Dyne's LD-F1 (D-O concept) build

[Dyne]

T-Minus 3 weeks

Only a little bit of time left to get this thing done.  I do have a spare week's worth of wiggle room, but that's not much, and I'd prefer to have the droid assembled by then so I can do some actual testing and relax a bit.

(I did say that I'm terrible at estimating how long things will take.  It's been a full month since my deadline to have the design largely wrapped up, and I'm still working on it.)

Indeed, we're now entering a race to make sure that there's actually time to get everything printed, since many of the parts that I have left will require quite a bit of time, even assuming no failures.  I may have to train someone to keep an eye on things so I can run some prints while I'm not actually here.  I'm also considering changing to a larger nozzle purely to speed things up.  If I haven't got most of the big parts printed in the next two weekends, I'll definitely do that.

We are currently up to 96 track links out of 106 in-hand plus 16 spares and one "iffy" spare (it's not really that bad, but it's slightly deformed on the top of one peg, so I'm keeping it aside), and I believe that the remaining ten are already done.  I've got all four sprocket bodies and 6 of the 8 toothed wheels printed, though I had to switch to black PETG for the rear parts because the spool of silver I had was just causing too many problems, even after swapping hotends.

I've got a new spool of silver and the leftovers from my original spool to compare with, so we'll see how that goes when I get around to using them.


Over the last week, I have worked on finishing up the chassis design as planned.  It's not quite there, but it's close enough to get many of the parts printed.  There are a lot of parts in here, so here's a breakdown of the structure:




This black model is the Rear Bottom Plate of the droid.  Like the Front Bottom Plate, it has holes along the sides for attaching the side plates.  It also has a couple of holes in the bottom and a rectangular recess that the battery sits in.  

You will also notice the rear curved section has a large central structure and two vertical openings.  These are to support the rear body shell hinge and to allow it and the two L-shaped brackets that attach underneath the rear body shell to rotate.

I probably should've added short walls along the edges to make the part a little less flexible, but it'll be stiff enough once the side plates are installed.




The orange part is the Rear Outer Side Plate.  There's another on the opposite side, of course.  This bolts to the Rear Bottom Plate and to a part later on.  One of the things I need to wrap up on this part is to add a couple of mounting points for the track carriers and idlers, which I will be working on in the next few days.

Also shown are the Middle Support for the lower stalk axle (white) and the Battery Cover (blue) that sits over that rectangular recess in the bottom plate.  I'm using my typical 5Ah 3S LIPO in this build.  The cover is not very thick and exists more to keep the battery in place and hidden from sight than anything, though I suppose it could give the battery a tiny bit of protection from random stuff bonking it.  

I didn't get fancy with decorating the Battery Cover; I figure I can always add some greebles to it later.  It screws to the bottom plate (from below) on either side and has a latch to hold it down in the rear.  In the front is the opening for the wires and balance leads.  Fitting it and its mounting points in this space (without changing the design of parts I've already printed to allow more clearance) required a bit of fiddling around, and the tolerance is pretty tight, but I think it'll work.



The purple models are the Rear Inner Side Plates.  There is a recess for the locknut on the axle, just as there is on the Forward version of this part.  I did not put a hex recess for the lower stalk axle because I want to be able to insert and remove the axle without disassembling the chassis.  The bolts will be mostly covered by the tracks anyway, and I can always make a magnetic cover if I want to later.

The pink part is the Rear Upper Cross Brace.  It bolts to the Rear Inner Side Plates to help prevent the chassis from splaying or folding, removing some of the stress from the bottom plates (the next part will also help, as will the locknuts on the main axles).



Forward of (and on either side of) the battery area is an important part, the "Electronics Box" (yellow), named such mostly because many of the electronics go here and I didn't have a better name for it.  But it also serves another purpose: It's the main structural connection between the front chassis and rear chassis.  

Remember in a previous post when I mentioned three M5 screws that go in the horizontal slots in each Front Outer Side Plate and allow the front part to slide for possible tensioning?  Well, there are two more M5 screws just aft of those (not in slots) in the rear section.  The insets for all of these M5 screws are installed in the sides of this part.

So ... electronics.

The fuse panel sits underneath this part, just forward of the battery on the Front Bottom Plate.  There will also be some terminals for the various ground connections in here, though I might have to DIY that.  I'm planning to put the audio transducer in the area forward of the fuse panel, underneath the front axle, also attached to the front bottom plate.

The raised platform above the front axle is where the ESP32 and voltage meter are mounted.  I've test-printed this part already, making sure I can attach any jumpers that I need to the ESP32 pins, as well as connecting to USB if I need to update Penumbra.  



And above shows the cover for the ESP32 and voltage meter (Olive green), held on with magnets in each corner.  I call it the Brain Box.  It's the sloped bit that sticks up out of the opening in the body shell in the completed droid.

I would like to put the droid's main power switch next to the ESP32 and voltage meter, but it's going to be tough to fit one with a high enough current rating into the remaining space (especially making it fit under this cover vertically, though I suppose going with a rocker switch could address that).

The brain box is the sole part of the droid's lower body that is currently printed in PLA, just because I already had some loaded at the time, and because in no way is this a major part.  If I want to add some more blinkies in the rear-facing surface of this, I can either cut an opening or just reprint it



The newly added Cyan part above is the "Electronics Box Lid".  It includes the curved dip that keeps the elbow joint in the stalks from lowering any further than it should, as well as a rear stop for the upper stalk to give it some support and remove strain from the mass of the head trying to wrench backward when accelerating.

It's a separate part mostly to allow me to get at the fuse panel without disassembling the droid.  Making it a separate part also helped reduce the height of support material needed during printing.  I separated it from the main electronics box just below that curved dip, so the latter can rest directly on the print bed at its lowest point.  If I want to, I can also attach some electronics (MP3 board, for example) to the roof above the fuse box or the sidewalls or whatever.


And that's it for the chassis structure.  Of those parts, I've already printed the Rear Bottom Plate, Electronics Box Lid, and Battery Cover this weekend.  I am printing the Lower Stalk Middle Support and the Rear Upper Cross Brace right now.  That leaves me needing the Electronic Box and the four Rear Side Plates (inner/outer, left/right) before I can do an assembly of the droid's lower body.

I also need to wrap up the body shell parts.  Those parts will have to be printed standing on edge because I don't want to cope with supports on the curved outward facing surfaces.  I already added some Baddeley-style breakaway supports to the opening in the flat part of the Front Shell, and once I add something similar in the curved portion, I can get that printed.



The rear shell also needs one of those supports, to have the rear body shell hinge added (basically just two arms which hold bearings to connect it to the rear axle), and to have the mount for the upper stalk's rear pivot added.


That leaves the track carrier and idler structure as the major design elements I need to finish.  As mentioned earlier, I have to get those at least partially modeled before I can start printing the side panels of the rear chassis, because that's where they'll attach.


It doesn't stop there, though...

I still plan to use the new traction pads, and to date I have zero out of 106.  These aren't strictly required, but they'll make the tracks look much better.  They take 45 minutes each so I can fit some in spare moments here and there when I wouldn't have time for a larger print, as well as printing bulk once printer time clears up.  Most will be silver PETG (if the new spool works) while maybe 10 - 15 will likely be in grey TPU.  I need to tweak the design slightly before I start them, because the clips currently have a tendency to break off due to the layer orientation.



Beyond CAD and printing, I did take the opportunity Saturday to do some quick priming of many of the previously printed neck and head parts, though it's looking very much like this droid will not really be fully prepped, much less painted, before the convention.  

I took the upper stalks apart for this.  They are meant to be glued together permanently so the seam toward the middle doesn't bow out and open a gap, and so the gaps that are there can be filled, but I haven't done any of that yet so it's still possible.

During disassembly, I realized that this creates a design flaw:  Once the stalk halves are glued together, there's no way to remove the rotation platform that sits beneath the head servos.  That becomes a problem if it breaks and I need to swap it for a new print.

You can't remove it because there is a hex nut on the top of each threaded rod that passes through the rotation platform.  Both are recessed into it, so there's no way to tighten or loosen them except by turning the threaded rods.  Which you can't get to (especially the forward one) because they are inside the glued-together stalks.

If not for the potential bowing and gap opening, technically the upper stalks wouldn't HAVE to be glued together.  They're securely held together at the bottom by the nuts that retain the bearings in the two lower pivots, and at the top by the M3 screws inserted through the top of the rotation platform itself.  I'll have to come up with some sort of solution for the middle, be it drilling screw holes, some sort of clamp, or only limited gluing toward the middle with something I can loosen later.