topic Re: Formulas in parameters or a better way? in Fusion Design, Validate & Document Forum

Formulas in parameters or a better way?

jeffescott — Tue, 04 Jun 2024 20:53:56 GMT

I am trying to calculate the length of a line. It is composed of arcs and circles.

I cannot get the a formula containing degrees to enter correctly. Not at all sure why.

Is there a way to do this??

or better yet an easier way to do this.

see attached file; sketch 4.....the line is the curvy construction line

Re: Formulas in parameters or a better way?

g-andresen — Tue, 04 Jun 2024 20:28:10 GMT

Hi,

1. no file attached

2. What do you want to calculate from which lengths/arcs?

günther

Re: Formulas in parameters or a better way?

jeffescott — Tue, 04 Jun 2024 20:56:20 GMT

I sketch 5 is a good one to work on.

File is attached to the first post....sorry about that.

Re: Formulas in parameters or a better way?

jhackney1972 — Tue, 04 Jun 2024 22:19:28 GMT

The attached video will show you the fastest way to get the length of the curved/straight line.

(view in My Videos)

Re: Formulas in parameters or a better way?

jeffescott — Wed, 05 Jun 2024 00:06:54 GMT

Thank you. This looks faster than a pipe body and i path.

i hope i can use it parametrically!

Re: Formulas in parameters or a better way?

laughingcreek — Wed, 05 Jun 2024 15:35:38 GMT

just selecting multiple curves will tell you the total length without doing anything else. it displays in the lower right corner-

but-

@jeffescott wrote:...i hope i can use it parametrically!

neither option shown so far will be parametric. your original approach will work if you get the formulas right. you're probably not canceling units correctly.

there also may be a different/easier way to achieve the end result you want, but we don't know what that result may be.

Re: Formulas in parameters or a better way?

laughingcreek — Wed, 05 Jun 2024 15:50:33 GMT

here's an approach using Sheetmetal to get the total length of the line in a parametric way. see attached. these are the features added to your model to do this-

the process will yield a dimension that reflects the total length-

plus side of this approach is it will work with splines also.

Re: Formulas in parameters or a better way?

jeffescott — Wed, 05 Jun 2024 20:02:55 GMT

thank you doh radians

Re: Formulas in parameters or a better way?

jeffescott — Wed, 05 Jun 2024 20:05:43 GMT

yup that is the way.....I am designing a serpentine spring. I need to iterate to the length with my spring program. I quickly get confused with all the variables...this makes it much simpler.

Re: Formulas in parameters or a better way?

jeffescott — Thu, 06 Jun 2024 15:33:57 GMT

This is almost perfect.....but

I changed the design rules to match my spring design in this case 5mm in x and 3 mm in z.

I am looking for the moment of inertia (the one for beam calculations) in the xz plane.

The answer is =5*3^3/12=11.25mm4.

This answer is not found in the properties section is it somewhere else?

I can just do it parametrically of course.

Re: Formulas in parameters or a better way?

laughingcreek — Thu, 06 Jun 2024 19:36:19 GMT

It's not here?

(these aren't available parametrically unfortunately.)

Re: Formulas in parameters or a better way?

jeffescott — Thu, 06 Jun 2024 21:13:17 GMT

I checked the properties....the moment of inertia is not the one I am looking for.

I need the second moment of inertia used for beam calcs. Specifically I xz....I the formula is b*d^3/12

b is the width of the beam h is the height of the beam for a 5mm x 3mm cross section that is 5*3^3/12=11.25mm^4. Pls note the units of Moi in the properties box is g mm^2.

if I divide by the mass 1.25g none are close to the correct answer.

See sketch Moi check body 6

Re: Formulas in parameters or a better way?

laughingcreek — Thu, 06 Jun 2024 23:07:25 GMT

ahh, second moment, didn't catch that. fusion doesn't do it directly. you can either do it manually if you want it to be parametric, or use the workaround found in this thread to get fusion to help you a bit 9but won't be parametric)

https://forums.autodesk.com/t5/fusion-design-validate-document/moment-of-inertia-should-be-in-mm4-but-fusion-show-it-in-g-mm2/td-p/7821997

Re: Formulas in parameters or a better way?

jeffescott — Fri, 07 Jun 2024 00:57:15 GMT

So my issue with manually in a user parameter. I can’t find a unit equal to mm4.

so i tried no units it works. Is there a better way