topic applying moments in Fusion Design, Validate & Document Forum

applying moments

maker9876 — Thu, 07 Jul 2016 14:40:16 GMT

I'm having difficulty working with Moments in the Static Simulation environment.

1) whereas the Force arrow is abundantly clear the Moment icon is hard to find, then hard to see (lots of zooming required) and I have doubts looking at it!

2) Normal to a face - given the just about perceptible arrows on the icon - is just about intelligible;

3) but am not confident setting up moments using the other methods;

=> it would be great to find a more developed explanation on the site.

Until then I'll carry on with dumb workarounds like fusing a bar to the point in question and applying an appropriate force to it!

Re: applying moments

innovatenate — Thu, 07 Jul 2016 21:12:22 GMT

I'm not aware of setting to modify the size of the constraints/load glyphs in the Simulation environment at this time. Would it be possible to share some screenshots of the issue you're grappling with?

I'm not sure if this helps, but I think of the "right-hand rule." If you stick your thumb out along the axis (normal to the face you've applied the load to), the Positive force direction is same direction your fingers "curl" in. I think this image might help explain this better:

The hard part may be to figure out which normal direction is positive. There is a 50/50 chance you'll get it right if you take a wild guess.

Usually I would just look at the glyph in canvas, but if that is difficult to read....

Another way you can check yourself is to examine the Reaction Forces on the Constraints after you've run the simulation:

The will break down the reaction forces along the primary axis. This can be helpful to understand how the load is being distributed.

I note that the moment dialog also contains different Direction Type inputs. You could apply the load using XYZ vectors outright (think of the right hand rule in association with the primary axis). Since the XYZ axis is always displayed in the simulation environment, it is very easy to determine how the load is being applied to a face this way.

Another good note, if you switch to XYZ vectors as the Direction Type at any point, the numerical values about each primary axis will be created from your previous input. This can provide some clue about which direction the load is being applied in before running the simulation.

*really wishing there was a thumbs up smiley right now.. 🙂

I hope this helps.

Re: applying moments

maker9876 — Fri, 08 Jul 2016 15:54:10 GMT

Hi,

Your explanations and clarifications certainly help.

Thanks.

I think what would really help in the interface would be a clear Arrow that shows the moment axis and it direction. (In the same way that there is a clear arrow indicating Force direction.) And perhaps a smaller arrow turning around it to leave no doubt.

At the moment (!) I'm zooming 10 times to look closely at the glyph and wondering where the axis might be (the right hand room helps but....) And then after the zooming it's not clear where the rest of the model is! Or looking at the numbers in the dialog and trying to figure out what they refer to in space. It's not that I'm numerically hopeless or have any particular difficulty with cartesian orientation; rather in Fusion360 in general and in particular when I'm working on a zoomed area of the model I've usually little or no idea which directions are X, Y and Z, and frequently little idea which is up and down! So being able to SEE the direction of the moment axis clearly and from far away would be immensely useful.

EDIT: re-reading your post I understand not everyone finds the glyph difficult to read! Can we at least agree that it's on a very different SCALE to the force arrow? It's MUCH smaller. Also some people work on 13inch high res laptop screens....

EDIT2: also note that for my way of working in Fusion360, things are set up visually rather than from a written plan. Which is to say I might eyeball the design to decide which direction I would like to twist something for static analysis. It's a pain to have to convert a) the drawing to cartesian coordinates (in my mind); b) to then decide the direction of the moment vector in cartesian coordinates relative to the point that it must pass through; c) then enter those guesstimated numbers manually; When the whole process could be eyeballed.