My caster mod (with pictures)

[picklito]

Thanks. I'd be interested to know how many degrees that adds.
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[crakarjax]

Originally Posted by picklito

Thanks. I'd be interested to know how many degrees that adds.
Posted via Mobile Device

Should be some basic geometry if you know the distance between the upper and lower balljoints, and the current angle.

Assuming 9" between ball joints and a currently vertical spindle,

3.14 * (4.5^2) = 64 (radius of a circle)

360 * (64 * .25) = 1.4 degrees (360 degrees in a circle times the fraction of the circle that is 1/4")

So 1" should net about 5.6*, 3/4" would be around 4.2* gain

[crakarjax]

I ended up grinding a small flat in the shaft and then drilling with a 5/8" masonry bit. I noticed in the process that I didn't need to sink the hole in the shaft at all on the sides because the locating pin sits flush with the seats as they slope upward -- I think grinding flats for locating would work just fine considering this, since a sunk hole is actually just removing material that doesn't need to be there. Using a cap screw might be a different story though depending on the head depth.

[picklito]

Originally Posted by crakarjax

Should be some basic geometry if you know the distance between the upper and lower balljoints, and the current angle.

Assuming 9" between ball joints and a currently vertical spindle,

3.14 * (4.5^2) = 64 (radius of a circle)

360 * (64 * .25) = 1.4 degrees (360 degrees in a circle times the fraction of the circle that is 1/4")

So 1" should net about 5.6*, 3/4" would be around 4.2* gain

Looks like you calculated the area of a 9" circle. I'd do the calculation by 'assuming' that we're swinging the lower ball joint forward around the circumference of a 9" circle with center at the (fixed) upper ball joint.

Circumference of a 9" circle would be: 3.14 * diameter = 28.26"

degrees per inch moved (around that circle) would be 360 / 28.26 = 12.7

This ignores the cosine error, of course, making my calculations a little larger than we'd actually get. So, compared to a vertical spindle...

moving 1.0" equals 12.7 degrees caster
moving .75" equals 9.5 degrees
moving .5" equals 6.35, etc....