Mechanical Pinwheel Calculator - Crank Adding Machine, Real Carry, Subtract, Multiply, Turn Counter

A working mechanical calculator you print yourself: a crank-operated pinwheel adding machine in black, brass and cream, about 220 x 137 x 112 mm. Set a 4-digit number with the four brass levers on top, turn the crank forwards to add it into the 6-digit result, backwards to subtract it, and turn it several times to multiply - the 3-digit turn counter shows the multiplier. A two-position carriage (x1 / x10) lets you multiply by 2-digit numbers (1925 x 37 = 071225 in 10 turns, as in the pictures).…

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