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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
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#2
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Orthoganol balancing - twinwheel grinders
On Nov 26, 1:07*am, Bob Engelhardt wrote:
I have a leaf blower powered by a 5 hp, 4 cycle engine. *It has a vibration due to an imbalance of the impeller/fan. *I've statically balanced it, with significant improvement, but I'd like to get it better. *Could I use this orthogonal balancing on a gas engine? *It runs about 3400 rpm, IIRC. Thanks, Bob I can not think of any reason why it would not work. Dan |
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Orthoganol balancing - twinwheel grinders
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Orthoganol balancing - twinwheel grinders
On Wed, 25 Nov 2009 22:38:22 -0500, Bob Engelhardt
wrote: wrote: On Nov 26, 1:07 am, Bob Engelhardt wrote: ...Could I use this orthogonal balancing on a gas engine? ... I can not think of any reason why it would not work. I guess what I was wondering about, without having my finger on it specifically, is whether the inherent vibration of a gas engine would drown out the impeller's imbalance. As far as being able to see it on the 'scope. But it has just occurred to me that I can do the orthogonal balancing of the impeller off the gas engine, on an electric motor. Turning on a motor would be a lot easier than pull starting the engine, for all those trials. And I could do it inside. I'd probably have to use a 3 phase motor & VFD to run at a speed that wouldn't overload the motor. Now, as to the procedure, is this right: 1. add some weight, w, to the "1" spot & measure the amplitude of the vibration 2. try the same weight at "3" & measure 3. put the weight at the location of lesser amplitude 4. put on an additional weight of w/2 & measure 5. move the w/2 weight to the other side & measure 6. put the w/2 weight at the location of lesser amplitude repeat 4 - 6 with w/4, w/8, etc If at any weight the 1 & 3 amplitudes are the same, skip that weight & go on to the next size. Repeat for the "2" & "4" spots. You didn't say, but it seems to me that it's possible that "w" is going to be significantly too small. I.e., all the weights will be on the same side, desperately trying to get big enough to balance. In anticipation of this, if "w" & "w/2" are both on the same side, start over with 2w. Also, the weights don't have to accumulate, they can be partially eliminated. E.g., if you have w at 1 & w/2 at 3, that's a net of w/2 at 1. Or, generally: if w/(n+1) is opposite w/n, then remove w/n & put w/(n+1) in its place. I don't see a real advantage to this, but maybe there is. And it's dependent upon accurately making weights 1/2 the previous size. OK, it's not a good practical idea. Thanks, Bob Motor drive is the way to go - there would be too much vibration from th gas engine. Belt drive is often more convenient than direct drive. You've got the balancing sequence dead right and it's important to stick to it It's only too easy to chase your own tail if you cut corners or if the balance weight placements are not correctly 90 deg apart Good luck Jim |
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