# Hart's A-frame Wheel

- Author:
- asifsound

- Topic:
- Square

Sqaure wheel by Hart's A-frame Linkage.

**Literally, this is "Invention of Square Wheel"**cf. related word : "Reinventing the wheel" (wikipedia, Reinventing the square wheel)Hart's A-frame is an exact straight line drawing apparatus.

**■ Characteristics:**① Shape is an exact square wheel. (size is changing: big ⇔ small. □OIO'I' is square. CO ⊥ CI ) ② Foot trace is exact straight line. (+/- 45° line or horizontal.) ----**not cycloid**curve. ③ Long stride. Tip: This method cannot be applied to Chebyshev linkage. (∵ Chebyshev shape is a left/ right symmetry, so, #4 foot goes under ground.)**■ max span this A-frame**Suppose, B(0,2+y), End(x, y(B)) [End is bent bar angle 180°, stretched.] where, x^{2}+y^{2}=(4+3)^{2}=7^{2}=49 ① x^{2}+(y+2)^{2}=(6+2)^{2}=8^{2}=64 ② ②-① 4y+4=64-49=15 then y=11/4=2.75 so, 2+y=4.75 x=√(49-121/16)=√(784-121)/16=(1/4）√663=6.437196595## New Resources

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