Baindl's Twin-Cranker

BAINDL'S TWIN-CRANKER

WHILE IN GERMANY last September for the Munich Show, I visited toolmaker Rupert Baindl, whose shop is located about 40 minutes outside of town. Baindl is a bearded man in early middle life who alternates between boyish enthusiasm and a kind of Viking-like impassivity. His shop contains the things you’d expect-a dyno, machine tools, prototypes and computers running three-dimensional modeling and finiteelement-analysis programs.

Some time ago, Baindl built a twin-crankshaft four-stroke Single. The two cranks are geared together to counter-rotate. Each has a connecting rod, both of which attach to the same ultra-lightweight piston via two stub wristpins. There are three potential advantages to such a scheme: First, the use of two rods completely eliminates the piston side-thrust of conventional engines, offering a potential reduction in piston friction. Second, by balancing at 100 percent of reciprocating weight, most primary imbalance is canceled, without producing any fore-and-aft shaking force. And third, because neither of the two cranks is centered under the piston, it is possible to lengthen the intake stroke to 190 crank degrees, and shorten the power stroke to 170.

I watched as Baindl inserted the two geared cranks into a case half, connected the rods to the

disc-like piston, and then demonstrated the motion. The billet cylinder head has four radial valves driven by conical cams in the style of Ludwig Apfelbeck. Instead of intakes on one side and exhausts on the other as in a conventional pentroof head, valves alternate-intake, exhaust, intake, exhaust. The vertical intake ports turn as they approach their valves, producing strong rotary charge swirl around the cylinder axis, which is useful in very shortstroke engines. Everythingcases, cranks, gears, head and rods-was made in this shop.

Baindl’s ambition doesn’t stop with this Single, for which there is no longer a racing class. The FIM’s proposal to add 990cc four-strokes to the 500cc Grand Prix class beginning in 2002 is a call for innovation. Baindl has designed a 990cc parallel-Twin with dual cranks, and has preliminary funding from a small group of interested persons to build such an engine. I watched its parts in fascinating animated action on the computer screen.

No technical problem frightens this man. Also in his shop is a prototype of a toroidal cylinder, oscillating/rotating piston engine. Again, everything is made inhouse-curved pistons, nut-shaped cylinder and all. I looked closely at Baindl to see if he ever sleeps, but he looks perfectly normal.

Baindl and his associates are realists, and know that despite early claims of 250-plus horsepower for other new GP fourstroke projects, the bike that wins races will be the one whose mass properties are right and whose torque delivery best matches what the tires can handle. Being self-balancing, Baindl’s compact parallel-Twin has more choice of location in a chassis than does almost any other engine type.

Kevin Cameron