# Tennisball challenge

Posted by Replace
 Tennisball challenge March 28, 2016 06:20AM Registered: 7 years ago Posts: 841
I would like to create a tennisball, (Not actually to play tennis :-)

So the challenge is to find a formula to subtract the specific tennis ball lining from the ball's sphere surface.

One idea I have is to subtract a partially sunk small sphere from the surface of the spere and than translate that smal sphere according to a formula that describes the specific line.

Impossible ?

Thomas

Edited 1 time(s). Last edit at 03/28/2016 06:20AM by Replace.

www.3daybreaker.blogspot.com

Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
 Re: Tennisball challenge March 28, 2016 04:29PM Registered: 3 years ago Posts: 493
Are you thinking about something like this?

Here is the OpenScad source I used for the above:
```module tennisball(
r, // radius of tennis ball
s, // width of seem
d, // deepening of seem
a, // skew angle
){
ca=cos(a);
f=sqrt(2-ca*ca)/ca;
difference(){
sphere(r);
for(a1=[[0,0,0],[0,90,180]])rotate(a1)
for(sz=[-1,1])scale([1,1,sz])
difference(){
rotate([a,0,0])cylinder(r1=0,r2=(r+1)*f+s/2*f,h=r+1);
rotate([a,0,0])cylinder(r1=0,r2=(r+1)*f-s/2*ca,h=r+1);
translate([-r,0,0])cube([2*r,2*r,2*r]);
}
}
color("red")sphere(r-d);
}

tennisball(r=50,s=10,d=1,a=25);```

Edited 2 time(s). Last edit at 03/29/2016 01:57AM by enif.
 Re: Tennisball challenge March 29, 2016 09:04AM Registered: 7 years ago Posts: 841
Yessss.. great
thanks !

I will give you credit on Thingiverse when I use it !

Thomas

www.3daybreaker.blogspot.com

Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
 Re: Tennisball challenge March 30, 2016 01:13PM Registered: 7 years ago Posts: 841
Here it is :-)

Knob

www.3daybreaker.blogspot.com

Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
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