Tuesday, March 9, 2010

Because It's Beautiful Part 2

Once I looked out over the mouth of San Francisco Bay with the eyes of a surfer. As the tide fell millions of gallons of water drained into the sea at the narrows below the Golden Gate. Yet, against this tide huge ocean waves rolled in from the deep against the flow of water.

My wife spreads the white top sheet over our bed. Standing at the foot she grasps end and with a deft snap sends a wave of motion down the length of fabric. The uncooperative end of the sheet whips itself into alignment and together we spread the coverlet.

There are moments on a motorcycle when an engine seems to come alive. It acts with an uncanny precision and willingness, it seems to almost sing. There is, of course, a reason for this. We speak of tuning an engine and imagine that this speak is figurative, but it often isn't. It's often literal. It turns out that calaculators used to design pipe organs work very well for creating good working four stroke exhaust systems.

Connected to an engine there is an exhaust and an intake. These are not just tubes routing fuel and gasses to and from the engine, they can perform useful work.A four stroke engine turning 5000 RPM opens its exhaust valve 41 times per second. Every time this happens a "slug" of air moves out of the engine and into the exhaust header. Once the valve is closed the "slug" of exhaust gasses keeps moving but since it's in a sealed pipe, the exhaust header, it creates a partial vacuum behind it.

In addition to the physical movement of gas described above pressure waves move up and down the exhaust pipe much, much faster than the physical flow of gasses in the header. When we lit firecrackers as children we felt that pressure wave. It wasn't wind, like the flow of gasses. Never the less, it could do "work" like remove a finger.

In my original example of waves traveling into San Fransisco bay against the tide I attempted to demonstrate that waves of energy can flow against current in the media that carries them. In the case of San Francisco bay both forces are powerful and move in opposite directions largely irrespective of one another. In the case of Priscilla spreading out fresh linen I wanted to show that a wave can move though media and release it's energy (flipping the end of the sheet into the desired location) once it "crashes" on the shore.

Exhausts are tuned by changing the length and diameter of exhaust systems and how they join together. The powerful pressure wave that escapes the exhaust port when it opens races down the pipe and is reflected back as a negative wave everywhere the pipe expands.

If things are timed right the negative pressure wave arrives just as the port is opening and sucks the spent gasses right out of the combustion chamber. If it's at the magical moment when the intake valves are open it can also suck clean charge in from the air box as well. Conversely there must always be a positive wave as well. That means that at some other RPM or throttle position the opposite is happening. A positive wave is arriving that is forcing dirty exhaust into the combustion chamber.

There are people that think that when you add an aftermarket exhaust to an engine that you are "uncorking" it. That, in some sense, is true. When we add a "slip on" exhaust or debaffle a stock muffler we are simply increasing the amplitude of the wave, making it more powerful. In a sense we are making the effect of exhaust tuning "more good" or "more bad". When the positive wave arrives forcing dirty air into the combustion chamber a slip on muffler this happen in a way that makes things much worse instead of simply worse. When the negative waves arrives pulling exhaust helpfully out of the combustion chamber we are making things much better instead of just better.

A well designed exhaust system works with an engine to so that its positive tuning effects happen in often used parts of the rev range or at places where the engine is weak and could use the help. Conversely it "hides" the negative effects behind engine strengths or in seldom used location.

I can describe the characteristics of exhaust tuning with some accuracy but so what? It can all seem quite clinical or logical or exploitable; like we can own it in some way. I feel a divide between knowing and wonder that I want to break down. I want joy and wonder to be part of the equation and support my world view with equal shoulders, even in reason's inner sanctum. It may be weird to understand exhaust scavenging as a wonder, but it is.

When I started to find the answers in bedsheets and ocean waves I began understand this: Something isn't beautiful because it works, it works because it's beautiful.

Saturday, January 23, 2010

Because it's beautiful.

The engine has moved into the realm where airbox volume and exhaust pipe length conspire to create a perfect storm and revs build magically. I am not sure what sounds angrier, the motor or the wind around my helmet. I’m a little startled to see how close the sun dappled pavement is, hanging slightly off the bike and looking at onrushing Wilton Road between the clutch lever and the rearview mirror.

We’re well into, “please step to the front of my vehicle and place your hands on the hood” speeds. Perhaps closing on triple the speed limit, but I am unsure of how it’s posted here. The bike comes upright. I concentrate on keeping my breathing even and steady, to stave off any panic that might come. My mind is, blissfully, given over to my body.

High on the ridge the road opens onto a straight boarded by meadow. I back off the throttle because there’s no sense in carrying any more speed between corners. In the high summer the light it is bright enough to bleach everything. The tans and greens of early August fuse into muted pallet joined at the hip with cicadas and the smell of bar-b-q.

For no good reason except the bike is fully upright, I drop two downshifts and let the motor pile against itself. The rear wheel hops and chatters until I squeeze the front brake. When wheel and engine speeds match and the rear hooks back up. Its sloppy technique, but I allow myself the pleasure of it.

The left turn is now at hand. The rider in front of me blinks off the long straight on onto Damant Road, which follows a brook of the same name into the valley. He rides like Hailwood, bolt upright on the bike, all long graceful arcs. I have no idea how it works for him, but it must.

I can’t see much into the corner, as the road there is deeply overhung with trees. The bright light of the open makes it look black to my eyes; but the front end is compressed and I am already off the side of the bike holding it upright by pushing the grip forward. I snap it into the turn.

Damant falls sharply away from the ridge, and the transition is abrupt. The whole bike goes light, with the suspension topped out. Everything is weightless midcorner at the exact moment I am shifting my body to the other side for the right hander fast approaching. My eyes come into focus, adjusting to the deep shade under the canopy, the bike touches down and we are away, like sparrows.

Later, that evening I am more than a little drunk and riders are gathered by a fire. I hear some conjecture about why the moon looks so big on the horizon and listen to their explanations. To my addled brain, none sounds right and offer this: “It’s because when you look at the moon on the horizon it’s distorted by the curve of the atmosphere, which acts as a lens.” I am drunk enough to listen to myself talk as if I someone else were speaking and I think, “sounds pretty good!” To my surprise I hear myself add, “but my mother, who is Italian-God bless her, would tell you “because it’s beautiful.”” And, just then, I know which answer is right.

Sunday, January 10, 2010

Olga's Story Part 1

We’re at a sidewalk table in front of Sam’s CafĂ©, the three of us, as usual. It’s warm, almost still hot. Our three black chairs, and a fourth vacant, surround the small metal table a little too crowded against the weekenders here that come to our main street on afternoons like these.

Luke is in fine fettle, and I shoot Barry a quick sly smile. Luke pantomimes the position of the motorcycles with his hands; held like knives in the air, leaning this way and that. He’s showing how earlier we had come against the chain of Harley riders just before approaching the best section of the mountain pass.

He’s becoming more excited now, the pressure of the whole situation: the potential for oncoming traffic to ruin things, how it all must go just right, judging their lean and hoping they would run wide so we could cut inside them and continue our morning unabated run by their rolling roadblock.

Having only two hands but explaining the location of many things in space Luke is pointing into the air all around him, recreating our run up the mountain in a small invisible world hovering above the empty fourth chair between us and the tourists on the street.

Luke and Barry and I have become older men than we once were, but somehow wear the role of middle aged men costumes. Luke has recently taken to waxed cotton gear and looking, somehow, “weathered”.

I look beyond them, not really hearing the story anymore, now watching he broad pink light reflect off the stained glass of the cathedral. Still, Luke is good at this physical story telling. I can see the whole road this morning as he has painted it in the air. I can feel the tension in his body, setting up the long chain of bikers for the pass. His hands whirr becoming the knife edged leaning motorcycles, then his hands are on the throttle and clutch, then pointing out obstacles or drawing curves for these ephemeral bikes to motor though.

He rubs his fingers together to show us sand, or covers the back of his palm his other hand for leaves. We are mesmerized. Even though both Barry and I were there this morning here we are there again, heroes nostalgic for a recent past and reliving it now.

At last, Luke gets to the pass, he pantomimes the three bikers lining up and running impossibly wide in the right hand sweeping turn. Barry and I both smile as he show us by creating a broad blocking arc with his left arm, as if to hug a round friend, he traces a quick arc inside this with his right hand. Us, streaking by heroically!

He rises from his chair, lips sputtering lips in pantomime motorcycle sound and hands on the bar, his left showing the upshifts as we shoot past. Now we’re running hot into the next corners, things are falling apart. Luke continues to point it objects in the air his hands and us as motorcycles knifing though the imagined landscape.

He hooks of foot around the empty chair he has risen from and, either in a moment of brilliance or clumsiness hurls it into the stream of sidewalk tourists before him. It clatters creating space for him to continue his story unabated and now frantic.

We had been frustrated, trapped behind the bikers, and now rushed headlong into the pass. Luke reaches out with cupped hands into the arc of tourists the chair has created and says quietly to them “a rabbit, you see, a little bunny, in the road” the tourists are immediately taken in. He’s now got a fake British accent, “my mates and I were going too fast on our motorbikes this morning, when at rabbit should appear on the road” and explains the pile up. Barry running a great distance on his front wheel, me into the woods, him slewing wildly and the silence thereafter.

The Harley riders, dispatched with great pomp moments before now parade past us serenely. The police await, fruitlessly, around the next bend

Luke, satisfied with his story rights his chair and sits down. The tourist, so taken in moments ago are a bit slow to leave. Nobody says anything for a moment or two. Barry lights a cigarette, the gap created by Luke’s antic closes up and the tourist continue in their stream to where ever they go. We look at out bikes parked at the curb.

After a time I say, “let me tell you boys a story as unlikely as it is true, of an old woman, a great love and a motorcycle” I close my eyes and again find myself in Olga Sleutin’s world. For a moment I just sit eyes closed there on the street with my friends, but in her cold room this springtime, on the third floor, above the garden.