Splines of fixed length?

Erik63 · 24 Jan 2014, 01:07

Hello,

Is there a way to make a spline that does not stretch? I need to bend a 4' bar along a spline so I need it to maintain its length.

Thanks for any help.
-Erik

mitcorb · 24 Jan 2014, 01:46

Is ShapeBender by Chris Fullmer the tool for you? Or FredoBend -part of FredoScale?

It would help if there were an illustration, or more information where the problem occurs?

Erik63 · 24 Jan 2014, 07:05

Thanks Mitcorb.

I think fredoScale will do what I need. It is hard to illustrate what I am after but what I am trying to do is bend a 4' metal bar around a curved form and I am try to use sketchup to figure out how to cut the wood template around which I will bend the metal. So I was starting out with a 4' long polyline and then using f-spline but that only fixes the ends so after I bend it the total length of the polyline increase. I was wondering if there was something that fixed the entire length of the polyline and not just the end. I hope this makes sense. Thanks for pointing me to FredoScale.

-Erik

gilles · 24 Jan 2014, 08:08

Draw the spline, convert to polyline segmentor say 20 segments, explode the curve, tape tool to resize one segment 1/20 of 4', recurve.

Erik63 · 24 Jan 2014, 17:25

Thanks Gilles I'll give that a shot.

Hi Mac1, the bar is rather thin ~3/16 think and .5" high and rather pliable (monorail track for track lighting). I figured there would be some spring back but I was just going to bend it with the form and then modify the form as needed to deal with the spring back. Thanks for the input.

-Erik

mac1 · 24 Jan 2014, 17:40

You can model almost anything in SU but question is what do you get physically when you are done. You are taking the metal in the bar to yield when it is bent so out side is longer than inside plus there will be spring back at the end of the bending process. IMHO you have to build the form different for a small dia. bar vs large. So question is what do you want the final product to be??
Suggest you do quick internet search and you will see the issues you will need to solve.
Quick check of local machine shops may save you cost in long run.

mac1 · 24 Jan 2014, 17:47

You did not note angle but for that you will have to worry kinking ?
Flexible track?

Erik63 · 24 Jan 2014, 19:21

Hello Mac1,

The angles will be smooth much like a sine wave so kinking would not be an issue. Yes it is a flexible track that allows to you bend the shape you would like within a certain maximum radius.