In the cutting-edge world of MotoGP, coverage of technical developments tends to focus on game-changing technologies relating to the chassis or powertrain. However, less glamorous components are also subject to constant evolution, including the humble chain. So the difference between a Pramac Ducati chain from one found on a road use bike is the thinness of the O-Rings and the mileage. A MotoGP chain can cost 12x more and only use for a race weekend. But at Regina Chain, what is developed on the race tracks, will be transferred to its road chains.
‘Roller’ chains have been the universally favored means of transmitting drive on motorcycles for many years and the chain is the the most practical means of transferring the drive. With the advantage of being lightweight, easy to pack and the ability to withstand the power levels produced by the most powerful bike engines.
Chains used in motorcycle applications consists of a series of short cylindrical rollers held together by side links. There are two types of link alternating in the roller chain, inner links, and outer links. The inner links have two inner plates held together by two sleeves or bushings upon which rotate two rollers, while the outer links consist of two outer plates held together by pins passing through the bushings of the inner links.
Despite appearing to be a very simple mechanism, the latest generation of racing chains has seen each of these parts optimized to the degree to ensure they provide the greatest possible strength for minimum weight. To put these improvements into perspective, a 1970s vintage GP racer produced in the region of 130 hp and would generally use a 530-size chain weighing about 1.24013662 kg/m Modern MotoGP racers produce more than 200 hp but run a 520-size chain that weighs only 1.14092569 kg/m. The chains have also become more mechanically efficient, sapping less power through frictional losses. A motorcycle chain has around 1500 part, all precisely fitted together. Precision is the key.
While much of this improvement has been down to the gradual development of parts such as the bushing materials, there have been a few key advances in recent years. One such advance is in the sealing mechanism used between the inner and outer links. Before riveting in the factory, the internal parts of the chain are filled with chain grease by vacuum. The sealing rings then have two purposes – to keep the internal lubrication in, and the dirt out, thus vastly improving the durability of the chain.
The load-bearing pins and bushings that enable a chain to bend over a sprocket have precious little oil to keep them happy. As if that wasn’t enough, high centrifugal forces that occur when the chain turns around the drive sprocket throws the oil out. The single biggest factor in chain wear is loss of lubricant, and the advent of O-ring sealed chains enabled the chain to keep its oil inside and stay lubricated where it counts. For most chains, O-rings are still the favored sealing medium, but in high-performance applications, a new Z-ring design has taken over.
The biggest problem with O-rings is that they create a large amount of friction between the sealing surfaces, a less than ideal situation. An Z-ring seal is exactly as it sounds: a seal with an Z-shaped cross-section. When clamped between the two side plates, only two points of the ring make contact, providing a good seal but with greatly reduced friction. The improvement is significant, claiming a reduction of up to 40% in friction over O-ring sealed chains.
Clearly this is only one improvement to what is a surprisingly complex component, and many factors – not least of which is correct installation and lubrication which are critical importance to ensuring a chain lasts a race distance.
But it goes to show that even the humblest of components still presents engineers with a never-ending scope for performance improvement.
Regina Chain is distributed by Bikerzone Sdn Bhd. No. 1042 (Plot 546) Phase 4, Prai Industrial Estate, Lorong Perusahaan Maju 2, 13600 Perai, Pulau Pinang. Contact: 012-288 1501