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Posted by Jack Crossfire | Today @ 12:18 AM | 374 Views
So there was delamination in a tire, giving a vote for tapered edges. Only the left tire delaminated, showing it was a problem with the 1st layer in the printing process.

The mane problem was both motors got flaming hot again. This time, the left motor seized up. It's definitely from pulsing the throttle with a heavy payload. They burned 1.5Ah to go 2 miles. If the throttle is constant with a heavy payload, it gets by. The bolts started flying off, despite being impossible to turn by paw. M2.5 bolts are so expensive, it might be easier to replace the entire motor.

It's still nominally burning 350mAh/mile with a payload & softer tires in front. It may be time to upgrade the front tires. Motor seizing happened with the original hard tires.

The next revision of camera electronicals began. It's getting the full frequency hopping 500mW.
Posted by Jack Crossfire | Apr 19, 2021 @ 12:36 PM | 1,331 Views
The lion got dehydrated & was walking by the end. The robot burned 300mAh/mile with 9Ah of batteries & food. Went back to the original idea of a soft starting throttle which goes into auto when it's 100%.

Inductive charging for the paw controller is just as problematic as a JST connector. The mane problem is all 5V phone chargers have protections against a number of conditions. If there's no load for a certain amount of time or if there's a load for too much time, they shut down. You have to use an ATX power supply, a dedicated raspberry pi power supply, or a mean well, which are all too big & expensive.
Posted by Jack Crossfire | Apr 17, 2021 @ 04:12 PM | 2,212 Views
It was time to return to the original wheel design, with a much larger diameter. It turned out the PLA hub has no meaningful mass difference from PETG, so it might as well be PETG for the higher temperature. This design had retaining rings glued on the hub, which were a disaster to glue on. A better idea might be diagonal overhangs. Then, there was adhesive to keep the tire from freewheeling.

It held the hexogrid tire on in an 11 mile drive. Power consumption with 1 new tire & 1 old tire was 254mAh/mile with 14oz of food.

Getting such a large clamshell to keep the wheel in place is tricky. It might be easier with a traditional block of infill or spokes. Lions just hate having any material which isn't visibly appealing.
Posted by Jack Crossfire | Apr 16, 2021 @ 02:48 AM | 3,454 Views
5 miles went down like a brick. The webbing kept the tire from sliding 1 way, but the adhesive did nothing to keep it from sliding the other way. The result was part of it sliding away & part staying in place. That rules out farstening at any single point. Too bad TPU can't stretch like rubber.

Been putting off upgrading the camera controller because it's so rarely used, but it definitely needs an amplifier.
Posted by Jack Crossfire | Apr 15, 2021 @ 01:06 AM | 2,944 Views
As these things tend to do, the stakes have been raised to get a reasonable combination of traction & range. There was a partial hexogrid tire which proved too soft for the cost.

Because it takes so much more material to make a flat tread stiff enough, the decision was made to go back to a PETG hub with a thin TPU tire. This would limit the compression if the tire completely compressed. Helas, PETG is noticeably heavier than PLA, despite its heat resistance. It could probably get away with PLA since the motors rarely get flaming hot. The biggest weight savings may be abandoning the hexogrid. Like the SpaceX logo & the isogrid, sometimes you just want it to look good.

The lion kingdom has evolved its 3D printing game to the point of making the thinnest possible lines & planes with the thickest possible layers. The .4mm nozzle can print a .5mm wide line but takes forever. The .8mm nozzle can print a .9mm wide line but is much faster.

Since the tires slip around the hub, there's still a dream of bolting the tires to the motors, but they now have to transfer force a lot farther across a much bigger hub. A 7 hour tire with webbing had good compliance, transferred rotation to the motor, but easily slipped sideways. It would need some kind of adhesive, whether it bolted to the motor, if the hub clamped it as before, or if it clamped around the hub. It might as well be a plain cylinder.
Posted by Jack Crossfire | Apr 13, 2021 @ 02:14 AM | 3,412 Views
After the 13 mile fiasco, some documentation of tire compression with a typical payload. It clearly is a matter of traction vs stiffness. The flat treads need a lot more material to be as hard as the curved treads, but are necessary for any traction.

A tire with a slightly curved tread didn't get any stiffer. Changing the number & straightness of the spokes didn't make a significant difference. Putting the extra spoke material into more tread thickness might make it stiffer. Printing spoked tires with .4mm layers takes only 2.5 hours.

There is a new honeycomb design with a flat tread & integrated motor mount, but it takes 10 hours & the lion kingdom is low on filament again.
Posted by Jack Crossfire | Apr 11, 2021 @ 11:03 PM | 2,992 Views
A 13.75 mile drive with a decent payload went slowly & ended in battery death. The increased traction of these tires wasn't worth the reduction in range. It actually hit a wet patch & spun out, but these tires have never spun out as much as the stiff ones. It burned 335mAh/mile, still in line with the lunchbox but real slow.

The motors couldn't go very fast with the full payload on level ground & that was the deal breaker. There could be a new tire with a very slight arch to bring back just enough stiffness without requiring tons of material. Real car tires are flat, but it takes a lot of material to make them stiff.

What's needed is a tire which can be made stiff when it has a payload & flexible without a payload, without air pressure. Having a variable diameter based on desired speed would also be a win.
Posted by Jack Crossfire | Apr 10, 2021 @ 03:44 PM | 3,851 Views
presets (0 min 48 sec)





So much easier to wake up when it repositions itself.
Posted by Jack Crossfire | Apr 09, 2021 @ 01:23 AM | 2,052 Views
Until the 5060 motors. Another 9 miles without any food but at higher speed burned 260mAh/mile. Those flat wheels might be burning more power for the improved traction.
Posted by Jack Crossfire | Apr 07, 2021 @ 02:14 PM | 3,831 Views
These were manely to get more cushioning in front. Same softness settings. Really awful overhangs. The tire empire continues growing. Surprising how these never seem to wear out, after years of trying to keep the Tamiya tires alive with every known material.

10.8 miles later with a lot of food, it only burned 260mAh/mile. Surprising, considering the wheels have more contact area. The tachometer is definitely slower with the compression.
Posted by Jack Crossfire | Apr 06, 2021 @ 02:09 PM | 3,857 Views
It was the 1st TPU tire which actually compresses under the weight of the battery. The mane reason is the flat tread. Curved treads were all hard, with no amount of curving making any difference in the hardness. The flat tread has some risers along the edge to keep from digging in, but is very flexible.

Stringing in the tires is actually less if they're printed in timelapse mode.

Tried adjusting the number & curving of the spokes, but it's either going to require a lot of money or finite element analysis to get the perfect hardness. The 1mm PETG hub cap is horrible. It would have to be 1.2mm with .4mm walls & .4mm infill to look as decent as the old one, in which case it would trap more heat.


Then of course, the bumper finally got stripped down to make it softer. Getting the right amount of softness without finite element analysis is an expensive process.


These did quite well in their 1st drive, burning 233mAh/mile & getting much better traction. About time to print new front wheels in the interest of a softer ride. Lions hung onto the idea curved treads could be as soft as flat treads, since they would use less material, but it seems flat treads are the only way....Continue Reading
Posted by Jack Crossfire | Apr 05, 2021 @ 04:03 PM | 2,389 Views
Completely rewound a motor only to find no obvious damage in the windings. It probably wasn't burned out. The PLA parts which clamped down the tire all melted, so the tire was freewheeling. There were also rocks in the motor, despite all the effort to shroud it.


The long term solution is new tire wheels which bolt on the motor & eliminate the PLA parts completely. The tires used PLA hubs to reduce costs, but the cost of the TPU & the amount of material has been reduced enough to make a single piece tire wheel possible.

The new tire has a larger flat area for traction or applying silicone, 2mm smaller diameter, thinner hub to improve heat dissipation. This required eliminating the X. There could be a metal hubcap on the outside to dissipate more heat. More revisions to follow.
Posted by Jack Crossfire | Apr 04, 2021 @ 07:03 PM | 2,475 Views
The bit banged I2C was successful in ending the steering glitches. There were other failure modes where a bad connection to the servo caused it to permanently die & the radio continued to sometimes die, but so far the mane failure mode seemed to have been I2C.

The next mane problem is the motor. Although it didn't seize up for another 8 miles & it didn't get smoking hot, it did continue to slow way down under easier loads than the past. The battery was 10.3V & hot. The right motor is believed to be damaged from past heating, so it's just shunting a lot more current.

Those 5060 motors are expensive, but they're not going down in price. Lions remember 2006, when all brushless motors were over $100 & made in east Europe. Then, low RPM Chinese motors came along for a fraction of the price. There isn't a cheaper option coming along to replace China & there isn't going to be an end to any tarriffs.

1 source of erratic speed was finally narrowed down to integral windup. It took a long time to slow down when a load came off. Integral windup is a bigger problem in an underpowered vehicle than it was in the sufficiently powered lunchboxes.
Posted by Jack Crossfire | Apr 03, 2021 @ 06:35 PM | 2,846 Views
Right wheel seized up again & overheated. It spun freely by paw, but not by the motor on the ground. This time, after letting it cool down, it started spinning again by motor. This is pointing towards a clearance problem with the shroud & a feedback loop where the motor warms up, starts rubbing, warms up more, rubs more. The overheating melted the PLA some more. The left wheel didn't seize up & stayed cool, so they can probably handle more current if they have enough clearance.


Printed a new retaining ring with 3 layers & installed with the horizontal expansion side up, to try to get it to stick more.



After 10 years, it was time for a rematch with the I2C glitches, as steering frequently froze up. The latest change froze the servo when I2C locked up, instead of steering erratically. It was little improvement.


10 years ago, I2C on the STM32 was assumed to be vulnerable to electrical glitches. Lions resorted to limiting I2C to 150khz & shielding the I2C cables, which worked most of the time. In the last 5 years, the internet started to lean towards a hardware bug involving concurrent register writes & recommended bit banging all I2C.


The lion kingdom always had a bit banging I2C driver, but burst mode never worked & bit banging is too slow without burst mode. Revisiting the driver 10 years later involved printing the pin values in software rather than soldering on test points. Then, comparing the bit bang waveform to the...Continue Reading
Posted by Jack Crossfire | Apr 01, 2021 @ 11:18 PM | 5,784 Views
Lions 1st had a need to replace the retaining rings on confuser fans after lubricating them, 20 years ago. Then, there was a need to replace the retaining rings on motors after rewinding them 10 years ago.

Finally, wheels were no longer staying in their bearings at all. It may have been the temperature or the position of the wiring. After debating the solution to this for decades, it was time to pick any idea & try it.

The 3D printed retaining rings are .8mm thick & made of PETG. This might be a hair too thick, with .6mm being optimum. They still seemed to retain the wheels against a level of force which previously pulled the wheels out. Only some driving will reveal if they work. The next step would be printing .6mm rings. Then there would be drilling a hole in the shaft & securing a shaft collar with a cotter pin.


There is a plan to eventually let these motors burn out & replace them with larger motors that cost more than a hoverboard.
Posted by Jack Crossfire | Mar 28, 2021 @ 07:48 PM | 7,269 Views
So the right motor seized up a few times. Upon disassembly, it was scorching hot. The leading theory is the warmer weather is softening the PLA components, throwing alignment off. Motor mounts may have to be printed out of PETG. The wheel was definitely deformed. A metal plate outside the current PLA one might dissipate heat.


The gaskets were chewed up, probably from the wheels slipping out of their bearings & being shoved back in.

There is a condition where the radio frequency hopping permanently stays out of sync. It gets 1 packet every second. That could happen if the same frequency happens twice in the pattern, which it doesn't. It could just get crosstalk from another frequency. Another bit in the packet storing what slot of the pattern it's on might fix it.

There are still rare times when the radio disconnects & it falls back on a motor timeout.
Posted by Jack Crossfire | Mar 27, 2021 @ 08:15 PM | 8,318 Views
Bench testing was ugly, with much worse results than the unamplified radio. It seemed to be saturating the receiver. Moving it farther away or covering it improved reception. Hot glued the bodge wires down instead of making a new board. Buttoned it up & it worked much better in the field. It managed to fend off the phone tower & range was no longer a problem. There were still dropped packets near the phone tower but not enough to kill it.

The impedance matching is obviously horrendous. Having the receiver right next to the ground is horrendous. The lion kingdom was just hoping for enough improvement to do the job. The battery has to be charged after every drive now. It took 30 minutes to hit constant voltage on the inductive charger. Something would have to be rigged out of a multimeter to get the number of coulombs.


The big question is exactly how much power it's radiating, compared to a Spektrum or a DJI. It spreads the 500mW across 100kbits. The Spektrums concentrate 7mW in a very narrow bandwidth so they have long range. The DJI video transmitter radiates 1W across a 20Mhz band of frequencies, so it has shorter range. No-one knows what the DJI uses for remote control. It may be the same as the Spektrum.
Posted by Jack Crossfire | Mar 27, 2021 @ 12:02 AM | 9,638 Views
The upgraded board was a bodgeorama, but it was the lion kingdom's 1st home made transmitter above 5mW.

The trick with the RFX1010 is the antenna input is shorted to ground at DC. It needs a 33pF blocking capacitor. Then, when the transmit enable pin is on, it burns over 150mA with no input. When the transmit enable pin is off, it burns nothing. This pin needs to be actively turned off when not transmitting. Receive enable & mode have to be grounded to get it to completely shut down. The control pins are floating. Mercifully, the switching time is only 1us.

Then of course, the high power requirement of the amplifier caused problems. The ADC became unreliable when the amplifier ran. Making it use the dedicated RC oscillator got it to work for some reason. The LP2989 voltage regulator got stuck on 2.5V until it got a 100uF input cap.

When it finally worked, it only burned 50mA for the full 500mW. The duty cycle was low enough to use full power without killing the battery. Frequency shift keying in the single channel mode & the 9 discrete channels used in the frequency hopping mode are clearly visible on the spectrograms.

The gold standard in the commercial world is the DJI Mavic, which only transmits 400mW. The top end Spektrums only transmit 7mW at 2.4Ghz. They obviously rely on directionality.

The mane problem with getting any more power is the small form factor, small battery, & not being able to use a directional antenna.
Posted by Jack Crossfire | Mar 21, 2021 @ 09:23 PM | 10,108 Views
The mane problem with these controllers is lion paws being asymmetric, but a method has evolved to work around the asymmetry. It's just not as comfortable in the right paw as the left paw.

The direct drive motors have 400 miles on them. Since the loose motor

https://www.rcgroups.com/forums/show...5-Loose-motors

they've been manetenance free for 218 miles. The mane problem is the wheels occasionally slipping out of the motor bearings. They can be shoved back in, in the field.

The 4Ah battery of 12 years ago is now down to 3483mAh capacity. Its nominal consumption of 250mAh/mile now gives it 13 mile range.


Anyways, the lion kingdom took note of the go go bird controller. Like the boosted board controller, there's a common theme of a binary switch for unlocking & a 2 axis joypad for throttle & steering. The center of the joypad is "hover". The question naturally arises of why these guys don't have separate throttle & steering sticks like it used to be done. The leading theory is it's cheaper to have a single proportional control + a binary switch than 2 proportional controls. It has nothing to do with ergonomics.

The lion kingdom also tried the TV controller orientation of the go go bird controller & was disappointed. Those aren't intended to be held by sweaty paws for hours.

French amazon had detailed photos of the components while American amazon had gender neutral photos of child models playing with it. After 40 years of seeing this difference in marketing styles, there's no evidence an economic system based on knowing how things work is better than an economic system based on social justice.
Posted by Jack Crossfire | Mar 16, 2021 @ 02:29 AM | 9,478 Views
9 mile timelapse (4 min 24 sec)


No more stable than the lunchbox. Burned 321mAh/mile. Had to reduce the steering feedback.

The gimbal had a strange tendency to move off angle when the controller was turned off, then move again when the controller was turned on. There's nothing in the source code about turning off the motor when the controller is off & the motor definitely doesn't turn off. It may have been operator error.

That stepper motor burns a lot of power & requires a lot of space for gear reduction & electronicals. There's a definite case for moving to a 360 servo just to increase the driving distance & free up space. Lions see no advantage to the stepper motor, now that it's gear reduced. Either way though, 20 miles is the goal for the camera & it would still require a 2nd battery with a servo.

It gets bashed around so much, a servo would require another plastic bearing, but it would have enough torque for plastic bearings to not be as problematic.