$fn=30;

function calcScale(scaleFactors, count, iteration) =
    scaleFactors[0] +
    (( scaleFactors[1]-scaleFactors[0]))*iteration/count;

module hullSweep(steps, rotation, offsetTo, scaleFactors)
{
    for ( i= [0:steps-2] )
    {
        scaleAmt1 = calcScale(scaleFactors, steps, i);
        scaleAmt2 = calcScale(scaleFactors, steps, i+1);

        hull()
        {
            rotate(rotation*i)
            translate(offsetTo*i)
            scale([scaleAmt1,scaleAmt1,scaleAmt1])
            children();

            rotate(rotation*(i+1))
            translate(offsetTo*(i+1))
            scale([scaleAmt2,scaleAmt2,scaleAmt2])
            children();
        }
    }
}

// Examples
// Horn #1
hullSweep(40,[0,0,4],[1,1,1.5],[5,0])
scale([1,2,1])
sphere(1);

// Horn #2
translate([50,0,0])
hullSweep(20,[0,0,4],[1,1,1.5],[5,0])
scale([1,2,1])
sphere(1);

// Short horn
translate([100,0,0])
hullSweep(40,[0,0,3],[1,1,1.5],[10,0])
union()
{
   sphere(1);
   translate([4,0,0])
   sphere(1.5);
}