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Originally Posted by Rick TYler
This raises a good question. On one of our prototype launchers, we've geared the Bigcim to spin a single wheel at a surface rate of 24 m/sec (twice the 12 m/sec limit). We are trying to get a high-speed camera so that we can directly measure the muzzle velocity of the ball, but so far we haven't been able to. I've been wondering how much velocity will be imparted to the Poof ball by the wheel. The upper limit on this prototype is 12 m/sec, but we haven't found out what the true speed is. Does anyone with better testing gear have any suggestions on how much the typical wheel underperforms theory? (We are using a pair of 8-inch Skyway wheels in the prototype -- low mass.)
Has anyone tried a traffic radar on the ball? Does it register?
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Don't have specific data for you. We're still trying to decide how to measure speed too.
Our drive wheel is a 8" pneumatic skyway "tough wheel" from the kit a year or two ago, with the tire removed and the wheel slot filled with rubber bungies on edge and zip-tied in. This was a prototype, we're now removing the bungies and will replace it with some filler, maybe styrafoam, and cover with silicone. Don't like this idea a lot, but it's the one we have at the moment.
However, we're hoping the ball gets up to near it's theoretcal full speed. We have the track wrapped around the wheel for about 80 degrees, with the spacing at about 6.75", so the ball stays in contact with the wheel for quite a long path. Hopefully it stops slipping and matches speed, although it will also slow down the motor/wheel so we'll have to measure what we ultimately come up with. We may add some flywheel weight to lessen the slowdown and get up to or near the 12 m/s sec goal.
Here's an idea (untested) about measuring the ball speed. Rather than using a high speed camera, what about doing a time exposure of the ball flying by in front of some kind of yardstick, and measure the length of the blur? Another way, also using long exposure, would be a well timed strobe light so you get the ball stopped in one frame in two places, and measure that distance. You could use a 1/10th second exposure then the ball should move just over a meter at max speed.
Bill