MAW-1 Mouse Droid

[kresty]

I dunno what to call it, so how about MAW-1 Mouse Droid for now.

Basically we're cloning MCK-Y for charity, trying to make the cloned droid a little more robust and kid-friendly.  It's based on MCK-Y's structure, with an R/C car frame and Lego panels.  Some of the folks of Bricklink have donated or discounted parts to help.  Hobbytown USA discounted some R/C parts, and Pololu and Sparkfun have helped with some of the other electronics.

One big pain is that something happened to the R/C factory that made the frame for MCK-Y, so they've been backordered most of the summer.  We managed to finally get one of the new frames in just the last few days.  

So far the panels have been built; next step is to modify the R/C frame to the mouse droid dimensions.  Then mount the shell and add the electronics.  

Working on the R/C frame today - trickier than I'd expected...

[kresty]

Well, that's annoying. While copying the droid, I discovered that MCK-Y's transmission is slipping in the rear output shaft. So I thought about it and realized that I have smaller wheels on front than in back. So that's about a 1:1.2 difference in gearing between the back end and the front end.

So I got some underdrive gears for the MAW-1 droids, but they're only 1:1.13 or so, hopefully that'll be enough. (I could also overdrive the front wheels, but that'd end up at 1:1.3 and miss in the other direction.

Or maybe just get Savage to teach me how to build some custom (metal) gears, he always ignores everything and builds his own parts, right?

[kresty]

I'll have to post pix later, but I've made much better hubs for the R/C -> Lego wheels. I forgot to test the hole diameter for the screw though and they're not tight enough I guess I'll need to reprint those.

[kresty]

Working on the front wheels today.  Already have the back wheels figured out, but needed to get the front done.  MCK-Y used spray foam in the tires, but that didn't work terribly well, as you can see from the cut-out section here.  The foam cured unevenly, and then also wore some.

Damaged Spray Foam Wheel

The rear wheels were a pain to get the fit for the "inner tube" correct, because I couldn't see anything.  But I figured this wheel is trash anyway, so I cut a section from the tire.  I realized I'd also then be able to put that on the scanner.  I fairly quickly corrected the profile and ran a test print.  It fits good enough the first try!

You can see my cross-section of the tire and the printed inner-tube fits pretty well on the wheel.  (the right is a little more gapped because I printed it on that side, and had to leave slope so it didn't need supports).

Section of new "innertube"

Now I'm printing a full "inner tube," which is something like a 6 hour endeavor.  You'll notice that there are hollow cores within my "tube" to help make it squishy.

I bought another used FF printer, which is good because the first one is acting up a bit recently.  The used printer had a few issues, however I was able to get it running.  I'd tried the Ninjaflex a tiny bit when I first got it, but the temperature wasn't high enough, so I couldn't load it.  This time it loaded and printed first try!  

Fingers crossed that the printer keeps behaving as I have several inner tubes to print.  4 fronts for both droids as the rears are already done, and preferably a couple spares.

[kresty]

Getting there!  Could use a few detail tweaks, but nobody'll know but me.  

Make-a-Wish Mouse Droid

Assembled and drives, tomorrow's task is sound.  Presentation is Saturday.

Good thing I'd gotten a spare printer because the old one died (burned up build plate heater connector - as in charred and smelling).  I was glad I'd stayed up.  However the new printer was able to finish printing the tire inserts.  (The rest had been printed a while ago.)

Assembly took a bit because I decided to "tweak" the bottom to have a support when the body is off the wheels.  Lara's keeps trying to mash the skirt, so we put some bricks (6 of them) in a stack in the corners so that it sits on those instead of the skirt.

Also improved how it goes on, with some guides to help align the body to the frame's plate that it snaps into.  Much easier that way.

[savagecreature]

Looks freekin' awesome. Very nice job

[kresty]

Thanks. It drives *so* much smoother than the old spray-foam-filled wheels. It's like driving a different beast. (Ok, less weight in this one too, but still). I'll see if I can post a video.

I'll miss MCK-Y's wobble once we get him updated too. Might have to put a rock in a foot or something

[kresty]

Hmm, I realized I hadn't really updated this....

MAW-1's interior is much cleaner than MCK-Y's.  Uses a normal RC battery and Bluetooth type speaker.  Line from RC controller triggers a few sounds.

MAW-1 Mouse Droid
Interior of 2nd generation Lego Mouse Droid built for Make-A-Wish.

[kresty]

The original door was Lego hinges.  From that we migrated to the 3D printed bricks that are used on the other side, but they wore and got loose.

So the 3rd generation door connection mechanism was used on MAW-1.  We have posts on the bottom that the door slides over, and then another tongued connection with magnets at the top.

Mouse Droid Door
Bottom Connection of Door

Mouse Droid Door
Top Magnet Connection of Door

[kresty]

We've also had trouble with the skirts staying on MCK-Y.  So for MAW-1 we were more deliberate about the connections to the body.

3D printed bricks don't have the "clutch" of real bricks, so we depend on the angled bricks being glued to a 'real' Lego brick, which then can be more easily (dis)connected from the droid repeatedly.  The front (or rear) section of the skirt has to be removed to get the body off of the frame.

MAW-1 Mouse Droid
2nd generation Lego Mouse Droid built for Make-A-Wish.  Skirt connections

You can also see the "kickstand" behind the skirt in the top photo. This is so that when the body is removed from the chassis, it can stand without collapsing the skirt. This was built in from the ground on MAW-1. We've tried to add kickstands to MCK-Y, but they keep failing

Mouse Droid Skirt Connection

We do the same thing for MCK-Y now (kinda), with the skirt connections. However, MCKY didn't have the skirt designed for that attachment mechanism, so the bricks are more awkwardly placed and it isn't as reliable as the MAW-1 droid.