Newton's Day vs. Michael's Day

Newton's Day

Today was the BEST day ever! I thought it was going to be just another everybody-leaves-day 'cause my girl-hooman woke up when the beeping happened and didn't stay in bed to cuddle AT ALL. That means it's a everybody-leaves-day. She put on her leaving fur and then drove off in her sick-box. Then my guy-hooman did the same thing...except he didn't drive off! He came back inside and changed into his staying at home fur and then he took me outside! I got to hang out in the front yard all day. I got to lay in the sunny grass and pee on the tree and some neighbors came over to play with me! Then my girl-hooman came home earlier than usual. It was the best day ever! I'm so tired now that I need a nap.

Michael's Day

I thought today was going to be just another workday, but boy was I wrong! I got dressed and went out to drive to work, but I couldn't shift gears. My clutch wasn't working. I went back inside and did a little research on the internet and realized that I had one of the necessary parts to fix the problem. Unfortunately, I didn't have the other part I needed, so Alison offered to go pick it up at lunchtime and work from home for the afternoon. So, I set to work in the driveway and took Newton out with me since he enjoys being outside. At least the weather was decent. I was hoping I could get the job done in time to go to work for a few hours, but I finished up at 5pm...it took me all day! I think I fixed the problem, but it still doesn't seem quite right so I might have to do some more adjusting. *sigh* What a crappy day. I'm so tired now that I need a nap.

P0097, A Miata Success Story

I must say my ScanGauge II OBD-code reader has paid for itself;  I've used it---in conjunction with the internet, of course---to solve another ECU-related issue with Mia, my Mazdaspeed Miata.

Over the last few days, the check-engine light began illuminating intermittantly, principally when acccelerating and turning simultaneously, as when pulliing away when you get the green turn arrow you've been waiting for.  The CEL has usually been accompanied by mild hesitation of the engine.  Today, Mia threw the code repeatedly.  Each time, the code was the same:  P0097.  After I got home, I went straight to Mazda-Speed.com, the forum dedicated to my exact car.  It turns out that P0098 means, to paraphrase, "intake-temperature-sensor voltage too low," and this code is frequently reported on the MSM.  It seems that the wiring to the intake-temp sensor rubs against the edge of the sensor housing anytime the engine moves, which can cut through the wiring's insulation, shorting of the signal.   That sounds like it could be what's going on, I thougt, and headed out to check under the hood.

Sure enough, the intake-temp sensor's housing is hexagonal, and its edge has a clean, 90-degree angle.  The sensors leads are insulated, but not physically protected from the housing against which they rest.  The signal line---I believe it was the signal, rather than the ground---was worn down to the conductor.  I wrapped each line in electrical tape, then wrapped the two lines together.  A quick spin in the car verified that I had indeed fixed the problem.  

It makes me happy to repair a twentysomthing-thousand-dollar* car with 10 cents worth of electrical tape.

* MSRP, not what I paid.

P2187, A Miata Success Story

Recently, Mia's check-engine light has been coming on intermittently. Thanks to my ScanGauge II, I've been able to read the code, P2187, and clear it to see under what circumstances it recurs. P2187, as the internet will tell you, is the OBD-II, code for "too lean at idle," or something to that effect. I poked around on Miata.net* and Mazda-Speed.com** and found that this code could result from a number of sources, including a bad manifold-air-pressure (MAP) sensor, a leak in the intake track, a bad oxygen sensor, and so on. We are still clearing out the garage in the Grondulbarn, so, as of this morning, I hadn't taken a close look in the engine bay to further diagnose the problem. In the last two days, I've also noticed, thanks to my boost/vacuum gauge,*** that the vacuum level at idle was about 10 inches of mercury, higher than the usual 20-ish. Finally, today, I observed that the car's maximum boost seemed to be around 6 pounds per square inch, instead of the normal 8.5. It was then, on the road, that I realized that there must be a leak in the intake, somewhere in or near the manifold. That would explain all three symptoms: Air leaking in at low load, when the gauge pressure was negative, would yield a lean condition and a too-low (in terms of absolute value) vacuum, while air leaking out at high load, when the turbo was spun up, would give too little net boost.

Unfortunately, I didn't---and still don't---know much about the vacuum systems of the car. At my first opportunity, I put the hood up and went right to the only vacuum line I knew of, the small-diameter line leading off the back of the intake manifold and going to the...something, where I had T'ed off a line to the sensor for my boost gauge. As luck would have it, the 3-inch line between the manifold and the T had several cracks! So, I drove to the nearest auto-parts store, bought a few feet of the right-sized vacuum line for a few bucks, and cut and installed the line using the leatherman that lives in my trunk. Et voila, everything returned to normal! I'm Brian with the overhead projector about my parking-lot repair, as I'm sure you can tell.

Anybody need some small-diameter vacuum line? I have plenty to spare.

* The largest online community dedicated to the Miata, which has great resources in the Garage section and also has one of the best-run automotive fora I've visited.

** A forum dedicated to the 5428 Mazdaspeed Miatas produced.

*** This gauge measures the pressure in the intake manifold, so it performs, I think, essentially the same function as the built-in MAP sensor, but instead of being wired to the car's computer, it has an analog display for the driver. Interestingly, the gauge's negative range (called vacuum) is marked mm Hg, and positive range (labeled boost) is marked in PSI. I guess those are the conventional units for these two measurements---at least in the hegemony of the Imperial System---but I think it's strange to use two different units to measure opposite signs of the same physical parameter.

An Ten Uh

I've long been a critic of powered accessories in vehicles. Power windows, door locks, mirrors and such increase cost, add weight, consume power, and decrease reliability compared to their manual counterparts. Unfortunately, my Miata, Mia, came with "power everything," and it has caught up with me after only half a year of ownership. A few weeks ago, my power reacting antenna failed, and in the lowered position. This failure meant that I could only listen to CDs in the car. Fortunately, my desire to listen to new music and the NPR withdrawal I've been experiencing has motivated me to address the issue.


I could have tried to repair the motor, but I elected to replace the antenna with a fixed one, and I was glad I made that decision when I pulled out the trunk liner and saw how enormous the OEM antenna/motor assembly was. The photo above illustrates the size of this assembly, most of which is due to the motor.


The new antenna is one of the stubby kind that are so common today. It's not the tiny shark-fin style, but it still looks fairly sleek. It has an amplifier built in, to compensate for its short length, which means it must be tied into the car's 12-volt system. Fortunately, since the original antenna was powered, that operation wasn't difficult. Even with the amplifier, the new antenna only extends down into the car about as far as the red marks on the OEM model.


After the installation, I confirmed that the radio works again. It sounds fine, so I'm quite pleased with this minor modification.

When I set out to take these photos, I realized that I haven't documented a couple of other small changes I've made to the car. More on that soon.

Popular Blogging: Nerf Modding, Alyson Hannigan, Mazdaspeed Miata

I looked over Industrial-Strength Science's hit history recently and several trends have emerged:

• One trend that is decidedly not new is that searches for phrases like "Nerf Maverick mod" produce the largest number of hits.
  
• Another trend is both new and surprising: We receive a lot of hits from Google Image searches for Alyson Hannigan. I find this surprising because no images of Ms. Hannigan appear on the blog, though I did link to numerous photos in this post.
• The third trend is also surprising. Searches for phrases like "Mazdaspeed Miata tire size" and "MX5 2004 tire 16 inch pressure" not only have pointed numerous folks at the blog, but also place us as the first result. Hunh.
  

It's Alive, It's Alive: Replacing a Dead Roomba Battery

Recently, after more than a year of good service, our Roomba robot vacuum cleaner stopped working properly. It would reverse out of its dock at the scheduled cleaning time, then immediately play the "I'm tired" music and return to its dock. This behavior indicated to me that the battery pack wasn't holding its charge, and a search of the internet revealed that many Roomba and Scooba owners were experiencing the same problem. Apparently, iRobot was cutting corners with the OEM batteries.

The internet also showed us that the battery pack was composed of 12 sub-C-sized 3000-mA-hr NiMH batteries and a thermistor wired to 3 connectors. I thought about buying some higher-capacity batteries and rebuilding the pack using the existing temperature sensor, but then I came across this item for sale. It offered slightly more capacity than the stock batteries and was cheaper to buy than I would pay for the same batteries, retail, plus it included a new thermistor. Thus, I decided to purchase it. Then I saw this pack, which offers 40% more capacity, and I knew I had to get it.

The new pack arrived last night, and we set about modding the Roomba. The major problems with this operation were unscrewing the odd, triangular (not Tri-Wing) screws that hold the battery case on---this ground-down Tri-Wing screwdriver wasn't a perfect fit---and pulling apart the glued-shut case. After Alison took care of de-casing the battery, I set about soldering the connectors onto the new pack while watching Top Gear. (I guess I should have said "whilst" watching Top Gear.) We charged the robot up overnight---the new pack takes 1.4 times as long to charge---and this morning, the Roomba vacuumed the floors without hesitation.

So, not only have we fixed the instant-fatigue syndrome, but the robot can now clean for 40% longer than it could when new. I'd call that a successful repair.

How-To: Fix Bunching, Moving Floor Mats

My floor mats have been driving me crazy! Perhaps a little explanation is in order. The driver's floor mat in my old-enough-to-drive-itself 1991 Honda CRX has always bunched up and moved around. Maybe my clutch-depressing technique is unusual. Maybe my tiny feet and stumpy legs are the problem. Whatevs. The point is, this issue has plagued me for all of the 11 years I've owned the vehicle. I was recently inspired the fix the problem by a post of the CRX Community forum. Here's how you, too, can have smooth, stationary floor mats.

Cut apart an old wire hanger. (Joan Crawford and my own mommie dearest would be proud.) Then straighten the 2 "shoulder" pieces as much as possible:


Next, bend them to an angle approximately matching the footwell of your car, probably about 45 degrees:


Place the mat over the edge of a coach or what have you to approximate the correct curvature and use duct tape to fasten the ends of the wires to the mat. It's important to get the bend in the correct location.


Add more duct tape to keep the hanger parts in place:


You may not have copious amount of adhesive hook-and-loop (Velcro) closures in your home liek I do---Take that!---but you can buy a box of a meter or so for a few bucks. Cut the hook side into 2 to 4 strips, whatever works best for the geometry of your mat, then stick them firmly to the underside of the mat. Be aware that you may have some kind of rubber mat built into your car's floor carpeting. You need to ensure that the Velcro will land on your carpet and not that built-in mat.


Take the mat out to the car, position it carefully over the spot where you want it, and press it down into the carpet. You may need to press on the curved area to put the correct bend into the wires.

I've had this hacked---ahem, customized---floor mat in my Rex for 2 weeks, and it hasn't bunched, moved, squirmed, or otherwise irritated me. I consider this little project a success.

Nerf Maverick Revolver Cylinder and Limiter Mods: The Belles of the Ball

I occasionally poke around on the SiteMeter page for Industrial-Strength Science. It gives me a heady, Big-Brother-like sense that I know way more about what people are doing on the internet than I really should. I find the By Referrals page (under Recent Visitors) to be the most interesting. It shows on what page a visitor clicks to be directed to The Official Blog of Team Grondul. There are many referrals from our friends' blogs, like ToddUlmer.com, briBreakfast Blogger, Diving into the Wreck, and, recently, Atomic Nerds. Additionally, there a numerous visits resulting from Google searches for assorted, seemingly random phrases. None of that surprises me.

What does surprise me is that, for the past few months, the single largest source of hits are searches for phrases like "nerf maverick mod." Apparently, a lot of people are interested in modifying their brightly colored and huge-but-harmless revolvers to reload more quickly and shoot slightly further. Who knew?

How-To: Nitro-to-Brushless Conversion: Part 6

Part 5 can be found here.

OK, this post isn't so much a how-to as an update on a previous how-to, but I feel that keeping the title consistent is important.

I've been quite happy with the performance of my brushless-powered Losi 8IGHT, but I couldn't resist tweaking it a bit. Below is a list of some of the changes I've made since my last post, several of which were predicted therein. Most of these changes are clearly visible in the photos that follow the list.

• I successfully tamed the motor braking. The car still stops quickly, but it's more controllable, and now I don't feel like I'm going to damage the motor every time I slow down. I really would have liked to use the disk brakes that came with the kit, but there just wasn't room for the servo required to operate them.
• I've replaced the batteries and speed-control's Dean's connectors with 5.5-mm bullet connectors. The bullets will have lower resistance at high currents. This higher conductance is important, since I expect to draw close to 200 amps for short periods.
• I added a second temperature sensor, this one is thermal-epoxied directly to the motor. Now I can monitor the temps of both the motor controller and the motor. I've found that both temperatures mostly stay below 130 degrees F, which makes me feel confident that I'm damaging neither component.
• I've replaced the single battery tray with 2 smaller ones, which allows me to hold 2 6300-mAh 2-series LiPo batteries. I've soldered the batts together in series, giving me a 4-series LiPo with 26% more capacity than my single 5000-mAh batt. This change should not only give me longer runtimes, but also higher currents and thus more power. Additionally, the new setup creates an almost perfect left-right weight balance. As a bonus, the new battery configuration also fills previously unused space on the left side of the car, making it look a little more efficiently laid out..
• I've mounted some Pro-Line Moab tires on orange Kyosho 10-spoke wheels, which are visible in the first pic. The tread on these tires has a good multi-purpose pattern, useful for on- and off-road driving. Additionally, these tires have transverse ribs on the inside, which helps prevent them from ballooning at high wheel speeds. Not only will these ribs keep more tire in contact with the ground, but they will also keep the tires glued to the rims. The wheels, by the way, are probably my favorite 1/8th buggy wheels; they are both well made and attractive.
  
• Speaking of tires, I also found some GRP Rally tires, which I mounted on orange Kyosho 5-slot dish wheels. These wheels and tires are visible in the second pic. In addition to being made of a surprisingly sticky compound, these tires have an extremely low profile, which not only keeps them from ballooning, but also reduces side-wall flex during corning. They don't absorb jump-landing impact as well as higher-profile tires, but that seems like a good trade-off, given that they are intended for on-road use. The major downfall of the tires is their outside diameter; they not only look too small on the vehicle, they also necessitate a significant gearing change. I'd really prefer tires with the same profile mounted on wheels about 10 mm larger in diameter. The wheels, meanwhile, aren't as attractive as the 10-spokers, in my opinion, but they do give the car a somewhat futuristic look, which I find pleasing. I think they certainly look better than the stock dish wheels. (These wheels actually look quite a lot like the wheels that come stock on the Honda Civic Hybrid, which, being a hybrid, is meant to look all future-y.)
  
• Gearing is, of course, determined by terrain, but I've been running mostly 15/39 on the road and 14/39 or 13/39 off. It's much easier to change the pinion gear (mounted on the motor shaft) than the spur gear (mounted on the center differential and holding the viscous silicone fluid therein at bay).
• Since my electrified car is heavier than the stock nitro version, especially with the larger batts, I've stiffened the suspension, cranking up the front and rear spring rate by 14% and 19%, respectively. I also increased the damping concomitantly. The suspension is now set to something much closer to the truggy version of my buggy.
  
• I've replaced the stock plastic steering knuckles (axle carriers), servo-saver arm, and servo arm, with their hard-anodized aluminum counterparts. This change should rigidify the entire steering system, resulting in better steering in high-speed situations with only a slight weight penalty. Several other hard-ano aluminum parts are available for the 8IGHT, but I'm not convinced that they offer improved performance or that, if they do, said improvement justifies the additional weight and cost. Incidentally, only the servo arm is visible in the first photo.
  
• I've also purchased a Pro-Line Crowd Pleazer 2.0 body, which I've painted almost identically to its stock counterpart. I don't think I like the CP2 as well as I do the stock body. I'll put up a pic later and let you be the judge.
• I haven't had a chance to measure the top speed of the vehicle to see if the larger battery and taller gearing had an effect. Certainly the car seems fast enough, and the acceleration is more than sufficient for my purposes.

How to Meat People and Be Loved

I think I've just found Nick's Halloween costume.

Touch Them with Your Own Noodly Appendage

Those members of the readership who both (a) are pastafarians---at least Brian---and (b) enjoy Halloween---probably all seven of you---may be interested in this article showing you how to make your own Flying Spaghetti Monster costume.

Mmmm...Fleshworms

I've certainly dropped the ball with respect to Halloween-hacking posts this year. Still, regular readers will know that Make's blog is the place to go to find inspiration for costumes, props, and even food. Food? That's right; check out these fleshworms. Mmmm...fleshworms.

How-To: Mod a Nerf Revolver: Part 2

My last post demonstrated how to modify the Nerf Maverick revolver to let the cylinder swing all the way out and spin freely. This post will show you how to mod the "weapon" to shoot slightly farther.

First, disassemble the gun as a I described last time. Then pull the cylinder out. Pry off the orange plug pressed onto the end of the axle, which will allows you to pull the axle out.


The cylinder is made of two parts. Unscrew and remove the back part, and you will see the orange spikes onto which the darts, which are hollow, slide.


Pull the spikes out, and you will find a spring and flow limiter behind each one.


Discard all 6 of the flow limiters and 5 of the springs. Put the spikes back in place and reassemble the cylinder, but don't put it back on its axle yet. This omission of the limiters and the springs will allow more air to flow to the darts.

Slide the reserved spring onto the axle. Then slide on the cylinder. The spring will help keep the cylinder pressed up against the plunger mechanism, thus preventing air from escaping between the plunger mechanism and the cylinder.


Now reassemble the revolver and unleash your fury upon your spouse. Or on a smooth, flat surface. Your choice.

In our testing, Team Grondul found that a gun with the cylinder mod from the last post and the mod describe herein fired, on average, about 5 or 6 feet further than a gun with only the cylinder mod, when all 6 darts were discharged from each gun while it was held at an angle of about 30 degrees.

How-To: Mod a Nerf Revolver: Part 1

A long time ago in a blog very nearby, I reviewed the Nerf Maverick revolver and promised to post a how-to on the mods I've made to it. Here, finally, is the first of them:

In stock form, the Maverick's cylinder only swings out about 20 or 30 degrees, just far enough to load a couple of darts at a time. Additionally, the cylinder doesn't spin continuously; its rotation is quantized into increments 360/6 = 60 degrees. These 2 shortcomings make reloading in the heat of a harmless, foam shoot-out time-consuming and frustrating. This post will show how to mod your Maverick's cylinder to swing out about 90 degrees and spin more freely, increasing both the reload speed and the all-important coolness factor.

Place the "weapon" down on its left side. Remove the 3 screws holding the slide together. Remove the slide.


Remove the remaining 8 or so screws holding the right half of the frame to the left.


Lift out the cylinder, along with the gray front and rear arms that support it.


Examine the front support arm, and you will find a nub that prevents the arm from swinging out of the frame.


Use a utility knife to cut off the offending nub.


You are now halfway done. Examine the left frame, just to the rear of where the cylinder would sit. You will find another nub, this one preventing the rear arm from swinging out freely.


Cut that nub off, too.


Now reassemble the gun.


The cylinder will now swing out all the way and spin easily, enabling quick reloading and fun, nontoxic Russian roulette.


Your newly modified Maverick can now be used to rain brightly colored, suction-cup-tipped terror down upon your young nieces and nephews. But not your dog; that's just mean.

The second modification can be found here.

How-To: Resurrect a Dead Trimmer

I own a small beard/sideburn/other trimmer that I get quite a bit of use out of. I don't use it to cut my hair evey 3 or 4 weeks; I have another one for that. Instead, I use it to make my sideburns the desired length and angle, to trim the hair around my ears---which lets me go another week between haircuts---and to trim the hair around the back of my neck after a haircut.* The particular model I own has several different-sized detachable cutting heads, which fact makes it extra useful.

Anyway, the thing started acting up on me not too long ago; it just wouldn't hold a charge. I suspected that the batteries were at fault, especially since consumer electronics containing rechargeable batteries often use low-quality batteries, and said batteries often loose their capacity after comparatively few charge cycles.

Not wanting to lay out the cash for a new trimmer when I could probably fix mine, I pried open the case, revealing guts of the device:


As you can see, it uses standard AA-sized cells. If I'd been more careful with my camera, photo below would show that the particular batteries in this model have a nominal capacity of 600-mA-hr.** That stated capacity isn't great, and I can assure you that the batteries were doing much worse than that in practice. I happened to have 12 rechargable double-As in the house at the time, all of which were rated with higher capacities. I wanted to reserve 2 sets of 4 for my RC transmitter, which left me with twice as many as I needed to fix this problem. Groovy.


There was just one very minor wrinkle. Despite the blurriness of the pic, you can see that the two AAs were permanently wired in series by a thin metal---steel?---strip. I duplicated this arrangement with my new cells using a short length of fine-gauge wire:


I inserted the new double-As into the trimmer, snapped the case closed, and charged it up. Guess what? No luck. Crap. And here I thought I was being soooo smart.


I realized, after cracking open the case and tracing the trimmer's wires more carefully, that I had put the batteries in wrong orientation, left-to-right. I repositioned them, reclosed the case, and recharged the batteries. It worked this time. Ta-daaa!

So, the take-home message is this: Don't let The Man keep you down by buying new consumer products when they stop functioning; reach for your tools instead.

* Actually, I usually get Alison to do that last part. Ah, the joys of marriage.
** Or mAh, if you prefer.

The New Robot in Town

iRobot's Roomba robot vacuum cleaner has been redesigned, and the new model looks to be just as hackable as the first.

How-To: Nitro-to-Brushless Conversion: Part 5

Part 4 can be found here.

We have finally arrived at perhaps the most interesting part of this how-to on the conversion of a Losi 8IGHT 1/8th-scale buggy from nitro to brushless/LiPo power: the installation of the motor, battery, ESC, and supporting components.

Here are a pair photos of the completed car without the body or battery:


This photo shows the 5000-mA-hr battery in place:


You can see a few important aspect of the car's construction from these pics:

• I've put everything except the battery on the right side of the car or along the centerline. Id did so because, as I said, the battery is quite heavy. With the 5-A-hr battery shown, the weight is distributed slightly to the right, but with the larger 8-A-hr battery, the left tires carry more weight so I think my arrangement is a pretty fair compromise.
• You may also be able to make out the custom speed-control mount/heatsink that I bent and cut out of 5052 (bendable) aluminum. I'm quite pleased with it; it places the ESC near the centerline of the vehicle and keeps the ESC running cool.
• The little circuit board thermal-epoxied to the top of the ESC is a temperature sensor. I plan to put another on the motor. Since the transceiver and servo run off a 5-V voltage regulator, I added a voltage sensor---really just a pair of wires with a Rx/servo connector on the end to the setup. You can see the leads disapearing into the ESC's input connectors in the photos.
• I've dispensed with the front and read disc brakes, which normally sit just ahead of and just behind the center differential. Instead, I'm relying on motor braking. It seems to me that disk brakes are more efficient, from a current-draw standpoint, but I just didn't have room for the servo that would actuate them.
• As I mentioned last time, I had to grind the motor/diff mount down to fit under the body. (The part was actually made to fit the Losi 8IGHT-T truggy.)
  
• Those of you who know me are aware of the significance of the number I've chosen to place on the wing.

Here're a few photographs of the car with the body on. I'm very pleased with this particular color scheme. It addition to being attractive---at least, in my opinion, which is the only one that matters---it has proven itself to be quite visible from distance. Incidentally, I wonder if Lokai and Bele could find common ground by agreeing on the virtues of this paint job.


Next: some shots of the car with road tires---Pro-Line Road Rages---mounted in place of the dirt-track tires---Pro-Line Crime Fighters¹ ---shown above. I also purchased some extra-knobby all-terrain tires---Pro-Line Badlands---for more rugged surfaces.

This last photograph shows how I measured the weight distribution. Yes, those are season box sets of Star Trek: Deep Space Nine. And yes, that is the second Trek reference in this post, but I'm not some kind of raging Trekkie; these boxes were the first objects I could find that are all the same thickness, and very close to the thickness of the scale.


At this point, the conversion is done, and I'm quite please with the way it turned out. The car accelerates like nobody's business. The acceleration is far better than a nitro-powered buggy can produce, since nitro engines' torque peaks at many thousands of RPM, while the motor in my buggy produces full torque at zero speed. The vehicle also hits remarkably high speeds. I used Alisons GPS receiver² to measure the top speed to be 41.8 mi/hr with a 14/48 pinon/spur and the road tires. (This test was done on a straight, nearly flat strip of asphalt with nearly no wind.) Additionally, the buggy remains flat---doesn't roll---in corners, and it can be slid very dramatically on smooth pavement.

I only plan minor tweaks from here on out. Here are some of the changes I'd like to make, in approximate order of precedence:

• Adjust the motor braking. It's way too aggressive at the moment.
  
• Add a second temperature sensor to monitor the motor itself.
• Add another strap (or some other component) to the battery tray to hold the larger, 8000-mA-hr batteries in place securely and cleanly.
• Replace the Deans Ultra Plugs I have on the batteries and the input to the ESC with 5.5-mm bullet connectors, like I have on the motor and the ouput of the ESC. Deans aren't really meant to be used over 50 amperes, while the 5.5-mm bullets can be run up to 200 amps.
• Experiment with gearing. A simple pinion change to 15/48 should put the vehicle just under 45 mi/hr. If that doesn't hurt the low-end acceleration, I might go to 15/47. I suspect 15/48 will be close to the ideal gearing, though.
• Experiment with the suspension parameters. The setup suggested by the manual is pretty good, but I think I should stiffen it up a bit, since the car is a bit heavier than the nitro version.
  
• Possibly solder the ESC directly to the motor to reduce loss and improve reliability. I'm not sure if that step will be necessary.
  

I would be remiss if I failed to point out that I got a lot inspiration and information from the forum at RC-Monster. com. Users BrianG and glassdoctor, as well as Mike Cronin, who runs RC Monster, were especially helpful.

Your comments and suggestions are welcome.

¹ Pro-Line's tire names, especially those designed for off-road racing, have a criminal theme to them. I addition to the aforementioned Road Rage and Crime Fighter models, there are also the Cell Block, Mugshot, Inside Job, and Dirty Harry. It not clear to me whether the Knuckles model counts.
² We have named the device Garmin Tanzarian.

Part 6 can be found here.

How-To: Nitro-to-Brushless Conversion: Part 4

Part 3 can be found here.

After a couple-month-long hiatus, during which I pursued some of my other hobbies, I recently returned to working on the brushless conversion of my Losi 8IGHT 1/8th-scale buggy. And to posting about it on Industrial-Strength Science. This part of my how-to concerns selection of the electronics and associated parts for the vehicle.

The motive force for the car, and indeed the centerpiece of the conversion, will be a NeuMotors 1512/2.5D. All Neu's 1512 motors are rated at 1200 W of continuous power and 2500 W for 30 seconds. This particular motor has a Kv rating of 2000 RPM/V, which means that, with the nominal 14.8-V potential difference supplied by my batteries, it should spin up to 29,600 RPM. That should be fine, because the 1512s aren't meant to spin above 60,000 RPM. The manufacture claims that this motor is "86+" percent efficient. I'm not sure how they measure that---it seems to me the efficiency will vary strongly with voltage/current/speed---but the point is this motor is much more efficient than any brushed motor. Here's a photo of the Neu:


As I think I said before, a brushless motor running off a lithium-polymer battery is truly 2 great tastes that taste great together. The high efficiency of the BL motor combines with the high current capacity and low load-induced voltage drop of the LiPos to deliver lots of power to the wheels, propeller, or what have you. For now, I'll be running a MaxAmps pack consisting of 4 LiPo cells in series. Each cell has a nominal voltage of 3.7 V and a capacity of 5000 mA-hr, so this so-called 4s pack has nominal voltage of 14.8 V and a capacity of 5000 mA-hr; the capacities do not add. This pack is claimed to be capable of putting out constant currents of 20 C---that's 100 amps-for a 5-A-hr battery---and burst currents of 50 C---250 amps for 5-A-hr. The downside to this pack is that, even though LiPo cells have much higher specific capacity than nickel-cadmium or nickel-metal-hydride cells, this battery is just plane huge. You can't determine the size from this photo, but it will be apparent when I show it in place in the vehicle:


Because brushless motors have electronic, rather than mechanical comutation, a brushless-specific electronic speed control is required. I've chosen a Quark 125-B Monster Pro, which is claimed to be capable of sustained currents of 125 A and 10-second bursts of 180 A. Here's a pic:


The Quark ESC has a built-in "battery-eliminator circuit," which is simply a voltage regulator that allows you to pick off 5 or 6 V from the supplied higher voltage to run the receiver and servo, rather than including a small "receiver pack" battery to provide that lower voltage. This BEC is resistive and thus inefficient. In order to reduce power consumption, I'll be using a transitor-base switching regulator, which is more efficient. Here's a shot of this external BEC:


To disable the ESC's BEC, I simply cut the positive power lead coming off of it; since that BEC is resistive, I believe that mod should prevent it from sucking up current. I should point out that Nick taught me that resistive power supplies are less noisy than switching types, but, since I'm not trying to build a fiber laser for optical metrology---at least not today---I'm more worried about efficiency than noise.

The only part I bought that was specificly---more or less---made for this project is a motor/differential mount I purchased from Mike Cronin at RC Monster. This mount replaces one of the diff mounts and allows the motor and its pinion gear to mesh with the spur gear on the diff. I said "more-or-less" because the part was actually made for converting the Losi 8IGHT-T, the truggy¹ version of my buggy. Since the buggy body is "skin-tight," while the truggy's encloses a lot of unused volume, I found that the mount rubbed on my beautifully painted body. So, I had to grind off the upper outboard edge of the mount. Here's a photo of the unmodified motor/diff mount; the modified version will be visible on the completed car:


To hold that ginormous battery in place, I also purchased a machined plastic battery tray from RC Monster. I modified this part as well, which I'll show you later.


I also custom made a mount for the ESC that places the speed control near the centerline of the vehicle. I don't have any photos of that mount, although I'm Brian with the overhead projector about it.

I mentioned before that I'll be using a Nomadio Sensor radio, which has several nice features, including telemetry and noise insensitivity. Here's a photo of the transmitter:


Part 5 can be found here.

¹ A truggy, at least in the world of RC, is a "truck" that is really a modified buggy. Typically, a truggy has these features:

• The chassis is a slightly lengthened version of a buggy's pan chassis.
• The suspension ams linking the wheel to the chassis are lengthened.
• The wheels arnd tires are truck components.
• The body is similar to the stylized "stadium truck" body found at the 1/10th scale.
  

i pwn j00, f00!

I've started writing sh shell scripts at work. How cool am I? I guess I should brush up on my Leet.

MAKE Yourself a Single-Speed

Regular readers know I'm enamored of single-speed and fixed-gear bicycles. Now you can join the one-gear movement. MAKE magazine's weekend project for this week is converting a bicycle to single-speed operation. You can check out the podcast here or the comic-book pdf-cast here.