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Archive for May, 2021
Posted by Jack Crossfire | May 30, 2021 @ 07:00 PM | 31,348 Views
The 1920x1080 reupload of Wargames revealed more detail about the pterodactyl which wasn't visible in the 720x480 version or the childhood memory. It wasn't clear if it was an ornithopter, but now we can see the wings don't flap. Nowadays, a gliding pterodactyl or even an ornithopter might not be very hard to make but in 1983, it was a big deal. It always symbolized Steven Falcon's supreme intelligence that he could get something that unusual to fly while everyone else flew normal planes.

There are many RC pterodactyls, but none look as good as the one in the movie. It's not clear if the one in the movie ever actually flew or if it was hung from a cable. It turned its head a few times, so maybe it used its head as a rudder. The Chinese pterodactyls have very large control surfaces & the lightest materials. The one in the movie might be possible using weight shift or wing warping & have a very bad glide ratio.
Posted by Jack Crossfire | May 29, 2021 @ 11:42 PM | 32,811 Views
It managed to not fall apart. Burned 286mAh/mile with 2 batteries & the 100mm lens. The mission was to photograph old signs before they're gone....Continue Reading
Posted by Jack Crossfire | May 26, 2021 @ 08:14 PM | 36,380 Views
7 miles with the 100mm lens burned 284mAh/mile. The 200mm lens drive burned 272mAh/mile. The 100mm is lighter than the 200mm. It might be hotter weather or vagaries in battery charging. At least the new bathtub has gone 24 miles without falling apart. Thoughts have turned to the lighter & faster focusing 100mm F2.0. It would definitely be better at photographing animals than the 100mm macro, but DSLR lenses are lucky to be used once in their lifetime.
Posted by Jack Crossfire | May 24, 2021 @ 10:29 PM | 14,013 Views
The lion kingdom finally decided to start replacing LIPO with AA for certain applications, after decades of LIPO being the future of everything. The mane problem is a lot of stuff uses less power than it used to & a lot of stuff is hardly ever used. Flashlights are a case where power needs have gone to virtually nothing. If LIPO's aren't used & they have any charge, they just puff. The bathroom scale got its puffed LIPO finally replaced with AA's. They'll leak like crazy, but last longer than a LIPO.

There is a desire to power the camera remote controls with a single AA to reduce their size, but they require a booster from 1.5V to 3.3V & the days when AA holders were sold in every corner Radio Shack are over.

Bathtub 4 went 8 miles on only 238mAh/mile. The motors still get warmer than the heat sinks, but hope abounds.
Posted by Jack Crossfire | May 23, 2021 @ 10:46 PM | 23,253 Views
Got both heatsinks installed. Having to work around the plastic limitation of 3D printing makes the heat sinks a really complicated affair. The captive nuts & springy TPU gaskets do make fabrication easier. The farsteners can't be as tight with gaskets, but that springiness seems to be what kept them in before.
Posted by Jack Crossfire | May 23, 2021 @ 03:21 AM | 26,950 Views
Nothing managed to fall off or overheat, for a change. It only burned 231mAh/mile with the camera pole, 2 batteries & a bag of cameras. Of course, the gimbal was off for most of it. It gives up a lot of cushioning to get that kind of efficiency. It could probably stand 20mm thick tires.

Mane St Laps (20 min 39 sec)

Printing began on yet another traction module. It's yet another attempt to fix the motor mount. Only the sides & bottom have to be printed. The parts are getting gnarlier. Finally put in captive nuts so the entire container doesn't have to be unbolted to access the motor modules. It only supports self locking nuts. To use another kind of nut, the side panels have to go back to the printer.

After many dreams of a better motor mount, the final solution was just bigger farsteners. An idea to split the traction module into a motor module & an electronical module fell over. It would require a lot of farsteners & the motor section would wobble more than it already does.
Posted by Jack Crossfire | May 21, 2021 @ 09:13 PM | 30,156 Views
7 miles with the giant DSLR didn't cause the overheating it caused last time. 1 motor was still un heatsinked so it wasn't very conclusive. Power consumption was 272mAh/mile. The heatsink stayed cold & the weather was colder. At least transporting the DSLR was proven possible.
Posted by Jack Crossfire | May 20, 2021 @ 02:40 AM | 34,917 Views
The journey began with the only aluminum sheet outside China. It was too thin to be very useful, but the alternative was a 3 week boat delivery. A 3D printed stencil & a lot of extra drilling got it to fit. It had a few sharp corners & is a bit low under the chassis. Just a matter of making a new 3D printed stencil with the desired shape.

Installing the motor module with heat sink is a truly awful experience. These motor mounts have continued to have farsteners coming loose. Using CA glue on PLA as threadlock was a failure. It held up, but claimed its 1st farstener. The next step would be using loctite on PLA, which doesn't bode well.

The existing farsteners may be overloaded. If the motor mounts extended all the way under the ship & attached to each other like a belt, it might hold up better. 2 farsteners could go under the ship & farsten the 2 motor mounts to each other. Then 2 more could go on each side, above the motors where they would be easier to access.

The traction module is due for a major refresh, along with new H-bridge boards, higher voltage capacitors. The steering module has been surprisingly trouble free, despite being the leading edge of the bashing.
Posted by Jack Crossfire | May 18, 2021 @ 01:43 AM | 24,345 Views
Some ideas for mounting a motor on a metal angle were conceived. The problem is the metal angle has to be as wide as the screw holes, the seal has to be a wider diameter than the metal & the tire has to be a wider diameter than the seal. It takes a very wide tire to enclose the encoder & large diameter for most of its width to enclose the seal. The encoder would have to go inside the motor & the metal angle would have to be little wider than the motor shaft. It would have to fan out inside the seal to attach to the motor screws. This doesn't allow any motor cooling.

So the existing motor modules with large diameter tires remaned. The C rings still tend to pop out if it hits the ground real hard, causing the wheels to slide out of their bearings.
Posted by Jack Crossfire | May 15, 2021 @ 03:45 PM | 35,721 Views
Testing of Starship Autonomous Delivery Robots in Silicon Valley (2 min 52 sec)

It was 90% autonomous, at least 5 years ago. It's slow & noisy, being based on a traditional geared transmission. It has 6 wheels with the 4 corner wheels powered. It gets up curbs by lowering its center wheel & resting on its rear wheel. It uses skid steering. The tires are even more minimal than lion tires. There's no suspension. It's quite large.

Routes are mapped in fine detail. They have limited ability to avoid obstacles. They usually stop when confronted by a human instead of going around. It goes 4mph.

Top 6 Delivery Robots - Self Driving (Autonomous) Delivery Robots (7 min 56 sec)
...Continue Reading
Posted by Jack Crossfire | May 10, 2021 @ 01:44 AM | 9,121 Views
The cheapest way to try to reduce the overheating motors was by shrinking the wheel diameter to the smallest possible size. 74mm was disappointing. Maximum speed was reduced to 8.5min/mile. Hill climbing with a payload was slightly faster. It was noisier. It was really noisy with a payload, because the internal structure of the tire created hard points. The mane problem was the low ground clearance. The motor modules got really chewed up. The minimum ground clearance seems to require 108mm wheels.

74mm wheels work for skateboards because the only exposed part is a narrow shaft. They steer by rotating the entire shaft of the front & back wheels. Since only the traction wheels have to be small to provide enough force, the front wheels can still be 108mm & have all the steering hardware. The motors in the rear have to be fully enclosed in the tires with only narrow shafts joining them to the chassis.

So there's still a problem of overheating motors as the weather warms. The latest theory is to invest in 1/16" sheet aluminum. Manually cut out hubcaps to dissipate heat out of the hubs. Manually cut out strips to dissipate heat from the motor legs.

Making those 74mm wheels was a lot of work, but it was still infinitely easier than before 3D printing. 20 years ago, it would have entailed many days of cutting & grinding or wouldn't even have been possible. A younger lion did spend many years on robots where a big part of those years was spent manually creating parts that could have been spun out by a 3D printer in days.
Posted by Jack Crossfire | May 07, 2021 @ 12:55 AM | 8,960 Views
This 1st PETG wheel got some farsteners to keep the tire in place. PLA looked a lot better, even when it was melted. The wheel is still a disaster to glue together. The rings were finally printed as C's to make gluing easier, but they always deform.

Then, there was a PETG motor plate. It was rigid enough to do the job, but it became clear that it was better if the motor plate melted before the motor destroyed itself. The PLA motor plate was a fuse.

There is a vision of bolting an aluminum sheet between the motor plate & motor to try to cool it. There just have to be large holes for the shaft & wires. It might have to stick behind the motor.

Then, there's reducing the tire diameter all the way down to 70mm. RPM would have to increase by 108/70. Wheel diameter is constrained by the size of the motor shroud which is constrained by the size of the motor legs.
Posted by Jack Crossfire | May 05, 2021 @ 08:55 PM | 8,917 Views
The PLA parts got quite deformed. There was 1 crack. At least this gave some more direction on where to add reinforcement. There's definitely a place where sheet metal could be bolted in, to try to dissipate heat. The wheel hub is definitely holding back a lot of outward force. Not sure how best to farsten it to the wheel. It would need a lot of farsteners.
Posted by Jack Crossfire | May 04, 2021 @ 10:25 PM | 9,486 Views
It was big enough to fit the giant DSLR lens & a shirt, with flexing. 5.2 miles later though, the motors were lava despite not undergoing any stops & starts. Morbid thoughts & depression then ensued. It's pretty worthless if it can't sling the DSLR around.

Upgrading to 5060 motors is fading away. A 3:1 belt drive is gaining favor, but the starting torque suffers. A pancake motor is gaining favor. Another idea is bolting the existing motors to sheet metal & the sheet metal to heat sinks, to give them some minimal cooling. At least the DLSR is worth the heft.
Posted by Jack Crossfire | May 02, 2021 @ 09:56 PM | 8,805 Views
So the trick with having a power switch is the switch disconnects the mane battery but does not disconnect the aux battery. Once the aux battery is connected, there's no way to know if the mane battery is on without feeling the switch. It wasn't on & at mile 13, the aux battery died. Decided to switch on the mane battery without disconnecting the aux battery, thus a dead battery & fresh battery were connected in parallel. There was enough resistance in the cables, the aux battery had enough capacity, that nothing even got warm. The aux battery just recharged.

The ages old question was thus answered. A fresh battery & dead battery can be connected in parallel, as long as the cables have enough resistance & the dead battery has enough capacity.

With this inefficient arrangement, it still went 18.7 miles at only 262mAh/mile.