Ultimate running aid

After another 8.4 miles & 4463mAh, it died.  It burned 531mAh/mile.    2.6 of those were in 19m21s, slightly slower than the last 2.6 mile speed run, but also heading upwind.

The transmission was finally opened & cleaned.  The counter gear & pinion gear had a lot of loose dirt & were dry.  The differential gear was lubed & clean.  The holes for lubrication were hard to seal.  Electrical tape was replaced with a more tenacious adhesive, which might have liquefied & gotten into the gears, leading to the sudden drop in range.  The source of the dirt is mysterious.  Despite not sticking, electrical tape might have actually been a more effective seal.

The Tacon 2400kV is quite a well made beast, but bolts encasing it have corroded.  According to blog posts, when the lunchbox was new, the brushless motor burned 283mAh/mile.  The brushed motor burned 413mAh/mile.  All the conversions to increase the payload cost it.

3 years of inferior steering controllers vs new tires.

A rare pristineness worth documenting.  

Washing robots in this century is as important as washing cars was, in the last century.

Another 10.85 miles with dual batteries burned 3441mAh + 3766mAh or  664mAh/mile.  Far below brushed motor range & half the rebuilt transmission range.  It wouldn't even make it to the last vending machine or the Alamo.  By the end, the weight of the 2nd battery had the tires skidding around the wheels again.  This was the same pair of tires which skidded before.  It traded places with the front tires, which stopped the skidding, & was rotated back to the rear because of wear.

Steering was solid.  Rebuilding the entire drive train & replacing the tires is a lot of work. Front tires might benefit from another toe out.

Toed out another turn & went another 11.1 miles on the same route in reverse, with the slipping wheels.  That burned 3258 + 3618mAh or 619mAh/mile.  A dramatic improvement, relatively speaking.  

A 6.5 mile drive had 1.9 miles at 10mph while carrying the shirt & burned 493mAh/mile, so pretty awful, but it might have been the speed.  Toed out the wheels 1 turn.  The buck converter finally arrived to replace the LM317 for feeding the servo.  The only thing at a reasonable price, within 4 weeks of delivery, was

https://www.amazon.com/gp/product/B00VI0L94C/

Thus began the operation to boost it to 6V.  It's based on the MP2307DN with a 47k for R1 & 10k for R2.  Replaced the 47k with a 55k to boost it to 6V.  

Went another 8.8 miles with this setup, at a cruising 9 minutes/mile, with headlights & the speaker.  That burned 410mAh/mile, so the BEC didn't do anything.  

Ready Player One made it to chapter 8.  It was excruciatingly boring, after the customary cliffhanger introduction.  Driving the robot for 10 miles while listening to the book is like being in the book. The sky gets darker & the LEDs get brighter as the cars full of ordinary mortals line up on their commutes. You bang away on the only game controller of its kind in the world, throwing down mile after mile on the only robot of its kind in the world. The lion kingdom wondered if the mane character ever had to pause the game because his running robot only had 10 miles of battery power.

What was originally a 6 miler became an 8.3 miler to get through as much of Ready Player 1 as possible.  Nosed in the left wheel another turn & had the headlights on.  The route was flatter than the last 11 miles.  The frigid night warmed up.  Burned 3422mAh or 412mAh/mile, so a slight but definite loss of efficiency.  

A 7.75 mile drive burned 3168mAh or 408mAh/mile, after adding a turn to the right pushrod to make it toe in more.  It carried a hefty load of food for the final mile.  Range correlates with the total number of turns in both pushrods, not which pushrod they're in.

Theoretically, marking the tires with chalk should give the toe alignment in the form of smearing.  The internet shows guys using string, but the wheels are too small & not the same spacing.

A 10.9 mile drive burned 4230mAh or 388mAh/mile, after adding another turn to make it toe in more.  It was a very hilly route.  

The battery was dead as a doornail, having burned 4500mAH or 430mAh/mile.  It carried the speaker & camera.  There were some hills, but it never had such short range, before.  The left pushrod was shortened by 1 turn to make it toe out more.  The right tire seemed worn in the center.  The steering is bulletproof in this configuration.  That leaves transmission overhaul.  Considering how it gradually lost efficiency after the last transmission overhaul, with no significant changes, the transmission is the leading suspect.  

The outside of the mane gears have been soaked, but there was no way into the differential or 1 inner bushing.  Overhauling it requires tearing down the entire vehicle.

Not sure understanding this much detail of every anomaly would make any difference before ordering a new vehicle.  There are many finer points with a new vehicle which are unsolved, like where to mount the batteries, how much more power it'll take to move such a large vehicle, what kind of motor would be most efficient.  Maybe the solution is to keep the lunchbox around for short range & small payloads while having a 3rd vehicle for camera mounting, long distances, & large payloads.  

Tests showed when the Hitec HS-311 was at 150Hz & buzzing, it sucked 900mA.  At 100Hz, it didn't buzz & dropped back to 200mA, so definitely check the PWM frequency.  Still, a brushless servo would get the ultimate range.  

An 8.35 mile drive with nothing but a speaker & no headlights burned 3200mAh or 383mAh/mile.  Still far below the good old days.  Steering was rock solid with P 200 D 200.  D had to be a bit lower without the camera.  Range anxiety makes it difficult to replace with a larger vehicle until the source of the increased burn rate is known.  The ideal vehicle would go 30 miles using 13500mAh.

That was as straight as lions could get it.  Even at 9min/mile, you can see how much is oscillates.  That was with P 200 D 1000 & bandwidth 0.9.  In a pinch, movies could be made at 10min/mile.  The servo & algorithm made a big difference, but it's still pretty awful range & tire wear.  It's a referendum on a new platform.

Anyways, experience has shown the $220 for what appears to be Chinese junk today eventually becomes the fair market price of the $500 items from Japan which appear to be high end.  

Burned 3926mAh going 6.45 miles, or 608mAh/mile.  The camera system with HS-311 made it as bad as a brushed motor.  Using P200, D1000, it was stable enough to be useful, at 9min/mile.  Any faster & the oscillations grew.  It burns through tires & servos at all speeds.

So the H-King Sandstorm was a very robust solution & buggies don't require as draconian modifications as the Lunchbox.  The buggy has been the winner, despite monster trucks intuitively having more payload capacity.  Trucks are about as unstable as buggies.  

Buggies need clearance for the tires, so they're leaning towards a very long design with payload bay between the tires.

All the hobbyking models are of course, out of stock.  The prices of what really exists are more than full sized cars, when servos, batteries, & motors are considered.  Hobbyking has a loose definition of scale.

Having built up 5 vehicles now, the thrill of building is gone.  It's more interesting to solve problems with software.

H-King Rattler ARR   18"x10.6"x5.9"   $152

Narrower than the lunchbox.  out of stock

BSR Berserker 1/8 Electric Truggy Updated (ARR) 20"x16"x8"  $400

Too big

Basher SaberTooth 1/8 Scale Truggy (ARR) 23"x17"x8.5" $220

Too big

Quanum Vandal 1/10 4WD Electric Racing Buggy (ARR)  16"x10"x5.5" $101

out of stock

Trooper Pro Edition 4x4 1/10 Brushless SCT (ARR)    21.6"x12.2"x7.5" $208

Definite contender.  The payload bay could go between the tires & ride below the tires.  Motor is in the middle.

Turnigy Trooper SCT 4x4 1/10 Brushless Short Course Truck (ARR) 21.6"x12.2"x7.5" $160

Out of stock.  Plastic version of the pro.

Team Associated 1/8 RC8.2e 4WD Buggy 18.5" x12"x4.4" $500

More than a full sized car.  

The lunchbox 12.5"x11"x5"

H-king sandstorm (tested) 14"x8.5"x4.5" $110

16"x5" payload

Tamiya 1/10 Top Force 2017 4WD Buggy Kit (out of stock) 15.7"x9.8"x7.4" $194

Too narrow

Losi 1/8 8IGHT-E 4WD Buggy 19.6"x10.2"x7.1" $500

More than a full sized car.  

The HKS-9257 arrived after 2 days & was the wrong size, so into the pile it went.  Such is the peril of modern, sight unseen mail ordering.  

The latest theory was an accidental observation that none of the servos can automatically recover if they're knocked out of position by a momentary force.  They usually get off by a certain amount & stall as they try to recenter, even if the force has ended.  The servo saver improved results by always exerting less torque on the servo than the servo exerted on it, so the servo didn't get knocked off center & the servo saver still had that center position to exert on the wheels, after a delay.  

The Futaba S3003 was particularly bad at centering itself, so replaced it with the only remaneing servo, an 18 year old Hitec S311, the very 1st servo bought by a lion.  It was slightly better at centering itself.  It didn't fit any servo saver, so choked up on the servo horn to increase the force.

The 8.2 mile drive with no payload besides the speaker & no headlights sucked 2956mAh or 360mAh/mile.  The servo itself might be a significant draw, since the LM317 gets hot & it buzzes when driven at 150Hz.  150Hz was a requirement to reduce oscillation.  P=200 D=0  & it had acceptable levels of oscillation, but wasn't totally solid.

A brief test with the polecam was most impressive.  P=100 D=100 with the bandwidth=0.9 managed to stabilize it more than any previous drive.  Things started looking up for the FIR filter, with the servo change.

Rather than invest any more in servos or algorithms, the decision was made to finally scrap the lunchbox after 3 years & many hundreds of miles.  Should put on the new tires & wear them out.  Lowering it by eliminating the suspension caused problems with steering which will probably never be completely solved & there are other vehicles which can do the job without any modifications. 

A novel way to fix a stripped hex head.  The light duty cutting wheel does the job.

Original servo saver.

Shorter servo head.