Dyne's MSE-4

[Dyne]

I posted about this on the Mouse builder's club forum, but I know Rebeldroids was intended to cover all of the non-Astromech droids, so I'm also posting a thread about it here.  Besides, this has the advantage of being the only droid forum that I can browse when I'm not logged in.

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At Dragon Con 2018, I finally had Artie Deco running and spent a lot of time in the Droid Play Area and hanging around my fellow builders.  I came back fired up to get a proper Star Wars droid running before the 2019 convention, but with no time (Dragon Con usually signals the end of most of my time for the rest of the year as I get busy with Halloween and other holidays.  I managed to post an update to my Treadwell build logg.  I also did some CAD work on a scale BB unit (BB-6).  But that was about it before I had to put things aside until after New Years.  I did purchase a Sphero R2 and BB-9E after the con, and received a Spinmaster BB-8 for Christmas.

Right after New Years, my schedule got massively disrupted, torpedoing my energy levels, my motivation, my sanity ... and my plans.

At the end of March, I managed to attend another con.  Though exhausted, I had a lot of fun and was reminded that I needed to get started on something in order to have any hope of meeting my goal in less than five months.  I also debated customizing my Spinmaster's identity (and restoring his sound/lights in puppeteering mode) by making an alternate dome to swap to.  But since I like having BB-8, I would be limited to using the body sphere as-is.

At some point last month, I decided that the quickest solution was to build a (3/4 scale) MSE-6, with SHADOW and a mostly 3d printed chassis that I'd design (because I find the notion of buying one for dozens of monies while having a 3d printer sitting around gathering dust to be slightly irksome).  The MSE-6 shell would be made of EVA foam, most likely.

"Wait... MSE-6?  Didn't you put MSE-4 in the title?"

Yes.  I quickly realized that designing my own chassis required research into things I haven't dealt much with, like suspensions and gearing.  Nothing I foresee having a big problem with, but it will require time to iterate on my designs and generally botch things up.

On top of that, about two weeks after the con, Seth Kelly tweeted about prepping his Nurse Droid build (which I hadn't been aware he'd started) for Celebration.  After Celebration, I learned that it was a modified Spinmaster ... and remembered my notions of replacing the dome on my own Spinmaster.  This got me started on the idea of going for a full conversion.  So I obtained a second, used Spinmaster and began work on BB-5M.

BB-5M isn't what this thread is about, but it explains why I'm lowering the priority of the MSE-6 build.  I'm not abandoning the idea, I'm just unlikely to get it done by Dragon Con.

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So as a warmup, I am building an MSE-4.  I recently saw the thread on the Mouse Droid club forum about the 3D printed tiny mouse droid at Celebration, and that sounded like fun.

I've always liked the idea of building an MSE-4 ... I explicitly compared my scaled-down MSE-6 to it, and one of the ideas I pondered early last year was trying for some sort of flocking algorithm and making a swarm of the things that travel around as a group.  But I'm resisting the urge to do crazy things like that.  This is a relatively simple R/C car build based on the same car that was used for the 3D printed droid that was in that thread.

This thread will be about my MSE-4.  As and when I work on the 3/4 scale MSE-6, I'll probably post here about it rather than making a separate thread.  I'll call it out when I do that.

[Dyne]

As mentioned, I'm using the same car that the 3d printable MSE droid was designed for.  

The car in question is the "Blomiky 4WD 9MPH High Speed Racing RC Car 1:43 Scale 2.4G 4WD Electric Small Remote Control Vehicle", which is $25 on Amazon.  Here it is with Sphero BB-8 and a dirty keyboard for scale.



There are three color schemes for the body, but I think that's the only difference.  I'm trying to decide if the double "4WD" is additive or multiplicative ... is it eight-wheel drive (Sleipnir?), or sixteen-wheel drive?

I debated using a 1:32 scale car instead, the Cheerwing Phantom (aka Crazon Phantom, among various other brand names).  It is a bit faster than the Blomiky, but that's a bit of a drawback ... it's so fast it can be a bit hard to control.

A more promising car along the lines of the Cheerwing is the JJRC LT832, which is apparently a Losi Micro-T clone.  The main advantage it has over the other cars is that it has proportional steering, which would make it easier to control than either the Blomiky or the Cheerwing.  I've seen it typically go for $35 (only $10 more than the Blomiky), but it's possible to find it below $30.  Unfortunately, I'd already ordered the Blomiky before I knew about it.  You might have to cook up your own method of attaching an MSE body, as the existing body is held on with clips, not screws.

Regardless, I'm doing my own thing for the shell, and still have ideas on some cute things to do to differentiate my build.  Because of course I do.  I can't do anything completely by the book.

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My car arrived yesterday.  It was reasonably packed, but they used broken off bits of styrofoam to do it.

I hate broken styrofoam. It's coarse and clingy and gets everywhere.

The Blomiky comes with a pair of three cell 3.6v 700mAh NiCd batteries for the car (plus two charging cables, a pair of AA for the transmitter, and a screwdriver). These give about 20 minutes runtime at full speed (not tested yet). I saw a comment by Blomiky on the orange car's Amazon Q&A page that said you can use a 1s LIPO instead (it'd only be only 0.1v higher at the standard cell charge). That would open up some possibilities for larger capacity, but I'm a bit wary. LIPO is 4.2v at full charge and 3v at minimum, whereas I gather that NiCd doesn't change much from rated voltage over a discharge cycle.  I'm sure the motor could handle it, but I'm not so certain about the speed controller or LEDs.

I decided to take some measurements of the car, in case anyone needs them.

• Overall Length - 145 mm
  
• Chassis Length (no bumpers) - 133 mm
  
• Wheelbase - ~83 mm on center
  
• Tire Diameter - 30 mm
  
• Tire Width - ~11.5 mm
  
• Track Width, Front - 75 mm
  
• Track Width, Rear - 79 mm
  

The wheelbase and front track width dimensions are more or less 30% of the Traxxas Bandit's equivalents. That's the scale factor I'll be using to plan the shell.

Each wheel is held on with a screw at the axis. The axles are all hexagonal with a minimal diameter of 4 mm, and the wheels use this to prevent slipping.  The tires do slip on their rims, though, especially when removing the screw.



The body is held on with four screws.  Front to Rear, these four screws are 110 mm on center.  Left to Right, the front screws are 28 mm on center, while the rear screws are 40 mm on center.

After removing the four body screws, you can lift the body off the chassis.  There is a pair of LED headlights attached to the body with hot glue.  



You can remove the hot glue and keep these, or you can unplug the LEDs from the board if you don't want your MSE-4 Droid to be illuminated.  I'll probably keep them on mine.

[savagecreature]

Cool stuff.
as everything makes me want to build everything, I was lookin' at stuff. Here's a link to the car on Amazon if anyone's interested.
Blomiky 4WD


I couldn't find a likely candidate searching for Cheerwing/Crazon Phantom, though.

This one, maybe?

[Dyne]

Cool stuff.
as everything makes me want to build everything, I was lookin' at stuff. Here's a link to the car on Amazon if anyone's interested.
Blomiky 4WD


I couldn't find a likely candidate searching for Cheerwing/Crazon Phantom, though.

This one, maybe?

That's the one.  I was a bit ambiguous; Crazon was just another brand name I knew was used for it.  I edited the post to be clearer.

This review video shows why I said it could get difficult to control:





And for completeness, here's the other car I mentioned, the JJRC LT832

[Dyne]

Seems legit.

I wonder if the slant on my greebles will be controversial...



Anyway, back to the build.

I had a hard time sorting out the various blueprints I've seen (when I put in the numbers, nothing seems to line up on the sloped parts, regardless whether I treat the values as 2D vectors angles or as true 3D values).  It's not a big deal.  This is an MSE-4, not an MSE-6, and I was just using the existing plans for approximate values. I don't really care about screen accuracy for this thing ... you only ever see them from a distance in one scene.


Took a few more measurements of the car to make this very rough version of the shape of the chassis, facing to the right.  This is mainly to try to make sure everything ends up inside the shell, so it isn't terribly precise. The angle on the rear bit of the chassis is just pulled out of thin air, by the way.



Also, from the front axle to the forward body mount screws is around 16 mm on center.

[Dyne]

Just a brief "minimal progress" update.

Since the last post, I constructed a foam core upper shell. I wasn't happy with the proportions, so I started redesigning it, experimenting with Fusion's sheet metal in the process.

However, I've been distracted with work on BB-5M since then. I hope to get some more work done some time in the coming week.

Sent from my SPH-L720T using Tapatalk

[kresty]

I guess I've been sleeping around here, I check back in and there's cool stuff going on! Thanks for sharing!

[Dyne]

No problem.

Recently, i came across a few of my old rectangular LEDs (seriously old, i think i got them from Radio Shack in the early nineties). One orange (really more a very red orange-red), one pink. I thought the orange one would look good installed in the front trench as the "miniature photoreceptor" (better than the car's original headlights, anyway)

As it happens, the speaker built into the spinmaster bb-8 that I'm turning into BB-5M uses exactly the same JST connector as the headlight leds, and I'd already cut the connector off to test the speaker with the BB droid's new amp. So over the weekend I checked the voltage (a bit shy of 4v), then wired the LED up with a 470 ohm resistor (more than it really needs) and the connector.

Sent from my SPH-L720T using Tapatalk

[Dyne]

Now that I've made significant progress on my BB-5M dome build and freed up a little of the pressure, I need to get cracking on the MSE-4, which I've barely touched since the last post.  With less than four weeks to Dragon Con, this will need to happen quickly.


Previously, I built a foamcore upper body and trench area.  I also picked up some 0.25mm black styrene with the intent of cutting out some skins.  There's no real reason for skinning it beyond the fact that i wanted some practice with sheet styrene (never used it before), that my foam core is Dollar Tree special (v. Poor quality foam), and that there was a gap in one interior corner where it didn't cut properly.  Also, it was being held together with scotch tape.




Step one was merely to trace the outlines of each side onto the styrene.  A white pen or a pencil would've helped visibility here, but i only had a black ballpoint or a sharpie at the time.  Good enough, with decent lighting.  Then I scored and snapped the panels off.  I didn't worry too much about precision, as I cut the edges a bit large so I would have some wiggle room.  Besides, I intend to putty the corners and paint later.

After cutting the pieces out, I decided to knoll them, since that's the hip new (not new) thing all the cool kids** are talking about these days.




The pieces were then attached to the foam core via Super 77.  




Protip: don't lay your clean parts on a surface that has recently been used for Super 77 spraying.  No pieces got stuck, but some minor bits adhered to the skins and will need to come off.

Now I just need to do all of these steps on the other sections of the body, sort out how to attach them, then proceed to puttying and painting.


** People that have clearly watched Adam Savage.

[kresty]

Ok, what's "knoll"?