Arc offset by distance and scale

[SCD_CAD]

I am trying to find a routine that will allow me to offset an arc by a distance and to a scale.

The offest command is very limited as to how far I am able to offset without the boject completely vanishing.

I am trying to make a flat pattern from a cone or something close to it. The routines and programs that I have found do not quite accomplish this very accuratll. They are always off on the upper and lower arcs and on the distance between the arcs. Tho this would not completely sovle my problem, it would allow me to get the distance between the top and bottom correct.

Thax in advance

[dbroad]

While I am not clear about your distance and scale issue or what is wrong with the offset command, I can offer advise on cone flattening. (For right cones)

1. Get the distance from the cone apex to any point on the base and save it. 'cal r=dist(end,nea)

2. Draw an arc with a radius equal to that distance (r).

3. Use the lengthen command with the total option to change the length of the drawn arc to be equal to 2*pi*(cone base radius).

4. Draw lines from the arc center point to each end of the arc.

5. Draw a circle of the same radius of the cone base tangent to the arc.

[SCD_CAD]

The offset will only allow for the distance an scale ration per what the AutoCAD program is set. If you wish to have the offset disance much greater you need to copy the arc and then scale it.

[steve216586]

You control the offset distance. Just type your "new" distance in the command line at the prompt.

[SCD_CAD]

I do not want the two arcs to have the same center point.

The default offset relies on one center point.

[steve216586]

What you are describing then is two arcs located ramdomly about a common arc with different radii and center points, plain and simple.  No "OFFSET" involved. Simple geometry will allow you to calculate the radii and arc lengths you are looking for based on cone height. I can't see that being automated.

[SCD_CAD]

I have found routines for it. They just don't get the legnth excat or the distance exact.

[bradleycjones46]

Hi, 

I am having a similar issue with trying to get two arcs seperated at a distance. In addition, I am trying to get the arc equal to a certain length. Can you share with me your routine for how you got the arcs at a certain distance? This will be much appreciated?

Thank You

[Kent1Cooper]

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@bradleycjones46 wrote:

... trying to get two arcs seperated at a distance. In addition, I am trying to get the arc equal to a certain length. ....

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@SCD_CAD may not still be watching [this Topic contains almost half of all Message they ever posted, and they have not posted anything since about 6 weeks after this exchange over 8 years ago].  But can you post an image showing what you mean?  It's not clear to me, nor is their original request.

[bradleycjones46]

The two arcs must be seperated at a set distance, the current distance is not correct.

[pendean]

>>>...the current distance is not correct...<<<
@bradleycjones46 Do you mean the two straight ends are difference lengths? That's because your outer arc was manually manipulated, if you OFFSET the inner arc to 32 for example then draw the liens from END to END, they are the same.

Why was the outer arc manually modified?

[Kent1Cooper]

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@bradleycjones46 wrote:

The two arcs must be seperated at a set distance, the current distance is not correct.

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Regular ol' OFFSET will achieve that for you, if you don't then change something so that they're no longer concentric.

For the desired length, LENGTHEN with the Total option will give you that.

[bradleycjones46]

Because it has to be a different length than the inner arc

[Kent1Cooper]

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@bradleycjones46 wrote:

Because it has to be a different length than the inner arc

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Any Arc that was Offset from another Arc will always be a different length.  Do you mean it needs to be a different length than the result of the Offset?  That would mean that Lines connecting the endpoints won't [at least can't both] be radial to the Arcs, nor perpendicular to them at their ends.

If that's what you mean, does the change in length need to happen equally at both ends, so the two Arcs are centered on a common radial line through their midpoints?  Or different amounts of change at the two ends?  If it's all change at one end, LENGTHEN with either the Delta or Total option [depending on the criteria] can do that.  If it needs to be equal change at both ends, I have a routine that will do that for you.

[bradleycjones46]

The Change needs to be equal at both ends. I'm trying to draw the flat pattern for a frustum cone

[Kent1Cooper]

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@bradleycjones46 wrote:

The Change needs to be equal at both ends. I'm trying to draw the flat pattern for a frustum cone

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OFFSET will handle that for you directly, if you are talking about the "pure" surface of the truncated cone.  What about the result of OFFSETting does not do what you need?  Do you need a pattern for sheet material that will have some overlap when curled around to make the 3D shape?