Archive for May, 2014


Miscellaneous Van Adventures: Fuel and Coolant

May 21, 2014 in mikuvan

Ongoing van facility improvements have been happening as the semester has been winding down, now that the 2.00gokart season is over.  Strictly speaking, I’m well past the point of needing to do something, but all of those boxes I’ve been getting from Rock Auto over the past few months are starting to be overbearing. I think I have a full roster of parts to replace or fix anything that could potentially wear out or break next – things like a new water pump (like I’m ever going back into that engine), a transmission rebuild kit (it was on sale, OK?!), enough oil filters for the next 100,000 miles, and so on.

I’m doing unnecessary part repairs for two main reasons – first, so that I explore more of the subsystems that might not have been touched since the Bush Administration (no, I mean the first one in 1988), and second because I’m putting off more bodywork. On that front, I’m glad to say that all of my back-alley work has survived the winter.

One of the things that I was going to do immediately last year, but of course dropped because Well It’s Working, is the C-Clamp of Thermostat Flange Retaining:

I noticed this flange had a broken bolt as soon as we dug into the engine bay in the very first van adventure of OPERATION: BAD TIMING. It was the cause of a minor coolant leak. The seller did mention it went through coolant and he just topped off the radiator as needed, so this was probably the root cause. I threw a 2.5″ C-clamp on it just to hold the gasket together and mostly resolved the problem for the next year.

Over many cool-hot cycles, the C-clamp began to creep and every once in a while I’d have to tighten it some more, or there would be small dribbles of coolant the next time I had to bust out Vanpower for backup. As summer approached, I figured I would need the cooling system functioning properly again. I caught a break during winter, where it had enough trouble keeping warm – keeping the heaters on would drop the thermostat needle to near cold after a few minutes in short trip operation.

It was time for the C-clamp to be returned to MITERS.

Step 1: Remove the upper radiator hose and thermostat flange to reveal the seized and broken bolt. Remove gasket in about 100 small pieces, because that’s how servicing this thing just happens: assume every gasket has already disintegrated by the time you lay eyes upon it.

Step 2: Apply heat guns, vise grips, and cheater bars for half an hour and shear the remaining stud off. This thing is in there hardcore.

Step 3: Decide to drill and tap a smaller bolt down the center of the larger one, instead of trying to drill this one totally out.

Step 4: Discover that your drill plus bits are too long to fit in the gap between the engine block’s flange and the radiator.

Step 5: Purposefully break two drill bits to make them short enough to fit. I executed two of my shop’s precious tap drill sizes to make this happen. I’m ready to be tried for war crimes.

But it got the job done. I punched a center mark as accurately as I could, then used the small drill bit to pilot and the large drill bit to break through the bolt. Luckily, the small tap wrench fit in the available space just fine. I threaded this hole in M6 x 1.0. The original bolt was a M8.

Finally, add high-temperature gasketing silicone compound and let it all soak for an hour or two, then tighten down the bolts a little more.

Pitching the system back together! I have yet to find a new droplet spot, so I assume it’s at least asymptotically solved.

Next up, Charles plays with gasoline!

The fuel system is one of the last things I have not looked into, besides the transmission (which I will accept is run by elves and unicorns). I know the condition of the upper half – injectors, filter, and the like, but not the fuel pump. I bought a fuel pump on Rock Auto months ago because I knew it was a part that could potentially wear out, and because it was on sale for $19.99. I figured if nothing else, I would use it as Chibi-Mikuvan’s motor coolant pump.

As Maker Faire Bay Area approached, I was entertaining the idea of driving cross-country to meet up with the west coast crew. Well, wouldn’t it be embarrassing  if the fuel pump quit halfway for some reason? At this point, I wasn’t sure of the exact operating mechanics of an automotive fuel pump, just that mine might be as old as I am.

To replace the fuel pump is a procedure which involves dropping the fuel tank from the underbody regions. Reading the service procedure for this was where I first learned that modern fuel pumps reside inside the fuel tank itself. Hmm, for some reason I always thought it slurped the fuel out through a straw or something. This is, again, where I point out that automotive engineering is an entire other world, knowlege-wise, from “mechanical engineering” defined broadly. It’s something which if you don’t pay attention to, you’d never know.

So up on stands we go! Prior to this was when I filmed vansaroundboston: a purposeful 30+ mile drive (that video was 1/3rd of it) to empty the tank to the last gallon. I unloaded this through the fuel tank’s drain plug.

First up in the service procedures was to remove the easy stuff. High pressure hose, return hose, and filler hose. This was where I figured the pump might have been worn out or on its last legs in some way – the service procedure called for disconnecting the power supply and then running the engine until it stalled from loss of fuel pressure. Well, I couldn’t even get it to start. My reading told me that there’s check valves and the like in the pump itself, so if those parts were leaking or failed, the pump would lose pressure instantaneously upon shutdown. So maybe this was a worthwhile gasoline-derived brain melting adventure.


The high pressure and return hoses coming off. There were a few other hoses and tubes to remove:

These disassembly drawings always show the part or subsystem in isolation, ignoring the fact that it was all buried in between 90 other parts, a frame rail, and the source of my oil leak. For instance, after the filler hose, high pressure hose, and return hose, I had to remove the vapor hose and fuel pump connector.

which is above the driveshaft and on the back side of the tank, you fuckers. Then, the vapor hose was literally impossible to get to in the stated order. If I, he who doesn’t look out of place in cosplay as Hatsune Miku herself, could not get his hand above the fuel tank with a hose clip plier to reach it, then how was anyone else going to?

I left these two connections to be removed after I unbolted the tank itself, which was also a Three Stooges-like experience, except there was one stooge only. When I untightened the four bolts retaining the tank, it didn’t budge. I banged on it from the side a bit to see if maybe there was another hidden bolt, and the whole thing falls onto my face.

Granted, it fell less than an inch, but it did weigh 15 pounds or so empty. I got a great black smear on my nose for this one.

After a half hour of avoiding the oil leak sludge Self-Applying Undercoat while underneath, here’s the tank! It sure looks like this hasn’t been touched in a little while.

Observe the green can of CRC brake cleaner. I actually like using non-chlorinated brake cleaner for everything, because it seems to be just high pressure acetone in a can. Mild, but effective in combination with the spray jet. I use it to clean the shop bandsaws, or, in this case, to chase grime off the fuel pump flange.

Real brake cleaner is made of tetracreepywhatever, is much more effective, and dissolves like everything. I have a few cans of this that I only break out if lesser solvents can’t do the job. Like leaded solder, I figure this substance is going the way of the dinosaurs for being not part of this complete breakfast, so I’ll enjoy its disconcerting odor while it’s not banned in Massachusetts, unlike in California.

Undoing the 5 bolts holding the flange on, I reveal the fuel pump unit. It has its own little pre-filter attached that seems well-coated in goo.

Here it is side-by-side with my new pump unit. The old one isn’t in bad shape. Though it’s been in an environment that’s been majority-occupied by hydrocarbon vapors, which tend to preserve steel, and it’s still this tarnished, so who knows how old it actually is? I couldn’t find a date code, but did find a Nippon Denso logo. Unless the last service for the fuel system used OEM parts, this might be original equipment.

Strapping the new one in now.

Reinstallation was straightforward. I called for backup for someone to hold the tank while I started threading on the bolts, which was a nasty surprise for him because I didn’t say anything about the layer of oil sludge coating the underside of the fuel tank. I’m sorry, Julian. It was, indeed, quite gooey.

After I had the old fuel pump out, I was quite curious as to what went into one. The Internet™ had told me it was a DC motor running an impeller-type (centrifugal) pump. What the hell? Why would you put a brushed DC motor with its sparking commutator and all into a gasoline tank?

I proceeded to machine this thing apart using a metal lathe:

First to get popped off was the end with the impeller. I just took a cutoff tool and jammed it in until something fell off. It seems pretty normal here. A volute shaped chamber and a many-blade impeller.

Many cuts later, I popped out the rotor of the pump. Okay, it really is a brushed DC motor running submerged in a bucket of gasoline.

Now, I know this is actually the best possible place for such a thing, surrounded by cooling, nonconductive, non-ionic fluid, above its vapor explosion limit, that carries away the brush dust wear… In the grand scheme of things, it isn’t bad. But you know that trope that says you know obscenity when you see it? Well, this is obscene. I’m now afraid of every car that drives by.

Inspecting the state of the commutator and brushes, I concluded that the fuel pump motor itself was nowhere near failing and could have run for many more miles. However, not knowing the service interval of this part, I’m still satisfied with its replacement.

I’ve replaced about all the subsystems that can be replaced now. What’s next? I suppose I have these little boxes full of driveshaft U-joint parts… or I could go do more bodywork.

2.00gokart: The 2014 Season!

May 11, 2014 in Electric Vehicle Design

It’s over!

Another spectacular season of 2.00gokart has been produced! This time, instead of holding the garage challenge like I have done in the past, I decided to reuse the “road course” that our group put together for the summer SUTD visiting students. Why?

As awesome and science-filled the garaging is, it’s kind of boring. It’s a great theory-to-reality comparison: the mostly-straight course (Let’s face it, 100 foot turn circles for a go-kart is basically just bad toe trim), is all uphill at the same grade the whole way, and of consistent traction characteristics. It’s easily analyzable by relatively simple first order estimates of gravity, rolling resistance, air drag, and drivetrain loss.

But its downsides are also many: there’s no line of sight from one garage level to the next, so we had to use a network of 2-way radios. The narrow concrete-lined end turns required padding or shielding to satisfy the safety office and make sure students don’t actually wham themselves (these two goals are mostly divergent). And of course, to collect the best data, only one team goes at a time, so there’s no head-to-head element, and a lot of waiting.

I  put together the road course idea because the summer students weren’t really in it for grade or explicitly to learn some engineering curriculum. Since that artificial carrot was gone, I figured that the final competition should be a lot more fun-oriented, and what’s more fun that running your peers over with a go-kart you build yourself?

This isn’t to say that science isn’t possible to do, since the Energy * Time metric works for any type of motion with two endpoints. It’s just that for a road type course it’s harder to predict without going into more advanced modeling of friction/scrubbing during turns, the impact of speed variations, and the like. For the summer, we did collect energy * time numbers, and it did provide practical insight into subjects like why two karts of basically the same powertrain layout could have drastically different scores.

With that said, here’s the media trail from just before the infamous “Milestone 7″ rolling-frame inspection, through the semester to the competition itself, ending with the compilation video for this year.

As the inspection approaches, it’s customary for students to find any open nook or corner to work on their vehicles. Usually it’s exactly where the vehicle died or some part fell off.

A common setup in the few days leading up: Food, drinks, headphones, Solidworks, and intent staring.

The inspection itself constituted a visual overview to check that your frame is rigid, your bolts are tight, and so on.

And, of course, the brake test. Your teammate pushes you to a brisk jogging speed, then you mash the brakes. My measure for passing is if the braking wheel could lock up – that indicates, at the least, that the vehicle’s available braking force exceeds its available traction. Karts with short wheelbases and rear brakes would of course excel at this test, albeit at the cost of actually being able to stop well in real life.

After Milestone 7, the teams have three weeks until their kart has to be done done (not just done, but like, done-done!). Good luck with that, Google Translate.

The last 3-4 weeks of the class are generally reserved for electrical work. I issue batteries once students put together their electrical systems and I or one of the TAs look over it real quick to make sure they aren’t immediately plugging it all in backwards. Later on is okay, of course.

In the final week, the shop enters tornado disaster mode.

Electrical system testing and debugging was some times performed live.

By which I mean, actually with live systems. I tried to discourage this practice, of course, but with no moral authority to stand on….

One thing I wanted to experiment with this year was getting onboard video from the karts. This was something I hadn’t had time to think about before, since the class before this point hasn’t been streamlined enough to “run itself” (so to speak). I investigated a few options, from GoPros to Sony Actioncams and the like, even the odd wireless webcam. I was looking for a combination of small  and unobtrusive, inexpensive (so that basically took out GoPros), and streaming video if possible. After some consideration, I remembered that there was a burgeoning market for no-frills small cameras that stuck to something and recorded: Cheap Chinese dashcams.

I only know them because I watch too many Russian dashcam videos. I honestly believe it should be a compulsory element of drivers’ education here, but Americans are probably too squeamish for that. Anyways, these Chinese dashcams offer a wide array of features – some have GPS, automatic G-sensor based file saving to capture the fucker hitting you while parked, voice and motion activation, etc.

All of those features aside, what you get is a relatively inexpensive ($100 or less covers it) camera that can record HD video and is easily portable, and that you won’t miss if it gets run over. I decided to forego streaming video for the ability to have many of them: By this time, I’d already worn down the class budget to a little stub.

Reading a little on dashcamtalk, I decided to go for the latest on the market: The GT680W. It’s resold under a couple of brand names in the U.S., but all of them talk to you in Engrish when you boot them up, as far as I can tell.

My only gripe with the GT680W ended up being its very short battery life. It has a very (very) small internal battery that’s only good for maybe 10-15 minutes of recording outside of a power supply. I’m guessing this was an acceptable compromise for a dashcam because most of the time it would be powered off the car’s 12V rail, and the job of the battery is just to close the video file when the power is turned off.

I provided a ball mount template to the students so they could devise their own creative mounting brackets for the camera’s stock ball and socket mount, which is seen above. Since they’re designed to hang from windshields, the ball mount it comes with doesn’t point back far enough to be used on a level surface.

Lots of dashcam footage was collected during the race, and some of it cam be seen in the highlights video!

As final inspection day approached, students began scrambling to finish important aspects of their vehicles such as the gaudy lighting and themed decorations.

During the week of final inspections, I set up a makeshift track around the conveniently looped shaped third floor of the building, mostly by setting traffic cones out and warning people working in the research labs that they need to yield before merging into the hallway. This was more or less when people started discovering that they should have listened to me when I warned them against chain drives…

The next thing everyone knew…


…it was race day! The track was set up the night before by myself and a few cohorts, so all we had to do in the morning was run power to the parking lot and set up the start and finish. All  of the pictures from here on are courtesy of shewu and Dane.

Being next to a power plant and all, you’d expect there would be easily-accessible outlets everywhere. No such thing – our only source of power for tools and charging came from a 150 foot extension cord run from like halfway inside the plant. I in fact had to walk around with a plant staffer for a minute before we even found one. Last summer, I used one that was much closer to the door, but this time when we tried, the circuit was clearly turned off, and the staffer was not an electrician, so he didn’t know where the circuit breaker for that one was.

A morning shot before we began at 9am and before this area became a total disaster too.

Driver’s meeting! I go over the track layout, the competition format, and various logistical issues such as the nearest class 1 trauma center.

At 9AM, runs begin with individual driver time trials – quite similar to Autocross. We rigged the karts with Wattmeters as per the usual procedure, so people could record their energy usage. Each driver got two practice laps and three scored laps.

Some live debugging going on. This team has a build blog! It needs updating! Hint, hint.

By midmorning, the pit area has become a tangle of power supplies, chargers, and soldering iron cords.

During the lunch break downtime & recharging time, I took a stab at my own course with Chibi-Mikuvan!

Having about 3 times the available motor power of my students, I of course, took the best lap time at 20.7 seconds. The quickest student team was 25.6 seconds. This is clearly indicative of my years of experience and accumulated skills.

Yep. Totally.

Chibi-Mikuvan catching a dab of oppo. I’ve now realized that it’s entirely possible on dry ground if I keep my weight forward a little (i.e. hang off the handlebars a little).

After the individual runs were finished, we entered Anarchy Hour, with multiple head-to-head races. Whoever had a grudge to settle from the term did it here!

Coming into the center hairpin turn just a little too hot…

Those fluff bricks were set up for a reason, and they performed admirably.

By this time in the early afternoon, vehicles from across campus had started showing up for Anarchy Hour. Seen here is bentrike, tinykart (not that tinykart, though maybe next time), and a few Electric Vehicle Team members.

Ben, of course, hands everyone their collective asses.

Watch out for this guy – not only did he revive LOLrioKart, whose wreckage  has been hanging in MITERS since 2011, but is up to plenty of his own no-good.

After everyone’s batteries finally ran down, it was time to pile the race apparatus back into the truck!

From here, the students have a final presentation this coming week to recap their builds and talk about their competition performance, then it’s time to clean up from the semester.

My thoughts for this time around:

  • I believe the class in its current form has reached a stability plateau. With more created lecture material, this semester I wasn’t running around answering basic reference questions so much as helping people with designs, which is good. The procedures for the semester are now well established and I feel like I can throw another race next week if I needed to. I think the class is very close to a fully exportable form, though that isn’t the primary goal.
  • More documented lecture material would still help. A few things I can think of immediately: Design for Maintenance needs to be its own thing. It should be a lecture of best practices and tips for making your creation easy to repair. Most people, myself included, have made things which require almost complete disassembly to change a simple part. Or, there’s 5 different screw heads and required driving tools to, say, move your motor mount a little. Another example would be more resource/parts appraising tips to go along with the lecture that is an overview listing. How do you know when two parts are the same across different vendors?
  • I think a different “secret ingredient” each term would keep it interesting. I also phrased it in the grand overview as a “ground point” for the design, but basically  it’s the free thing I give to students that they can accept if they’d like, so the less experienced can start somewhere. This term, it was the 8″ Harbor Freight Pink Tires for America which many teams took because it freed the budget up for something else. I’m heavily considering something ridiculous like omniwheels for the summer season. Anyone have experience with Vex omniwheels in a high speed traction application?!

And finally, as promised, the highlights video. Doses of insulin for your impending diabetes are to the right.

So ends another season of 2.00gokart! I have some shop organization to do in the coming weeks before the Singaporeans get here, and I also hope to finish the last little details of Chibi-Mikuvan.

After the races were over, I decided to try using a GT680W in its intended application. Well, to be fair, I don’t think they meant for it to be used in this particular mounting configuration…

I approve of the night video capabilities of this thing, which I think is almost equivalent to my 2010-era handheld camcorder, except without optical image stabilization. Being so flat, it buffers in the wind too, contributing to quality loss. I think for a $90 camera there is not much more to be asked.

The Turbulent Rise of Chibi-Mikuvan

May 02, 2014 in Chibi-mikuvan

After much engineering ado, it’s time for tiny van shenanigans!

This test was the first done with the NiMh modules from the Ford Fusion battery whose construction was detailed previously. I’d say subjectively the pickup is as strong or even stronger because of the added traction of doing it outdoors, coupled with the much larger wires (no more 12 gauge and Deans connector bottleneck) of the LiPo test pack. However, since I don’t have (yet) a Wattmeter-to-150A-Anderson-Powerpole adapter, I haven’t metered it proper. I do know that indoors, I’m traction limited at 3600 watts (as in no matter how hard I gun it, the rear wheels will just slip, leaving a thick trail of itself on the waxed linoleum hallway floor and making the reesarch center administration murderous).

One of the potential plans is to get a Cycle Analyst digital dashboard system or similar. Or, since I already have processing power in the back, and the salvaged current sensors from the Fusion pack, to just make my own.

The terrible sound at 0:47 was the pinion of the angle grinder gearbox slipping its taper seat, unscrewing itself, and then falling off. It continued to jiggle and tumble in the gearbox as I pushed everything back upstairs. It’s now repaired – I didn’t torque the locking screw properly the first time because it’s in a hard-to-access spot where a regular hex wrench couldn’t get to.  After this experience, I cut down a standard L-shaped hex wrench until the short leg did fit.

To complete this round of build details, here’s the last bit work on the battery pack before the outdoor test.

After adding the tie rods to hold the endcaps together, I decided that an intelligent thing to do would be to make an easy way to lift the battery with one hand. I used the left over black 1″ wide cargo strapping which was part of the ratchet strap holding the electronics deck down, along with some rivets and washers, to make a handle. This worked out great, and I have enough of the strap to make 2 more batteries at least.

This is how the battery mounts in the frame, with the two knobs on the sides. Since this is a less than half sized battery from the original design, and the two knobs up front are directly opposite one another on the same axis, the pack can pivot forward and backward right now if the knobs aren’t super tight. Clearly not optimal. I’ll probably just resolve this by adding two bars to the front and rear of the battery pack, such that once dropped into place, they can no longer pivot.

Once I confirm that design, I have enough modules from the Fusion battery to make three more spare packs. The knobs allow the battery to be dropped out quickly, so having a ton of spares on charge during a PRS race makes sense.

And a “press shot” outside in the parking lot.

What’s missing at this point is the water cooling system for the Trackstar motor.  After the numerous high-power takeoffs during the test, the motor was hot but not unhappy hot – I could still hold onto it. But, it’s clear to me that if I want to run above 1000 watts for a long time, it’s going to need the water cooling loop. This will come after the 2.00gokart race when things quiet down a little bit.

It also doesn’t have the wye-delta switching contactor assembly I wanted to incorporate, but I’m of the opinion that the speeds attainable by the Delta termination is utterly unnecessary for an event like PRS. The project top speed under this condition is north of 40mph, which is a domain already well optimized by, like, real Mikuvan.

Here’s the final details…

Cheat Sheet


I started this project as a museful distraction in October of last year after returning from the New York Maker Faire and mingling with the Power Racing Series folks for the third year. Having seen the league grow immensely, I decided to finally enter something while exploring new and unusual components for hobby builders (my usual MO) while also wanting to see a change away from the “model year bloat” I saw in many teams, who started using heavy forklift motors and other salvaged industrial components. Hence, the focus on R/C electronics and non-lead chemistry batteries.

Work on the project began more in earnest with this season of “2.00gokart“, since I figured I needed to have an instructor vehicle to troll my own students with.

The project was my first jump into making a composite bodied anything, motivated in part by the bodywork repair I’ve had to perform to real-Mikuvan.

Build History

In chronological order up to the previous post, here’s the process of Chibi-Mikuvan creation from conception to implementation:


The project is named Chibi-Mikuvan after its principal design predecessor, the Chibikart twins which were the “prototypes” for the design class I teach today, and my 1989 Mitsubishi Delica known familiarly as Mikuvan.

It has little to do with Chibi-Miku-san though a few large decorative decals would not look out of place on the shell. I’m an avid follower of the crowdsourced synthetic Japanese future girl-pop that you’ve never heard of world of Hatsune Miku and Vocaloid. That’s literally the most concise way to fully describe it, as I have learned over many difficult discussions about what the inglorious shit is it that’s playing all the time in my shop.



  • Top Speed: 25mph (as-geared, Y-termination)
  • Acceleration: to 25mph in < 3 seconds
  • Braking distance: < 30ft from top speed
  • Skidpad: Uhhh, gimme a sec.
  • Clearance: Still not enough for the Maker Faire cable protectors
  • Drivetrain: RR layout, 1 speed, spool axle (no differential)
  • Dimensions: 50″ L, 28″ W, 24″ H
  • Weight: 113lb with battery
  • Seats: 1, though if Chibikart was any indication to go by, up to 7.

Bill of Materials

Here’s the latest iteration of the BOM (5/1/2014 version), which contains at least 95% of everything on the thing, short of the trivial like zip ties. I went into much more detail than the average PRS list; the quality is a little more closer to what I expect out of my students when it comes to found parts and used parts. Everything, to the degree possible, is given a Fair Market Value which sort of artificially inflates the cost a little. While technically over the PRS $500 statutory budget, I believe this is a more realistic representation of the cost needed to replicate this once.

The BOM has 3 cost categories. First is the actual money I spent. I had a fair amount of parts already on hand, but did have to buy things full-price like the Ford Fusion battery pack and the motor & controller. Next is the PRS rules based accounting, exempting some things like brake parts. Finally, what this vehicle would cost under my 2.007 EV Design class rules, where some raw materials are provided to the students so they only need to count materials if they need to be purchased additionally.

Future Work

I plan to finish building the water cooling rig in the coming weeks, as well as play with the nice automotive-grade Hall Effect current sensor salvaged from the Fusion pack. For the telemetry/dashboard, all I’m really interested in is instanteous volts, amps, watts, and cumulative watt-hours spent, and all of that info can be gleaned from a voltage sense (easy) and current sense (also easy with the sensor). I do need to build more battery packs, and create or buy a dedicated Giant NiMH Battery charging solution. I have a Hyperion 1420i charger that can blitz into this pack well, but having more chargers would be essential in a race scenario.

Also, make more silly magnetic stick-on anime faces.

And as usual, some fun times in our proving grounds, the spirally garage: