Sunday, May 30, 2021

Progress with probe kit build

It's been a while since I've posted an update. Rest assured we've been working massively hard. :) For now, here's a bit of news about work I've done to -- hopefully ;) -- improve the way the probe is built and make it easier to put together.

The "new" design is a throwback to some of our earlier work, using four thru-bolts to hold the whole assembly together. The bolts are #4-40; previously we were using #6-32, which is honestly way too big. This solves a number of problems with previous designs --

  1. Building 3D printed parts to axially locate the internals made these parts complicated.
  2. Relying on the outer polycarbonate tube to hold things together meant that, during assembly, everything flopped around.
  3. Drilling holes in the polycarbonate tube is nontrivial -- easy for a well-equipped shop, but not something that's easy for a kit builder to do.
The result is as you see. Meanwhile, notice that our new material of choice is translucent blue PETG, which has proven to be extremely good at reproducing detail. We have high hopes for this stuff.

These renderings show the probe from the outside, from the "top" and "bottom" (the battery is now on the bottom):

You can see how we have preserved the previous method of attaching to the mount, with the two screws with standoffs coming off the back -- except now, these screws are part of the continuous thru-bolt assembly going the entire length of the probe. Next, here is a detail of the temperature sensor board, which sandwiches in the 3D printed parts and will now be wired to a screw header terminal:

The pressure sensors are pretty much as before. Note that we are relying heavily on the plastic threaded and barbed connectors you may have seen us using previously:

The sharp-eyed among you might notice we only have 5 holes in the probe nose now; no "static" hole or static probe. This is a new result and one which we hope to talk more about soon. For the moment, we note that this is a really promising direction.

The assembly sequence is shown in the below photo album. Note how, once the thru bolts are assembled, the entire circuitry and plumbing are exposed to be worked on, after which the outer tube can be installed.

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