tapered rod

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tapered rod

KM6VV
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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Re: tapered rod

thehans
Subtract cubes from the sides or intersect the tapered end with a centered cube.

On Tue, Mar 27, 2018, 12:45 PM KM6VV <[hidden email]> wrote:
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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Re: tapered rod

KM6VV
Thanks for the reply.

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





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Re: tapered rod

nophead
You can use trigonometry to work out the angle e.g.  atan(h / dx) where  h is height and dx is the difference in radius of top and bottom.


On 27 March 2018 at 20:50, KM6VV <[hidden email]> wrote:
Thanks for the reply.

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





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Re: tapered rod

KM6VV
OK, I get it.  the entire cube is translated or rotated at the require angle,
and then difference'd.

Thanks.



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Re: tapered rod

Parkinbot
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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Re: tapered rod

KM6VV
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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