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Archive for August, 2021
Posted by Jack Crossfire | Aug 29, 2021 @ 12:14 AM | 22,164 Views
The lion kingdom finally upgraded to colored filament. A high vis paw controller was seen as the biggest win from colored filament. Orange was the closest PLA color since there are no high vis PLA colors.

Gootube videos extoll the fluorescence & shine of a $60 filament vs a $18 filament, but lions seriously doubt there's any difference in fluorescence. It's going to be covered in sweat.

It was time to model in all the lessons of the last 6 months. It got a few more M2.6 screws. The decision was made to skip M1.7 screws, since the amount of PLA required to make a standoff would nullify a smaller screw.

The original grey controller was quite soiled.

This was the 1st deployment of the clicky momentary pushbutton. What a great click it is, but it was absolutely worthless when running.



The electronicals had extreme water damage. It surprisingly only entered the clamshell facing away from the lion, a retrograde motion of the normal sweat path.


A trace perished & got a bodge wire replacement. The other traces got a tinning. This board is in the twilight of its years.


Then it got a hot glue potting.


A few wires got replaced. There were 3 hours of damaging a wire to replace a wire, going around the board.


The mechanicals were an epic disaster. It seems the orange build series filament does better at 200C than 210C. At 210C, the layers were expanding randomly. Tolerances were also way off, from bed leveling deviations....Continue Reading
Posted by Jack Crossfire | Aug 27, 2021 @ 01:34 PM | 22,329 Views
The next container update features TPU corner bumpers, updated headlight areas, & many other tweeks. Every recompute now takes 40 seconds. Using sketches instead of discrete polygons didn't make any difference. The lion kingdom still wonders what benefit printed containers have over the ages old coroplast containers besides looking better.

The corner bumpers introduce M1.7 self tappers. They can always be doubled in thickness. The bottom panel can be reused. Only new side panels have to be printed.

Making the M1.7's possible & optimizing the mass will require automated bed leveling, possibly the most overpriced accessory in the 3D printing mafia. The lion kingdom found a slightly cheaper copy of the bltouch.


https://www.amazon.com/gp/product/B08P4L4BTL


It's just a solenoid, hall effect sensor & magnet. It would be $5 in any germane phone, but it's $32-$50 because 3D printing is an agile methodology, trendy startup, 5 trillion doll hair industry. The hall effect sensor gives a very precise height measurement of a magnetic pin. The solenoid alternates between retracting the pin & extending the pin. Installing it will include finally ripping out the cooling fan, making a new cable bundle.
Posted by Jack Crossfire | Aug 25, 2021 @ 11:20 PM | 11,630 Views
After 48 hours of printing, the 1st 60mm wide wheels arrived. If these can't get around on gravel, nothing below a scooter can. It immediately became obvious that they're hard to install. There's no way to see the motor holes down those wide hubs.

There's no easy way to detach the hubs from the tires so they can't be glued. They're so wide, it's going to be really hard to steer. The original lunchbox was 290mm across. These are 320mm. The next tires should be 45mm wide, at most. They should also have 5mm more TPU, since the tread pattern is not flexible.

These use a 10mm honeycomb + 5mm tread to allow the same hubs to fit the smooth tires. It was later decided printing all new hubs was more convenient than changing the tires on the same hubs. Obviously, they're only going to be on when an offroad drive is planned.

The original lunchbox tended to have its hubs crack where the right angles are. The hex hubs have a lot less material in the key right angle, but benefit from wrapping around the motor. The hex could be extended all the way to the bolts, but it would be expensive.


It might have been easier to stick the original lunchbox tires on, but they had less range & were expensive. The worst case 3D printed tire is cheaper than a $5 lunchbox tire.
Posted by Jack Crossfire | Aug 24, 2021 @ 12:54 AM | 13,854 Views
It went up the test trail in 4m33s. The smooth tires went uphill in 5m11s. The smooth tires went downhill in 4m9s. In exchange for this slight improvement, they were much noisier on pavement, despite the helical treads. They actually handled bumps & hit the programmed speed about as good as the smooth tires. The 5mm treads acted just like another 5mm of tire radius.



They dug a lot more into the gravel. The next step is to widen the offroad tires & finally update the paw controller to address some teething issues.
Posted by Jack Crossfire | Aug 22, 2021 @ 04:44 PM | 19,616 Views
Bay bridge tempo run (6 min 39 sec)



A trackstar finally began its new life as a 360 stepper motor.


As a stepper motor, it needs to commutate really fast to get 1 revolution every 4 seconds.

At 5V, it burns 500mA. At 6V, it burns 1A & gets hot. Its key advantage is it doesn't need to be powered to stay in 1 place. Timelapse mode still requires the full current, so it can't be given the 1A. The standby current when it doesn't move is 50mA. It doesn't have as much torque as the stock servo.


New mounting hardware was printed. The servo must be screwed in before the carbon fiber. There should be enough torque for clothing to not jam the rotation, but you never know.

While this turns very smoothy with very little power, it's still a horrible design. It uses an L6234 for the previous motor to directly drive the servo motor, even though the servo already had the electronicals for driving the motor. It would save a lot of space to reprogram the servo to do all the motor control & have a much smaller board outside just read the radio. The mane compromise was to give up empty space for less time programming.

The C8051F330 in the servo can be programmed with an arduino & the pads are pretty obvious.




It easily did 7 minute miles going downhill, with the wind. The lion was wiped out after only 2 miles at this speed. The full 20 minutes considered a tempo run were at 7m34s/mile downhill, with the wind. It was...Continue Reading
Posted by Jack Crossfire | Aug 20, 2021 @ 12:36 PM | 35,915 Views
After much fighting with Freecad's lofting tools, a better way emerged. Extrude a single layer, then make a discrete model rotated for every layer. The problem with lofting to get a helix is it constricts the center like twisting a sheet of paper. The 96 discrete models require manipulating an STL file in C. To retain some layer adhesion, it had to use parallel treads instead of V's. Getting a V tread would require moving the treads much closer together.
Posted by Jack Crossfire | Aug 19, 2021 @ 02:40 PM | 25,045 Views
There's not much layer adhesion when .5mm walls are diagonal. .2mm layers get better overlap but double the print time.
Posted by Jack Crossfire | Aug 18, 2021 @ 02:05 PM | 28,759 Views
The answer is no. You can't 3D print a water pump & expect it to last. Someone had to be the 1st to document it.
Posted by Jack Crossfire | Aug 15, 2021 @ 05:40 PM | 20,314 Views
A 4 hour cleaning job revealed the motors did a better job sucking rocks from the trail than a street sweeper. The leading theory is most of them got in through a wire passage. Adding tape around the motor assemblies might keep some rocks out. Flexing of the motor shrouds may also have let smaller rocks in.

1 screw had worked loose. After permanently farstening a screw by CA gluing it, the next attempt at thread locking a screw to PLA was to apply just a drop of CA glue.

A tire with a defective layer split in 2. There's no layer adhesion in .5mm thick walls of TPU, so the tires are held together by their 1mm thick treads.

There's no doubt driving on trails entails a lot of cleaning, no matter what. The container shed a few pounds of dust. There's no way to clean the radio panel without disassembling all the electronicals. If the electronicals get wet, the connectors corrode.

Since it's used for transporting food, it might be worth fabricating a bag for it, with a hole for the camera, a flap for accessing inside. The bag needs to be taped on the underside or it needs some kind of bungy cord on the underside. Dust gets in from the rear, where the tires throw it up.

There's a lot of material coming off the motor rotors where the PLA hubs flex in & out. It may be dirt getting between the hubs & motor, acting like sand paper. A leading idea is to make the hubs out of TPU but still have separate hubs & tires. There are implications for the place where the hubs bolt on the motor.
Posted by Jack Crossfire | Aug 14, 2021 @ 11:28 PM | 16,453 Views
Alameda creek (7 min 3 sec)


The 15mm tires improved handling of bumps without dramatically decreasing range. There is always room to do more, though. The 1st 8 mile attempt on gravel ended after 6 miles when the battery died. The camera mount + freewheeling tires burned 575mAh/mile. The smooth tires provide the most traction for TPU on pavement but are worthless on gravel. A treaded tire is required.

A rock got into the right motor, making it intermittently stall.

Layers have begun coming off the tires. This eventually stopped with the last set. The helical pattern has now worn into the outside, but they're still totally silent on pavement despite the pattern. The tires have to be printed as mirror images for the helical pattern to point the right way. Offroad tires would need a V tread instead of a straight line.

There has been a growing wishlist for the vehicle.

Treaded tires for offroading.
Wider container ribs near the top. Thinner container ribs near the bottom
1mm thick PLA under the headlights.
Smaller holes for headlight zip ties.
Screw on corner farsteners for the container.
Convert the camera mount to a 360 brushless servo. The servo needs its mechanical stop ground off & the motor needs to be wired to the outside with 3 wires.
Posted by Jack Crossfire | Aug 04, 2021 @ 11:40 PM | 36,027 Views
The last tires got very high efficiency but couldn't handle bumps. They also got noisier & noisier at slow speeds because the interior structure was perpendicular to the motion. Eventually it was almost as bad as a gearbox, so the next step was a helical tire. They also got slightly thicker to try to handle bumps better. The material is still under $2 per tire.

The trick with Freecad is lofting a perpendicular tire 1st, then rotating the 2nd outline. It also requires lofting in the part designer. Lions have no idea how the part designer tools became the standard in Freecad when every other CAD program is happy to rely on the simple part tools.

There was a new castillated mechanism for attaching the retaining rings. It made most aspects much easier but gluing was more tedious. The castillations made the hub look cracked ahead of its time.

The old wheels were truly bashed. The 1mm tread & .5mm TPU honeycomb cracked in many places....Continue Reading