Note: The content from this log was on Sept. 4

With the results from Test #02 along with Leo’s buoyancy calculations, it was time to try another test. 

Objectives of the test

• Verify the external wiper moves along with the internal wiper while in water
• Verify the ballast works
• Compare the results with the conditions from Test #01 (wave height ~2 cm) to Test #02 (wave height ~15 cm) to Test #03 (wave height ~20 - 30cm)

This is what the new setup looks like:

Here it is, the external wiper working, underwater and even with the waves!

Read on for the results and more info

The waves were particularly high for this test. Good conditions to stress test it a tiny bit more:

Here’s the buoy being pushed around underwater with the current, and the wiper is attached and working!

It’s exciting to see that result. Might seem small, but it allows moving on to the next step of the larger release mechanism. 

Here was one of the fails. The block that attaches to the lid fell off due to being heavier with the ballast now.

Worth a try, but nope, a rock did not help:

This was an interesting moment in the test when the ballast detached:

That scenario gives a preview of what the release mechanism result would look like - a buoy floating on the surface:

Let’s see if this similar result can be achieved with the next design. 

Here are the learning lessons from this test:

What changed

There were a few changes to the setup. Most notably, there’s clamps on the ends of the buoy that attach in 2x 1kg peanut butter jars. The new batteries arrived, so there’s an 18650 cell attached to a 3d printed bracket behind the circuit board. This eliminates the LiPo that was attached to the inside wall preventing the servo with internal wiper from moving properly. The neopixels were not lighting up after test #02, and this remained unchanged due to scheduling. 

The lipo batt was curved slightly after removing from the nalgene:

Here’s the 18650 on the batt clip:

What worked

• External wiper confirmed to work in the water!
• Achieved less buoyancy with the two containers filled with sand and water

What didn’t work

• Containers filled with rocks (contained air pockets)
• Containers filled with dry sand (contained air pockets)
• Trying to attach rope to a rock and use that as ballast
• Forgot to print a proper attachment point for the rope, so it was attached to the ring on the nalgene lid

Here’s the rocks and air in the container - this didn’t work, so it was changed to sand, then changed to wet sand - which did work:

What needs to change for future version

Actually, that’s it for iterating on this! The hypothesis about the wipers has been validated now, and the next step is to work on the release mechanism assembly design. That’s what the large hdpe piece will be used for.

Guiding the preparation for the next test is the release mechanism.

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By the way, here’s what the peanut butter jars look like in case anyone was wondering :)

(And yes, it is very unhealthy *and* delicious)