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Archive for September, 2021
Posted by Jack Crossfire | Sep 30, 2021 @ 02:33 AM | 20,475 Views
After 3 miles with the locknut motor plates, the right motor let out the magic smoke. It manifested itself as a loss of torque despite accurate commutation. There was no evidence of the encoder failing, the locknuts getting loose, a stall, or debris. The motor just stopped providing torque & overheated after successfully ascending part of a hill.

Decided to rewind it over the next 4 hours & see if the problem happened again. Sadly, the 32 AWG got tangled. If 32 AWG gets tangled, the only solution is to cut it off & throw it away. It can't be untangled. Ended up doing 2 of the fields in the last of the 26 AWG & ordered another spool of 26 AWG since there is going to be a lot of magic smoke.

What's probably going to happen is a switch back to self tappers. There was no evidence of the locknuts causing the failure, but they were the only explanation. The best explanation is the rebuild was slightly off, causing the encoder to miss just enough to suck more power but not stall. The overheating would have caused the motor to stall before burning up, with self tappers. The locknuts allowed it to overheat without stalling until it died.

Chinese direct drive motors don't have these problems because their sensors are epoxied into solid steel & their motor mounts are solid steel to suck away any heat.
Posted by Jack Crossfire | Sep 28, 2021 @ 11:38 PM | 26,796 Views
It occurred to the lion kingdom that the use of self tappers as load bearing farsteners has been a disaster of biblical proportions. The latest thinking was to use captive 4-40 locknuts & hot glue to farsten the locknuts. The new motor module still managed to have acceptible tolerances with the .8mm nozzle.

The hot glue actually seemed to work. If it got in the way, it managed to be compliant enough for the screw to not push it out. The captive nut walls are still too thick. The nuts aren't going to break PLA. It's going to compress.

The mane unknowns are if the 4-40 bolts are going to stay on as well as the self tappers did & if the motor will find another way to stall when it overheats or if it'll just destroy itself.
Posted by Jack Crossfire | Sep 26, 2021 @ 03:59 PM | 31,680 Views
The answer is yes. Running a swamp cooler hydrated the TPU. It's not an internet myth. Swamp coolers, bathroom exhaust, & rain storms destroy TPU. If TPU absorbs water, it makes structurally weak prints. You can get away with baking it in an oven & storing it outside, but best results are going to require food dehydrators & enclosing the printer.

The lion kingdom is keen on making a dehydrator out of a peltier cooler & heat sink. A peltier cooler is seen as a more useful heater than a resistor, since the cold side can extract water. In this case, all the air in the filament chamber would be recirculating over the heat sink with the goal of manetaining a certain temperature. If the chamber is too hot, the peltier shuts down. If the chamber is too cold, the peltier turns on. The only fresh air comes from the cold side of the peltier junction. If the cold side is above a desired temperature, no new air enters. If the peltier junction is below a desired temperature, new air enters.

The theory is this system gives off heat on the outside of the chamber. There could also be a way to switch between outside & inside air for cooling the heat sink. It requires both temperature & humidity measurement. A dehydrator isn't as efficient at making water as a water generator though. A dehydrator has to be concerned with the humidity of its exhaust while the water generator doesn't care about the humidity of its exhaust.
Posted by Jack Crossfire | Sep 25, 2021 @ 10:23 PM | 27,693 Views
The lion kingdom couldn't even print the same exact tire without something going wrong. The pancake tire was as soft as sponge while the lofted tire was a brick. The slicer put slightly more material into the lofted tire, despite failing to print sections. The lofted tire also had less curved sections. It's strange because the pancaked offroad tires were as hard as rocks. Another theory is the filament was more hydrated in the pancake tire.
Posted by Jack Crossfire | Sep 24, 2021 @ 03:56 PM | 18,883 Views
After continued motor overheating, the latest theory is the motor wiring is getting snared in the encoder, causing the motor to stall. It's a tangled mess after many rebuilds. The right tire, right wheel, motor cover, motor plate all need to be reprinted. It needs to be rebuilt, with the cable untangled. It's a several day job. The short term solution is keeping the wires under tension so they don't flop into the encoder.

The CAD model doesn't show any obvious way for a cable to get into the encoder. The cables are on the outside of the TPU.
Posted by Jack Crossfire | Sep 22, 2021 @ 08:11 PM | 25,535 Views
Heat sinks went in on


May 20 & worked well for a few months. Then came another case of a screw coming loose, the encoder going out of alignment, & the motor stalling. It quickly overheated & melted the PLA, feeding back into the stall. The heat sink was initially only slightly warm. The good news is the heat sink quickly got hot. It definitely took out some heat. The motor cooled down more quickly than it did without it.

The lion kingdom stopped using PETG because it's heavier than PLA & it requires enormous heat to print. The melted PLA has never permanently killed it. What's really needed is a screwdriver which can tighten the screws in the field. Those screwdrivers are gigantic.
Posted by Jack Crossfire | Sep 20, 2021 @ 09:55 PM | 16,168 Views
There is a plan forming to replace the current fleet of 3 cell batteries with 4 cell batteries of varying size. There would be 1Ah, 3Ah & a 4Ah. 4 cells are believed to have more range per Ah than 3 cells. The mane reason for a 1Ah is for trips under 2 miles. It's a lot easier to lug around a 1Ah than a 4Ah. There's still a desire to use a phone for 1 more mile. It would be charging the traction battery in USB host mode or it would have a direct battery connector soldered in. A phone equals a 4cell of 660mAh.

No matter what, the voltage is going up to 16.8. It takes a lot of volts to run a direct drive motor.

It should be noted the lion kingdom tried rubbing the electrodes together from a battery which was discharged all the way to 0.5V. There was rubbing lithium on graphite, lithium on lithium, & graphite on graphite. They never exploded or got hot. Part of the trick is it was all the way at 0.5V. Big clive had the electrodes burst into flames, but his may have been only down to 3V.

The experimentation on Lipos that abounded 15 years ago is no more. Even electroboom never bothered with lipos. Sometimes, it's not the danger as much as the fad.
Posted by Jack Crossfire | Sep 16, 2021 @ 11:00 PM | 11,933 Views
So the lion kingdom finally got a set of retaining rings & the tool for ending the motors slipping off. It should now be possible to use wide offroad tires. 1 fell swipe of the full faith & credit ended a year of problems. Full faith & credit is sometimes worth a lot more than being creative.

The tool is too big to fit in the 6mm retaining rings, but is necessary to put them on. Once on, the tool can easily fit to take them off. There is a choice between angled tips & straight tips, but they're all different sizes. The smallest tip is only straight. What helps is using a metal shaft to twist apart the retaining ring just enough for the tool to get in.
Posted by Jack Crossfire | Sep 15, 2021 @ 09:25 PM | 13,301 Views
Pressing down on the board in just the right way got the servo to glitch reproducibly. Only after thoroughly cleaning the PWM trace, the problem finally appeared.

There was a micrometer scale break in the trace, completely invisible when it was dirty. It's believed to have been there since the board was made. The board was made with a dedicated buck converter for the servo. An xacto nicked it while cutting a wire to the buck converter. The oldest photo is too small & dark, but some grotesque unsharping reveals 3 slightly brighter pixels in a row where the break was spotted later.

The break only cost $35 in unnecessary new servos. The previous $150 of servos were bought during the lunchbox days to solve common wear. Fixing it required soldering a jumper wire, despite such a small break. Merely tinning it wouldn't do the job.

With the electronicals working again, it became clear that the steering is still loose. This PID controller might need a highpass filter.
Posted by Jack Crossfire | Sep 13, 2021 @ 03:42 PM | 14,802 Views
The SPT died the same way the Hextronix died, a sudden full left lockup followed by intermittent restoration after wiggling the cable. Power cycling it did nothing. It's been 7 years of chasing erratic servo behavior. Most of it might be pots & motors wearing out. The last few have been converging on the wiring.

The cable has been already replaced. Replaced it again. This one is coming down to a loose solder ball or dry solder joint. So that's 2 days of not going anywhere because of a retaining ring, dead servo, dead 3D printer.
Posted by Jack Crossfire | Sep 11, 2021 @ 11:41 PM | 14,048 Views
Sharpied the final designs on. PLA+ is shinier than PLA, making it look slightly more upscale, but PLA+ is expensive so the lion kingdom didn't order any more after the container.

Sadly, the latest retaining ring popped right off. 1 problem is it can't be inserted bed side up, so it has a bevel which just slides off. After a moment of grief & debating destructive shaft modifications, the decision was made to spend $25 on a set of steel retaining rings & a retaining ring tool. It was as much as a new motor.

The problem with modifying the shaft was how a more robust PLA retaining ring would slide on. It would entail removing the encoder. Getting the right tool for the job was the only way.

The quest to print a new retaining ring with the right bevel revealed the hot end was stripped. It's aluminum & lions turned the nozzles as tight as the stock nozzle. The stock nozzle had red threadlocker. Heat blocks are sold in bulk because apparently they do strip all the time, but the lives of the grub screws & ceramic heater are sketchy & it becomes exponentially more painful to break down the parts in order to replace less.
Posted by Jack Crossfire | Sep 11, 2021 @ 01:10 AM | 15,695 Views
After several days, all the panels were done filament depositioning. None of the 228mm ones had any showstopper defects, though they improved over time. The last panel was a narrower one with no bed heating, but the 228mm ones definitely required it.

There was an attempt to evolve joining the segments to use PLA zigzags. This was the 1st attempt at expensive printed tape. The mane problem was clamping it to get the adhesive to stick. Magnets were terrible. It really needs a big, expensive jig. 1 piece goes on the flat side. The other piece needs pins pressing on all the facets of the other side. The final solution was spraying water to accelerate the glue, but water leaves a white film.

Despite the artifacts, the zigzags were visually lightyears ahead of duct tape. The mane issue is how they look when light shines through the panels.

The corner bumpers had a lot of delamination. They definitely needed 2mm walls & .32mm layers, but the TPU absorbed a lot of water from the lion kingdom's air conditioning.

Lighting used a slightly improved hot glue process & no solid core wire after all the solid core wire broke in the last container. The 3D printed containers have a lot more flexing near the corners than coroplastic.

The standard storage compartments went in with duct tape since duck with zip ties has been very robust....Continue Reading
Posted by Jack Crossfire | Sep 09, 2021 @ 12:04 AM | 21,012 Views
The lion kingdom's oldest battery finally succumbed after 12 years. It was $90 in a Hobbytown retail store. After its flying years, it must have rolled 1000 miles. It had a self adhesive velcro for flying which was ripped off at great expense before its driving career began. It spent 2 days draining into some LEDs, then got the short circuit of death.
Posted by Jack Crossfire | Sep 07, 2021 @ 11:54 PM | 21,517 Views
Blender has proven essential for doing certain final pass booleans & transformations where Freecad falls over. The models from Blender can be printed the same as models from Freecad, but it's another moving part.

It feels like the lion kingdom would save a lot of time & effort by using Fusion 360 instead of Freecad with a pile of workarounds in Blender. There's just the memory of Blender becoming the world's standard 3D animation program after lions used Maya for years. Then kicad became the world's standard EDA program after lions used Eagle for years. Arguably, Altium Designer is now the world's EDA program but kicad got a lot of publicity a few years ago.

Lions have come to rely on being able to access a lot more than 10 CAD files at any given time. These CAD files stay in the same directories as software & electronical files. They're all managed by the same git repositories with synchronized revision histories.

It would be another hoop to have the CAD files exclusively online in an autodesk server while all the other bits are still on the gits. Then, these CAD files would have to be constantly toggled read-only to get beyond 10. The revision histories would have separate checkins. The lion kingdom uses Comca$t internet which constantly goes down for days at a time but is never quite worth the hassle of switching out of.
Posted by Jack Crossfire | Sep 06, 2021 @ 08:29 PM | 20,351 Views
400 miles ended with a shredded tire, burned out servo & cracked rod end. The Hextronix died after 394 miles. It was a motor burnout. In went the SPT.

The decision was made to make a helical front tire like the helical rear tires. Because of the round tread, it couldn't be a simple C program that replicated & rotated an STL file. This one performed 96 boolean operations in Blender to create individually rotated layers, over 6 minutes.

Freecad is so bad, Blender has proven useful for final pass booleans, but it doesn't do parametric models, can't import a scene graph from FreeCAD, or have a model history.
Posted by Jack Crossfire | Sep 05, 2021 @ 03:47 PM | 27,031 Views
The lion kingdom's 1st 228mm wide part was a historic moment in Ender 3 lore. The Ender 3 was only marketed with a 220mm printable width. It was made possible by a 3dtouch & a lot of firmware hacking. The truck's container can now be printed in 8 segments instead of 12. If only lions could afford an Ender 5 Plus, the container would require 5 segments, but lions only have 1 part which requires such a large printer. An Ender 5 buys a lot of ramen noodles for someone in Shenzen.

The other new part was a new retaining ring. This retaining ring is more rigid, but it still can't compete with metal....Continue Reading
Posted by Jack Crossfire | Sep 02, 2021 @ 01:45 AM | 30,225 Views
So the 60mm treaded tires made it up the test trail in 4m33s, the same as the 30mm tires. There was subjectively no obvious improvement in traction, but speed highly depends on how much gravel the driver goes over. They didn't materially affect the steering. They might have made the very fastest turns slower.

The mane problem is they had so much mass, they instantly popped the motor's retaining rings off. There are ways to make the retaining rings permanent, by drilling into the motor shafts.

The mane evidence of improved traction is they left much less of a mark than the 30mm tires, so they were pushing forward more instead of throwing dirt back. Another section of trail with less gravel showed them going much faster than the 30mm tires, but it was bugger all distance for estimating speed from GPS. A shift of a few GPS readings makes the speeds equal.
Posted by Jack Crossfire | Aug 31, 2021 @ 09:35 PM | 26,403 Views
After suffering with a paw controller which was barely audible for 8 months, the lion kingdom finally reprogrammed the sounds to increase the loudness. Aural cues are the only way to know the auto throttle setting. The original sounds were centered around what was thought to be a single resonant frequency. The problem is loudness drops off catastrophically away from the resonant frequency.

In reality, the piezo buzzers in toys have 2 resonant frequencies. The one in the paw controller has a fundamental of 4264Hz & an overtone at 8528Hz. Instead of centering the sounds around a single resonant frequency, they need to be centered exactly between the 2 resonant frequencies & bounce between the 2 to be reasonably loud.

Bouncing between the 2 resonant frequencies made things a lot easier. There's just enough of the inner tones to convey some meaning while most of the meaning is conveyed by the order & timing of the 2 resonant frequencies.