Belt-drive motorcycles are absolutely nothing new. Although some bikes in the early 1900s had actually currently embraced chain drive, numerous had not, and galleries worldwide are replete with old bikes putting on leather or reinforced rubber belt-drive hvacs.
In the bad aged days, these primitive systems were not much of a trouble, considering that power output from the contemporary engines was, to claim the least, modest. By concerning 1912, as engine outcome climbed, also those motorbike producers which had actually been utilizing belts switched to chains, or-in a couple of cases-to shaft drive.
At the time, this made sense. After all, engine property development was continuing faster compared to belt-material modern technology. Yet belt style remained to improve, driven greatly by industrial applications along with in automotive complementary hvacs like follower belts and also cam drives. Much boosted by new rubber and cord formulations, belts at some point re-emerged as a bike final drive on cruisers, especially on the Harley-Davidson FXB Sturgis of 1980.
The turning on technology was a DuPont Kevlar solution used in just what belt producers call the “tensile participants”, or cords within the rubber belt that provide the needed strength and stretch resistance. The rest, as they say, is history, as well as cruisers these days are most likely to showcase belt drive compared to not.
Long after we ‘d come to be accustomed to seeing belts on cruisers, something surprising happened. BMW decided for belt drive on its brand-new F800 series of sporting activity twins, adhered to soon by Buell, with its brand-new 1125R sportbike. Buell, with its lengthy association with Harley-Davidson which company’s engines, already had experience with belts on some of its models and also was perhaps more likely to check out belt drive on sport devices, yet the BMW was a real shock. However, I believe the thinking was similar.
Belts are lighter than chains, and also help in reducing unsprung mass at the rear wheel. Roller chain suspended between the countershaft and rear sprockets has more wrap at the rear wheel, and thus places more of its weight there. Unsprung mass is among Erik Buell’s significant preoccupations, and also he does his utmost to lower it.
However reduced mass is not the belt’s only virtue. Belts are quieter, do not rust, stand up to toxic wastes and call for no lubrication. Anyone who has cleaned oil splatter off the rear wheel, swing arm and suspension pieces of a motorcycle will attest to the worth of that. And also though motorcyclists are much more inclined to enhance noise from their mount, often by fitting a loud pipe, there’s something to be said for a decrease in driveline noise.
A typical, contemporary belt is comprised of a synthetic rubber envelope including an aramid cord structure, with a high-modulus rubber material (called tooth stock) making up the rectangular teeth that comply with their mirror image on the drive wheels. Veyance (manufacturer and also marketing professional of Goodyear Engineered Products, including motorbike drive belts) calls the tensile-member product Flexten, and also it is a multi-filament helical weave that is looped endlessly around the belt area much like we see in modern tire construction.
Among Veyance’s certain strategies is to encapsulate each bundle of filaments in an adhesive material to decrease friction and also abrasion in between the packages as the belt goes about its company. The tooth side of the belt is finished in what’s called facing material, and this is an important part of the belt because this is what makes contact with the pulleys.
A degree of compliance is required for perfect consistency to the pulley-block profile along with significant abrasion resistance. Baseding on Veyance motorcycle project designer Brian Wegele, who functioned very closely with Buell on the 1125R project, his company’s facing material uses a blend of polyethylene and EPDM synthetic rubber cross linked by vulcanization.
Much of the development help facing product was done for NASCAR cam-drive belts, and also as a consequence the material can withstand operating temperature levels of 300 degrees– possibly a bit warmer than it will hop on the back of your bike.
An intrinsic property of aramid cable is that it does not stretch. So there’s no should incorporate axle adjusters on a motorcycle, nor suffer the placement challenges that come with them. Because the swingarm and drive wheels go to various ranges from the rear axle on motorcycles, producing asymmetrical distances when the bike’s suspension deflects, belts as well as chains both need some play to accommodate the variation in length.
On chain-driven bikes we just leave some slack, but belt-drive bikes can exploit more elegant solutions. Such as the tensioner wheel seen on Buell’s 1125R, which is loaded against the belt and visibly rotates backwards as the bike rolls along. This system takes up slack, helping to eliminate the driveline jolt or shuffle one commonly experiences when you open the throttle on a chain-driven bike.
BUELL BELT DRIVE SYSTEM
There’s inertial mass to think about with chains, too. Just as it needs power to accelerate the back wheel, so it does to accelerate the hefty mass of metal that makes up your typical chain. Still, some of you are doubtless thinking that belt drive can’t match chain when it comes to high-power applications, right? Actually, they can. One might have to widen the belt somewhat to take care of serious horsepower, but the material has impressive strength. Aramid on a per-pound basis is stronger compared to steel.
Baseding on Wegele, Veyance has damaged a brand-new chain at 8,000 lbs/strand compared to their Flexten product at 9,000 lbs/strand. And also the company is searching for carbon fiber tensile participants that need 11,000 lbs/strand to get to the failure method. There is, according to Wegele, no reason that belt-drive could not be made use of on modern-day sportbikes of any sort of displacement.
The innovation is currently being pushed by escalating power and also weight in the cruiser section, and Wegele is positive that Veyance could fulfill any power transmission difficulty. He states that even the fatigue and failure characteristics of belts are benign. Typically, he says, a belt will certainly exhibit terminal wear problems on a “limp-home” basis rather than a “walk-home” one. Belts will typically lose teeth as well as offer palpable evidence of their distress well before a disastrous failing occurs. Moreover, belts do not harm their pulleys in the way chain distorts tooth profiles on a sprocket.
Observant readers might recall that a Buell 1125R racing in the Daytona 200 retired because of belt troubles, but Buell spokespersons point out that the bike was competing without the common belt covers. They state that rubber deposit from the track was flung from the tire onto the sheave’s edge where it gradually built up till it started pressing the belt sideways off its track. The belt itself was great, there was just a threat of derailment.
But racing is maybe the only environment that does not favor the belt, which’s mostly considering that racers need fast final-drive ratio changes. Belts cannot be damaged then secured back with each other once again, so their lengths are unchangeable. To change proportions you have to lug wheels and also belts of varying size. It’s possible, simply troublesome. Given that most manufacturing sportbikes are chain driven anyway, it’s not a problem that will certainly arise till even more producers change to belts. If they do.
Thus, racing applications for belts are currently pretty much restricted to blowers as well as key drives. Oh, as well as to the periodic Buell. The endless aspect of belt construction postures a few challenges for belt replacement, since-unlike chains-they could not be reduced and also rejoined, yet that’s something that can be taken into consideration during the motorbike’s layout stage.
None of this suggests that chains will disappear anytime soon. For something, chain could coil smaller sized sprockets compared to could belt. Chain will gladly accept chain wheels down at about 3-inches in size, whereas belts need pulley diameters of at the very least 4.5-inches if they are not to begin really feeling troubled. As well as since the countershaft sheave is big, so should the wheel pulley expand so as to get the ideal final-drive proportion. Some people may not like the look of a huge belt pulley-block on the rear wheel. Chains are narrower than belts also, and also because they bestride the sprockets, create a quite slim complete package.
There have been very remarkable renovations in chain modern technology, as well. Improved metallurgy has resulted in greater tensile strengths, while modern production procedures have boosted resistances and also assembly strategies. The biggest bugaboo with chains is that they are not flexible. Rather, individual links are allowed to pivot on bushings at both ends of every web link. The difficulty has actually been to beat the wear that happens at the relocating elements that allows longitudinal play. The play allows the chain to stretch past its operating restrictions, to the point where its consolidated web link pitch no more matches that of the polygonal gears on which it rides.
Effective greasing decreases the wear, however outside oiling can just presume in mitigating bushing wear, so makers developed the smart idea of packing grease inside the bushings, and afterwards closing the end plates (which relocate connection to each various other) with O-rings. That considerably raised the life span of chains, but we quickly discovered that the O-rings were susceptible to put on as well as environmental attack from threatening cleansing products or from the solvents in unacceptable lubricants.
However a lot of customers have actually caught on now, and also ensure that chain lube containers suggest the solution is suitable for usage with rubber O-rings. Now we are seeing variations on the O-ring theme, with X-rings that supply multiple lubrication swimming pools and seal factors, as well as from chain producer RK Chains, an unique brand-new twist called the XW-ring.
This web page from the supplier’s website most likely clarifies it more clearly than we could. Keep in mind that the content right here includes RK’s claims, unproven by MD
Obviously, chain producers are not ready to give up their massive participation with motorcycles. Neither need to they. Yet it behaves to see a choice to the noise and mess of chains, as well as the extra unsprung weight of shaft drive. Today, belt-drive has made significant invasions right into the cruiser market. The large inquiry is just how much the innovation could permeate the remainder of the motorcycle model spread. It’s visiting be a fascinating tug-of-war.