The discussion revolves around methods for measuring the rotational speed or angular velocity of a golf ball and other projectiles. Participants explore various equipment and techniques, including high-speed video, laser tachometers, and strobe lights, while considering the challenges associated with these methods.
Participants express a range of opinions on the best methods for measuring rotational speed, with no consensus reached on a single approach. Various techniques are debated, and challenges are acknowledged without resolution.
Participants note limitations regarding the effectiveness of certain equipment for small, fast-moving objects and the need for specific conditions (e.g., lighting) to enhance measurement accuracy. The discussion also highlights the dependence on the definitions of rotational speed and the specific context of the measurements being taken.
I saw a non-contact laser tachometer. Is it able to detect the rotational speed instantaneously when the golf ball passes the laser? Or do I have to hold the laser into the moving golf ball for a period of time before it can detect the rotational speed?Quantum Defect said:Something like a strobe/tachometer could work, but it might be tricky to do for a small moving object.
Kariege said:I saw a non-contact laser tachometer. Is it able to detect the rotational speed instantaneously when the golf ball passes the laser? Or do I have to hold the laser into the moving golf ball for a period of time before it can detect the rotational speed?
Thanks
I understand but here I think I'm just examining from a 2 dimensional view. So particularly I will look at backspin. But can I just hold the tachometer and point the laser to the ball and it's track? Can it detect the rotational speed in that way? I've seen the high speed video, they seem very pricy since the video camera should be around 1000fps, so I'm just trying to look for an alternative.Quantum Defect said:I think that this will be difficult to do with something designed for working on cars. The ones I saw required affixing reflective material on the object -- I suspect that they are simply measuring the flashes of reflective light as a function of time to come up with the angular velocity.
With the golf ball, as @Doug Huffman noted, you have something small moving very rapidly across the field of view, possibly rotating around more than one axis, so the chances of having the relective bit come back into the frame is unlikely.
I suspect that fast video (as Doug noted) will work the best. I don't know what kind of equipment that the "Super Slo Mo Guys" use, but something along those lines might be able to track the rotational velocity as the golf ball leaves the tee.
Some consumer cameras for ~300$ can shot at 400-1200fps which should be enough for a golf ball. The resolution is low, but if you know exactly where the ball is, you can place the camera close enough to see the marks. You just need to catch the ball on two frames. Checkout the Nikon 1 for example, maybe some friends have it.Kariege said:I've seen the high speed video, they seem very pricy since the video camera should be around 1000fps, so I'm just trying to look for an alternative.
Kariege said:Ok I'll probably go out and ask for a camera rental then. Thanks everyone
A.T. said:These clips were shot with the Nikon 1 J1, so you know what to expect. Note that youtube re-encodes them, the original quality is somewhat better.
400FPS:
1200FPS:
I would paint half of the golf ball black, to get the best 1D rotation reference. Also use as much light as possible, ideally direct sunlight.Kariege said:nice, the 1200 fps looks just right with a sufficient resolution. First I thought it will be difficult with a 320x340 video.