the centerpoint of the arc's "circle"....that's where my thinking stops short....

[Charles_Shade]

I did try creating two arcs that met in the center. No problem getting the endpoints of both to move but the radius is the key. That increased with the drag and therefore did not maintain the arc.
Moving the center point so that the radius changes; and in this case becomes less, is what needs to happen.
Regards, Charles Shade

[norm77]

Exactly. Just like modifying the mid point grip. I thought of stretching the center point and the same amount to the end points except in the opposite direction; but I think that would only work if the arc was a full 180 degrees?...

-Norm

[Charles_Shade]

It's a beat horse.
The two arcs still have that same center grip you cannot do anything with so I don't suspect that moving the ends are going to accomplish anything.
If you do figure out how to do it you may become a hero around here.
Regards, Charles Shade

[norm77]

Good to know! 🙂
Thanks for the help all.

-Norm (Hero in training?)

[Anonymous]

This is my best solution. It requires two operations: set the height then correct the width. I tried a variety of ways of using chained actions to stretch the ends of the arc automatically but it doesn't seem to be possible to both scale and stretch the same entity. I've also included my failed attempt in the attached file in case anyone knows a way to fix it. It works once after resetting the block but then breaks.

[Charles_Shade]

Very Cool
I don't think having to Reset the DynBlk would be a big deal if the size changed. Certainly easier to tug and pull again instead of recreating.
Regards, Charles Shade

[norm77]

> {quote:title=Golden_Goose wrote:}{quote}
> This is my best solution. It requires two operations: set the height then correct the width. I tried a variety of ways of using chained actions to stretch the ends of the arc automatically but it doesn't seem to be possible to both scale and stretch the same entity. I've also included my failed attempt in the attached file in case anyone knows a way to fix it. It works once after resetting the block but then breaks.

Any idea why it ("failed attempt") works only the first time? What steps did you take to make it?

-Norm

[Charles_Shade]

I'm gonna guess the negative multipliers are the culprit. If the Offset Angle could be set in such a way...
Regards, Charles Shade

[IanH5033]

Nearly there! See attached DB (Test2), I've made the 2 horizontal lines and the arc into 1 polyline. Insert at mid2p (Charles Shade will be after me for that!) and set arch radius before anything else. Then you can stretch to suit arch width and overall width (both stretches are mirrored to right hand side).

Only one problem!!!! Base point moves vertically by 10% of radius stretch and I can't figure how to overcome this - I've tried moves and stretches but they seem to mess up other parts.

Perhaps somebody else can see a way round it.

Ian

[IanH5033 · Accepted solution]

I found the glitch in my previous post. When creating the block the centre of the arc needs to be aligned with the horizontal lines, then you can scale the arc without the base point moving - see Test 3 in attached. As before, insert at mid2p and set arc height before stretching widths to suit.

Hope this works for you.

[Charles_Shade]

Excellent!
Another one of those I bet it can be done just haven't figured it out yet.
Its distinctiveness will be assimilated into the collective...
Regards, Charles Shade

[IanH5033]

Thanks.