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| Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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Orthoganol balancing - twinwheel grinders
On Fri, 31 Jul 2009 20:35:43 +0200, Robert Roland
wrote: On Fri, 31 Jul 2009 15:05:13 +0100, wrote: the job can be done with an oscilloscope and an old 2" computer loudspeaker That's brilliant, Jim. How about adding some sort of synchronization signal? Paint a white dot on the cup and use a photo transistor connected to the scope's other channel to get a reference to make it much easier to figure out where to add weight. I have played with that sort of system but it gets complicated. For the comparatively small balance improvement needed for a twin wheel grinder the stark simplicity of the speaker plus 'scope is all that is needed. Is a grinder fast enough to use self-balancing similar to what they do in CD-ROM drives? I think it's simply some sort of drum with loose steel balls inside. I'm pretty sure that would work but I've never tried it.I think the system is a bit like my cup but with the edge of the cup rim turned in to retain a partly filled complement of balls. Wen run up to speed the balls space themselves out into a pattern that cancels the unbalance. Jim |
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#2
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Orthoganol balancing - twinwheel grinders
wrote in message ... On Fri, 31 Jul 2009 20:35:43 +0200, Robert Roland wrote: On Fri, 31 Jul 2009 15:05:13 +0100, wrote: the job can be done with an oscilloscope and an old 2" computer loudspeaker That's brilliant, Jim. How about adding some sort of synchronization signal? Paint a white dot on the cup and use a photo transistor connected to the scope's other channel to get a reference to make it much easier to figure out where to add weight. I have played with that sort of system but it gets complicated. For the comparatively small balance improvement needed for a twin wheel grinder the stark simplicity of the speaker plus 'scope is all that is needed. Is a grinder fast enough to use self-balancing similar to what they do in CD-ROM drives? I think it's simply some sort of drum with loose steel balls inside. I'm pretty sure that would work but I've never tried it.I think the system is a bit like my cup but with the edge of the cup rim turned in to retain a partly filled complement of balls. Wen run up to speed the balls space themselves out into a pattern that cancels the unbalance. Jim Another method is available and is normally referred to as the "No Phase Method" where like the scope and speaker coil method you don't have any reference marks. Larry Meidell who is a rather famous helicopter vibration expert wrote an article for the Experimental Helo magazine whereby three locations were used at 120 degree angle separations were used for trial weight positions and then a graphical solution was made using the initial vibration level reading and the three additional readings using trial weights. The result shows at what angle and how much weight is needed. Several books have been published showing this method. I've have successfully used it on my tail rotor and one of the magazine readers balanced his tail rotor using just a dial indicator in lieu of an accelerometer and the "No Phase" method. An article describing that experiment also ended up in the Experimental Helo Magazine. If anyone is interested, let me know and I can check with the author and see if he is willing to release the article to all. Send me an e-mail at the address below. Stuart Fields Experimental Helo Magazine. |
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