How much backspin can a paintball get?

[ScatterPlot]

Just wondering how much backspin a paintball gets from a flatline (in RPM's). I was wondering cause I was reading through a bunch of the Dimpled Paintball stuff and saw it was talking about backspin, etc. I did some calulations and at 300 FPS it takes a backspin of about 80 RPM's to get the ball to carry it's own weight. That's not too terribly high, I don't think. With a dimpled paintball it would probably be even less. Just wondering.

[bjjb99]

Would you mind putting some of your calculations up for us to see? A spin rate of 80 rpm seems very, very low when it comes to backspin induced lift. At 300 fps and a target 100 feet away (ignoring velocity loss as the paintball travels downrange), you're looking at 0.33 seconds from muzzle to impact. According to your calculatoins, the ball will have completed less than one half of a revolution during its flight, and that seems way too low to generate sufficient lift to counter the ball's weight.

If you want the maximum rotation rate of a paintball that could normally be induced by a flatline-like barrel, just take the paintball's exit velocity and divide it by the paintball's circumference. This would represent the paintball rolling along the barrel at whatever exit velocity you've chosen. At 300 fps, I get around 1685 revolutions per second, or a bit over 100,000 rpm.

BJJB

[ScatterPlot]

I don't actually know any calculations, I have a program called FoilSim that I downloaded off the internet that does stuff with airfoils and stuff like that. There's a "ball" mode that I put in stuff about a paintball, but I guess I did it a little wrong somehow . I can't remember where I found it, but if you'll google it I bet you can find it.