Jack Crossfire's blog - RC Groups
Jack Crossfire's blog View Details
Posted by Jack Crossfire | Today @ 05:15 AM | 160 Views
After extensively reviewing every hard drive, it became clear that the entire painstakingly entered DVD database was lost forever. Every time the root hard drive was backed up, the /var & /usr directories somehow got omitted. Mysql had an annoying habit of putting all the databases in /var. The only way to find anything is now to copy every surviving DVD to a 4TB hard drive.

There was 1 more firing up of the 4.3GB Quantum, the lion kingdom's very 1st hard drive. It was apparently reformatted & last used as a dedicated TV, in 2001. The date codes are a bit corrupted. It made strange hisses & clicked a lot, but it still seemed to work after 20 years. DMA had to be configured as 16 bit. Perhaps these were normal sounds, 20 years ago. The lion kingdom has no memory of what this hard drive was last used for, but it does remember greater joy when so much iron was mobilized to access a file.
Posted by Jack Crossfire | Nov 19, 2017 @ 06:42 PM | 402 Views
The 1st tests applying anti stiction to spherecam went a lot better, but were not perfect. At 9min/mile, it seemed immensely more stable. At 6min/mile, it was probably about as good as 9min/mile without anti stiction, but not perfect. The P had to be reduced & D increased. Stiction amount had to be increased.

There's no doubt that stiction was the key to stabilizing it, but it was only tested on a 100 meter course. It was also tested with a full 2 traction batteries, spherecam battery, & speaker. It would not be as stable with the minimum payload.

Also, it was discovered that the last 2 guy wires were unnecessary for stabilizing the pole. There was enough static pressure between pole & vehicle to keep it from swaying sideways. A bit of duct tape & shimming would add a little extra friction, even though the adhesive doesn't stick it down. There should be enough stability to attach a carbon fiber extension to the existing pole, if a lighter camera in a higher position is desired.

The decision was finally made to move ahead with vlogging gear. While a wireless headset was being planned for years, a more practical system was a wired headset attached to a phone worn by the athlete. The phone would power the headset over USB & receive audio over the headphone jack.

There is no commercially available headset which captures decent audio, is wireless, & can monitor itself. The best commercial solution would use FM radio to transmit &...Continue Reading
Posted by Jack Crossfire | Nov 18, 2017 @ 11:37 PM | 916 Views
Anti stiction was implemented for this one. The trick was determining when the steering needed to change direction & kick the servo. The zero crossings of the P error were a good indicator of when the steering needed to change direction, although I & D also factored into the servo direction. The decision was made to rely on P error so the algorithm wouldn't feed back into itself. It waited until the zero crossing + a little hysteresis, then added a fixed amount to the I term to kick the servo. Using 1 degree of hysteresis & 3% for the kick completely solved the stiction problem. Not using any hysteresis or using too much kick made the steering oscillate. It was so tight, it could stay on the path for a nearly quarter mile with no steering inputs.

Also, the transmission was lubricated through the holes for the 1st time. The tape didn't stop the oil from leaking out, but hopefully it kept dirt out. Oil leaked out the bottom. It was so quiet after lubrication, you could hear the servo.

The speed was set to 10min/mile. Burned 3886mAh +4477mAh or 331mAh/mile. This was finally near the predicted range, but manely from increasing the speed. The lion can't manetain that speed for every run.
Posted by Jack Crossfire | Nov 18, 2017 @ 03:05 PM | 1,006 Views
In modern times, there's no need for bodging a webcam on an optical microscope. Documentation is better achieved with a DSLR macro lens. The next step up is a cheap USB microscope. The working distance is too short on the Amscope. The angled light is dim & creates too many shadows. The incandescent lightbulb gets flaming hot. It takes too much space. Its only redeeming factors are it's stereo, it has a higher framerate, & it was free. Soldering with the lag of a USB microscope & without depth perception might be challenging.

This microscope came in handy for soldering, but never for documenting. The webcam experiment was a rite of passage. You can get decent photos by holding a phone cam exactly the right distance from the eyepiece. It won't work with a DSLR.

Webcam on a 40x microscope (2 min 49 sec)

Posted by Jack Crossfire | Nov 16, 2017 @ 01:17 AM | 1,122 Views
After another 25 miles of listening to transmission noise, the decision was made to tear it down again & relube it. The counter gear was the only dry gear. Drilled holes to make it easier to relube without tearing it down. The mane problem is plugging the holes.

The 2nd 25 miler burned 4036mAh + 4605mAh or 345mAh/mile. It was much lower because the speed was increased to 10:30/mile. The motor got more efficient when it got faster. The lion also got more efficient, burning only 1 Clif Blok instead of 2.

The next problem is steering deadband. A lot of play from the servo saver makes it drive erratically. That was a buster to jockey for 5 hours. The servo needs to kick it when it reverses direction or it needs knowledge of the rod position.

There's increasing P gain & adding extra offset to I when the steering reverses direction. Steering constantly reverses direction by 1. Finding the minimum amount of reversal to be considered a real reversal would be tricky.
Posted by Jack Crossfire | Nov 12, 2017 @ 01:39 AM | 1,071 Views
Finally achieved 25 mile range on a vehicle. It only carried food for the lion & the headlights ran for 2/3 of it. The right front tire interfered with the new battery clamp, but it was otherwise flawless. Brushless motor, wheel alignment, ball bearings were key to getting this range on the lunchbox.

It burned 4370mAh +4907mAh or 362mAh/mile, so well above the predicted burn rate. The transmission oil may have worn out. To feed the lion, only 2 Cliff Bloks were required. The speed was reduced to 12min/mile, to aid the lion. That reduced the animal burn rate while it may have increased the machine burn rate.
Posted by Jack Crossfire | Nov 10, 2017 @ 11:45 PM | 1,193 Views
The battery popped out for the 1st time in 3 years while running down some hills at 10mph.
Posted by Jack Crossfire | Nov 07, 2017 @ 12:08 AM | 1,706 Views
It was always the same driver kit available anywhere in Shanghai for a buck, & the only way this many bits could be under $25 is if they were made of the softest steel & would only last for 1 teardown, if you were lucky, but the ifixit packaging was 1 of a kind. The magnetic case with grid to organize your screws, perfectly angled bits, not perpendicular but angled, perfectly sized foam insert just exudes the kind of quality that couldn't be a bog standard Shanghai street hustle, but something hand crafted just for the kind of user whose laptop looks like a work of art with an Apple logo.

To be sure, the only reason anyone bought this kit was the #5 pentalobe bit to fix his Macbook Pro. While they've always marketed their kits as aftermarket, there really is no other supplier, so it wouldn't be surprising if the genius bar used the same kit....Continue Reading
Posted by Jack Crossfire | Nov 04, 2017 @ 07:43 PM | 1,292 Views
The 1 week order delay finally ended & the journey to replace all 9 bearings began, manely rebuilding the transmission. The counter gear & the rear wheels were finally replaced.

A 13.2 miler started out super quiet & got slightly louder after 12 miles, as it was with the previous transmission rebuild. It could be more easily relubricated with WD40 to maximize the range. The evidence is the bushing inside the counter gear was causing most of the noise, since it got super hot & spun super fast.

With no payload but a speaker, headlights on, & hilly terrain, it used 2065 + 2305mAh or 331mAh/mile. A new record low consumption which could go 27 miles, but with no payload. With cold weather & no need to carry a shirt, the 27 mile range could be a realistic goal. A lion can only manetain that speed for 16 miles, so at a reduced speed with a payload, we could have a vehicle reach the end of the valley for the 1st time. The counter gear bearing must have been sucking a lot of power.

Did another 6.75 run with it. The 10mph test revealed no material improvement in steering oscillation. Noise was still reduced, but not as much as the Sandstorm. Despite headlights, 13 miles of wear on the lubrication, 3km at 10mph & a return trip with 10oz of food, it still only burned 2215mAh or 318mAh/mile.
Posted by Jack Crossfire | Oct 31, 2017 @ 02:32 PM | 1,183 Views
Berkeley run 3 (5 min 18 sec)

Ever so slowly getting closer to the perfect video. Figured out by this point, no-one cares about the VR mode.
Posted by Jack Crossfire | Oct 29, 2017 @ 01:23 AM | 1,528 Views
Another go at fixing the steering oscillation through PID gains & gyro padding led nowhere, so the next theory was back to the culprit of the Ruckus oscillation: worn bearings. The plastic bearings were definitely loose & the lunchbox was much more stable when it was new. It'll be another long, slow UPS delivery to do what used to take a run to the hobby shop.

Then came the revelation that the right front inside tire was completely ground off again & the left front inside tire was wearing out much more slowly. The experiment in lowered suspension was still a disaster. There was a slight boost in efficiency, but they were now off on only the right side. It wasn't the camber or the toe in. This is a real stumper. Those tires are expensive.
Posted by Jack Crossfire | Oct 28, 2017 @ 01:49 AM | 1,461 Views
The quality is hopeless, compared to any other method. There's no way to survive watching a movie in VR goggles. Tried a phone with 2560x1440 resolution. The screen was chopped off in the corners & the screen door effect was more obvious than the 1920x1080 phone. As the pixels get smaller, the proportion comprised by the gaps grows. Only objects behind the screen are viewable. Objects in front of the screen are too close to your eyes, in the goggles.

They do have a niche. They're flat out, the only way to view 3D color images on a phone & they're cheaper than all the other methods. Medical visualization might benefit from this kind of portable 3D imaging. By the time smartphones appeared, the 3D craze was gone. Phone support for polarized glasses only lasted for the 1st few years, on some rare models. There are no shutter glasses with IR dongle commercially available for phones. The era of shutter glasses is over.

Lions are some of the few animals to have watched movies using shutter glasses as well as polarized glasses. The shutter glasses for IMAX were real painful & left a mark on your forehead. They had a small amount of ghosting, even with film. They had extra speakers in the goggles which did nothing. The only movies lions saw with shutter glasses were Space Station 3D & Titanic: ghosts of the abyss. They were quickly replaced by polarized glasses.
Posted by Jack Crossfire | Oct 26, 2017 @ 07:12 PM | 1,368 Views
The lion kingdom hasn't finished Passengers yet, but already knows how it ends. It's visually stunning & makes you think about the logic, but otherwise is a disaster on autopilot. It would have been infinitely better if the heroine was revived by an accident of fate rather than the man deciding his pleasure was more important than her survival. The importance of the man's desires is the premise of the entire movie. If you don't agree, it's a 2 hour wait until she finally finds out he woke her up on purpose.

It would have also been better if the heroine woke the man up, but this is not 1999 anymore & audiences are a lot more conservative.

The days are long gone when lions thought you could figure out someone was your true love just from watching her videos & writing. The idea of popping a woman out of hybernation & instantly having her fall in love with you, with no arguing, health problems, stepkids, or ex husbands, is insane. In reality, they would spend their lives on opposite ends of the ship. If no-one else is there to witness it, there is no economic benefit or social status to gain from the man & relationships don't happen. She certainly wouldn't have been in love with a guy who needed upgraded breakfasts from her gold plan.

Surely, they would have had kids & the kids would have continued to their destination, continuing their lives as it were, but the movie doesn't end that way. Perhaps it was a superposition of the audience's values that...Continue Reading
Posted by Jack Crossfire | Oct 23, 2017 @ 01:53 AM | 1,305 Views
EEVblog #1032 Part 4 - John Kenny Keysight Interview (32 min 14 sec)

This episode had a few good nuggets.

Home runs are few & far between when designing new products. It takes a lot of failures to get a win, no matter how good you are. Unfortunately, our industry is structured as 1 startup per product, rather than a bunch of products directly under 1 venture capital fund, so there's a massive overhead of breaking up & reconstituting new teams just to get the point of creating the failures. Many home runs fail because the extra step of reconstructing a new team failed.

The best easter egg in a device with no display is a message in morse code that's sounded in any way it can make sounds or blinked through LEDs.
Posted by Jack Crossfire | Oct 21, 2017 @ 03:08 AM | 2,618 Views
On the day the RS-25 & the BE-4 were both test fired, Musk's comeback was a picture of his shoes in front of a bunch of jack o lanterns.


Does he dress up at home? Based on the spynet, he wasn't at home. The pool didn't match, but it wasn't much different than his 1st mansion.


Bet you didn't know Elon Musk was slowly buying up an entire hillside on Chalon Rd, Bel Air. Is he going to build a launch pad? Is he going to build a massive transit center for his tunnels? Is he trying to get a better view of his rockets landing? Is he buying more room to store his toys?

It's probably more practical, like storing wealth in real estate. It's currently $100 million. It's not a very diverse portfolio, but more practical than a house in Idaho. To be sure, he doesn't really have $20 billion in cash. It's private equity valued at whatever the fed deems necessary to ensure total employment, but worthless if he sold it all at once.

Looking at the photo of the shiny shoes by the pool, the lion kingdom wondered how someone not much different than the rest of us could achieve so much more. He's not supremely intelligent like Steve Jurvetson, but only an incremental step above the rest of us. He's not very good at giving speeches or interviews. His highest formal education was 2 bachelor's degrees from UPenn, in economics & physics.

He has above normal intuition about problems & finding ways to solve them by rearranging existing technologies, but not by much. His 1st company was founded with $28,000 of his father's money, or $280,000 in today's doll hairs. Theoretically, his father also paid for all his education, leaving him debt free. Even then, if the lion kingdom had $280,000 of dad's money, it would probably go in a bond fund.
Posted by Jack Crossfire | Oct 20, 2017 @ 01:16 AM | 2,317 Views
This works quite well, for what it is. The iPhone 6+ gives 960x1080 in each eye, which is actually higher than the lion kingdom's 1st x86 computer which did 800x600 . The Samsung Galaxy 8 would give 1480x1440 in each eye, high enough to replace a Macbook air. The LG Tribute would give only 640x720 per eye.

The computer generated 3D scene in Goog Cardboard is quite convincing. Unfortunately, it's not so easy to get 3D videos which work in it. A rectangular 3D movie can disregard which way your head is pointing. A spherical movie needs to look behind different objects based on where your head is pointing.

The mane limitation is lack of software, now that the VR craze is over. Nothing works on the LG Tribute which is actually light & cheap enough to use in the long term. There's no way to play your own spherical photos on it. Youtube videos don't play on it. Any software needs a wireless gadget to replace the touchscreen.

Its mane use so far is viewing someone else's stereo rectangular photos in color. It's quite an improvement over the anaglyphs of 15 years ago, despite much lower resolution. A 10 year old lion would have gone crazy over them. Unfortunately, no video player is smart enough to wait for a magnetometer trigger to start playing, so it's already over by the time you get the goggles on.

At $11, it's not worth writing a custom app to make these goggles more useful. If they were really worth anything, the biggest payback would come in the...Continue Reading
Posted by Jack Crossfire | Oct 18, 2017 @ 04:59 PM | 1,641 Views
Stabilized spherecam at 10mph & timelapse (1 min 50 sec)

1st motion stabilized spherecam footage. No more black borders.

It could almost pass for usable. There was a lot of math in rotating the spherical image. The solution was in an obscure library


For motion tracking, the transformation needs to be centered around a movable pivot, so it really needs to do 3 transformations. It first moves the pivot point to the center of the image, then performs the requested transformation, then moves the pivot point back to the pivot point. The fastest solution on a modern CPU is applying 3 matrices to each pixel instead of copying the image 3 times. Combining the 3 matrices through multiplication didn't work, so it's a very slow process.

Stabilized spherecam with VR mode on (1 min 50 sec)
...Continue Reading
Posted by Jack Crossfire | Oct 15, 2017 @ 01:46 AM | 1,860 Views
Spherecam did its 1st 6 miler with some hops to 10mph. The steering was extremely erratic. The roll cage didn't have to be used. Steering oscillated enough for the video to be totally unusable without stabilization.
Posted by Jack Crossfire | Oct 14, 2017 @ 06:13 PM | 1,838 Views

The ones he answered weren't that bad. Impressive that they developed a new alloy for the turbopump & claim scaling the engine up will be a very simple process. Starting with a subscale engine may go down as one of those brilliant decisions which got us to the stars or might not, but it does require tooling for 2 engines. It's hard to believe the entire development programs for the F-1, RS-25, RS-68, RD-180 were done with the full scale engine.

Other mane points:
Header tanks will have such low heat leakage, they're planning on keeping them subcooled for all those months without active cooling.
The nose will be pointed towards the sun, so no view of Mars getting big in the window.
Development program will use full scale BFS's doing atmospheric hops like the grasshopper.
He expects to exceed airline safety because airlines only have 2 engines while the BFS will now have 3. It's more complicated than that, but classic Elon.
The RCS thrusters are based on the Raptor combustion chamber rather than a clean sheet design like the Dracos.
Posted by Jack Crossfire | Oct 14, 2017 @ 02:01 AM | 2,331 Views
Spherical video rover (2 min 56 sec)

It utilized the roll cage extensively. Acceleration had to be as slow as possible & it needed lots of ballast. It only fell over axially. It's not useful for high maneuverability. There's no hardware stabilization, but the equirectangular mode isn't very jarring. In VR mode, it would look awful. The equirectangular mode got a better response from viewers, so they'll just be uploaded in this mode.

A spherical cam can raise its height mathematically even if it isn't on a pole, but quality suffers. Another overhaul of the firmware got the acceleration to where it didn't flip over with the cam on. Starting the motor takes a very complex state machine, but it's amazing just how far you can go with sensorless motors. Steering & bumps are still going to be problematic.