imported post
imported post
Tom's new bike (maybe)
The All New BMW G450X
This bike shows what can happen when a company known for its engineering and design excellence (BMW) takes a fresh look at a market segment. This is not a rebadged Husqvarna but
a completely new bike designed over the last 3 years by BMW on a clean sheet of paper. While BMW has had great success over the years racing its GS models in endurance events, this is its first venture into the lightweight enduro category. This bike truly represents some innovative thinking when it comes to enduro design. High-tech solutions can been seen in both the engine and chassis in keeping with the cross-country sporting tradition of BMW.
This is not a modified motocrosser set up for enduro, it is a purpose built enduro bike. The engine boasts the latest fuel injection and computer-controlled three-way catalytic converter. This bike will be completely street legal and can be easily converted from a dual sport to full race and back again. The whole concept of the BMW G450X is based on keeping the mass concentrated as near as possible to the center of gravity, giving it a clear advantage over the competition both on and off road.
Witness the unique under the seat fuel tank. Wet weight will be just under 260 lbs.
Design.
The G450X looks like a BMW! The dynamic "Flyline" design makes the bike recognizable as a BMW with the familiar "beak" front fender shared by all GS models. The bike looks like it could "ride to win" in competitive races. The standard color is "racing white" with blue accents typical of BMW.
Patented swing arm mount.
The most innovative feature of the BMW G450X is the coaxial mount of the swing arm and chain pinion. The swing arm pivot has been mounted through the hollow gearbox output shaft so that there is no longer any change in length of the chain on compression and rebound over the entire spring travel. The chain tension remains constant, independent of the swingarm position. Obvious benefits to this design include a reduction in "chain slap" for more effective transfer of power, less wear on the chain and sprockets, and a considerably longer swingarm (approx. 30mm longer) than conventional designs which will provide better traction and more effective absorption of suspension loads. While the swingarm must be removed in order to change the front sprocket, BMW says that an experienced mechanic can replace it in under 15 minutes and, because of the much lower wear of the entire final drive, sprocket changes will be less frequent.
Innovative frame concept.
The frame of the BMW G450X is absolutely unique in the enduro world. Built of thin walled but high-strength stainless steel precision tubes welded to forged mounting points, the entire main frame weighs less than 19 lbs. and is extremely stiff. The frame also uses the motor as a stressed member further reducing weight and increasing rigidity. The lower bow of the frame tubes runs directly from the swing arm pivot to the steering head. On the other end, the upper bow of the frame creates a direct connection between the suspension strut mount and steering head. The wheel forces are braced centrally on the frame over the suspension strut so that the light aluminum rear sub-frame only needs to bear the weight of the rider and not any structural frame loads. The 18-inch rear wheel is suspended in a square aluminum swingarm directly linked to an Ohlins rear shock with wheel travel of 12.6 inches. The front suspension features a 21-inch front wheel and 45 mm, fully adjustable, upside-down Marzocchi forks with 11.8 inches of travel. The exact geometrical data of the chassis is subject to final fine tuning activities and will be made known at a later date.
Engine.
The 449cc single-cylinder DOHC 4-stroke engine of the G450X is a completely new engine for BMW. The engine features a compression ratio of 12:1, is started by a permanent magnet electric starter (a kickstarter is unnecessary thanks to a full size battery and fuel injection), an automatic decompression function with a centrifugal force valve lifter which reduces the power demanded by the starter and a compact four-valve cylinder head that shares many technical elements with the K1200S. For example, the intake valves are operated by valves on cam followers while exhaust valves are operated by tappets. This results in a very compact design that is still capable of turning high RPM's. The crankshaft and connecting rods are fitted with roller bearings The two ring piston is weight optimized and forged.
A balance shaft reduces the vibrations typical of a single-cylinder engine. The constant mesh five-speed transmission is a wide ratio gearbox for optimum performance in enduro racing. In contrast to conventional designs, the BMW G450X clutch sits directly on the crankshaft and is configured as a wet clutch with a diaphragm spring.
This design spins the clutch discs 4 times faster than conventional designs and can be made considerably more compact (25% of the normal size) without compromising power transfer.
The engine is fed with oil by a wet sump lubrication system. Two oil pumps, a pressure pump and a suction pump, use the same oil to lubricate both the gearbox and the crankshaft.
The engine is tilted forward by approximately 30 degrees which provides several advantages including a lower center of gravity, more space for the air intake allowing a generous airbox located high on the bike, and room for a single lightweight radiator and electric fan.
Despite the powerful alternator and electric starter, the high-performance engine of the BMW G450X weighs no more than those of the average competitors' bikes (less than 66 lbs.). The exact power and torque data are not yet finalized but
the final design should boast 50 BHP and 35 ft lbs of torque!
