How do I curve a ridged object

[ianhughes7UFVF]

Hi

I have this ridged arm that I have created in Fusion.

Its for a B9 Lost in Space Robot.

I would like to curve it so that it looks more realistic. Like this:

I think this is something that probably is done in the Patch part of Fusion using a sweep, but I have no idea how to use that in this context.

Once again, any help would be greatly appreciated.

Regards

Ian

[chrisplyler]

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@ianhughes7UFVF wrote:

But what was getting me stuck is calculating the distance between the 3 planes for each rib. My drawing as yours has a 45 curve. There can only be 21 ridges in the arm as per the original prop and I fundamentally plan this to be straight then curved then straight again, so really probably on 7 ridges need that curve. So is there an equation that I can use to work out the distance between the 3 planes for the ridge, taking into account the 45 degree angle, the diameter of the circles for the ridge and the distance along the curve.

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Don't think of it as a "distance." I mean, it is one of course, but that's not the answer you need.

It's easier if you want ten ridges, but the math is the same regardless. If you've got a 45-deg arc, and you want ten ridges along it, then each one should occupy 4.5-degrees of it. That's why my Planes-on-a-Path positions were 1, 0.95 and 0.90. The total between the two outside planes was equal to 1.00 - 0.90. A 0.1 difference. 0.1 can be called 10%. So my first ridge occupies exactly 10% of the 45-deg arc.

The numerical value of those divisions depend on which end of the arc you put them on, and which way you drew the arc in the first place. If you had started at the other end, those positions would instead have been 0.00, 0.05 and 0.10.

If you want, say, seven ridges along the arc... Take that 45-deg and divide it by 7. Then figure out what percentage of the 45-deg arc your result is, and put the three planes a little further apart as required. Hint: It's a lot easier if you make the arc some number of degrees that is a whole multiple of the number of ridges you want. For example, if you want eight ridges, make the arc 32-degrees, or 40-degrees or something like that. That keeps you from having to input long decimal strings and hoping you have enough precision.

The radius of the ridges must, of course, be some value less than the radius of the arc, or the ridges will clash through each other on the inside of the bend. How much less depends on how much width the ridges occupy. I would stick to ridge_radius =< 1/2 arc_radius as a starting point, and adjust downwards after checking the results if necessary.

Multiple curves could be achieved by making separate sections and putting them together, although it might just be easier to use another method at that point, as @davebYYPCU  pointed out.

Two of my sections jointed together with a Revolve:

Screencast will be displayed here after you click Post.

d11da8b0-f359-4355-addc-a8a4ebde90c2

https://knowledge.autodesk.com/community/screencast/d11da8b0-f359-4355-addc-a8a4ebde90c2

[davebYYPCU]

Ok, now that you have Described the path.  Different ball game, the curved bit is just part of the whole thing.

How many sections, will be on each segment of the path.  

first line has (a) sections, curve has (b) sections, last line has (c) sections, a + b + c = 21

From your previous attempts, we will go with 6 degrees, for the bent segment, 11 segments, 66 degrees. Change the curve angle from 90 degrees to 66 degrees.

use Dimension, on the two straight lines in the sketch, make them construction.

Now 0.5 and 0.1 in the Plane on a Path will work, as Chris said.

For the straight sections, their spacing is 10% of the curve length.

Might help....

[davebYYPCU]

But there is an easier way to avoid the Plane on Path calculations.

Draw the single segment, on lines at 3 and 6 degrees.  Put planes on Angle and Intersect the curve for the profile.

Measure the length of this curve trimmed back to 6 degrees, then extend it to the end of the circular pattern.

Make the straight segment, with the length of the curve you measured.

Make one straight segment, pattern and then mirror that to the other side.

Most of the work is set out in Sketch 1.

[chrisplyler]

Well, technically, you don't HAVE to have the arc go all the way through the bend.

You can just create a small arc representing one segment. Then you can put the planes at 0.00, 0.50 and 1.00.

Make the arc include whatever angle you want. Let's call that angle A. Let N be the number of segments you want. Just be sure that when you do the pattern, that the total degrees of the pattern is equals A*N, and that the quantity equals N+1 (suppress the extra one if you want).

Say you set up your arc to be 5.25-deg. Each segment will occupy 5.25-deg. And say you want 9 segments. So make the first one on that small arc, then pattern using 47.25-deg and quantity 10, and suppress the extra segment. Easy.

I only did the full arc in my video as a visual aid. It isn't necessary for the construction. The only reason you might need the full arc is if you're going to Sweep the smooth interior, but you could Revolve it instead and then you wouldn't need the full arc at all.

[ianhughes7UFVF]

Hi

Well, I worked it out combining your directions. Plus my son helping my dense brain.

Thank you chaps for your directions.

This may not be perfect but it appears almost right.

I need to create a 3d bearing to join this to a second curve.

Kind Regards

Ian

[davebYYPCU]

Correct, until you need a midpoint line to mirror the straight sections.

[chrisplyler]

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@davebYYPCU wrote:

Correct, until you need a midpoint line to mirror the straight sections.

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Do you mean in a straight>bend>straight situation? You don't NEED to mirror anything. But if that's easier for you, sure.  Still, if it helps you make the math easier, you can use a short arc for one ridge, and make a longer one to put a plane on for the mirroring.