Post #800968 by TheLuckyParrot on Tue, Feb 25, 2020 4:31 PM

SHIPWRECK, PART 3

Here we have the final video done back BEFORE I got distracted (NOT the final update or video to the Shipwreck progress reporting itself). It is a motion study that helped me determine things like arc motion and distance and speeds. As I mention in the video I ended up not using this exact mechanism. I DID use the named model ship and I did use the same vertical stand and hinge. But as I was in the final phases I learned that the cute little blue servo I am using in this study video is not durable. Maybe it's a good thing I had so much time to complete this because in the intervening months (from which you all are being spared) I handled that study item a lot and I toyed with the motion a lot and I accidentally got the chance to abuse the servo more than I would had I gone straight to build.

Here was the problem that did not show up in this study. At rest we want the ship to be "level at sea". The way servos work is that you have to tell the servo to be at some rotational position. Most servos have 180 degrees of travel so you have to tell the servo to move to some value from "0" to "180". Servos are also very fast so I needed to include some extra software code to take tiny little pauses between each step so that it not turn the ship into a rocket. In my case I chose that "level at sea" position to be angle 0 because I wanted to have the maximum amount of motion with which to work, hence level equals "0" and full sink could be anything up to "180". The ship is supposed to be sitting level while not in action, meaning that the servo is supposed to hold at position "0". But the ship and the pad upon which it sits are not weightless. Over time this tiny bit of weight started to be too much for the servo to hold at "0", and the weight pushing down would move the servo to "1". The servo would realize that it is not at "0" and go back to "0". But it still could not hold the weight. Rinse, repeat. This would end up with the ship oscillating. And the oscillation was not controlled by my commands so there were no tiny little pauses to keep things in check. And that would all quickly get out of hand and at the speed of electricity the whole rig would start thrashing violently!! I was lucky enough to learn this before things got bolted together and it would be too late to re-engineer and rearrange everything to accommodate a stronger (and therefore LARGER) servo. AND I was lucky that I was far enough along that the ship stand itself was glue down else the entire rig would have launched itself off the workbench and destroyed my model ship! Losing the ship would have been disastrous, since everything is all sized to fit together tightly and it would be impossible to get another model ship that exact size and shape. The whole thing would have had to be scrapped and I would have had to start all over.

But I did survive it all, as you will soon see.

Here then is that final study video from back in April of 2019. After this post, I will create and show photos of the final mechanical monster that went into all of this. All that before showing you the video of the final solution in perfect working action.

https://www.youtube.com/watch?v=VcTNwdwaKEE&feature=youtu.be

[ Edited by: TheLuckyParrot 2020-02-25 16:32 ]