Since last time’s disappointment with the performance of the “Alt-Kart” set up with Mars BLDC motor and malfunctioning (now dead) Sevcon PMAC controller it’s been on my summer list to make the kart fast- not perfect, just cheap dirty and fast. To that effect, and to celebrate the ending of summer vacation (classes start tomorrow, Monday) Micah and I got together on Friday to make it happen.

I picked up a new sprocket hub and keystock from Comet to get the chain drive back in working order.

I had to use a puller to remove the old sprocket hub, you can see the gouges where the deformed edges of the axle keyway scraped through the bore.

I filed the smooshed edges of the keyway to bring the OD back in under 40MM, you can see where the damage was. I cut the new key to fill the keyway end-to-end, so I was not concerned about the torque-transferring ability of the connection.

All fixed. The new sprocket hub has a much improved clamping design than the old one, the whole assembly feels very tightly put together. I can’t imagine it coming apart in the way the old one did.

Micah had this D&D 6.7″ series wound motor from his electric RX-7 project earlier this year. We judged that it would be a highly suitable motor to take the kart to stupid levels of quickness, with the added bonus of sliding in and bolting right up with the same pattern and shaft as the Mars BLDC. Of course it weighs three times as much and lacks the convenient axial flux design, so all that weight is on a significantly longer lever arm off the thick but admittedly not-designed-for-stiffness mounting plate.

In our proud tradition of shady fixes involving lumber, Micah devised a 2×4 strut resting on various chassis pieces and held together with conduit clamps and screws, plus a ratchet strap around the motor. Shady indeed- but it kept the slop in the chain drive from causing the rear of the motor to bounce up and down- score!

After fighting with the hardware configuration of a Sevcon 4qd 48v/300A controller for a while (even with the *expensive* calibrator dongle there are a bunch of settings you can’t change without a secret password) and indeed seeing it sort-of work we settled on switching it out for the simple, brutish but eminently functional Alltrax. You may note the toasted main fuse- it’s actually still intact, and after blowing our nice looking fresh fuse in a regrettable flying-lead incident it got the job done.

With the Alltrax’s simple requirements we ended up driving the Kilovac contactor with an entirely independent 12v supply composed of four (counterfeit) A123 cells. Just like the Killacycle! Except theirs are doubtless genuine.

At this point we took it out for a drive on the same 36 volt set of batteries that were installed with the ill-fated brushless system. Aside from issues with our hose-clamp jury rigged throttle pedal slipping around the results were quite positive- good pickup and speed, remarkably quiet and smooth.

But as I assured Micah, it had to happen- we strapped another three battery packs onto the kart for a full 72V.

With about 180 LBS of lead batteries in tow and somewhere around 40hp peak the kart was entirely transformed. I doubt I actually ever hit full throttle on account of the acceleration being so incredibly strong. Any easy jab of the throttle resulted in instant neck-snapping torque-thrusted acceleration. It felt quicker than the Tesla Roadster I rode in in July. I was even impressed with the handling and steerability. The steering and chassis felt incredibly direct and communicative. Maybe it’s just because I haven’t driven karts before, but I loved it. It didn’t have much trouble with scrubbing on tight turns even with the immense extra rear-biased weight. The good design of the chassis really shows in that regard.

We ran the motor up until the speed leveled out with the wheels off the ground- the axle was spinning about 2700 RPM max, corresponding to somewhere around 90MPH ground speed. I think I only hit 30 or 35 in the tiny space we tested in, but it accelerated extremely responsively at any speed. In trying to hit the highest speed I could I found myself unable to keep on the throttle for any more than a few seconds at a time without the kart starting to lose traction and get squirrely. If only we had access to a larger flatter area to test drive…

I was curious about the slidability of the kart, so I turned hard and laid on the power- it started sliding beautifully for a second before ping-whizzzzzzzzzzzzrrrrrrr the chain popped off. I figure the combination of the new chain stretching, the overall slop of our setup and the chassis flex in the hard cornering conspired to allow the chain to hop off- fortunately unlike last time there was enough slop that the sprockets, shafts and hubs seem no worse for wear. At this point it was getting late, we were satisfied with our results and didn’t want to push our good luck with not getting in trouble further so we took the kart apart and went to go get some cheeseburgers.

Of course, now that I’ve had a true taste of just how incredibly fun this kart can be to drive I’m seriously looking forward to doing it better and more permanently- but for now I’ll be storing the stripped kart to work on other things. It’s time will come.

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I’ve designed and had manufactured several PCBs over the last couple years for the Battery Regulator project. I’ve focused on using through-hole parts, using surface mount components infrequently only when necessary. Even after spending hours condensing the components and finding clever ways to rout traces to maximize the use of board- space I find the design rarely looks particularly dense or crammed. SMD parts to the rescue-

This project was conceived as a challenge, not out of necessity. I wondered if I could condense the circuitry required to drive a 10×10 RGB LED matrix (based on the EMSL Peggy 2 schematic) onto a small single two-sided circuit card, with no wasted space around the edges. This presented a couple challenges. I routed all the row circuitry horizontally on the front of the board, but since the row traces must be unbroken, all the column traces must be on the back of the board, attached via vias. This means the only space for support circuitry was between the ten column traces. Grouping the column traces in sets of two leaves four wider open strips, but only connectible to each other horizontally between the rows of LEDs on the front of the board. I was truly interested to see if it was possible to fit all the required connections or if I would run into insurmountable routing puzzles. About ten hours later I had drawn up all the footprints and traces- it looks like it’s not an impossible problem at all- it actually went together pretty elegantly.

Now the real question- to build it or not. I suppose the corillary to the “design a tricky high-density SMD based board” challenge is “assemble that tricky high-density SMD based board”. And of course, besides being a soldering challenge, it would be a pretty nifty little widget if it does in fact work. I’ve taken it as an opportunity to try out Sure Electronics‘s seriously cheap PCB fab service. (search eBay to find it) Depending on how long it actually takes to get these boards and their quality once they get here their service could be a really excellent bargain. Then it’ll be to Digi-Key for a bounty of 0805 passives, SOT-23 transistors and TSSOP-24 ICs. And to eBay for a bulk pack of “5050″ or “PLCC-6″ RGB LEDs.

We’ll see how well my fly-by-night land pattern artestry holds up to the real challenge of actually putting the thing together. Fortunately the ATmega 168/328 microcontroller will be a DIP300 package held in a standard socket with legs bent out and surface soldered- I decided a socketed mcu would probably be a good thing given that I didn’t add an ICSP header, only a FTDI style TTL serial header (SIL header fit between the rows of LEDs). Everything else is in a .025 pitch TSSOP package. We’ll see how it goes. I’m going for “learning experience” with this one. If it works that’ll be the icing on the cake.

And yes, I’m calling it the “Twinkle Tag”.

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First Man had Fire.

Fire would be found in a pit or later a fireplace. With fire came soot and smoke.

Eventually Man put his fireplace behind a pane of glass, eliminating smoke in his dwelling.

And again Man figured out that he could have a fireplace burning gas that did away with smoke and the necessity of building and tending a fire.

Today Man has built a fireplace (The Moron Fireplace) which burns gas with fake logs for the singular purpose of decoration, not heat. Indeed this fireplace (THE MORON FIREPLACE) expels the heat generated by the flickering gas flame OUTSIDE the building. On purpose.

This is excess in living. This is how we know we’re better than those who can’t afford to heat their homes.

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Since I already posted about my experience at Refuel 2010 now it’s time to look at who all else was there.

I was excited to see Palatov Motorsport’s cars. I visited the Palatov shop last July in Portland but at the time the dp1 was out of the shop and the dp4 hadn’t been built yet. They brought the dp1e electric racer and the dp4 hayabusa-powered mini-racer. The dp1 is powered by a Remy PMAC motor and impressively compact Rinehart Motion Systems inverter, coupled with a healthy Thunder Sky battery pack. While solidly in the prototype phase, the car is coming along quite impressively and makes quite an impression in person. From looking around the Remy website I suspect the motor they’re using is from Remy’s “off the shelf” series of motors designed for hybrid drive systems. It uses an interesting construction technique they call “HVH- High Voltage Hairpin”. Basically, the windings are made of rectangular wire slotted very neatly into the stator laminations, for measurable improvements in power density and efficiency. It’s really a very sexy looking motor.

(Taken from the white paper available at http://www.remyinc.com/hybrid.asp)

Palatov says he’s planning on selling a EV drive system based on the Remy motor and RMS inverter. It’ll be very interesting to see what the price point for that sort of a system will be.

The dp1e looked great on the track, they took a close third in the time trial after the Kleenspeed WX10 racecar and the Wrightspeed X1. Given that both of those are AC-150 powered, with approximately double the peak power of the dp1e it’s not a surprise, but impressive how close it came.

See the rest:

I didn’t get a good look at the Kleenspeed racecar with the hood up, but I saw the AC-150- a good starting point for a real fast machine. I’ve got to say, I’m more interested in cars that push the boundaries a bit with more experimental motor systems, especially in this day of booming growth and diversity in brushless motors.

I’d seen the Wrightspeed X1 before, and while the specs and performance is way up there, the big lithium brick/ariel atom/AC-150 formula isn’t all that new and exciting these days. Of course it works well!

Also representing the AC Propulsion AC-150 was the EBox and original T-Zero. The T-Zero still holds up well as a very unique and well constructed car.

eeVee motors brought one of their Honda Civic based conversions. It’s a pretty tidy package. Azure AC-24 and ThunderSky pack. Good combo. Funny sounding power steering pump.

The borderline nuts Capstone CMT-380 Diesel turbine series hybrid supercar showed up as I had seen before at the Maker faire. They didn’t do much driving in it, not sure if it was having issues or if they’re just precious about it. It’s quite an impressive car in a totally crazy in the head sort of way.

Speaking of being precious about a car, EV4U custom conversion’s Beetle was there, with fresh paint and a caretaker extremely apprehensive about getting it messed up. Other than that, floodeds and a Curtis. Move on, nothing to see here. If he had driven it on-track my car wouldn’t have earned the distinction of being slowest. (… wow, that’s some snarky attitude)

Optamotive brought their X-prize contender “E-Rex”- despite looking a bit rough around the edges (work in progress) it seemed to run alright. It’s definitely got potential.

Finally, Jeff McCabe brought his 928 conversion, complete with a very nice looking pack of Taiwanese cylindrical LiFePO4 cells. If I had the cash this is definitely a direction I’d like to go with the MX-5. His motor and controller are similar to mine, but the performance of the Lithium pack really sets his car on another performance level.

Unfortunately I didn’t get a chance to check out all the bikes and other three-wheelers. It was an interesting spread of EVers represented here- looked like everyone enjoyed themselves. I had a great time, enjoyed seeing the spread and meeting new people. Looking forward to next year! I’ve been inspired by a ride in the stupid-fast Tesla Roadster to build something electric, lithium powered and really fast. Probably the Kart. We’ll see.

See Part one for my personal experience at the event.

Thanks very much to Miles K. for photographs.

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Now in its second year, the REFUEL all-electric expo and race at Laguna Seca Raceway was held last Sunday, the 11th of July. Held by Speed Ventures, it’s an opportunity for owners of electric cars or motorcycles to drive on track in a track-day setting, as well as compete in a time trial style race against the other electrics. I missed the event last year but made a point to attend this time, and to my great satisfaction was able to bring the electric MX5.

It was a bit of a stretch to get the car down to Monterey, arranging trailer and towing facilities around my friends’ schedules, but in the end things worked out well- the car made it down and back safely with no incident. There was even enough space to bring the electric bike and electric recliner- both of which fulfilled their purposes very well and were great fun to have along.

We arrived at about 8:30 AM after about three hours on the road and found the racetrack hidden in thick fog. By the time the first session came around the fog had burned off though, leaving beautiful sunny, breezy weather for the rest of the day. I made it out for two sessions on the track, for exactly two laps each before the batteries were too soft to continue. Coming over the big hill to the corkscrew corner on the second lap was accomplished at near a crawl.

I had a good chance to get more of a feel for how the new Rudman regs perform, mainly how much additional convection cooling they need in operation- I had to keep chasing the overheating reg around the pack with an electric fan. It’s definitely good to be putting some cycles on this pack, it’s clearly starting to work itself out and become more balanced. The battery I thought was weak and having self discharge problems seems to be behaving better. I am wondering if perhaps my old balancer system was causing a higher quiescent discharge on it than on the others.

My car was the only one driving on track with lead batteries, and one of only two brushed DC powered cars- it’s not a surprise that it was the slowest car out there. Despite that it was incredibly fun and gratifying to take around the track- and what a beautiful track. Sure I could have done better racing in practically anything gas-powered, but that’s not the point. Finally after three years working on the car I can drive it and charge it at a racetrack 120 miles from home- that’s really something. The car is unique- smooth, quiet and really pleasant to drive, even reasonably fast when fresh off the charger. Two laps, about four and a half miles of hard driving is pretty much the limit before the voltage sag completely destroys the driveability of the car. According to the Cycle Analyst that’s about 12-16 AH in- I’m not sure if this is a reasonable useful capacity out of the 55AH Optimas or if they have suffered in the last year they’ve been sitting full but rarely cycled.

The bike performed excellently as usual as a speedy runaround, and was passed around a bit for test rides. The electric recliner was the real star of the show. Sitting out of view in the truck while remote-crusing it around the paddock was stupid fun. We maneuvered it over near the Palatov Motorsports trailer and distracted them from their cars for a bit with some antics that Dennis ended up mentioning on his site (See dp1e section, 7/9/10 post). Then at the end of the day I traded a ride in the chair for a ride in a Tesla Roadster- something I had never managed to get before. Suffice it to say the Tesla knocked my socks off.

All in all, a fantastically successful day.

See part Two for my thoughts about the other cars that showed up to the event.

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Despite the troubles I was having before, the DC/DC converter has mended itself and appears to be working entirely as it should. It looks like the problem was caused by enabling the converter with the ignition signal before the precharge was done. The idea being that the precharge circuit is usually used in situations where the converter is disconnected from the pack when the ignition is off, so that it soft-starts itself and starts running on its own when it is energized. The enable input apparently overrides the soft-start procedure. When used with the enable input the converter is supposed to be connected to the pack all the time. The converter is usually not meant to be run using both like I am. So, if I switch on the pack and then switch on the ignition too soon it will close the main relay inside under the cap charging load, which probably caused the relay contacts to lightly weld shut. I spoke to Belktronics about the problem, they recommended testing the precharge circuit by attaching the converter to the pack through a 110v lightbulb- the first time I did it I got a big flash as the caps charged. At some point after then the fused contacts seem to have un-fused and the precharge circuit works OK again. I just have to make sure to always leave it adequate time to precharge before enabling it.

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After having the last couple weeks of my life stolen by first illness, then jury duty, I’m finally back in control and ready to get the stuff that needs to get done done to make the projects that need to happen happen- like the car and the kart. I didn’t shave until I was booted from the jury selection- It’s probably just superstition but hey, it can’t hurt to cultivate a “you don’t want me on your jury” look. What a relief to get out- the trial presentation for those selected will likely stretch into August. A real messy attempted murder case.

So, what’s up now? I’m making plans to get the electric MX-5 down to Monterey on Sunday for the Refuel expo/trackday/event at Laguna Seca. I’ve installed a set of MK3 Rudman Regulators to replace my home-built balancer setup as I discussed before. I’ve given the car a couple of test cycles to try to figure out what is really working and what’s not- the new regs look promising but need to be dialed in. There appears to be one really weak battery that is limiting the performance of the whole pack. And the brand new Belktronix DC/DC has something going on that I need to figure out. It’s blown a couple of HV fuses now (where do I recognize this scenario from?) If I can’t get it working it won’t ruin the weekend however, the aux. 12v battery seems to be up to the task of running the car. I got about 15 miles of driving today with heavy vacuum pump and headlight use before the aux battery ran hit the Zilla’s cutout point, and it wasn’t fully charged when I started.

It’s the little things that stack up and become seriously frustrating. The cycle analyst reports wildly varying and totally wrong current readings while charging the car, while seeming about correct under discharge. Even my Fluke 337 current clamp meter is acting sketchy and not entirely trustworthy, particularly for voltage or resistance measurements. There’s definitely something wrong with it.

So, like usual with the practice of trying to get stuff to work there is the sweet and the sour- some things go right the first time, more often things need more attention. Patience and perseverance.

I’m really looking forward to the event on Sunday, I know some people I want to see will be there and I expect plenty of people I will enjoy seeing but haven’t thought of will show up as well. Hopefully the Miata performs OK. Looks like my friends and I will also have the electric recliner in tow. After reworking the battery box today it is even more solid, and stealthy than before. Good stuff. Sadly we didn’t get a chance to set up the remote-controlled auto-recline feature. Another day.

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Last week I rebuilt the kart with fresh fasteners and axle bearings, plus picked up a steering wheel and some #35 sprockets. Then, once the Mars motor looked repaired and good to go onto the kart I picked up a handful of 7/8 keyed #35 sprockets from Surplus Center. The parts were forecast to arrive on Thursday- so I made plans with my friends to bring everything to Laney and try to get the kart running. I came in at two and got started- about eleven hours later the kart was driving, a half an hour later it was broken, and finally at about four in the morning we all went home.

Miles drew up the motor mount plate in CAD and cut it out of 3/16 mild on the CNC plasma table. It’s bolted right to the outer bearing frame support with slotted holes to adjust the chain tension- the stick he’s using is to help support the motor while he tightens the plate in.

Micah made up all the cables out of 6GA welding cable. We didn’t find enough lugs locally at any sort of reasonable price so we made “lugs from the ghett-o” by smashing copper tube around the wire, filling with solder then drilling. A little trick I learned from Home Power Magazine about ten years ago. I mounted the Sevcon Millipak controller, contactor and fuse, and made up the control panel, throttle, and hall sensor wiring harnesses.

See the rest–

Micah set up battery mounting using only the best pallet-wood and ratchet straps

A dead cushman carcass was ransacked for the 0-5k throttle pedal mechanism, which Micah cleverly secured using hose clamps.

Igniton and forward/reverse switches. Classy purple switch cover courtesy of Surplus Center. Of course.

(warning: there’s a little F word in the video)

So, what happened? Let’s just make a list:

• The axle was binding in funny ways at first, we assumed it was the chain but realized the chain was not tight in any particular way while the axle was binding. Turned out it was the axle bearing set-screws interfering with the slot-shaped cut-out in the motor plate. Since it was slot shaped there was non-constant interferance, and because the rubbing pushed the screws counter clockwise it wasn’t possible to simply “wear in” as the screws kept backing out and rubbing worse. I simply pulled the setscrews out (badly mangled, but really loose) and that problem went away.
• Violent motor cogging- somewhere in the electronic commutation system (hall sensors, wiring, controller) it’s getting bad sequence information, causing awful cogging and jerking torque output. Not sure what’s at fault exactly. You can really hear the effects in the wheels-up video above. It seems to be worst at around 1/3 speed and throttle. It usually clears up with higher speed and doesn’t really seem to manifest at very slow speed while starting out. It did this on the bench before we did the motor repair hacking as well.
• Directional confusion- the Mars motor is set up to spin CCW, the fan is only effective while spinning CCW- which I think is correct for most motorcycle applications. In order to put the motor inside the frame not outside we need to spin it CW. I wired up the motor exactly to the recommended diagram which meant we were operating the controller in reverse. Either due to a reduced speed reverse algorithm or a significant timing bias in the motor the kart ran far faster backwards than forwards. Which is somewhat entertaining but mostly stupid.
• Fusing Stupidness- Before even putting the kart on the ground we blew the $20 150A fuse I had just bought. Not sure exactly why, given that it’s a 250A controller and slow blowing fuse- I suspect it had to do somehow with the cogging problem. It’d be real nice to get that solved- good for the batteries, controller, motor, drivetrain… well everything.
• Parking ticket- I got a big effing parking ticket for being parked on the street at about 12:50. Street sweeping. To their credit they did then bring a sweeper through. But it was one of those great ones where you’re walking to the car as they’re writing the ticket. Ok, moving on…

All of these things were non-optimal but did not prevent driving the kart around.

Then the mishap that ended things for the night- Due to a combination of the sprocket carrier axle-clamping screws not being tight and the awful jerking cogging-torque from the screwy commutation the sprocket holder key jiggled out, then the chain derailed. Casualties- the key was smushed up pretty good, the keyway suffered a bit, and the sprocket carrier became a bit pretzel shaped. Turns out that if a chain in a system without any give in the chain-path length derails it’s going to deform the weakest part of the system. In this case the aluminum sprocket holder. At least it wasn’t the motor shaft (though I should probably check that carefully)- that would be significantly more expensive. So that’s probably one of the reasons kart suppliers sell “sprocket guards” – a bit of insurance against chain derailment. Maybe worth it.

So I will pick up a new sprocket carrier and a new key, this time I’ll get one that is the entire length of the keyway- so that there’s nowhere for it to escape to, and to fortify around the mooshed part of the keyway. Then we should be back in business, for some faster gear ratios and higher voltage…

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Here’s the short version: Because we are cheap, my friend picked up a Mars “Brushless Etek” BLDC motor from Ebay user “megadan” who has been selling these motors for about half price, with the catch that they are shipped with an odd and difficult to deal with shaft adapter (I’m starting to get used to this reality of cheap and surplus motors)

The first plan we had for removing the shaft sleeve adapter was to cut the end off then hold it in a vise and use a pin to beat the motor shaft out from inside it.

Cutting the end of the adapter was uneventful, so we found a pin and started hammering on the shaft. Seeing no movement we beat on the shaft pretty good. Then I noticed the motor had bound up and wouldn’t spin anymore.

Turned out the hammering caused two magnets to come unattached from the rotor plate. You can see the left magnet in the photo protrudes further from the rotor than the right magnet, it has stuck solidly against the stator. Still no movement in the shaft adapter.

The next day I figured out a better plan for removing the shaft adapter- I used a dremel cutting disc to cut a slot in the sleeve right above the keyway, using the keyway as a relief to cut through the sleeve without cutting into the shaft. The adapter sleeve was held on the shaft purely through friction, no internal keyway. Given the tightness of the fit I would guess it was an interference fit assembled with thermal expansion. After slitting the sleeve I ground out the motor-side of the sleeve in the corner that the dremel cutting disc was unable to reach. I pounded a screwdriver into the slot and the sleeve slid right off. With careful grinding and cutting I managed on only nick the motor case and shaft.

So now, an adapter-less but seized motor. Time to disassemble. But how? There’s just one screw on the outside of the motor that holds it together. Other than that it is held together by the axial magnetic force of the rotor -> stator and the friction fit of the shaft through the rear bearing. There are three metric (M5?) tapped holes in the rear case that can be used to attach some sort of puller rig.

This can only end badly

I bolted the front case to the welding layout table (conveniently spaced holes) and whipped together a plate to bolt to the puller-holes out of some scrap. A 2×4, bottle jack and some bolts and nuts complete the picture. And yes, this is surely a Miller-recommended usage of the Dynasty welder cart.

Spoiler: it ends up working—

*crack* *pop*

Umm, doc? I think we need some more POWAH here

No problem!

Well, there’s your problem right there.

Nothing a whole great smear of epoxy can’t fix

Good as new (that’s not saying much, really)

In order to reassemble the motor I thought more control of the rear case decent would be in order to try to minimize the chance of shaft binding and case snapping. I didn’t know when planning that the force required to press the tailshaft through the rear bearing would be much greater than the magnetic pull between the rotor and stator. So I set up a reverse-puller using three scissor jacks.

Although I ended up whacking the inner bearing race over the shaft using a tube an soft hammer anyways the tri-jack rig was extremely easy to control and secure feeling, I was happy with how it worked even though it was probably not actually necesessary. If you’re attempting this, be sure to keep an eye on the hall sensor wire, pull it back through the grommet as the the motor halves approach.

The freshly rebuilt motor spins freely now and appears to work OK. I didn’t make a mark on the case before pulling it apart so I may have slightly altered the timing (the hall sensors are on the inside of the front case). I don’t feel confident that the motor is as really as good as new, but after seeing the inside of the motor I’m not particularly inspired by the quality of manufacture all around.

Regardless, I think it’ll be a good start for the Kart 

I’ll tidy this up a bit

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It’s absolute overkill. Over a pound of 6061 aluminum, every part CNC machined and yes, it’s just a scotch tape dispenser. This is the creation of the Advanced CNC class at Laney College as taught by Bob Rice. I programmed and machined all the parts from drawings using MasterCAM, a Chevalier toolroom mill and a Haas SL lathe. All the threads were single-point cut and threaded holes rigid tapped. Every part required at least two operations, every face is machined.

1/2-13 threads

1/4-20 threads

The cutter serration was created using a wedge tool I ground from a broken center-drill, plunged into the part with the spindle off and indexed to simply form the teeth. The tool was plunged .030 deep every .025. I wrote the gcode for that bit manually.

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