The trick to efficient OnShape cad design, I’ve realized, is to design each component in an assembly spatially in place using offset planes etc. That way alignments are visible as you build. You can check assembly view as you work on the part view, to make sure holes etc line up.
Conversation
It’s interesting how much this is an REPL like in programming. I literally had calipers handy and was measuring COTS components as I went, like the 2s lipo battery (2 blue cylinders), turnbuckle link, and ball joint between rocker hinge and body, to make sure it would fit.
1
4
You discover design constraints/needs as you do this. For example, that white connector on the battery is supposed to plug into the 3-pin header on the board near it (this is a Beaglebone Blue robotics board). But it’s too short to come around from the bottom the way I’d planned.
1
2
So either Plan A: add an extension cable (which needs room) to keep the battery on the lower deck or Plan B: put the battery above the board, raising the center of gravity and making the rover more top-heavy than it already is.
1
Two more. In assembling-while-designing, I realized my original plan to have a completely covered top deck wouldn't work. The BBBlue antennae need to stick out there, plus need top access to gpio headers to connect stuff on payload deck. So ended up with a nice big hatch hole.
1
The second one: while sketching this out, I hadn't factored in that the turnbuckle (red rod a few tweets up) is too long for the differential bar to be on the main body... so now I had to add a tail plane to hold the differential bar (on perseverance this is in the middle)
1
3
Whew, finally figured out how to do mate connectors correctly. Now I have this aluminum strut mated via a slider joint to the rocker hinge
1
4
My rover body is going to end up tiny relative to the undercarriage. This is because my 3d printed part dimensions are limited by my printer's build plate (120mm square, but effective max more like 100mm square)
1
2
Ran out of steam, but printed out a roughly to scale side view so I can sketch to visualize the rest. Not bad.
2
4

