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Don’t even ask why individuals are racing baggers, that are cruiser bikes geared up with baggage and a big entrance fairing. It’s only a truth—individuals like one thing totally different, and when given the selection, are inclined to favor extremes. When the viewers likes the present, crucial query has been answered.
Drawback is, baggers as they chug from the showroom usually are not a lot use on a racetrack. Lean one over past about 35 levels and components drag on the pavement. In case you persist, one thing grounds exhausting sufficient to jack the tires off the bottom and the bike and rider develop into a mud cloud.
Baggers are heavy, and if acceleration equals thrust divided by weight, we now have a job forward of us:
1) Maximizing thrust by growing engine energy and…
2) Minimizing weight by eradicating all components not important to going quick. Nicely, not fairly—class guidelines correctly require a stock-ish look, so the massive tour fairing and one thing that no less than seems to be like luggage should stay (Rule 2.7.11.11 h: “Every saddle bag should be capable to enclose a 13.6 x 5.4 x 9-inch field and be no less than 2,200 cubic inches of quantity. Materials is free.”). To forestall “lightweighting” from changing into ridiculous, a minimal weight of 620 kilos was set. (Builders in some Nineteen Sixties auto drag racing lessons used acid-dipping to eat away extra steel!)
As a result of the USA nonetheless has a robust hot-rod neighborhood, engine energy isn’t exhausting to return by. Within the case of Harley-Davidson, the corporate provides a big V-twin crate engine of 131ci, and the Screamin’ Eagle catalog provides higher-performance components. Past that, guidelines permit conventional porting and different hot-rod strategies. Wanting sending in a bee-sized surveillance drone to carry us dyno screenshots, all we now have is claims of 155 to 165 hp from the most effective engines of the current second. When it comes to particular energy that’s a reasonable 1.22 hp per cubic inch.
Associated: Harley-Davidson Prepares for Daytona
Racing just isn’t about tech specs. It’s about riders wrestling 10 variables without delay whereas staying on the observe and preventing for place. It simply so occurs that individuals just like the deep and syncopated roar (due to uneven firing intervals) of a large V-twin at 7,000 rpm (that’s the rulebook redline for the Harley). Do not forget that these engines have been designed to offer peak torque at 3,000 to three,500 rpm for sturdy on-ramp and freeway passing efficiency, and to just about wheeze out at 5,000 or so. But right here they’re, surviving at peak revs jacked up by 40 p.c. Simply attempt boosting the height revs of your common 14,000 rpm literbike engine and see what occurs when the tach hits 20,000. Components all over the place.
And now cornering clearance. Construct a jig to rigidly maintain two sheets of plywood at an included angle of 110 levels (which means a max lean angle to both aspect of 55 levels) and attempt to roll your bike via it. One different factor: Compress the suspension two-thirds to simulate midcorner experience peak. Something that touches plywood should be eliminated, modified, or raised till that contact ceases.
As you look at the bike you see many modifications. The luggage are carried excessive, so the rider’s seat can be tall. You see this when the primary rider is available in after just a few laps and stops. To keep away from falling over, he has to scooch to at least one aspect of the seat and level his toe to succeed in the bottom. Tall.
The massive 2-into-1 pipe is routed excessive on the suitable, above the projecting timing case. Why didn’t Harley put the cam within the cylinder Vee as is completed on each good outdated American V-8 automobile engine? As a result of there’s no room. Harley’s conventional Vee angle of 45 levels is half of a V-8′s 90.
As a result of the engine, with its lengthy four-lobe cam pushing the timing cowl out on the suitable and the forged main drive cowl swelling on the left, width throughout footpegs is finest minimized by machining the peg mounts as a part of billet aspect covers. Aid is just some keystrokes away.
The entire bike is lifted up, requiring us to consult with the principles relating to how this may be accomplished. The body is probably not modified, which suggests none of that Kel Carruthers–fashion sawing off the steering head and welding it again on at an angle that accelerates the steering. Keep in mind the 1200 Sportster class, through which the bikes have been so jacked on the rear? Doug Chandler referred to as that “the stink bug look.”
Longer fork legs and a higher swingarm droop angle elevate the bike.
The explanation for utilizing Öhlins totally adjustable suspension is that it constitutes a extremely adaptable system that has an extended historical past of dealing with racing issues. The unique suspension was designed for a totally totally different set of targets.
Associated: Why King of the Baggers Racing Is So Standard
What are these two Öhlins suspension accumulators doing there, tucked between rear fender and bag on both sides? The inventory bike has twin shocks, that’s what. And the swingarm whose movement they management begins life as 255 kilos of aluminum billet that’s chewed away by CNC to develop into the 18-pound truss construction we see.
One other complication is that this bike begins life with a quiet, maintenance-free toothed-belt drive to the rear wheel, however to transmit the modified engine’s energy on the observe it has been changed by a curler chain. That is Rule 2.7.9.10 d: “Closing drive belt techniques could also be transformed to chain kind techniques.”
Ideally a swingarm for a belt-drive system might keep fixed rigidity if pivoted on the gearbox sprocket axis, however a pivot that low, with the chain rigidity produced by a big engine, causes the rear suspension to squat throughout acceleration. I used to be advised that over the vary of rear suspension journey, superb variations in chain slack happen. To accommodate them there’s a rugged backside run chain tensioner whose improvement required some trial and error.
These bikes do wheelie throughout acceleration, regardless of their lengthy 64-inch wheelbase. That’s higher than the choice, which may consequence from an excessive amount of wheelbase: to spin somewhat than speed up (keep in mind that not like dragstrips, roadrace tracks usually are not shiny with glue). This means to switch weight to the rear tire throughout exhausting acceleration is one more reason to construct these bikes as tall as they’re.
Rule 2.7.11.1 c states: “The unique place (of engine, steering stem or pivots) is taken into account because the place through which the manufacturing bike is provided and should be retained.” Meaning the one method to velocity up steering from the unique 26-degree rake angle is to elevate the rear of the chassis greater than the entrance. Path could be diminished from the ultra-stable inventory 6.8 inches by use of billet fork crowns having offset totally different from inventory. For every inch we increase the rear of the bike, we cut back steering rake by 1.1 levels.
Öhlins suspension is used entrance and rear, topic to Rule 2.7.11.2a which says, “Suspension worth caps might be $6,000 for Forks and $2,000 for Shocks.” Makes me marvel what the value of that trick swingarm is, below the rule that requires customized components to be accessible on the market inside six weeks of their look on observe. One factor’s for certain: There isn’t a low-cost racing.
That truss swingarm is only one of an amazing many intelligent CNC components on these bikes. Crew principal Jason Kehl had mentioned, “You’ll see numerous CNC components on this class, however you’ll additionally see that not all of them actually work.”
Brembo offers 330mm twin T-Drive discs of 6.75mm thickness up entrance, with calipers described to me as “one step beneath these utilized in MotoGP.” Though the brakes look small compared with this 620-pound bike, brakes are sized not for weight however for the kinetic vitality the engine can put into the bike. Harley’s KOTB bike’s all-up weight is 40 p.c higher than that of a MotoGP bike, however kinetic vitality is proportional to velocity, squared. If a bagger approaches the Daytona chicane at 170 mph however a “winged marvel” brakes from 220 mph, the ratio of the squares of these speeds is 1.67—greater than compensating for the higher weight of the bagger.
Wheels are Core Moto solid aluminum (Titusville, Florida), in conformance with Rule 2.7.11.6 b: “Wheels can both be produced from aluminum alloys or the homologated materials.” Entrance rim width is 3.5 inches (within the ‘70s that was a big-bike rear rim width and we thought it was large) and rear is 6 inches. A considerate individual has triggered directional arrows to be milled into the rim sides.
Tires are Dunlop slicks. There was a proposal below dialogue to require use of DOT avenue tires in KOTB, however that’s extra of what’s been heard in MotoGP—proposals to cut back “dangerously excessive” nook speeds by ordering the spec tire maker to make unhealthy tires. Precisely how unhealthy would you want? Is your authorized group able to defend your unhealthy tire plan in opposition to legal responsibility lawsuits? Ah, I believed not. Higher to depend on racing slicks made for the job.
Talking of which, when the solar went down and the testing stopped, I spent a while wanting on the rear tires. The standard “seashore mark” put on prolonged to a few inches in need of the tire edge on the suitable, the place the rubber regarded extra polished than used. Later, at dinner, with rider Travis Wyman on my proper, he mentioned to me, “You’ll be able to’t get lots completed whenever you’re down on the tire edges with this sort of energy.”
I needed to know extra however time was up.
Earlier, one of many engineers had spoken of the “management regulation” (program) relating movement on the rider’s proper wrist to the opening of that large motor-driven butterfly. When non-racers have ridden these bikes, he mentioned, they’ve commented on how gradual, even boring, their preliminary throttle is. Avenue guys, it appears, are excited by one thing faster-opening, extra aggressive. However aggressive apparently doesn’t lower it whenever you’re down on the tire edges with such large cylinders banging away like Venture Orion.
Or might it’s one thing else? Simply what occurs on these bikes when chain pull acts on the inventory positions of gearbox sprocket, swingarm pivot, and the swingarm droop required to maintain the bike from grounding? Questions for subsequent time.
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