Abstract: A board game includes an enclosure having a playing surface containing a plurality of squares in an array, wherein each of said squares is a trap door. The squares on each half of a centerline across the surface are controlled by control panels on opposite sides of the enclosure. Each control panel has a plurality of switch mechanisms connected one each to a square for moving the square out of the plane of the playing surface. The switch mechanisms are actuated by removable buttons fitting within an array of holes in the control panel. The array of holes corresponds to the array of squares on one half of the playing surface. Not all of the holes receive buttons, i.e. the number and location of the buttons is determined by the rules for play, and the buttons can be arranged asymmetrically with respect to the centerline.

Abstract: In an internal combustion engine, a piston is prevented from wobbling about its wrist pin by including parallel linkage arms between the piston and a follower gear on the crankpin of the connecting rod. The follower gear orbits a stationary gear, but does not rotate. The follower gear is coupled to the stationary gear by intermediate gears. The stationary gear is coupled to the engine block so that it does not rotate about the main journal of the crankshaft. Rotation of the follower gear is prevented by choosing gear ratios such that their product is one half. In an alternative embodiment, the linkage arms between the follower gear and the piston comprise shafts with a bevel pinion gear at each end. One end engages the follower gear while the other end engages a sector gear concentric with the wrist pin.

Abstract: A pair of circumferential sliders are positioned symmetrically on opposite sides of a piston, an inner surface of each circumferential slider being connected to a respective bevel rack gear. The rack gears are driven by bevel pinion gears that are attached to opposite ends of a wrist pin connecting the piston to a connecting rod. A pair of passages extend from the top of the piston to a pair of opposite, symmetrically positioned windows that are enlarged and reduced as a crankshaft connected to the lower portion of the connecting rod rotates in order to apply combustion or compression gas pressure in a cylinder to opposed varying areas of the cylinder wall so as to offset the varying lateral component of force applied by the connecting rod to the piston.