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

[kresty]

Better than what I did for toolbox. He has static axles that I just drilled holes for,  and then printed a "lock" that fits in the threads. That, in turn, is kept from falling out by a lego brick.  My system barely works.

[Dyne]

Better than what I did for toolbox. He has static axles that I just drilled holes for,  and then printed a "lock" that fits in the threads. That, in turn, is kept from falling out by a lego brick.  My system barely works.

I guess it's appropriate for Star Wars that some of our droids are constantly riding the edge of not working.

Sent from my SM-A326U1 using Tapatalk

[kresty]

I guess it's appropriate for Star Wars that some of our droids are constantly riding the edge of not working.

Yea, when glitches happen at shows, I do point out to the fans that the droids in the movies are always being repaired by Luke or Chewie or Anakin or somebody!  So, it's quite realistic!

[Dyne]

Apparently I am incapable of getting stuff done with my droid builds unless I have a con deadline staring me in the face.

My last real update was in post #50 near the beginning of October.  On top of my usual late year activities, a variety of real life issues have been killing my motivation and making me highly distractable, so I made literally no progress between then and the end of January (how unprecedented, I know).  

As it happens, I did make plans awhile back to attend a convention this coming weekend.  Since LD-F1's drive was still nonfunctional at the end of last month, it was time to start getting productive...


The first thing to take care of was getting a replacement 58T secondary belt for the starboard track printed -- without that, droid no drive straight and there'd be not much point in carting him to the con.  I installed the new belt this past Friday and was reminded that it's kind of an annoying process (compared to the smaller 40T belt) because the drive pulley and the outer idler carrier both have to come off.

In addition, I've printed two complete sets of spare belts (the second set mostly because the first set came out stringier than I liked).  I made the later belts slightly thicker for additional strength.


I'd used my spare intermediate pulley at Dragon Con, so I also needed to print more in case another comes apart on me.  I now have three spares and might print another if I have leftover filament, but I'm also considering altering the small 10T pulley on this part to be 12T instead.  This will gear the droid down a little, but that's fine.  The benefit is that a higher tooth count will make the pulley thicker and less likely to delaminate like the busted one did.  The downside is that I might end up needing to design, print, and install slightly longer secondary belts.

I've also tightened the loose servo horn that kept coming off.  Hopefully it will stay attached.  Although now that I think of it, I have no idea if it was centered, so I'll probably need to fix it again.


With the major repairs and necessities mostly out of the way, I decided to do some weathering.  LD-F1 is an exploration/scouting droid, so he gets pretty grungy.  I've given him a muddy brown color with some green hints on the main chassis to imply some slight grass stains.  His tracks also got a small amount of weathering to go with the natural weathering they picked up from the Marriott carpet at Dragon Con (not shown).




While I was at it, I also shortened the antenna by somewhere in the neighborhood of 1.0 - 1.5 inches, added two thin strips of aluminum tape below the orange doodlemabob, and gave the antenna some light grime as well.  The paint didn't stick very well to the styrene tubing because it's neither sanded nor primed, but it'll work for now.


The last thing to take care of was to actually make some progress on the side panels covering the track mechanics, which are the final cosmetic pieces.  I eventually want to list the droid in the Holocron app, and this is a necessary step for that (rewiring so I can conceal the internal electronics properly is the other requisite, but that'll have to wait).  After some tweaking of the designs that I posted back in October, I finally started printing the necessary parts a day or two ago.  

Both of the panel mounts (the yellow parts) have been printed.  You can see the Starboard mount below.  It gets four M4 brass inserts in the positions shown.



Those are used for M4 screws that hold on four countersunk ring magnets.  (The photo below shows them attached with socket cap screws because I need to go buy some more countersunk screws.)



The other four holes (red in the CAD shown in October) are for attaching them to the idler bracket.  This is what the assembly looks like in place.



The external panels also have holes for inserts to attach the matching ring magnets, but I can't show you that because the first one is still printing.  While I can likely get all four sections printed and assembled later today or Wednesday, it's unlikely I'll be able to fully paint and weather them until afterward. (Edit: It warped. Likely due to the level being off kilter and the relatively small contact area. Might be able to heat bend it into shape.)


Also, I pretty much have to work with what paints and parts I already have on hand right now.


This is more a project for after the convention, but I am probably going to integrate the middle joint of the neck and the Electronics Box Lid (cyan part in Post #30) of the droid.  This will make the visible portion of the droid's neck static and mostly eliminate the lower neck stalks -- they take up a lot of space inside the chassis that I can use for other things, and are serving no purpose without an actuator.

Doing this will hopefully also make the neck less wobbly. The rear panel of the chassis will still lift up for accessing the battery compartment and the electronics, but I may add some magnets to keep it from bouncing open when driving. My only concern with the idea is whether the four brass inserts that the screws holding the lid thread into will be strong enough to support the entire moment arm of the head and neck without pulling out of the part or breaking it.

Maybe if I can alleviate some of my real life issues, I'll get some of that done by Dragon Con later this year.

There are a few more items on my medium-term to-do list, in rough order of priority.

• As it stands, the head rotation is on the left potentiometer of my radio while the head tilt is on the left stick's X axis.  I am considering revising the R/C model to swap these.  I'd also likely want to disable the return to center spring on the X axis; the head frequently loses its center, so the control would need to remain where I put it like the pot does. Not too involved but I'm not sure I'll get to it.
  
• Rewire the current fuse setup so I can put the ESCs and receiver inside the droid and cover up the switch, as originally planned.  I have to figure out where I put the rest of the fuse holders that I planned to use.
  
• Moving the ESP32 to the body and setting it up with Penumbra will allow me to run the droid via Bluetooth Nav controllers if I want to, but it necessitates a fair amount of rewiring and coding.
  
• The lower stalk and fuse panel removal and front wiring cleanup may clear up room for the originally intended transducer for audio output in its place but I'm not holding my breath.
  

In the longer term, I eventually would like to redesign the droid's drive wheels.  The belt system is a bit of a pain to deal with (the middle pulley axle is barely secured, changing belts requires disassembling half of the track just to get access, the M3 locknuts don't hold the axle securely, etc).  Maybe I'll put in something like a coaxial planetary gear housed inside the front (drive) pulleys.

[kresty]

I like using brass inserts for mounting, they work well in printed stuff.

[savagecreature]

I have the same "have to have a deadline problem".
I still really enjoying this build. I'm trying to use it as inspiration to get back to some of mine.
it's robotics season right now, though, so that absorbs pretty much every minute I'm not at work.
soon.

[Dyne]

I tried heat bending the warped part.  That helped a little and it works for now, but I'll likely reprint that section before i put time into finishing the new parts.  The other 3 side panels were all printed successfully.

We arrived at the con and I drove the droid for several hours today, until his battery (and mine) started running low.  One belt came off when I drove too fast, but I was able to just pop it back in place on the pulley.

The side plates are working great.  No issues with the mounting system that aren't due to the warping or to the rear roller axle being slightly too long.

[Dyne]

I still really enjoying this build. I'm trying to use it as inspiration to get back to some of mine.

Thanks.  I'm still a bit surprised that he's been as popular as he has.

I've been enjoying hearing kind comments about LD-F1 this weekend, both from fellow builders and the public.  Reminds me not to be so hypercritical of my work and compulsive about pointing out the flaws to everyone.

Saturday went very well.  We had a total of two R2-D2s, one droid they call Jayne, one DeAgostini R2, one mini A-LT droid, one BB-8, one mouse, two scrubbers, and LD-F1.



The droid drove fine right up to the end, when i decided to play with high speed.  As usual, that triggeted a belt failure,  specifically the port inner belt broke, much like happened on the other side at dragoncon.  I took a pic of the track being dismantled to replace it.  The two black screws are for the voltage regulator mount on this side.


From there I'll pull off the idler carrier, pull off the 40T outer belt, and pull off the drive roller on the left, put on the new 58T inner belt, put the roller back on, move the belt into place around both the pulley and the roller (which can be a chore), then reassemble and tighten the mechanism.  

Rejoining the ends of the track is theoretically easy, but for one person it can be a bit of a chore to hold both ends aligned AND to insert the filament segment that acts as the hinge pin.

[Dyne]

I know a lot of people will be away at Celebration right now, but I've made a little progress since February. Specifically, as of the end of March, the side plates for the tracks (which are the final parts of LD-F1's exterior bodywork) have been painted and weathered.  In the last photos that I showed, those parts were just raw black plastic and were hard to make out.
 
I don't have a photo of this, but before I began working on the paint job, I used a hot tool to weld the inboard seam between the two halves of each side plate, a place where it wouldn't be visible.  This was done to prevent the two parts from flexing easily at the joint and thereby cracking the paint job.

Then, I began filling the gaps, priming, and sanding to remove the print lines.

After doing as much of that as I could stand, I sprayed the parts with Rust-o-leum Bright Chrome.  This was to provide a metallic undercoat for weathering, which I figured would be exposed the most on these sections of the droid's body since they would see the most wear and paint removal.

The chrome exaggerates some persistent print artifacts in a few areas, like inside the circular surrounds at each end, especially on the port side plate.  In practice, the three foot rule applies.  Given how low the droid sits to the ground, these are difficult to see under normal conditions and viewing angles.  A lot of it is also covered by the paint and grime.  If the artifacts end up bothering me in the future, I'll make some thin styrene covers to glue into the circles.




After the chrome had fully dried, I used toothpaste to mask off some bits of the side plates ... mostly the exposed edges of the plates where they contact the track, the leading edges of the angled panel details, and some of the protruding circular surrounds.

Then I added a few coats of Gloss White spray paint.  I probably should have used the Flat White that I used on the rest of the droid, but I was low on that. (I also sort of forgot that the first layer of paint after the Bright Chrome sometimes tries to orange peel.  I should have given the chrome a light sanding where I knew the white paint was intended to remain intact, but it ended up working out in the end without that.  I just needed to go lighter on that first coat of white.)


After several coats of white, I let the paint cure for a few days and then sprayed it with the Satin Clear to bring the gloss finish back down to match the rest of the droid, and to seal the unweathered paint job.  I did this BEFORE wiping away the toothpaste mask so that the satin wouldn't dull the metallic.  Once the clear coat had dried, I started to wipe away the toothpaste mask.

Results were mixed; either removing the toothpaste after it had been drying for a few days caused it to pull away some of the shininess, or else the toothpaste had reacted with the chrome.  Either way, the metal isn't quite as uniformly shiny as before.  That's fine, as long as there's SOME shiny to catch the eye.

I was also able to expand on the chipped edges and add some realistic scratches with my thumbnail, and later with a wire brush, before the white paint completed the process of bonding to the chrome.

I then started applying mud and grime color to the middle regions of the side plates, moving outward.  When I got near the circles on either end, I used painter's tape to mask around the areas that were to be painted orange to match the droid's trim.  I did the orange with brushed acrylic in several coats, for opacity and smoothing out the brush strokes.  I ended up with some free natural weathering due to the painter's tape lifting a few sections of the white during removal.


Once the tape was off, I finished adding mud and grime to the circular areas.

Near the end of post #54 you may recall that I mentioned that one of the side plates had warped -- the one placed in the port front corner of the droid.  Rather than reprinting it as I was considering, I decided to keep the part and just going heavy on the masking/scratching in that area -- as if LD-F1 had rammed into something and the collission had caved in the surround, as well as the raised plate detail, with a lot of the paint getting abraded away in the process.


I may yet go back and make these parts a bit more grimy and possibly add some rusting.  But he's pretty close to (aesthetically) complete.

[Dyne]

With the external cosmetics largely complete, I decided to try and sort out some mechanical and electrical issues in LD-F1's head.  

First, however, I made my life a lot easier by wiring up a cable to let me power the droid from my benchtop power supply (ring terminals on one end, XT60 female on the other).  This way, I don't have to fool with installing a battery in the droid just for testing stuff.

Then I removed the shorter white colored side of the head so I could see what's going on in there.  Below is the view into the head.


On the right side, you will see a 9g servo on the back wall and a vertical white tube near the edge.  The servo is new; it's intended to raise and lower the white tube (which is the stalk for the droid's antenna).  Getting this working requires running a new signal wire into the head from the R/C receiver in the body, as well as designing a mechanism to translate the servo's rotation into lift, which is a bit awkward due to the suboptimal mounting position.  I'm thinking of a disc shaped servo horn, with a little arm extending back toward the rear wall of the head.  This arm sits underneath a horizontal arm that'd be attached to the base of the antenna, pushing it up or letting it down as the disc rotated.


The most obvious issue that I see with the rest of the stuff in the photo is that the ESP32 holder has broken free from the back wall and is hanging at an angle.  It's not visible in the pic, but one or more jumpers/pins are also bent at weird angles and potentially loose.  This would explain the issues I saw at Dragon Con, where the ESP32 rebooted whenever the head would look downward or tilt (presumably the board was losing power).  However, when I took the last photo in my previous post, I noticed that the front LEDs were not powered on at all.   This means either the microcontroller has died or something is entirely disconnected.  This will be a bit awkward to fix without removing the head shell entirely, so I haven't gotten to doing much yet.


As mentioned back in post #54, when I reattached the servo horn that had come loose at Dragon Con (the one that's furthest from the camera) back in February, I did so without really re-centering the servo.  I knew I'd eventually need to fix that (if I didn't, I'd have to keep the transmitter stick trimmed in order to level the head, which reduces the movement range).  While looking at this, I also found that the tilt servo linkages were set to different lengths, so I fixed that.  

While the head is open, I can easily access the servo on the port side of the droid's head.  Unfortunately, the one that I really needed to fix was the starboard servo.  I can tell you that it's a big pain to work on that one, whether the head is open or not.  At least that slotted "vent" on the starboard side of the head allows me to see inside and sometimes stick tools in.  But the only way to make the starboard servo easy to work on is to remove the exterior shell of the head entirely.  I could do that, but as I recall, it was even more of a pain to get the head attached properly than it is to work on the starboard servo.  (I may yet have to do it anyway to sort out the ESP32 issues, but I'd rather not.)

While moving the head around to test my fixes on the servo horns, I noticed that the bracket holding each tilt servo flexes a bit more than I'd prefer.  I may print up and glue a brace between them, which I was considering doing anyway, or else I'll revise the parts for strength.


In the image below, you may notice that some of the wires that stretch across the head rotation gears are a little wavy.  That's because they were getting caught in the teeth, which can't be good.  I have printed some C-shaped cable clips, and I am gluing these to the interior head in order to secure the wiring away from the mechanism a bit better.



Stepping away from the head, I mentioned back in post #36 (and again in post #54) that I suspected I should have pulleys with higher tooth counts in the belt drive in place of the current 10T pulleys.  This was because I knew this size made the print a bit thin and weak near the flange end.  And as it happened, one of them did indeed shear off at that exact spot during Dragon Con.  

This would make the belts a bit less likely to slip (more teeth to engage the belt and a tighter fit), and possibly less likely to break given a larger pully means the belt wouldn't be making as sharp a bend, but I also know doing this would change the gear ratio. I haven't committed to a change yet, but I did pop into Fusion and model a 12T version of my motor pulley, just in case I wanted to use it at some point.  

I eventually want to convert all of my LIPOs to LiFePO4, which are substantially safer. Without building my own pack, the closest thing I've found to the current battery in size and capacity is a 3S LiFePo4. That'd lower my nominal voltage from 11.1 to 9.9, thereby decreasing the droid's raw speed quite a bit. But if I ignore the battery change, here's the impact a gearing change might have on the droids performance:

I originally calculated LD-F1's drive back in post #9, and arrived at a raw value of roughly 50 mph at nominal battery voltage, assuming that he had no gear ratio at all (therefore he'd have little torque beyond what the motor produces, and the motors would stall instantly under the load).

Since I wanted enough torque to actually move the droid, and a top speed closer to the range of 2 to 4 mph, I needed a gear ratio near the range of (50/2) = 25 to 1 (slower, more torque) and (50/4) = 12.5 (faster, less torque). Because the primary belt goes from a 10T to 30T pulley, and the secondary belt goes from a 10T to a 42T pulley, the droid is currently geared to a ratio of (30/10) * (42/10) = 3 * 4.2 = 12.6 to 1, so he'd be pretty close to the fast, lower torque end (max speed of 3.97 mph)

Except ... I was intending at the time to use a belt for the tracks rather than the current link + traction pad setup, so I ignored their thickness and got the raw 50 mph result by assuming a 4 inch diameter for the drive sprockets. In reality, the current modeled radius from the axis of the drive sprocket to the center of a traction pad is 54.665 mm, which gives a final diameter of 109.33 mm or 4.304331 inches. Thus, LD-F1's raw ground speed with no speed reduction is actually higher than ~50 mph. It's more like 54 mph. That makes the desirable gear ratio between 27 and 13.5 to 1. He is already below that, and with the current gear ratio his current max speed is more like 4.29 mph.

Replacing one of the 10T pulleys on each side with 12T would make the ratio (30/12) * (42/10) = 10.5 to 1, which would give LD-F1 a top speed around (54/10.5) = 5.14 mph. Replacing both 10T pulleys on each side would make it (30/12) * (42/12) = 8.75 to 1 ratio, with a top speed of (54/8.75) = 6.17 mph.

In truth, LD-F1 could probably stand to be a little bit faster than he currently is, at least if I can keep max speed from breaking/throwing his belts.  But those increased speeds do come at the cost of decreased torque.  I'm not sure how much loss of torque I could get away with for LD-F1, but I do know carpet can sometimes give him slight problems with turning as it is, as will some uphill climbing. Right now both are more due to belt slippage than stalling, but lowering the torque too far could easily exchange a minor problem for a major one, so I don't think I care to go as low as the 8.75 to 1 ratio.

I'd probably only want to replace a single pulley on each side to get the 10.5 to 1 ratio. I'd have to decided whether to replace the 10T motor pulley or the 10T part of the compound intermediate pulley. It should probably be whichever is more prone to shearing, which suggests the compound pulley.

Of course, going up to 12 teeth isn't the only option here. I could replace both 10T pulleys on each side with 11T versions, and I'd get similar numbers to what I get from a single 12T pulley (ratio of 10.42 to 1 and top speed of 5.18 mph). I'm just unsure whether 11T would give enough additional strength in the parts and grip for the belts to bother with.