Modenas KR3
From Wikipedia, the free encyclopedia
 | |
| Manufacturer | Team Roberts |
|---|---|
| Also called | Proton KR3 |
| Production | 1997–2003 |
| Predecessor | None |
| Successor | Proton KR5 |
| Engine | 500 cc two-stroke V3 |
| Transmission | Chain |
The Modenas KR3 was a racing motorcycle designed and built by Team Roberts and funded by the Malaysian motorcycle company Modenas. The bike was used in the 500cc class of grand Prix motorcycle racing from 1997; however since 2001 the bike was renamed as Proton KR3 due to increased involvement of the Malaysian automobile company Proton. Both Proton and Modenas are owned by Malaysian conglomerate DRB-HICOM.
The KR3 was used until 2003, when it was replaced mid-season by the four-stroke Proton KR5 MotoGP machine.
Background
The origins of the KR3 lie with the strained relationship between three-time 500cc champion Kenny Roberts, team manager of the Factory Yamaha team, and the Japanese manufacturer. After his top rider Wayne Rainey became paralysed from the chest down due to a crash he sustained at the 1993 Italian Grand Prix and Yamaha's rivals Honda and Mick Doohan took multiple titles, Roberts became increasingly unsatisfied with Yamaha's working method in the mid-1990s. He was constantly unhappy with the progress of their bikes and even complained many times publicly that the factory did not listen to his feedback on how to improve their YZRs.
Because of this, he made an announcement that surprised everyone in 1996: at the end of the season he was breaking away from the Factory Yamaha team after 25 years of close collaboration, working together with the Modenas company to create a new motorcycle for the newly formed Team Roberts in 1997.[1] The main reasons why Modenas decided to work together with Roberts was for two reasons: The company hoped that some of the technology would eventually make their way into their future models, and that participation in the 500cc would make their brand more known amongst the public.
Development
The KR team decided to move the base of operations to Banbury, in the Motorsport Valley[2] in the United Kingdom where some Formula 1 and race car teams are based, and began working together with Tom Walkinshaw Racing (TWR).
They decided to create a unique three-cylinder, two-stroke, 500cc machine since the rules at the time gave three-cylinder machines a 15 kg weight advantage over the usual four-cylinder bikes (minimum weight of 115 kg instead of 130 kg).[3] The idea was that the lower weight allowed the bike to be more agile and carry more speed mid-corner. This was also deemed as an advantage as the racetracks during this time had more corners than long straights for the four-cylinder machines to utilize, some examples being Shah Alam and Donington Park. However, they also were aware that a three-cylinder bike would make less horsepower compared to a four-cylinder one. To solve this problem, the team focused on improving volumetric efficiency (how much fuel-air mixture the engine could induct).
The engine design was supervised by Warren Willing and Bud Aksland, the father of the team's manager Chuck Aksland, and was built by TWR. They created a 498cc engine with "square" dimensions i.e. same bore and stroke figures of 59.6 mm x 59.6 mm. The Vee-angle between the cylinders was very wide set at 135°[4] with two cylinders down below and one up top. The engine lacked a balance shaft with a view to improve efficiency and weight, however that feature caused severe vibrations.[3]
The frame was designed to give the bike better handling characteristics. The KR team worked with chassis maker Fabrication Techniques, which resulted in an aluminium twin-spar "deltabox" frame that was reportedly smaller and lighter than conventional Japanese designs at the time. The headstock featured eccentric carriers which would allow adjustments of the steering's rake angle and trail. There were also eccentric carriers in the swingarm mount which were created to adjust the height of the swingarm pivot. These were completely new and unheard of at the time. Even the fueling system was ahead of its time, the team adopting electronic carburetors without float bowls which used ducted air to atomize the fuel, much like a fuel-injection system. KR hoped that such a setup would avoid the fuel from emulsifying from intense vibrations. Arrow made an exhaust system for the engine. The result of this was an engine that produced 160 hp in the early years. The bodywork was designed in such a way that it would wrap tightly around the frame for a smaller frontal profile. Consequently, the radiator was moved to under the seat where ducts supplied cooling air to it.[5]
Evolution
During 1998 a brand new engine (Spec Two) was developed featuring a reversed layout (two cylinders up, one down) with an included angle narrowed to 114°[4] and a balance shaft. It was designed with the help of Japanese engineers Yoichi Oguma and Mike Maekawa and many parts were manufactured by Japanese suppliers with final assembly done at Team Roberts' workshop, excluding TWR. Conventional features were adopted, such Keihin carburetors instead of bespoke units and the radiator placed at the front.[3] Compared to the older unit, the new engine was more reliable while producing around 170 hp on unleaded fuel (mandatory since 1998). However it was also longer and heavier, causing handling problems due to the altered weight distribution.[4] In 1999 the problems worsened, due to the switch from Dunlop to Michelin tires and the departure of Warren Willing who left the team to join Suzuki.[4]
For 2000 Roberts produced a Spec Three engine with a vee-angle of 112° and a relocated balance shaft, resulting in a shorter and lighter unit while keeping the reliability and performance of the Spec Two engine.[4]