Designer's Corner

August 25, 1997

Scotch-yoke redesign

Redesigning the yoke in a classic scotch-yoke engine adds dwell to the piston motion at the top of each stroke. Advantage? Substantially reduced unburned hydrocarbons and NOx, and exhaust gas temperatures of 477F to 819F.

The yoke frees the flywheel to turn for a portion of its rotation while the pistons remain stationary. Combustion occurs in a fixed volume for more complete burning of the fuel/air mixture.

Available in a two-stroke configuration with four-cylinders displacing 25.23 cubic inches, the engine is targeted towards portable generators, water pumps, and lawn and garden equipment.

Yoke design increases dwell angle to maintain constant cylinder volume during initial combustion. Reduced hydrocarbons, NOx, and exhaust temperatures result.

Richard Davis, Zero2000 , 557 California Avenue, Boulder City, Nevada 89005, (702) 459-1207, Web: .

Innovative interconnect

Soldering a ball-grid array to a low-mass adapter subjects the BGA to less thermal stress than direct soldering to the motherboard. Also: An adapter allows BGA insertion/extraction.

A threaded heat sink, part of the Pop-Top(R) BGA socket adapter system, offers three further benefits.

First, the sink's retention clip lines up adapter pins and sockets for quick positioning. Second, sink screw-down forces socket penetration. Third, sink travel limits insertion depth, lowering extraction force.

Socket adapter's limited insertion stroke protects devices and fragile solder joints by reducing extraction force.

Ann Cibelli, Advanced Interconnections Corp. , 5 Energy Way, Box 1019, West Warwick, RI 02893, (401) 823-5200.

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