Why are Motorcycles So Pollutive?

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Why are Motorcycles So Pollutive?

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Let's start with a little-known fact: Motorcycles do not emit less than cars. There's a wealth of evidence to support this but if you want a snapshot, just look at the current EPA regulations - emissions regulations

This is how many grams of hydrocarbons + nitrogen oxides new road-legal motorcycles are allowed to emit per mile traveled, viewed alongside the comparable figures for large SUVs and cars. The California Air Resources Board estimates that even though motorcycles travel less than 1% of the miles covered by Californians, they account for about 13% of the smog - an astonishing figure.

This is surprising, because motorcycles are fantastically energy-efficient - both tank-to-wheel and well-to-wheel, to reuse terminology from my previous post. Even heavy Harleys and hardcore Hayabusas seldom get less than 35mpg. My own 2008 Yamaha WR250R gets an EPA-estimated 71mpg.

The good fuel economy coupled with the world's tiniest gas tank means I can get even farther away from civilization before getting lost and running out of fuel.

(as we can see, energy efficiency and air emissions are two distinct concepts of sustainability. In this post, I limit myself to discussing air emissions, to keep things in scope)

There's a sliver of good news for two-wheeled environerds, however: As CO2 emissions seem to scale proportionately with fuel consumption, motorcycles do emit 25-40% less carbon dioxide than comparable cars. As we know, CO2 is the chemical compound most commonly associated with global warming (both natural and anthropogenic).

But how does it make sense that ultra-lightweight motorcycles, powered by essentially miniature versions of the engines found in cars, emit so much more nitrogen oxides and hydrocarbons, even though they get great gas mileage and emit substantially less CO2? The answer starts with catalytic converters.

Go stick your head under your car and look for one of these box thingys sitting somewhere along your rusted exhaust pipe. These little cans have been on every street-legal car in the US since 1975. Catalytic converters are useful because they chemically reduce smog-causing nitrogen oxides to relatively innocuous elements, nitrogen and oxygen. They also oxidize toxic carbon monoxide and oxygen into carbon dioxide, and they turn leftover hydrocarbons into more carbon dioxide and water vapor. Modern 3-way catalytic converters have drastically reduced the annual emission of nitrogen oxides from vehicle exhausts in the last couple of decades alone; this has had a tremendous impact in helping replenish the ozone layer and putting a lid on the severity of acid rain in the US. These little cans are great, but they're not magic - they convert harmful combustion byproducts (nitrogen oxides and unburnt hydrocarbons) into somewhat less harmful chemicals (principally, CO2). Despite this tradeoff, they do great net environmental good because the additional quantity of CO2 emitted as a result of their use is far less harmful than the nitrogen and unburnt hydrocarbons that would spew out of exhausts otherwise.

Catalytic converters aren't the only emissions control systems on your car. Other devices help too - like air injection systems (which help catalytic converters work more efficiently at lower temperatures) and evap canisters (which keep the noxious chemicals in your gasoline from evaporating out of your tank into the atmosphere). These have been a success story in cars for years; why don't they work on motorcycles?

It turns out these gadgets - in particular, catalytic converters - are pretty fidgety. Catalytic converters alone have to contain precious metals like gold and titanium to function properly and this makes them quite expensive - typically adding $1,000 or more to the price of a new car. They're also heavy, bulky, and some only work above a certain operating temperature (that's why some cars idle really fast on startup - to warm up the emissions equipment quickly).

All of these characteristics of emissions controls - bulky, heavy, expensive, temperamental - have been made to work in the context of cars that weigh 4,000lbs and cost $20,000, but they are antithetical to everything motorcycle. They don't scale well in applications smaller than a car; a good catalytic converter, along with a host of other emissions-regulating components, might only add 5-15% to the weight and cost of a car, but the same system on a motorcycle could possibly double the MSRP, choking the small engine and burdening the lightweight chassis with a lot of proportionate extra mass.

In addition, motorcycles models in America are typically sold in far fewer quantities than car models, so bike manufacturers lack the incentive to invest substantial fixed costs into refining their engines to reduce emissions. Gas bikes have to scrimp on their emissions equipment, and they pollute the air accordingly.

It gets worse when you consider how often motorcycle exhausts are gutted or replaced after leaving the factory. There exists an entire subculture of humans who live for opportunities to bolt more shiny things to their shiny rides.

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I have not been able to locate a number for exactly how many two-wheelers run completely derestricted exhausts, but my anecdotal observations suggest that a large proportion of riders do it - every time you hear a motorcycle roar past at more than ~84 decibels, it's likely running an aftermarket can (the maximum sound law varies by state, but manufacturers usually just produce one model that is 50-state legal). This market for aftermarket exhaust systems is composed of well over 200 companies - each one shinier, louder and more pollutive than the last.

These systems, labeled for "show" or "closed-course use only", are frequently sold to street users with a wink and a tacit agreement not to inform the authorities. Modifying your vehicle's emissions equipment is illegal in the US (even for non-road engines) and aftermarket pipes are seldom equipped with even the pathetic catalytic converters found in stock motorcycle exhaust pipes.

These are not practical people.

While sometimes these exhausts are installed for purely cosmetic reasons (the vanity of the typical chromed-out hot-rodder cannot be overstated), sometimes riders have no choice but to rip out the anti-emissions components and replace them with derestricted substitutes. This is because some motorcycles - mostly offroad-biased competition bikes - are too "choked up" by their anti-emissions gear to even run properly. For example: The KTM EXC enduro machines, street legal since 2007, are infamous for being practically unrideable from the dealership. The evap canisters cause the bikes to stall at intersections, while the excessively lean air-fuel mixture causes erratic engine performance and overheating. Of course, the first thing a rider does after buying such a bike is rip off all the emissions "junk", rejet the carburetor so it burns more fuel and replace or derestrict the exhaust.

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This is a lose-lose-lose scenario - manufacturers are forced to charge more for emissions components that riders consistently scrap, so these bikes are still dumping loads of noxious chemicals into the air and nobody's happy.

So, in answer to our title question: It's not just that gas motorcycles are inherently pollutive - it's a complete failure for our laws to correspond with either the goals of sustainability or the interests of riders. The status quo is not merely unsustainable; it's nonsensical.

It's true that there have been some technological gains in recent years that limit the insanity - most notably, the gradual replacement of mechanical carburetors with electronic fuel injectors for fuel delivery has allowed for very precise control of the quantity of atomized gasoline that enters the cylinder during the combustion cycle. Done well, this reduces emissions without burning up the engine or ruining its performance.

There's still a long way to go before gas-powered motorcycles can earn their reputation for environmental friendliness and efficiency. The question that remains is: Can motorcycle emissions control technology move faster than the politics of sustainability, or is the gas-powered two-wheeler soon to go the way of the banished two-stroke?

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On the Supposed Energy Efficiency of Electric Vehicles

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On the Supposed Energy Efficiency of Electric Vehicles

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Recently I was invited to speak on a Princeton sustainability panel about my budding startup, Comet Motorcycles. Comet designs and produces small runs of electric motorcycles. Because it's based on a cruiser-style platform, it can carry an enormous 24kWh lithium-ion battery pack (the same size as one in a Nissan Leaf) mounted very low in the frame, giving it the longest range of any production electric motorcycle - about 200 miles of mixed riding, according to models based on research performed by MIT's Electric Vehicle Team.

Normally, Comet does not emphasize the eco-friendly side of electric power - we aim to produce the best motorcycles possible, which happen to be electric. However, seeing as this was a sustainability panel, I decided to bring up some points why gas motorcycles are so much more pollutive than people realize - even more pollutive than gas-powered cars! (at least in terms of non-CO2 output). Anyway, I was going over some of the common value propositions of EVs - zero engine vibrations, reduced heat output, and increased energy efficiency compared to an equivalent gas vehicle (which are typically about 17-21% efficient at converting the gas in their tanks into useful energy). At this point, I was interrupted by an audience member who started shaking his head and loudly repeating "That's not true, that's not true! Electricity from the grid is only 33% efficient!"

To flat-out cut off a panel speaker as an audience member, you must be pretty convinced you have a really important, undebatable point. As we shall see, the efficiency of EVs isn't quite that clear-cut, but it's definitely worth addressing if you're going to claim one way or the other. After all, you have to plug your EV into the grid, right?Nissan_Leaf And getting the energy from that grid - which generates its supply of power using ancient coal plants - to run your vehicle can't possibly be more efficient than burning gasoline in an onboard internal combustion engine, right?

Wrong.

To understand this question of EV efficiency, we need to decide what we mean by "efficiency". There are three such concepts that I'll deal with here:

"Tank-to-wheel efficiency" - as the name implies, this is how efficient the vehicle is at taking energy stored onboard and turning it into useable motion.

"Infrastructure efficiency" - this describes how efficiently we can take energy from the "source" (the ground, the well, a chunk of uranium, the sun, the tides, what have you) and put it into your tank.refinery-at-dusk Refineries, power plants, chargers, relays, ports, ships that carry barrels of crude oil across the Gulf - this is a big category for the refining and distribution of automotive-grade gasoline, as well as the generation and transfer of electric power using various source fuels (coal, LNG, solar, tidal, nuclear, etc.). This is also extremely difficult to estimate and you have to view the efficiency of different fuels in terms of opportunity cost and scale - that's a topic for a different post, so we'll just use worst-case estimates for now to get a lower-bound estimate of the efficiency of EVs over internal combustion vehicles.

"Well-to-wheel efficiency" - This is a measure of how much energy from the source fuel ends up as useful energy produced by your vehicle's power plant in the form of motion. By definition, then, this equals Tank-to-wheel efficiency x Infrastructure efficiency, and it's the most relevant, honest and all-encompassing measure of how energy-efficient our vehicle is. (note: To stay within appropriate scope for a blog post I restrict myself to discussing the well-to-wheel energy efficiency of EV vs. gas; I avoid making any claims with reference to the cost or emissions of EV vs. gas)

So first let's talk about the tank-to-wheel of a gas vehicle verses an EV: The EPA estimates that gas vehicles are about 17-21% "tank to wheel" efficient. A Tesla Roadster is about 79% efficient "tank to wheel" (88% chemical storage and conversion, 90% driveline efficient). Here's the point at which most Tesla drivers declare victory and zoom off. Well, we're not done here.

How much energy from the grid's source fuel actually ends up in your Tesla's "tank"? Let's go with the worst case scenario:coal-plant When you burn coal in an old-generation plant you are able to harvest 30% of the thermal energy originally stored in the coal into electricity (newer IGCC plants can bump this number up to over 60%. However, you then have to transmit and distribute that power to home users over the grid - there you lose about 6% of the energy that you generated. (100%-6%) x 30% = 28.2%. This is how much energy from the coal you burned that you actually get at your house where your Tesla is. The efficiency of Tesla chargers is about 92% according to the manufacturer. You multiply that by 28.2% and you get how much of the coal's original energy ends up in your Tesla's "tank" (battery pack): 92% x 28.2% = approx. 26%. Now you multiply that number by the Tesla's "tank to wheel" efficiency and you get 79% x 26% = 21%.

So what we've calculated is that a Tesla Roadster, running off of the least efficient coal plant you can find in America, is around 21% efficient well-to-wheel. That is - coincidentally - exactly the EPA's upper estimate for the tank-to-wheel efficiency of a gas car.

All the Tesla owners just rage-closed the window, but think about what I just said. A Tesla is as energy-efficient as a gas car, assuming that the refining and distribution of gasoline is 100% energy efficient. But I got news for you. It ain't.supplychain-1 Gasoline is actually really hard to refine and distribute. Building crude oil pipelines, lighting up gas stations, making everyone drive to those gas stations to fill up, carrying gas around in big gas trucks, etc. - the infrastructure required to distribute gas is titanic. The refining of gasoline from crude oil alone takes away about 15% of the energy. It's almost impossible to accurately account for all of the other energy-consuming hoops that gasoline has to jump through to get to your gas station and into your tank. So for the sake of being as generous as possible to gas-powered machines, we'll call that efficiency 100%.

Conclusions: We have calculated an extreme lower bound estimate for the added efficiency of an electric car over a highly efficient gas car - 15%. Are electric vehicles 100% efficient? No, not even close. But are gas vehicles as good or better? Definitely not. It takes some calculation and attention to accounting methods that aren't practical to present verbally, but make perfect sense when on paper. This is why you should probably leave the the more arduous arithmetic to the guy with the projector.

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Let's Ramble About Stringed Instrument Bows

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Let's Ramble About Stringed Instrument Bows

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A string instrument bow is a wooden stick with horsehair on it. It actually resembles a bow [and arrow] when you look at it - there's a bendy wooden arch that stretches some string/hair. You hold it at the heavier bit (the "frog") and you pull it along the string. It's really hard to make a good sound like this (I've been trying for ages). However, once you get it, it projects and yields a sustained, beautiful tone. But that never happens. Here follows the fiddly (ha) mechanism at the root of your never ending frustration. To make sound, the grippy rosined horsehair first grabs the string and pulls it to one side, in the direction of the bow's travel (as if someone were pulling the string to pluck it with her finger). The string liked where it was before the bow started pulling it, so it resents this displacement. At some critical point, the string gets fed up and its tension causes it to break free from the hair (as if the finger that was holding the string before now releases it). The string then vibrates at its natural frequency - that of whatever note you're playing on the instrument. Simple enough. The bow displaces the tensed string and releases it, just like a finger plucks a string.

Except the bow's job isn't done. A bow grips, displaces, releases and re-grips a string hundreds, even thousands of times a second depending on the frequency at which the string is vibrating. This is why sound from a bowed stringed instrument can be loud and sustained, as compared with plucking.

However, bowing a stringed instrument is Really-with-a-capital-R hard. You have to apply the correct amount of pressure with the precise bowspeed to make the sound you want. Roll, pitch and yaw are also important - each one can change the sound you're getting as it varies the amount of hair in contact with the string. As you get farther away from the frog, the natural weight of your right hand combined with the heavy frog lessens and you have to compensate by applying a very specific amount of torque to the stick via your right pointer finger, pivoting against your thumb. It's actually a lot to think about and it takes years of practice to iron out all the nails-on-chalkboard squeakiness. I'll let you know if I ever get there.

Many string players underestimate the importance of a good bow - they spend all their money on a violin/viola/cello that fits them perfectly, and they settle for whatever is available when it comes to bows. A good violin (or whatever) can give you loud projection, good feedback and a lot of colors to play with. A bow, however, doesn't just change your sound - it changes you. A good cello might give you a tone made from honey but a good bow inspires you to shape every note as if it were a beautiful tree in a massive forest for which you are Chief Executive Landscaper. Good bows feel agile, responsive and predictable. Good bows are rare and they jump out at you from nowhere.

Rosin is important, too, and it all comes down to preference - how grippy it wants to be, how thick, how sticky it is when it inevitably gets on your left fingers and on your fingerboard, dagnabit. Applying a small amount of rosin frequently (2-3 swipes every hour of playing, depending) yields more consistent results as compared with gobbing it on infrequently.

There used to be this brand of rosin called Tartini Green. They made the best cello rosin in the world. Then they got shut down for some reason or other. I still have a sliver of Tartini Green left in a sealed box in my room, along with a few other precious trinkets. I figure maybe someday I'll get someone to chemically re-make it, if that's even possible. Or maybe I'll just keep it for myself. I'm sentimental like that sometimes.

Anyhow, after Tartini went belly-up, rumor had it that another company had taken their formula and was making the same stuff again. Of course I immediately found the stuff in question - Andrea "A Piacere" green solo rosin - and tried it out. I'm happy to say it's good - but I don't think it's Tartini Green. Then again, the last time I played with Tartini Green was at least six years ago, so my comparison might not be the ideal scientific measure.

Back to bows - since this blog is about me, me, me, I might as well give you a brief history of the all the bows I've had since my first full-sized one, which is about as far back as I remember.

My First Full-Sized Bow. Yeah, I remember absolutely nothing about this one, my parents bought it for me with my first full-sized cello. It worked fine, I guess.

That Dark One Over in the Corner. I put far more thought into my second full-sized bow. I tried every bow at every Houston luthier I could find, including a place called the Houston Bow Shop (they're hard to find online behind all the archery results, but they're there). Finally, at a place called Lisle Violin, I found the one for me - the bow that would take me so far in playing. It's a dark bow. Very light, reasonably rigid. It was ideal for the technical passages that I wanted to boss through. Lisle didn't seem to know what it was and frankly, I never followed the names of all the makers - this was in the days before the internet and I don't much care for name-following in the first place. To my indifference, I soon forgot the name etched into the side of the frog that would later give me quite the surprise.

The Guthrie. Fast forward a couple years to 2007 - I had moved to England and was passively shopping around for bows at a place in Wales called Cardiff Violins (they are fantastic, if you ever get the chance to visit them - great people and a great selection of instruments). I wasn't really sure what I was looking for but I felt confident that I would know it if I found it. I found it in the sheer rigid predictable perfection that is my Lee Guthrie bow. To this day, I've never played another bow that is so easy to use. I had never heard the Guthrie name before but when I took this bow to my teacher at Bowdoin the following summer (Peter Howard), his eyes lit up with recognition. Here I had been all the way to Wales and picked up this bow that, as it turns out, was made by a former civil engineer in the same place where I was made - St. Paul, Minnesota. Pretty cool.

Elias Guasti. Another couple years passed. I had bought a new cello from Reuning Violins in Boston (another wonderful shop) and while I was happy with my Guthrie bow, I really wanted to find one that matched particularly well with my new instrument. So I did the rounds - checked out every instrument shop I could - until I found a very special-sounding bow once again at Cardiff Violins in Wales (the same place where I had gotten the Guthrie a few years prior). This bow, a very late product of Elias Guasti, wasn't as predictably easy to play. It was a little lazier, a little more spontaneous when you put it to the string - but something about it pulled a special sound out of Mira that I could only vaguely imitate with other bows. What's more is it inspired me to think more about my tone, which (as I discussed earlier) is a very important trait for a bow to have. So I bought it. Snag: I only have room for two bows in my case. The Guthrie occupied the coveted right-side pocket and The Dark One was spare. I figured I'd have to leave one in my room so for the first time in years, I pulled the dusty old Dark One out of its pocket and had a look - what was the name of who made it again? To my astonishment, it also bore the (extremely feint) "E GUASTI" name on the side. On two separate continents separated by several years, I had somehow picked two brothers - one young, one old - out of a crowd of hundreds (if not thousands) - and for completely different reasons. The Dark Guasti I picked because it was light and easily flicked, fun and carefree. The later Guasti (also dark-ish, I guess) I picked because it made this subtle but important impact on my sound. Kinda spooky. To this day I usually play the Guthrie when I just want to play for myself but when I'm planning on doing a lot of extra work to make a performance truly exceptional in terms of tone quality, I'll break out the newer Guasti and practice it for a looong time until I get used to its quirks. My obsession with knowing my right-hand technique backwards and forwards as it applied with this particular bow may or may not have contributed to a small stress fracture in my right second metacarpal bone in summer of 2012 but we'll leave that adventure for another blog post.

The Impulse-Bought Carbon Fiber Bow from Amazon. I always half-wanted a carbon fiber bow. It'd be cool because I wouldn't have to lose my mind over humidity or worry if I'm taking care of it properly (the hair still expands and contracts with humidity a bit but fmeh meh feh fmeh). On the other hand, I'd heard from everyone that they're just not very good for playing and you get what you pay for. A bow for a reasonably serious college student might run $3,000 but the CF bows can be magicked to you from Amazon Prime for as little as $30 if you nab them on sale. I had this Amazon-must-be-used-for-everything mentality in my junior year of college so I decided what the heck, cheaper than a rehair (which my "proper" bows both needed), worst thing that could happen is it would be bad. Surprisingly enough, it's actually quite good! For all this talk of "good response" and "special tone" and predictability and whatnot, you can get a perfectly capable bow for less than a rehair. This particular CF bow is almost totally neutral in every way - not too bouncy, nor too lazy, reasonably predictable and just sort of average-feeling. It's consistent between playing sessions and it even sounds A-OK in the few performances in which I have dared to use it. The cool thing about a bow like this is because it's so neutral, it allows you to focus on your technique. Ricochets? Average. Sostenuto? Average average average. Legato? At the midpoint between every other bow I've ever played. If you're short on cash, buy a bow like this and go spend that other ~$2,950 on lessons or time off work to practice.

The Baroque Bow. The Music Department was gracious to loan me a snakewood Baroque-style cello bow for me to use in their Baroque Cantata class, for which I would be playing mostly continuo cello parts. If you've never tried it, it's really cool to see what that kind of bow nudges you into doing. It can be played like a modern bow, but it's very easily flustered in faster off-string passages. It feels kind of like trying to put the family truckster around a technical racecourse - lots of rolling, lots of bouncing around and not a whole lot of control (entertaining, though). There's more of a definite bias toward the lower half of the bow and the sound feels denser overall - I've heard that's because the snakewood is physically much denser than pernambuco wood, if that makes any sense. It loans itself nicely to continuo playing - emphasis at the starts of notes, plenty of time to plan out the perfect distribution and bowing patterns to match vocalists' consonants, etc. I wouldn't play a concerto on it but playing old continuo parts can be challenges unto themselves. Thanks to the aforementioned traits, the Baroque bow also complements certain interpretations of the Bach solo cello suites if you plan it out right.

These are my assorted ramblings and I'm afraid I haven't got much of a conclusion from all my experiences with bows. Play every bow you can get your hands on, pick the one you like most - the price won't tell you if it's good or not. Buy one that will inspire you to play it and somewhere in those hours in the practice room when you're feeling beat up, maybe you'll look down at that stick in your right hand and figure "at least this ol' thing hasn't given up on me yet."

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