The mechanism consists of two pantographs. The first pantograph consists of links 1, 2, 3 and 4. The second, of links 1, 4, 5 and 6. Link 1 turns about fixed axis A. Link 4 turns about fixed axis C. Link 4 is connected by turning pair F to link 3. Links 4 and 7 are connected by turning pairs F and F' to slider 8 which moves along side a of frame 9. Links 5 and 6 are connected by turning pair D to slider 10 which moves along side b of frame 9. When stylus B follows the out line of a plane figure, pencil K draws a distorted projection of the figure. The total distortion of the scale of the figure equals 1/2. Besides, the additional distortion of the scale along the x axis equals A͞D/A͞F, so that the total distortion along the x axis equals t/2. To obtain such projection, the lengths of the links should comply with the conditions: A͞A’=A͞’D=A͞’’D; D͞D’=D͞’F=A͞’A’’, A͞B"=2C͞C'=B͞’’B=2B͞’B’’=2B͞’B=2A͞"F=2F͞'F", F͞F'=A͞"F" and A͞’’C'=A͞C. Under these conditions, points A, D, F and B lie on a straight line, and the distances A͞F and F͞B are equal. If the position of point D is taken so that τ=0 .577, i.e. A͞D=0.577A͞F, then the projection drawn by the mechanism is isometric.
$1199$LG,Ge$