Its really poor form to quote oneself, but sometimes one just can’t help it.
I’ve been thinking for a while about the fundamental changes that our reliance on vehicle electronics have helped cause in the automobile and motorcycle design fields. All of the so-called electronic driver or rider aides have allowed us to create a kind of ‘artificial stability’ which has taken the place of creating fundamentally stable vehicles.
That mediation is in the process of being written, but this piece, which appeared on the Internet BMW Riders listserv more than 10 years ago, was the first time I dealt with the issues of tractability and fundamental stability under less than optimum conditions.
Maybe it was the fact that my ride home from work Thursday night involved significant amounts of sleet and light snow. Or maybe it is the fact that Maryland’s weather report is looking at something like a 40 degree temperature drop across the next 20 hours or so, and that I haven’t felt my fingertips since I got out of bed this morning.
Whatever it may be though, taken all together this just seems like the right story for this slippery, freezing day. And it will give us a place to start when I talk about the physics behind ‘Rolling Physics Problem’.
***
Riding On Black Ice Redux
(or how i learned to quit worrying and love the beemer…)
Generally, you can’t teach people anything.
Oh, you can attempt to impart information, sometimes even useful information, and in rare instances, you can even attempt to impart wisdom. But when it comes right down to it, there are some folk for whom only first hand experience teaches and everything else just bounces off.
Now we’ve had some heated conversations around this campfire lately about how to ride motorcycles when traction conditions don’t seem to favor same. In fact, with all the heat, one would think that all of the ice would have melted, but no matter.
These conversations, when they weren’t causing me to spit coffee out my ear — Thanks, Chip! — caused me to flash back to how I learned that riding on black ice is ill-advised. I will state for the record that all of the herculean feats described here were performed under uncontrolled conditions, in the middle of a busy public highway at rush hour, using not-quite-enough-safety-equipment-for-my-tastes-thank-you-very-much, and that their description here should not be interpreted as any type of endorsement or inducement to attempt same as crunching, disfiguring injury, maiming and/or death can reasonably be expected to result.
Whatever would we do without proper legal advice, eh?
I’ve spent most of my adult life in Maryland, a state that folks will quickly point out doesn’t really have a true winter. I won’t dispute that claim, having earlier lived in upstate New York and New Hampshire, both of which clearly do.
But therein lies the attraction of the state to motorcyclists, and the danger, as well. It rarely goes below freezing for extended periods of time in Maryland, and far more customary in our “winter” months are nights below freezing and days in the mid forties.
Freeze. Thaw. Freeze. Thaw. Freeze Thaw. Sometimes 7 times a day.
A perfect recipe for black ice formation.
The Toaster, as it appeared at the time.
Back in my poverty rider days, my toaster tank Slash 5 was daily transportation come hell or high water. I discovered that the high water part was nearly as ill-advised as the black ice on the day after Hurricane Agnes came through Maryland, but that is another story.
My daily commute then took me from my apartment in Cockeysville, a northern Baltimore suburb, to Linthicum Heights, a southern suburb with a location placing it at the intersection of I-95, the The Beltway and the Baltimore Washington Parkway — if you were trucking anything in or out of Baltimore, this was the place to be.
It was mid-February, and the previous night we had likely had several of the previously mentioned freeze and thaw cycles. I was probably less than a mile from my destination, having flailed the toaster down the Jones Falls Expressway into the city, jogged a few blocks west across the city center, and run down Russell Street onto the Baltimore Washington Parkway. I had done 20 plus miles on a freezing morning, and was happily lost in thoughts of a warm cup of coffee once I got to the office. I was a big Kenny Roberts fan at the time, and as I hit the ramp from the BW Parkway onto the Beltway, I was heeled over and smoking, hanging off just a little to the inside. The ramp ahead looked clean and dry.
Appearances can be deceiving.
As I hit maximum lean, something strangely disconcerting began to occur. The rear end of the bike began to gently, but firmly walk out. I know, that in me, anyway, huge doses of adrenaline make everything go into slow motion, so that may have been happening here. But the rear end headed toward the outside of the corner, and the further around the corner we went, the further left the rear end went.
“DO….NOT…..GET…..OUT…..OF…. THE GAS…..”, said the little riding instructor that lives in my head.
Listening intently, I stayed well into the throttle and shifted my weight back to the bike’s centerline, and slowly panned my head to the left as the bike’s forward progress began to appear more progressively sideways. Finally, by the top of the ramp, the toaster was at full left steering lock, the rear tire was spinning to beat the band and together we were doing a great impression of Grand National Dirttrack legend Gary Nixon, right down to my adrenaline locked jaws looking like GN’s race face resulting from several too many broken/wired jawbones.
As the ramp straightened back out, something wonderful began to occur. Just as the bike had sloooooooooowly walked out from under me, now, it slooooooooowly walked back into line. At the point where I’d normally be looking over my shoulder and accelerating into beltway traffic, the wheels were all pointed in the general direction of travel, and I was looking over my shoulder and accelerating into beltway traffic.
My office location was at Hammonds Ferry Road, whose exit is less than a 1/4 mile from the thrill ride I’d just completed.
My corner entrance speed on that ramp was, understandably, somewhat more conservative.
My workmates were accustomed to poking at me for my hard-core winter riding habit.
“Hey Hotshot, you need a cup of coffee?”
“No thanks, I AM AWAKE.”
So, in an AEsop fable, this would be the point where someone with baritone voice intones, “SO, what have we learned?”
And that question cuts right to the core of why I ride BMWs. On a tactical level, I now understand that pavement that looks dry doesn’t necessarily have to be. The BW Parkway ramp in question was a particularly porous mix that is unique to Baltimore, in my experience, and from the perverse mix of stick and slide, i would say was a 50-50 mix of dry pavement separated by black ice — the spaces between the pavement grains were filled with water that then froze.
On a more fundamental level, though, it was an object lesson in applied physics, and underscores why they should continue to stress that subject in public education, especially for folks who might want to drive someday, and doubly so for folks who might take up motorcycling. Does anyone remember their lesson in phenomenon called gyroscopic precession? Gyroscopic precession is the strange force which pushes a spinning object 90 degrees from its axis of rotation.
The Honda CB750/4 that I owned right before I bought my /5 had a transverse motor with an engine flywheel that spun inline with the wheels. When one lost any combination of front or back wheel traction, the precession of the engine flywheel would almost instantly push the front tire off line, wash it out and put you down on the pavement before one could even give voice to the “Oh, shit” that the situation demanded. After this happened a few times….”ouch!” ….. “ouch!”……”ouch”…..etc…. most folks will start looking for a better way. I know I did. (Ouch!)
The boxer and classic K brick engines have transverse flywheels — the flywheel spins across plane of the wheels. When one loses any traction, the precession of the engine flywheel has a much less dramatic effect on the alignment of the bike — the whole machine may slide towards the outside of the corner, but absent other upsets, the wheels basically stay in line — in effect, one gets an extra fraction of a second to gather it up and correct things — a second chance at it. This transverse flywheel layout is a much more forgiving type of platform, from a basic physics and stability perspective, than most other motorcycle engine configurations — most V twins, L twins and inline transverse twins and fours. Just BMW, The Gold Wing and ST1300 and MotoGuzzi seem to have built their bikes around this realization. For competition, the extra turning effort is a competitive negative — but for thousands of miles on the street, that extra chance can have you ahead by a lifetime.
So personally, I have stuck with transverse flywheel BMWs, and they have helped me save my own bacon more than once.
Oh yeah, and I try to avoid riding on black ice.
Rolling Physics Problem 