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Archive for January 3rd, 2014

Planetary Gear Bearing: Now With Knurling!

OK, I couldn’t resist. Tweaking a few lines of code wrapped a knurl around emmitt’s Gear Bearing¬†for enhanced griptivity:

Knurled vs original Planetary Gear Bearing

Knurled vs original Planetary Gear Bearing

That image has desaturated red to suppress the camera’s red burnout. It looks better in the realm of pure math:

Planetary Gear Bearing - Kurled - solid model

Planetary Gear Bearing – Kurled – solid model

Reducing the tolerance parameter to 0.4 produced a surprisingly rigid, yet freely turning, bearing that required no cleanup: it popped off the plate ready to roll!

The heavy lifting in the OpenSCAD source code remains emmitt’s work. I replaced the outer cylinder with a knurl and simplified his monogram to stand out better amid the diamonds. This is the affected section:

... snippage ...
translate([0,0,T/2]){
	difference(){
//		cylinder(r=D/2,h=T,center=true,$fn=100);
		render(convexity=10)
		translate([0,0,-T/2])
			knurl(k_cyl_hg=T,
			k_cyl_od=D,
			knurl_wd=5.0,
			knurl_hg=5.0,
			knurl_dp=0.5,
			e_smooth=5.0/2);
		herringbone(nr,pitch,P,DR,-tol,helix_angle,T+0.2);
//		difference(){
			translate([0,-(D/2+4.5),0])rotate([90,0,0])monogram(h=10);
//			cylinder(r=D/2-0.25,h=T+2,center=true,$fn=100);
//		}
	}
	rotate([0,0,(np+1)*180/ns+phi*(ns+np)*2/ns])
	difference(){
		mirror([0,1,0])
			herringbone(ns,pitch,P,DR,tol,helix_angle,T);
		cylinder(r=w/sqrt(3),h=T+1,center=true,$fn=6);
	}
	for(i=[1:m])rotate([0,0,i*360/m+phi])translate([pitchD/2*(ns+np)/nr,0,0])
		rotate([0,0,i*ns/m*360/np-phi*(ns+np)/np-phi])
			render(convexity=10)
			herringbone(np,pitch,P,DR,tol,helix_angle,T);
}

I also added a few render(convexity=n) operations to improve the preview, but that’s just cosmetic.

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