I'm designing a steam engine eccentric rod, and I want a tapered cylinder
(which I have) that has also been flattened on the top and the bottom.  How
do I add the flats on top of the taper?

Thanks!

scale = 25.4; // for imperal
$fn = 100;

/* center body rod (should be flatened rod) */
BodyLen = 1.753 * scale;

//BodyCtrBigEndDia = 0.1642 * scale;    // flat
//BodyCtrLtlEndDia = 0.09375 * scale;

BodyCtrBigEndDia = 0.3125 * scale;  // dia
BodyCtrLtlEndDia = 0.1875 * scale;

cylinder(h = BodyLen + 2, d1 = BodyCtrBigEndDia, d2 = BodyCtrLtlEndDia,
center = true);

http://forum.openscad.org/file/t2193/eccentricRod.png

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Thanks for the reply.

I thought about that, but how do you 'angle' the cubes to form the necessary
taper?

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OK, I get it.  the entire cube is translated or rotated at the require angle,
and then difference'd.

Thanks.

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In case you are heading for a tapered cube with rounded edges you can try
something like this:

$fn=50;
linear_extrude (height = 200, scale=0.09375/0.1642) // flattend tapered rod
offset(3) square([8, .01], center=true);

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Thanks!
That certainly did it.  I put in my other parameters.  I'm going over
'offset', although I don't fully understand what's happening.  I was OK up
to creating a tapered cylinder (easy).

//
---=======================
/* center body rod (flatened rod) */
//EccentricRodBodyLen = 1.753 * scale;
//EccentricRodBodyCenterOffset = 0.4142 * scale;
//EccentricRodBodyCtrBigEndDia = 0.1642 * scale;    // flat
//EccentricRodBodyCtrLtlEndDia = 0.09375 * scale;

/*

• center body rod (flatened rod)

*/

module Body()
{
difference()
{
translate([0, EccentricRodBodyCenterOffset - 2, 0])
rotate([-90, 0, 0])
linear_extrude(height = EccentricRodBodyLen + 3, scale =
EccentricRodBodyCtrLtlEndDia/EccentricRodBodyCtrBigEndDia)
offset(2.5)
square([EccentricRodBodyCtrBigEndDia, 0.01], center = true);

        /* clean up little end Bore */
translate([0, EccentricRodCtrToCtr, 0])
  linear_extrude(height = EccentricRodLtlEndBossThick, center = true)
    circle(d = EccentricRodLtlEndBore, center = true);
}

}

http://forum.openscad.org/file/t2193/EccentricRod.png

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