Cycle News - Archive Issues - 1970's

'" '" "f I lL THE TH'EORY ... en M ~ / ~ FOR CAFE ROAD RACERS w Z W ...J U > U PARTm: THE MYSTIQUE '. OF "LINE" ". \ by Lane Campbell This business of "line" gets treated wi th a great deal of mystery and reverence by casual spectators, bench racers and middle of the pack privateers alike. Watching Agostini or Carruthers or duHamel carve their way through a field of lesser men, some twit is always bound fo say, "Wow! He must really know the better line through there." Sure he does. He's very likely also got more nerve than the guys he's passing, plus the truly great rider knows his line instinctively. Poor saps like you and I who must rely on our intellect alone are always about one step behind in the learning process and a couple of seconds a lap off the pace. Still, with the assumption that a little knowledge is better than bloody ignorance in this case, let's look a bit at this business of taking the fastest ljne. ....... A _._8 Fig. 1a and 1b: Increasing radius (left) and decreasing radius (right). Two bugaboo .comers that, if entered blind, will throw a rider's judgement off the first time through. The A line illustrates the standard apex, approach and exit of a novice rider entering one of these curves cold. The B line is that of someone who knows these corners, illustrating the modified approach, different apex and more favorable exit that results. Note especially that in the decreasing radius corner A 's line runs out of road. This implies that the B line is the safe strategy for entering any strange blind corner cold. 7241 Orangethorpe Buen. Park, CA 90621 • • •• ~ MEANS MAlOO (allO Penton & Monark) 714 521·2420 ~JN'· 'WHAT PRICE Y ..:~ Shoutdel' Klocker's SALES & SERVICE 6624 Atlantic, Bell, Ca. (213) 581-3983 SAFETY? Irs Cheop When Y"" Buy The Best From Jim Covis Motosporf Elbowplds ••. Chest pr011!Clor1 ••• Basqvarna (b) (6 ) P'Ch •.•• _ Shin gu.nk Mouth guatdl. . . •. K~P'dt ....•.. And lots more ovoiloble . . . . . . . . . . SOLD BY BETTER CYCLE STORCS THRQUGHOUT THE WORLD. CHECK WITH YOUR LOCAL DEALER. JIM DAVIS, Bo. 1002, BurlM"k. c.lifomia 91505 First off let's get straight in our minds why we're trying to comer fast in the first place. Asidefrointhe'sheerlaJlout fun of it we're trying to get from point A to point B over a wiggly bit of road as fast as possible without exceeding our personal limits or those of the motorcycle. Spoken in exact terms this means achieving the minimum elapsed time (ET) for a given mstance without falling off or encroaching on someone else's lane. Remember that with a motorcycle this gives y,?u considerably more leeway than someone with a car because you on your bike can play the same games legaily within your own traffic lane that a car requires the whole road to do. outside edge of the road limits your options to loosen your line before going off weed cutting. In other words if you enter a given corner and clip an apex on a given line at or near your limiting speed you're largely stuck with holding that line come hell or high water. This leaves little room for evasive maneuver in case you meet that unexpected chuckhole or other obstacle in the road. So I guess it's obvious you save this business of committing 100 per cen t to every comer for ei ther a closed road circuit or a lonely 'stretch of road you know extremely well. Still if you limit yourself to cornering at, say, 0.75 g to have some safety margin, a good line will still get you through a given section faster than a lousy line. Now let's recap. In Part I, I showed how a very simple, elementary racing line through a very simple comer would net you a measurable benefit in speed and ET. Unfortunately I only uncovered a piece of the iceberg: the idea of trying to fit the largest possible circular curve (in other words, the max constant radius) within the limits of a given patch of road. This simple line takes you from the outside, clipping across the in-.ide verge, and then drifting to the outside again. This basic racing line has three parts: an approach curve, an apex (or clipping point) and an exit curve. ow if you talk line with your bench racing buddies you'll hear a lot about thjs apex thing. It's also called a clipping poin t and it's a big thing wi th the sports car crowd also. What an apex (or clipping point) is is it's the spot where you just kiss the inside verge of the roadway somewhere near the midQle of the curve. It's a fairly important little gimmick because it's generally the point you aim for during your approach curve and its placement determines the direction of your exit curve. This last statement may take a bit of explaining. It e,specially appHes when you're deeply committed in a comer. When you're committed you're on or near your limjt Qust under 1.0 g's in our earlier examples); this makes it impossible to tighten your line without first killing some speed. You can't tighten up because at constant speed -his would require more g's cornering ower than you have available and the So with that bit of argument out of the way we ge t back to the apex. Since we're tal king about fIrmly commi tted smooth curves, the apex has a lot to do with the placement of the exit curve and there are several kinds of corners where this is quite important.· Look at Fig. Ia and lb. These are the change up corners you meet quite often on the older hill/country roads that were built back when your road builders followed the natural terrain rather than bulldozing a straight line right through it. Fig. Ia is an increasing ramus comer which means that as you go into it, it loosens up, that is, its ramus of curvature increases. If rider A goes right on and apexes it at its midpoint he winds up taking it sharper, tighter and slower than he could have. Taking B's line the rider has pulled his apex up road, made an early apex, which pushes his exit line outward, and allows a much greater ramus and therefore a higher limiting speed through the comer. Fig. Ibis the real bugaboo of the fast road rider: the decreasing ramus comer. It tightens up as you go into it; cutting a midpoint apex results in a line that runs righ \ out of road. So the play here is to push the apex down road, cutting a late apex, which tightens the exi t curve and allows the rider to make the corner without bobbling or worse. It's the chance of meeting an unknown decreasing ramus on a strange road that makes many riders wary; they'll intentionally e!'ter any blind curve a

• Cover