Strange behavior of spiral conveyors

I’m getting started with VC 4.8 Professional, and running into something very odd.

I have a set of Spiral conveyors that sometimes animate products moving up the spiral correctly, but other times animate the product just moving straight from the entry point to the exit point, “phasing” through the body of the conveyor like something out of Star Trek.

It’s not just animation – I have all the spiral conveyors set to the same speed, and the ones taking the “shortcut” get their products to the exit point much faster.

The oddest thing is that this behavior changes semi-randomly. I’ve had this happen several times now – when I make edits to other parts of the layout that have no direct connection to the spiral conveyors, the conveyors may (randomly) switch between “correct” and “shortcut” behavior.

This isn’t fatal for my simulation, but it’s very odd. I can’t figure out what’s causing it, why it randomly flip-flops, or how to fix it.

Here’s an example screenshot. At this run, the furthest conveyor was “spiralling” properly, but the other 3 were all shortcutting. You can see the products passing through the body of the conveyor.

Most likely this is due to the path frames. Does the spiral conveyor comes from eCat? Or you created the spiral conveyor? It would be nice if you could upload the layout.

The Spirals are direct from the VC Conveyors library, no modifications aside from height/speed/capacity.

I’ve attached the layout, and a short vid of the behavior.

Uploading: SpiralStrangeness.avi…
Spirals.vcmx (783.9 KB)

I guess you remove path frames accidently. The most left conveyor has many frames, the most right conveyor only has 2 frames.

Hm! I wonder how that happened. I don’t recall doing anything different to the first spiral vs the next 3.
The only “odd” thing that happened was that I created all 5 Spirals by copy&paste, and found that when I “inverted” the 5th spiral (which was the last paste), it affected the first 4 spirals too. I ended up having to ctrl-Z my way out, then delete the 5th spiral and import a “clean” one from the ECatalog.

Oh, well. Now I know how to fix it. Thank you.

…oh, my, this is bizarre. So, I just deleted the three misbehaving spiral conveyors, and replaced them with clean ones from the ECatalog. A quick test showed all of them working correctly.

But then, I modified the speed of each conveyor, singly, to match my original specifications… and now one of the three “fresh” conveyors has suddenly started “shortcutting” again (the others are still fine). And I know I didn’t touch the Path setup on it – over the course of 5 minutes, all I did was a successful test run, the speed changes, and then another test run, where the shortcutting behavior appeared again. I never even had the Modelling tab open at any point between the two tests.

These sprial conveyors appear to be extremely “brittle”.

I think it’s due to DoFrames script of the spiral conveyor.

ength = 3.1459*2*(comp.Angle/360.0)*((r1+r2)/2)
h_angle = 0.0
if length > 0.0:
  h_angle = asin(comp.Raise/length)

When comp.Raise/length is smaller than -1 or bigger than 1, e.g., Raise it too big or radius is too small, then asin(comp.Raise/length) will get error, that will makes path frames only has in frame and out frame. Next time when error happens, check your output panel, there should be a error message, simply enter other numbers in range.

Coming back to this after a bit. And there’s definitely something wrong with how VC is handling these spiral conveyors.

SItuation: I had two conveyors running perfectly, and two doing the “straight line” behavior. I stopped the sim, deleted the two spirals that were misbehaving, then did a copy&paste of one of the working ones to replace the deleted ones. Made sure I did nothing else.

Ran the sim. The two “new” spirals ran perfectly. The spiral I had copy&pasted started teleporting product from the start to the end. And I made no changes to that spiral, at all. No error messages in the output window at any point in this entire process.

It’s great that you know how to reproduce it, could you record the process, let’s check what we can do about this.

Record… as in screen video capture? I’m not sure, I’ve never done that. I’m also uncertain I can repeat it at will – I wasn’t trying this time, I was just fixing up the spirals so as to make my sim video look better.

…okay, I just tried it again. I cleared the output window, then deleted the misbebaving spiral conveyor, copy&pasted one of the properly-behaving ones in its place, and ran the sim again. The copy behaved correctly, the copied began doing the straight-line behavior. No messages.

And, just to frost the cake, the 4th spiral conveyor, which I did absolutely nothing to… changed from operating correctly to doing the “teleport” behavior.

All 4 appear to have all their frames in the “pth” branch of the Model, too:

It would be great to see how you produce it by capture the screen, could you upload this file? frames are there but flow is straight up, thank you.

…I think it knows I’m recording. As soon as I had the screen recording running, I was unable to recreate the issue.

When I turned the recording off, I was able to recreate it again, but as soon as I restarted the recording… :exploding_head: