Creating an arc or a curve with changing radius along the way.

[assen_pandov]

Hello i want to create an arc or curve with 600mm lenght and to be 30m radius in the center and going smoothly to 26m radius at the end . So something like 26-27-28-29-30-29-28-27-26. How can i find the coordinates to build spline or how to connect smaller arcs and to keep it as 1 curve and be smooth?

Any suggestions?

Thanks in advance

[richard_387]

Have you investigated a Transition Curve, also known as a Clothoid or Euler Spiral?

[assen_pandov]

Hi. When i was searching a way, chat GPT wrote me about Clothoid,but i couldn't find a way. If you know how it's possible, please give me some info..

Thanks!

[richard_387]

It is a long time since I had to hand calculate transition curves, but I am sure the equations are out on the web.

Nowadays, I rely on AutoCAD to curve fit and don't worry about the individual elements.

Why do you need such a curve? Transition curves are from one radius to another, but not there and back again. Perhaps some further explanation of your need and any constraints and fixed points would give a more useful response.

[assen_pandov]

it's about speed skating skate profile, the skates are more flat in the middle and round at the end i tried to do it with spline, but it didn't came well, i try to find a way to do it with the arc without losing the smoothness of the arc...

[richard_387]

I think that when you use a spline, you do not have control over the radius. Splines do have their uses, but for drawing a shape that has a known radius for a known distance, it would be easier to actually use arcs that you know what radius and how long they are.

I usually find it easier to draw a complete circle of known radius and then make it an arc by trimming it or breaking it and making it the correct distance.

I do not use AutoCAD LT so I don't know the correct commands. I merely responded to this thread because of the implications of geometry. Good luck in your drawing.

[tramber]

There is one thing i can and want to tell, in case. Because some don't know :

When you created a first arc you can hit ENTER to repeat (that is known) but you may also hit ENTER again and right away to be relied to the other (tangency). Unfortunately, it doesn't allow any setting of any kind (radius, center).... too bad, isn't it ?

[vladimir_michl]

Try the Lisp utility KLOT.LSP (clothoid) on https://www.cadforum.cz/en/how-to-draw-clothoid-in-autocad-tip9699

If you have AutoCAD LT 2024+, you should be able to APPLOAD this Lisp and use the KLOT command to draw a transition curve between an arc and a line segment.

Vladimir Michl, www.arkance.world  -  www.cadforum.cz

[RSomppi]

I can think of a couple ways to do this utilizing TTR snaps. Place alternating circles for every other radius and then fill in the gaps with TTR. (My first drafting job was drawing plans for custom inground pools and the vast majority of them we mostly curves.)

[assen_pandov]

Thank you for the info.. i don't have autocad 24+ but i will read it and see if i can understand something.. math is not my strongest side unfortunately...