At where I work (not a surveying company, and surrounded by sales "people" unfortunately), only 2 others in the company have AutoCAD experience. One of the sales "people" (to his credit) Is good at reading paper drawings. Not to his credit is he absolutely refuses to believe "us CAD users" that certain things CAN NOT be done.
The latest frustration is a pdf drawing showing arc length and radius of a part. (Yes, this is a curved part). I have now told this "person" about 50 times that I need a chord length or other info to be able to draw this. The other CAD users have now told him the same thing.
He WILL NOT take our word for it. Nor contact the customer for more info. Tries to throw me under the bus for not being able to do what can not be done.
At this point,I will not tell him I have an old TDS software at home that I could figure this out with. It would be much easier if he would just simply contact the customer. But NOOOOO, he won't.
/Rant Off
Any COGO program can calculate a curve from arc length and radius. ANY COGO program. I'm not a CAD guy but if CAD can't handle it that's pretty lame.
Also, be careful to NOT assume the arc is tangential.
If their tangent curves you should be fine.
If they're non tangent curves I understand your frustration. It's kind of like metadata and GPS. We have a surveyor in our neck of the woods that makes all his curves slightly broken back there all non tangent. I call them floating, broken back, curves.
What's so funny is the tax assessors are demanding chords. Bearing and distance. Because of this guy so it helps me haha!
Based on what you've given shouldn't this work?
5729.578/R = D
Then
Delta = L*100*D
Then
((Sin 1/2 Delta)*R)*2
Won't you get your chord length from that?
I work in a steel shop with 2d cad. I do not have a cogo program at my disposal, I certainly don't expect the company to buy one. I have a hard enough time with "basic" math..... and there wouldn't be another person here who would have the ability to check my calcs if I transposed a number or something....
It would be easier and Much faster for the sales "person" to contact the customer for more info instead of fighting with me about the way that CAD works, but oh well...
Draw a circle with the radius provided. Determine the ratio of the arc length to the circumference of the circle. Then apply that ratio to 360 degrees to determine the angle that would create that arc length. Boom ! Done !
that arc (defined by length and radius only) can be spun around and around... concave to any direction.
the missing element is Direction.
First assume tangent on Both ends (if that math works)
if Not, then you need a radial bearing, a tangent bearing, chord bearing, coordinates of at least two points on the arc, or maybe something else.
@ John you actually have a cogo tool .... draw it in Acad.
good luck explaining that to someone that thinks Acad can calculate the missing curve data, they lack understanding of geometry.
I will have to play with the Cow's suggestion, I might be able to get something going with that.
(Edit: if I get that working, I certainly won't tell the sale person. At this point it's principal that when I say I need more info to be comfortable making the drawing, they Need to get me that info. By calling the customer. If I was half as talented as they think I am, I swear, I'd be somewhere else making Significantly more money! I know how little I know about CAD and math.)
Peter: at least where I work, the folks "know" that AutoCAD has a "magic button" for anything and everything. The apparent problems is that I don't know which button that is. And they can't tell me for some reason. Never mind they have Zero experience with any CAD and I have a few years.
The presumption is that it is tangential to the lines in and out if no cord direction or radial direction is given. (Of course the bearing of the cord is 1/2(delta) and delta is the difference in the bearing in and the bearing out.)
I have worked with many old plats that have curves going into reverse curves and compound curves spaning across several lots with only arc lengths, and radius info, it's a pain if the lot lines intersect in between these curves. I usually calc the lot lines and the curves desperately then force the curve data into the lot lines.
It would sure help if you had picture of what you are talking about, there may be a simple solution.
Draw a circle of the stated radius, trim out a small portion of the circle, type "len" to start the lengthen command, type "T" for total, enter the stated arc length, pick one end of the arc and the arc will lengthen or shorten to the entered arc length, draw a line from one end of the arc to the other, this is your long chord, if it needs to attach to 2 endpoints of other geometry then use the align command to align to these points.
Excellent guidance with the correct software functions.
John, post: 442942, member: 791 wrote: if he would just simply contact the customer. But NOOOOO, he won't.
Why not? From a business perspective the guy's an idiot. Successful businesses use "COMMUNICATION" which contributes to success.
FL/GA PLS., post: 443615, member: 379 wrote: Why not? From a business perspective the guy's an idiot. Successful businesses use "COMMUNICATION" which contributes to success.
I would agree with you, the guy is an idiot. He would rather waste my time and his because he is of the firm belief that he knows more about AutoCAD than I do, even though he has never used it a day in his life.
I have lost count of the times he has stood over my shoulder watching while I show him that his way simply does not work. It would have saved hours so far if he had simply contacted the customer for more info instead of doing things the most painful way possible.
Edit: Yes, this guy is making himself look bad to the customer and likely blaming my supposed lack of knowledge about CAD which he knows not one thing about.
billvhill, post: 443127, member: 8398 wrote:
It would sure help if you had picture of what you are talking about, there may be a simple solution.
I started a new thread with the latest info on these drawings, including the drawings themselves. As far as I can tell at this point, I have been given incorrect dimensions as I can not make either arc work.
Sorry, John. It's really easy to draw an arc of certain radius and length in CAD. Orienting that arc in some way is a different matter.
FL/GA PLS., post: 443615, member: 379 wrote: Why not? From a business perspective the guy's an idiot.
Generally I agree. But in this case he would be exposing the limitations of his staff. It's better if the customers don't see how the sausage is made.
What about this?
Give drafter chord bearing and chord length, and tell him to fit an arc on it at the specified radius. If it is tangent, that is fine. If not, that may be fine too, if close enough for you. In the field I don't think I have ever measured a curve that is absolutely tangent to anything, although they should be and are usually implied that way. Observe it to see if it is reasonably tangent. Normally we like to give chord, chord bearing, and radius. Maybe drafter can figure that out. Also, get him to draw perpendiculars off the pc and pt and intersect them and compare to radius to give you a guide for reasonableness. If he won't even do that, tell him to bend grass toward his house and don't come back.
I'm sorry, its pretty basic math, not a CAD thing at all. On the other hand, if the "sale guy" is so sure how easy it is, he should do the math for you and show you how to do it.
Though I drew the arcs to the specs, neither arc length agreed with the drawing provided. I had the chord length and radius correct, but one arc length was off about half an inch, the other further (don't remember how much off the top of my head).
All the numbers should agree between my drawing and the PDF, but I can not make them all match. Should someone here draw them in cad, perhaps then we can attempt to find out what is really going on. The numbers generally point in the correct direction, but, well, if I can't get all numbers to match with the info given, something is wrong.
