Shawn & Lara need a Toolbox... Droid?

[kresty]

Well... where else do you stick all those tools you have to take to shows with you?

Playing around with a model loosely based on Lars' 3D model.  Tracks might be a little too big (but kind of in a good way, they're less rectangular and more square, which might match the photos better).

Colors are going to be a serious pain.  It has sort of a brown/red/rust color, but there's not really anything that color in Lego.  Some other close colors don't even begin to have decent parts for this build... So this might be close.  But I'm wondering about mixing in other colors for "weathering".  That's not a trivial task though, so pretty undecided.  I confess I've actually considered more traditional model weathering techniques.

Tracks (maybe) for Toolbox Droid
Playing around with models.

For reference

[kresty]

Well, the tracks are going to need something flexible to connect them, so I'm playing with that.  I liked the Ninjaflex we used for the Make-a-Wish Mouse Droid wheels, but the bit left over from that isn't a good color for the Toolbox.  So I decided to take a chance on some TPU from ebay (trulyfoxsmart).

I'm pretty happy with how it's behaving.  We mainly got black, but thought the red might work for a few since the droid's so weathered.  (You won't be able to see most of this between the treads anyway)

Ties between treads of the Lego Toolbox Droid tracks

We're putting 2 of these between each pair of treads, 10 of those per side, so we need about 30 more of these! But this gives an idea of how it works.

I'm pretty happy with this stuff so far. It's not being as finicky as the Ninjaflex, though it feels a little different when printed. First attempt was a little too thick for the Lego to fit snugly, but the rest have been great so far.

Printing at 226 with 50 degree bed on clean glass (getting leveling right is a must). It needs to be slower at 1800mm/min (1/2 my normal speed). Interestingly the default settings 50% of that for the first layer proved too slow to be reliable. I bumped it up to 90% for the first layer and since then it's been printing cleanly on the Flashforge.

At Rizz's prompting, I tried it on the CR-10. I didn't do that earlier because flexible filaments and Bowden tubes aren't supposed to play well together. But I thought this filament might be stiff enough, so I gave it a go. Same speeds as the Flashforge and it's doing reasonably well. Maybe a little "muddier" (I don't think it can retract very well, 'cause it's jammed into the tube as far as it can go). But certainly feasible if you really need something and have a CR-10.

[kresty]

I was asked about the TPU fumes - I didn't find anything terribly scary about it on Bing. Our space is fairly open and we have an air quality monitor that mentioned VOCs being a little high - but probably within the normal variation, maybe not due to the printer. I did notice a little smell when I reentered the room after a while and considered ventilating it or slowing down, but it was very mild and hasn't gotten worse.

[kresty]

Oops, there are 22 link/tread bits on each track, not 20.  Original pix has 4 curving around each end and 7 on the top/bottom flat sections.  So that's 44 links, not 40.  And somehow I missed a x2 - I have 2 ties to print between each tread.  So instead of being over 1/2way done with the print, I'm barely 1/3 of the way done.

I sped up the print speed to 2200mm/min - so far it looks like it's doing OK.  Also printing 2 up (was doing one).  So ~2/hour instead of 1/45 min?

Also figured I may as well use more red, so I'm now running both printers.  (I wanted a little red, but if I need 2x the parts, then 2x the red is the same proportion).

[kresty]

Ok, testing the track fit/look - it's Long all spread out! Most of it still needs the detail layer added.

Lego Toolbox Droid Track

And then wrapped around 3D printed drive wheels

Lego Toolbox Droid Track

These six sections are playing with the detail level. We want it mixed up a bit to look like the weathering of the model. Also tried painting a tad, and the black stripes on the top-left edge are experimenting with traction.

Lego Toolbox Droid Track Color Test

Having never played with tracks before I'm running into some trouble. I'd like to add drive teeth - at least a little - but then the spacing needs to be regular for that to work. The wheel is supposed to fit 10 treads around it in a circle, however it's a little small. Probably going to increase the diameter a bit and see what happens.

Wheel with Tracks
Wheel was supposed to have 10 segments of track fit around it.  It's a bit too small.

[kresty]

Working on modeling the drivetrain and frame stuff this weekend. Trying to get it to behave a bit, happy with my progress.

The wheels seem a bit overly complicated. Originally they were two-part wheels with a small "hub" because I wasn't sure what my axle would look like with my hub. Once the wheel proved to be too small, I ended up separating the outer rim as well (so that it could be reprinted without having to redo the middle bit).

Now I've figured it out, so the hub now has a 26mm bearing for a 10mm shaft and attaches to a sprocket on the other side. (on one end - the other end is freewheeling).

Exploded view of my wheels

I made my own 4 lobed key thing for the sprocket and inner hub. There are screw holes to allow them to be screwed together. That'll keep the rest of the wheel fixed as well, clamped between the hub & sprocket. Sprocket is only on one end, the other end just has a plate.

The inner hub and main gear are keyed

I've also been pondering idler wheels. A real tank/caterpillar/whatever tracks are kind of like two sides of a square - tracks way out on the edges. Lee built this thing with really fat and long tracks, which make it unstearable. My thinking is that if these idler wheels are "lower" than the main wheels, then maybe I can get most of the weight to rest on the bit of track between these wheels on either side - which is more like a real tracked vehicle's square ratio. And maybe then it'll turn. Maybe.

Pondering idler wheels
Thinking if I can get some of the weight onto idler wheels, that are more centered and off of the main wheels, that it might turn better

The final diagram is as far as I've gotten so far. The center spine will probably need to be shorter, just stubbed in. Black thing is a space for the battery maybe. Motors will fit her if desired (I might move them, but if they're "high", they'll help pull the ends of the axles up to counteract bowing?) There are braces on the axles to maybe help keep the axles stable.

Working on Drivetrain

It's worth noting that my wheels are on bearings and both axles are static in this current design. That seemed structurally stronger and avoids having to try to figure out how to get the left & right sides having different axles.

[kresty]

Finally getting a little closer. This is working on the driveshaft. Unfortunately it's taking a while as my 10mm bearings don't like to fit on my 10mm shaft. So I've been trying to sand the shaft - which isn't particularly easy.

Toolbox Droid Driveshaft
My driveshaft without the wheel. The orange/red wheel in the other picture fits between the two black parts (which can screw together).

Toolbox Droid Driveshaft End
End of the driveshaft with wheel in place. This end has a drive gear, other end freewheels.

[kresty]

Well, that's hard.  My 10mm driveshaft is like 10.05mm.  And my 10mm bearings are like 9.95mm.  So getting them together has been challenging.  But now I have 6 ends that fit.  Next step is seeing if I can thread the ends.  (If not, I'll need some other way to keep the wheels from falling off.)

Eventually I want 4 rods, but the stock was only 36".  The idea is to have the main front/rear wheels and then 2 idler wheels in the middle.  I'm hoping we can actually get much of the weight onto the idler wheels to make the droid turn easier.  (So the end wheels would actually be a little, hopefully invisibly, in the air)

This kind of idea:

Not sure how well I'll be able to get it to work, but I think that about the only chance this thing has of actually being able to turn is by getting the load/friction on the tracks out to the edges and not quite as long.  If you look at a tank or a caterpillar, their track profiles are more like two sides of a square than these two huge rectangles.

[kresty]

Finally have enough parts together that I can start to put the chassis together. Spec'd at 1/2" wood, but I had 1/4" available (plus laser is tough on 1/2"), so we're gluing them together.

Starting to Assemble Toolbox Chassis.

[kresty]

I'll digress a bit... The axle rods are proving really annoying.  The 10mm axles didn't fit into the 10mm bearings (which are apparently about 10.05 and 9.95 mm respectively).  So I had to sand the rods.  And thread them.

Which eventually worked:

After hand sanding one end, I did the next by sticking the rod in a drill.  Much faster.

I also printed a couple discs for a guide to cut the steel rod, which worked really well:

Putting them just far enough apart for the saw blade.

Normally they were together.  But I spread it apart to take a pix (and because this one's getting loose.  I'll have to print another if I want more).

But the resulting edge was cleaner than I could've ever done without my silly disc things.