Cannot raise to power and square root

[danpayneuk]

Hi 

I am currently trying to set parameters for a some chain ring designs.

Inserting the required formulas has been fine until this one.  

I try to add the following sqrt( F_ ^2) - (( 1.4 * dr )- p / 2 )^2

however due to F_ being another parameter it does not allow it to work.  If I change F_ so that it is a number then all works fine.

Is this something that can be fixed?

[TheCADWhisperer]

I do not see units handling in your equation.

[danpayneuk]

I chose inches in the drop down menu.

I have also tried with no units in the drop down menu and neither worked

[TheCADWhisperer]

You must take account of canceling out units in your equation - just like in HS Math class.

[TheCADWhisperer]

Once you File>Export and then Attach your *.f3d file here - I can generate proper equation.

Here is one example.

[danpayneuk]

Hi Please find attached the f3d file as requested. I am also having a further issue regarding parameters and constraints when it comes to altering them, but I will discuss that in another post, unless preferred to keep it all in one post. Many thanks

[JDMather]

You have several errors in your construction. I recommend that you simplify the sketch to create only one tooth "valley" and then pattern feature rather than sketch. I recommend that you not create more than one entity at a time without fully defining your sketch at each and every step.

[JDMather]

The Attached document refers to SolidWorks and an Excel Spreadsheet, but the sketch construction technique is absolutely identical. As I find time - I will try to create example in Fusion 360 using your parameters. Bottom line - 1. Constrain every single entity as you create it. 2. Sketch only one tooth.

[JDMather]

Open the Attache file. Note that I create one entity - the Pitch Diameter and fully define it (turns black) and change to Construction (as it really is).

[JDMather]

Next Roller Clearance. Note that sketch is fully constrained.

[danpayneuk]

JDMather, thanks for your replies. I will look at the attached links and files. If I have any more questions I will come back to you. Thanks for for time looking at this.

[JDMather]

Angle A Note that the sketch is fully constrained. See a trend going on here?

[JDMather]

Angle B Note that sketch is fully constrained.

[JDMather]

yz offset Note that the sketch is fully constrained.

[JDMather]

W offset What do you notice about the sketch?

[JDMather]

One tooth profile.

[JDMather]

Pattern Feature is much more computationally efficient.

[danpayneuk]

Wow thanks for all the updates. I have just been looking over them and especially the last showing the pattern feature. The main reason for the parametric modelling is so that I can change the number of teeth and the model automatically update correctly. It appears the one you have drawn has the same issues as what I was finding. If you change the tooth count (n) the model does not correctly remodel as would of hoped.

[JDMather]

---

@danpayneuk wrote:
... If you change the tooth count (n) the model does not correctly remodel as would of hoped.

---

I didn't look at setting the number of teeth as parametric - I just typed in 16.

I will take a look tomorrow at setting the number of teeth parametric so that the part updates correctly.

[danpayneuk]

Hi JDmather

Did you possibly look at the reason why when altering the N value the model does not rebuild correctly?

I have tried numerous things and if changing more than once, especially for example n=16 to n=36 and then back to n=16, the model does not rebuild correctly.