Improvements in Calculators

9446. Ionides, A. G. April 18. Slide rules. - A circular rule for use in connexion with calculat i o n s concerning internal - combustion engines and motor-vehicles comprises primarily three scales A, B, C. Scale A, denoting volumes swept out by the piston, and scale C, showing gradients, are provided on the base of the instrument, while scale B, showing ton-miles per gallon of fuel, is arranged on a pivoted sector. Three fiducial marks 8, 9, 10 are provided, and by suitable manipulation of the sector, the ideal and actual ton-mileage and gradients can be ascertained, given the volume figure on scale A. In order that this figure, if not given or known, may be determined, a number of other scales as shown are provided, both on the base of the instrument and also on a disk and sectors. These scales denote such quantities as car mileage per gallon of fuel, R.A.C. and brake horse-power, cycle and car taxes payable, number and diameter of cylinders, length of stroke, gear ratio, road-wheel diameter, weight of car, speed of vehicle, &c.