OpenROV 599 — Build Diary 02

[2 May 2015]

An old shop trick of mine, to avoid disasters.

An old shop trick of mine, to avoid disasters.

Today I began assembly of the infrastructure of the ROV — that means “cementing acrylic.” I’ve never done this before (other than styrene models), but I dutifully watched the TAP plastics video that the instructions pointed to. Even so, I think I was still a bit unprepared for how free streaming the cement really was!

None the less, things progressed steadily without too many hiccups. Copious notes are in my OpenROV599 CompBook, but I capture the important points here for reference. The “STEPs” labeled are the step labels in the instructions [2014-03-20 version in the version history].

The pieces for today all laid out.

STEP 003: I got the first two pieces aligned pretty well, but the third one was off just a tiny smidge; you can’t see it well by eye, but I can certainly feel it. Shaving it down with a knife didn’t seem to be workable, and I didn’t want to sand it for fear of rounding off the whole assembly, making contact surfaces problematic.  I test fit it onto the Lateral Shroud Support, and it seemed tight enough, so I didn’t worry about it.

STEP 004: Note in this phase of the instructions, the piece is referred to as “top piece of internal structure” and as “top plate“. It is called top plate on the line schematic drawing shown in Step 2 of the instructions.

IMG_5951

It’s not easy to see from the instruction pictures which way it all goes together. If you look at the Top Plate face on, it kind of looks like a barn — the handle is aligned in the vertical direction of the barn, with the finger holes close to the roof, and the horizontal piece (the Lateral Shroud Support, bonded to the handle) parallel to the floor.

STEP 005: Not all the parts used in this step are named in the instructions. They are (corresponding to the line schematic in Step 2 of the instructions): Horizontal Motor Mount, Axial Shroud Supports, and Vertical Motor Mount.

motorMount

Note that the shape of the holes in my Vertical Motor Mount are not the same as those shown in the line schematic — mine have slightly rounded inner edges, rather than flat edges. This was the first step where I had to really pay attention to the pictures and try to understand how to put the parts together — it’s hard to see what is going on with that clear acrylic!

IMG_5952

I did my bonding at this stage in 3 steps: (1) Bond motor mounts to the left Axial Shroud Support. (2) Bond motor mounts to the right Axial Shroud Support. (3) Bond the interface between the Motor Mounts.

STEP 006: This took me a little while to decipher from the pictures how to put this sub-assembly together. The pictures are not obvious, and hard to parse. The motor mounts are bonded to one end of the Axial Shroud Supports (see last step). The open edge of the Vertical Motor Mount bonds to the lower face of the Bulkhead (under its central U shape); the edges of the Axial Shroud Supports also bond to the Bulkhead (on either side of the central U shape), with the tabs fitting into pre-cut slots.  When correctly put together, the Horizonal Motor Mount is parallel to the Bulkhead.

The Bulkhead Brace is laminated onto the long edge of the Bulkhead to make it double thick. It is under the central U shape of the Bulkhead, and contained by a slot formed between the Axial Shroud Supports and the Bulkhead. Tabs on either end of the Bulkhead Brace match tabs on the Bulkhead.

As noted in the instructions, some later kits have larger plastic heads on the end of the Bulkhead Brace than shown in the pictures. That is true of my Bulkhead Brace — the brace is large enough to cover the tab holes in the Bulkhead.

STEP 007: Join the two major sub-assemblies at this point, and then add some bracing.

CONCLUSIONS TODAY:

(1) Photographing clear acrylic so it makes sense is HARD (mine, shown here, and the OpenROV guide photos just don’t always make sense!). To this end, pushing parts togther and handling the structure and looking at it from all angles while staring at the pictures is crucial to getting it all together right. Sometimes to figure it out, I had to step ahead a step or two to see where it was all going to fit together.  Don’t pick up the cement until you’re sure you got it right!

IMG_5972(2) The acrylic cement is crazy stuff. Holding tension on parts means there were a few times it ran under my fingers too. That means there are several places where my fingerprints are molded into the infrastructure. Oh well; that just means 200 years from now, when marine archaeologists find Jack on the bottom of Lake Michigan, they’ll be confident this was really my OpenROV! :-)