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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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#1
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Balancing a fan
I got so much help on my sprayer, I'm trying again...
Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl |
#2
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Balancing a fan
On 5/14/2010 7:07 AM, Karl Townsend wrote:
I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. I bet you can whip one of these up in no time! http://www.youtube.com/watch?v=bBzviKTPMrg --Winston |
#3
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Balancing a fan
What comes to mind to me. The fan has to come off the shaft
(might be dificult). Take a ball berring that's larger than the shaft hole in the center. Drill a counter sink on the end of a shaft. Put the ball berring on the end of the shaft, and the fan on the ball berring. Ends up looking like a crude lamp shade. That should give you a rough idea which is the heavy side. Similar to balancing lawn mower blades. -- Christopher A. Young Learn more about Jesus www.lds.org .. "Karl Townsend" wrote in message anews.com... I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl |
#4
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Balancing a fan
Karl Townsend wrote:
I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Something like this, only bigger? http://www3.towerhobbies.com/cgi-bin...&I=LXHY61&P=ML Before you dynamic balance, can you check the static balance? If the static balance is perfect then I'd doubt that the thing is out of dynamic balance. If those bearings aren't as free as free can be then you've got a problem. How much of a pain is it to take the fan out? Could you use the "knife edge" with the fan shaft on a couple of angle irons, corner up? Or: can you take the shaft out, and make an adapter so the thing will go on a truck tire balancer? -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com |
#5
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Balancing a fan
Karl Townsend wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Remember that any vibration would relate to the rotational speed of the item out of balance. Can you get your hands on a resonant reed tachometer? The RRTs are recommended for isolating vehicle driveline vibrations by identifying the frequency of the vibration so you can correlate it to which driveline components rotate at that frequency. As for fan balance, if you just take the drive belts off you should be able to turn the fan by hand to identify any issues. Mark the fan and spin it by hand a few times and see if it is stopping near the same orientation each time. Again, I doubt it's the fan since I expect it's spinning a lot faster than the 540 RPM PTO and won't have a 9 Hz period if it has an imbalance. While you have the belts off to hand spin the fan, it would be good to check both drive and driven pulleys for runout with a dial indicator. |
#6
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Balancing a fan
On Fri, 14 May 2010 10:02:20 -0500, "Pete C."
wrote: Karl Townsend wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Remember that any vibration would relate to the rotational speed of the item out of balance. Can you get your hands on a resonant reed tachometer? The RRTs are recommended for isolating vehicle driveline vibrations by identifying the frequency of the vibration so you can correlate it to which driveline components rotate at that frequency. As for fan balance, if you just take the drive belts off you should be able to turn the fan by hand to identify any issues. Mark the fan and spin it by hand a few times and see if it is stopping near the same orientation each time. Again, I doubt it's the fan since I expect it's spinning a lot faster than the 540 RPM PTO and won't have a 9 Hz period if it has an imbalance. I agree. I also don't see how fan imbalance would generate torque ripple. I would suspect some aspect of the drive line between PTO and gearbox: pulley, bent shaft, any couplings or U-joints, etc |
#7
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Balancing a fan
"Karl Townsend" wrote in message anews.com... I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl From the text Mechanical Vibrations written by Den Hartog: If you have an out of balance shaft rotating at less than the "Critical Speed" and you approach that shaft with a pencil or a felt tip pen, the mark will be made on the "heavy" side. Add wts to the opposite side from the mark. However if the shaft is rotating at more than the "Critical Speed", your pencil/felt tip pen will mark the light side and wts must be added to the same side as the mark. If you are unfortunate enough to have the shaft rotating at the "Critical Speed" the mark will be made 90 degrees after the heavy side. This concept has helped me balance helicopter main and tail rotors down by factors of 4 below the normally acceptable levels. However I do have an electronic balancer that uses velocimeters to measure the magnitude of the vibration and a photo sensor to give me the "pencil" mark. We did have a subscriber to our magazine that balanced his tail rotor using just a dial indicator and a graphic technique developed by the Russians. I think that I could make a copy of the article describing that technique available if you want it. Stu Fields Experimental Helo magazine. |
#8
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Balancing a fan
"Don Foreman" wrote in message ... On Fri, 14 May 2010 10:02:20 -0500, "Pete C." wrote: Karl Townsend wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Remember that any vibration would relate to the rotational speed of the item out of balance. Can you get your hands on a resonant reed tachometer? The RRTs are recommended for isolating vehicle driveline vibrations by identifying the frequency of the vibration so you can correlate it to which driveline components rotate at that frequency. As for fan balance, if you just take the drive belts off you should be able to turn the fan by hand to identify any issues. Mark the fan and spin it by hand a few times and see if it is stopping near the same orientation each time. Again, I doubt it's the fan since I expect it's spinning a lot faster than the 540 RPM PTO and won't have a 9 Hz period if it has an imbalance. I agree. I also don't see how fan imbalance would generate torque ripple. I would suspect some aspect of the drive line between PTO and gearbox: pulley, bent shaft, any couplings or U-joints, etc Pete and Don, I also agree. I've said it CAN'T be the fan vibration for years. But I also can't find anything else wrong. And its not for a lack of trying. I'm about to pop $11,100 and trade it in for a new used one. Julie's not to keen on that idea, but only because we haven't got the money. karl |
#9
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Balancing a fan
Karl Townsend wrote: "Don Foreman" wrote in message ... On Fri, 14 May 2010 10:02:20 -0500, "Pete C." wrote: Karl Townsend wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Remember that any vibration would relate to the rotational speed of the item out of balance. Can you get your hands on a resonant reed tachometer? The RRTs are recommended for isolating vehicle driveline vibrations by identifying the frequency of the vibration so you can correlate it to which driveline components rotate at that frequency. As for fan balance, if you just take the drive belts off you should be able to turn the fan by hand to identify any issues. Mark the fan and spin it by hand a few times and see if it is stopping near the same orientation each time. Again, I doubt it's the fan since I expect it's spinning a lot faster than the 540 RPM PTO and won't have a 9 Hz period if it has an imbalance. I agree. I also don't see how fan imbalance would generate torque ripple. I would suspect some aspect of the drive line between PTO and gearbox: pulley, bent shaft, any couplings or U-joints, etc Pete and Don, I also agree. I've said it CAN'T be the fan vibration for years. But I also can't find anything else wrong. And its not for a lack of trying. I'm about to pop $11,100 and trade it in for a new used one. Julie's not to keen on that idea, but only because we haven't got the money. karl Before you go blowing a big wad of money on a new blower, spend a day checking the things we noted. It should not take that long to check the fan for imbalance, the pulleys for runout, etc. This isn't that complicated, it's just an organized process of isolation and elimination. |
#10
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Balancing a fan
"Karl Townsend" wrote in message
anews.com... I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Fluke makes (made) a hand-held analyzer for dynamic balancing. Proly not super cheap, but fast, quick, accurate. And proly not as expensive as it once was. Saw it used, never used it mysef. Field HVAC techs use this. Might want to ask the assholes on alt.hvac what their experiences are. And if they have any experience, it's good news, cuz if those assholes can use one, anyone can. I googled fluke dynamic balancing, didn't get much, but didn't look long, either. Heh, mebbe an auto place, that does dynamic wheel balancing? -- EA Karl |
#11
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Balancing a fan
"Tim Wescott" wrote in message
... Karl Townsend wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Something like this, only bigger? http://www3.towerhobbies.com/cgi-bin...&I=LXHY61&P=ML Before you dynamic balance, can you check the static balance? If the static balance is perfect then I'd doubt that the thing is out of dynamic balance. Yeah, but you would need almost laboratory conditions, as the rotation magnifies imbalance forces according to V^2/R. small = big! If those bearings aren't as free as free can be then you've got a problem. How much of a pain is it to take the fan out? Could you use the "knife edge" with the fan shaft on a couple of angle irons, corner up? Or: can you take the shaft out, and make an adapter so the thing will go on a truck tire balancer? I suggested dynamic balancing at a good garage, altho come to think of it, I haven't seen this in a while Altho, ackshooly, VP Tires, Yonkers NY does dynamic balancing -- $10 per tire. Puts weights on the inside AND outside of the rim, per the pyooter. Great place. Vinny at VP said static balancing went out with horses'n'saddles -- direct quote. Whether he could do Karl's squirrel cage is another story. BUT, if Karl were to go to a place like this, and himself make the mounting adapters, I'm sure it would work, altho these machines might be used to measuring more forces from big tires/rims than a squirrel cage might offer. The Fluke gadget is the real solution, and actually sumpn that might be a worthwhile purchase in a number of shops, as it proly pays for itself in bearings. Even on the flywheel/pulley of compressors, etc, or multi-step pulleys in old drill presses, etc.. -- EA -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com |
#12
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Balancing a fan
On May 14, 10:07*am, "Karl Townsend"
wrote: Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Jim Pentagrid recently posted about how he balanced a bench grinder using a small computer speaker with a lump of clay added to turn it into an acceleromete I will try to find the thread for you. Dan |
#13
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Balancing a fan
On May 14, 5:17*pm, " wrote:
On May 14, 10:07*am, "Karl Townsend" wrote: Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Jim Pentagrid recently posted about how he balanced a bench grinder using a small computer speaker with a lump of clay added to turn it into an acceleromete I will try to find the thread for you. * * * * * * * * * * * * * * * * * * * * * * * * *Dan Orthoganol balancing - twinwheel grinders July 2009 Dan |
#14
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Balancing a fan
wrote in message ... On May 14, 5:17 pm, " wrote: On May 14, 10:07 am, "Karl Townsend" wrote: Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Jim Pentagrid recently posted about how he balanced a bench grinder using a small computer speaker with a lump of clay added to turn it into an acceleromete I will try to find the thread for you. Dan Orthoganol balancing - twinwheel grinders July 2009 Dan I've been driving around St.Cloud today. Found a place that balances flywheels and drive shafts out of large earth construction equipment, My dinky 40 horse fan with only a two inch shaft is a toy for them. Anyway, I'll tear the whole machine down to indivdual parts. Then I can recheck runnout of each individual component also. probelm is, i know I'll find runnout when I check this accurately. Karl |
#15
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Balancing a fan
How about this for a hypothesis:
There is nothing at all wrong with the fan, itself. Something got sucked in and is stuck between a couple of blades. Pete Stanaitis ----------------- Karl Townsend wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl |
#16
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Balancing a fan
On 2010-05-14, Karl Townsend wrote:
"Don Foreman" wrote in message ... [ ... ] I agree. I also don't see how fan imbalance would generate torque ripple. I would suspect some aspect of the drive line between PTO and gearbox: pulley, bent shaft, any couplings or U-joints, etc Pete and Don, I also agree. I've said it CAN'T be the fan vibration for years. But I also can't find anything else wrong. And its not for a lack of trying. I'm about to pop $11,100 and trade it in for a new used one. Julie's not to keen on that idea, but only because we haven't got the money. I presume that you have tried static balancing the fan? If not, that would be a lot cheaper to try at least. Mount the blade on a shaft of proper diameter. Set up two straightedges as level as you can get them. Place the shaft on the edges, and observe whether it tends to roll until one specific point is always down. If so -- add weight opposite it until you no longer observe this. Since you have no way to know the dynamic balance, add the weight in the middle of the vanes (squirrel cage -- right?). If you then see another point become the one which heads for the bottom, add more weight opposite that -- unless the heavy spot is where you just added the weights -- in which case reduce the weight a little. Dynamic balance is a lot trickier to manage -- you need expensive tooling for that. Oh yes -- while you have the blower off its original shaft, check the bearings for play. Good Luck, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#17
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Balancing a fan
Karl Townsend wrote: wrote in message ... On May 14, 5:17 pm, " wrote: On May 14, 10:07 am, "Karl Townsend" wrote: Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Jim Pentagrid recently posted about how he balanced a bench grinder using a small computer speaker with a lump of clay added to turn it into an acceleromete I will try to find the thread for you. Dan Orthoganol balancing - twinwheel grinders July 2009 Dan I've been driving around St.Cloud today. Found a place that balances flywheels and drive shafts out of large earth construction equipment, My dinky 40 horse fan with only a two inch shaft is a toy for them. Excellent. Anyway, I'll tear the whole machine down to indivdual parts. Then I can recheck runnout of each individual component also. probelm is, i know I'll find runnout when I check this accurately. It's not aerospace stuff, so it won't be perfect. The trick is in comparing the amount of runout measured to the parts location in the drivetrain to determine if the runout is significant. |
#18
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Balancing a fan
On 05/14/2010 01:23 PM, Existential Angst wrote:
"Tim wrote in message ... Karl Townsend wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Something like this, only bigger? http://www3.towerhobbies.com/cgi-bin...&I=LXHY61&P=ML Before you dynamic balance, can you check the static balance? If the static balance is perfect then I'd doubt that the thing is out of dynamic balance. Yeah, but you would need almost laboratory conditions, as the rotation magnifies imbalance forces according to V^2/R. small = big! If those bearings aren't as free as free can be then you've got a problem. How much of a pain is it to take the fan out? Could you use the "knife edge" with the fan shaft on a couple of angle irons, corner up? Or: can you take the shaft out, and make an adapter so the thing will go on a truck tire balancer? I suggested dynamic balancing at a good garage, altho come to think of it, I haven't seen this in a while Altho, ackshooly, VP Tires, Yonkers NY does dynamic balancing -- $10 per tire. Puts weights on the inside AND outside of the rim, per the pyooter. Great place. Vinny at VP said static balancing went out with horses'n'saddles -- direct quote. Whether he could do Karl's squirrel cage is another story. BUT, if Karl were to go to a place like this, and himself make the mounting adapters, I'm sure it would work, altho these machines might be used to measuring more forces from big tires/rims than a squirrel cage might offer. Have you considered how much power it would take to spin that squirrel cage on the dynamic balancer? You'd have to do something to keep the rotor from pumping air, perhaps a disk (precisely balanced, of course) to cover each end. -- Bob Nichols AT comcast.net I am "RNichols42" |
#19
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Balancing a fan
On Fri, 14 May 2010 07:13:46 -0700, Winston
wrote the following: On 5/14/2010 7:07 AM, Karl Townsend wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. I bet you can whip one of these up in no time! http://www.youtube.com/watch?v=bBzviKTPMrg That's a static balancer, Pooh. He probably needs dynamic balancing. Karl, ask around for vibration monitoring companies. When I worked for Palomar Technology (one of them, who was bought out by SKF), they had techs who would check everything up to and including the 30' turbines at SDG&E' steam/electric plant. Or ask the bearing folks directly. Either that or to pull the bird, apple, or mouse out of the fan blades. -- Work and struggle and never accept an evil that you can change. -- Andre Gide |
#20
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Balancing a fan
"DoN. Nichols" wrote in message ... On 2010-05-14, Karl Townsend wrote: "Don Foreman" wrote in message ... [ ... ] I agree. I also don't see how fan imbalance would generate torque ripple. I would suspect some aspect of the drive line between PTO and gearbox: pulley, bent shaft, any couplings or U-joints, etc Pete and Don, I also agree. I've said it CAN'T be the fan vibration for years. But I also can't find anything else wrong. And its not for a lack of trying. I'm about to pop $11,100 and trade it in for a new used one. Julie's not to keen on that idea, but only because we haven't got the money. I presume that you have tried static balancing the fan? If not, that would be a lot cheaper to try at least. Mount the blade on a shaft of proper diameter. Set up two straightedges as level as you can get them. Place the shaft on the edges, and observe whether it tends to roll until one specific point is always down. If so -- add weight opposite it until you no longer observe this. Since you have no way to know the dynamic balance, add the weight in the middle of the vanes (squirrel cage -- right?). If you then see another point become the one which heads for the bottom, add more weight opposite that -- unless the heavy spot is where you just added the weights -- in which case reduce the weight a little. Dynamic balance is a lot trickier to manage -- you need expensive tooling for that. Oh yes -- while you have the blower off its original shaft, check the bearings for play. Good Luck, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- Don: We have an example where a man made a jig to turn his tail rotor, a simple fan, from his helicopter, by an electric motor. He used a dial indicator and a graphical technique developed by the Russians, to determine the amount and location of the correcting weight. In theory it takes 4 spin ups to determine the amount and location to put the weight. Then a 5th spin up to verify. I've had some success with this method on a tail rotor of a helicopter that had a critical speed kind of close to the operating speed. That is the good news. The bad news is even some Phds who specialize in vibrations can't explain why some of the steps are done. They revert back to "Well it does work". |
#21
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Balancing a fan
On Fri, 14 May 2010 09:07:51 -0500, "Karl Townsend"
wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Video? Pictures? Audio? Airplane to spray it ! SW |
#22
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Balancing a fan
Existential Angst wrote:
"Karl Townsend" wrote in message anews.com... I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Fluke makes (made) a hand-held analyzer for dynamic balancing. Proly not super cheap, but fast, quick, accurate. And proly not as expensive as it once was. Saw it used, never used it mysef. Field HVAC techs use this. Might want to ask the assholes on alt.hvac what their experiences are. And if they have any experience, it's good news, cuz if those assholes can use one, anyone can. I googled fluke dynamic balancing, didn't get much, but didn't look long, either. Heh, mebbe an auto place, that does dynamic wheel balancing? A place that does big truck driveline balancing is a place to start, although they will be limited in the diameter they can swing---also inquire one or 2 of the mfgrs of heavy duty balancers--they like to refer customers to a place using their machine... jerry |
#23
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Balancing a fan
spaco wrote:
How about this for a hypothesis: There is nothing at all wrong with the fan, itself. Something got sucked in and is stuck between a couple of blades. Pete Stanaitis ----------------- Karl Townsend wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Very astute guess , Pete, probably a rat or snake ..Jerrry |
#24
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Balancing a fan
On 2010-05-15, Stu Fields wrote:
"DoN. Nichols" wrote in message ... [ ... ] I presume that you have tried static balancing the fan? If not, that would be a lot cheaper to try at least. [ ... ] Dynamic balance is a lot trickier to manage -- you need expensive tooling for that. [ ... ] Don: We have an example where a man made a jig to turn his tail rotor, a simple fan, from his helicopter, by an electric motor. He used a dial indicator and a graphical technique developed by the Russians, to determine the amount and location of the correcting weight. In theory it takes 4 spin ups to determine the amount and location to put the weight. Then a 5th spin up to verify. I've had some success with this method on a tail rotor of a helicopter that had a critical speed kind of close to the operating speed. That could make things rather exciting. :-) That is the good news. The bad news is even some Phds who specialize in vibrations can't explain why some of the steps are done. They revert back to "Well it does work". That is better than "It shouldn't work" at least. :-) O.K. But the rotor is similar to a standard room fan blade, rather than the squirrel cage blade, so the dynamic balance is not that far from the static balance. With a squirrel cage blower, whose length is similar to its diameter, the dynamic balance points can be very different from static balance, depending on luck. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#25
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Balancing a fan
On Fri, 14 May 2010 19:38:48 -0700, "Stu Fields"
wrote: "DoN. Nichols" wrote in message ... On 2010-05-14, Karl Townsend wrote: "Don Foreman" wrote in message ... [ ... ] I agree. I also don't see how fan imbalance would generate torque ripple. I would suspect some aspect of the drive line between PTO and gearbox: pulley, bent shaft, any couplings or U-joints, etc Pete and Don, I also agree. I've said it CAN'T be the fan vibration for years. But I also can't find anything else wrong. And its not for a lack of trying. I'm about to pop $11,100 and trade it in for a new used one. Julie's not to keen on that idea, but only because we haven't got the money. I presume that you have tried static balancing the fan? If not, that would be a lot cheaper to try at least. Mount the blade on a shaft of proper diameter. Set up two straightedges as level as you can get them. Place the shaft on the edges, and observe whether it tends to roll until one specific point is always down. If so -- add weight opposite it until you no longer observe this. Since you have no way to know the dynamic balance, add the weight in the middle of the vanes (squirrel cage -- right?). If you then see another point become the one which heads for the bottom, add more weight opposite that -- unless the heavy spot is where you just added the weights -- in which case reduce the weight a little. Dynamic balance is a lot trickier to manage -- you need expensive tooling for that. Oh yes -- while you have the blower off its original shaft, check the bearings for play. Good Luck, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- Don: We have an example where a man made a jig to turn his tail rotor, a simple fan, from his helicopter, by an electric motor. He used a dial indicator and a graphical technique developed by the Russians, to determine the amount and location of the correcting weight. In theory it takes 4 spin ups to determine the amount and location to put the weight. Then a 5th spin up to verify. I've had some success with this method on a tail rotor of a helicopter that had a critical speed kind of close to the operating speed. That is the good news. The bad news is even some Phds who specialize in vibrations can't explain why some of the steps are done. They revert back to "Well it does work". I think I saw that Russian technique described somewhere along the line. The technique may be incomprehensible to some PhD's because a coherent, linear-thinking approach may fail to derive theory supporting it. It may be a technique that uses bits of disjoint theory and perhaps some assumptions that aren't generally supportable, but works most of the time and/or perhaps all of the time in most real-world cases -- one of which may be tail rotors. I led an R&D team that developed a self-balancing washing machine some years ago. Interesting problem because of severe cost constraints of the whitegoods market and ill-defined boundary conditions. Example: consumer washers are never bolted to concrete, and some set on the flimsy floor of a doublewide. The structure was comprised of stamped sheetmetal and some plastic, certainly not cast iron like machine tools or tire balancing machines. There were a ****load of resonances, and many of them weren't very predictable. In addition, this washer went much faster than traditional washers in the spin cycle, because it could self-balance. That reduced energy necessary for drying. Barely-damp clothes peeled off the drum with pronouced dimples in them. The team used a technique using oversensing and SVD (singular value decomposition) sometimes used in aerospace guidance & control systems. It worked! At least a dozen patents were spawned. Then politics and corporate infighting rendered the project stillborne. |
#26
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Balancing a fan
On 5/14/2010 7:14 PM, Larry Jaques wrote:
On Fri, 14 May 2010 07:13:46 -0700, wrote the following: On 5/14/2010 7:07 AM, Karl Townsend wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. I bet you can whip one of these up in no time! http://www.youtube.com/watch?v=bBzviKTPMrg That's a static balancer, Pooh. He probably needs dynamic balancing. I 'spect that if the cage were in balance statically, it wouldn't exhibit any pathology in application. Yes? No? (...) -- Work and struggle and never accept an evil that you can change. *Then* get tossed out on your can. --Winston |
#27
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Balancing a fan
On Fri, 14 May 2010 09:31:32 -0700, "Stu Fields"
wrote: "Karl Townsend" wrote in message tanews.com... I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl From the text Mechanical Vibrations written by Den Hartog: If you have an out of balance shaft rotating at less than the "Critical Speed" and you approach that shaft with a pencil or a felt tip pen, the mark will be made on the "heavy" side. Add wts to the opposite side from the mark. However if the shaft is rotating at more than the "Critical Speed", your pencil/felt tip pen will mark the light side and wts must be added to the same side as the mark. If you are unfortunate enough to have the shaft rotating at the "Critical Speed" the mark will be made 90 degrees after the heavy side. This concept has helped me balance helicopter main and tail rotors down by factors of 4 below the normally acceptable levels. However I do have an electronic balancer that uses velocimeters to measure the magnitude of the vibration and a photo sensor to give me the "pencil" mark. We did have a subscriber to our magazine that balanced his tail rotor using just a dial indicator and a graphic technique developed by the Russians. I think that I could make a copy of the article describing that technique available if you want it. Stu Fields Experimental Helo magazine. This is analogous to resonance in an electrical RLC circuit, wherein "critical speed" is resonant frequency. The response to excitation of such a circuit will be in phase well below resonance, lag by 90 deg at resonance, and lag by 180 deg well above resonance. All phase angles between 0 and 180 will occur somewhere between way below resonance and way above resonance. The speed (frequency) bandwidth of this region of uncertain phase angle depends upon the "Q", or sharpness of the resonance. |
#28
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Balancing a fan
On Fri, 14 May 2010 19:01:25 -0500, "Karl Townsend"
wrote: wrote in message ... On May 14, 5:17 pm, " wrote: On May 14, 10:07 am, "Karl Townsend" wrote: Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Jim Pentagrid recently posted about how he balanced a bench grinder using a small computer speaker with a lump of clay added to turn it into an acceleromete I will try to find the thread for you. Dan Orthoganol balancing - twinwheel grinders July 2009 Dan I've been driving around St.Cloud today. Found a place that balances flywheels and drive shafts out of large earth construction equipment, My dinky 40 horse fan with only a two inch shaft is a toy for them. Anyway, I'll tear the whole machine down to indivdual parts. Then I can recheck runnout of each individual component also. probelm is, i know I'll find runnout when I check this accurately. Karl Didja stop at Scheel's for bullets, brass, powder or primers? If so, how's the stock sit looking there? |
#29
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Balancing a fan
The team used a technique using oversensing and SVD (singular value
decomposition) sometimes used in aerospace guidance & control systems. It worked! At least a dozen patents were spawned. Then politics and corporate infighting rendered the project stillborne. Reminds me of a company I used to work for. There's a reason I dropped the huge salary job and now farm for a living. Karl |
#30
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Balancing a fan
Didja stop at Scheel's for bullets, brass, powder or primers? If so, how's the stock sit looking there? How'd you know my ulterior motive to go shopping with the boss? 2000 small rifle and 1000 small pistol primers. ordered .223 rifle lead from Midwest and 9MM from Berry. Got the brass covered. But i do have a new problem. I can't seem to keep the lead and primers in the brass. And the neighbors keep asking about the noise. karl |
#31
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Balancing a fan
On Fri, 14 May 2010 22:16:49 -0700, Winston
wrote the following: On 5/14/2010 7:14 PM, Larry Jaques wrote: On Fri, 14 May 2010 07:13:46 -0700, wrote the following: On 5/14/2010 7:07 AM, Karl Townsend wrote: I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. I bet you can whip one of these up in no time! http://www.youtube.com/watch?v=bBzviKTPMrg That's a static balancer, Pooh. He probably needs dynamic balancing. I 'spect that if the cage were in balance statically, it wouldn't exhibit any pathology in application. Yes? No? How the hell do you answer that question with a y/n? Sheesh! Wrong, sorry. It can and does in reality. I found that when I worked at the body/frame repair shop with a Hunter balancing machine for auto/truck tires. You can balance to static perfection and still have a very noticeable OOB condition due to dynamic imbalances, which rip the spinning object out of a smooth axial path and beat the bearings to an early death. Work and struggle and never accept an evil that you can change. *Then* get tossed out on your can. But there's still less evil in your world as a result of your actions. Painful justification, wot? -- Men never do evil so completely and cheerfully as when they do it from religious conviction. - Blaise Pascal |
#32
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Balancing a fan
On Sat, 15 May 2010 04:59:52 -0500, "Karl Townsend"
wrote: The team used a technique using oversensing and SVD (singular value decomposition) sometimes used in aerospace guidance & control systems. It worked! At least a dozen patents were spawned. Then politics and corporate infighting rendered the project stillborne. Reminds me of a company I used to work for. There's a reason I dropped the huge salary job and now farm for a living. Karl Weird how that works. One time I was installing a new electronic device in everyone's cubical. This area was pretty high security in a bureaucracy and the women administrators were gathered together discussing if I had clearance to be there. I held up 8 fingers and stated this is 7and then the inverse. The head one turns to the rest and said he's clear. If anything made sense something was fishy. There must be a good book on this subject, somewhere. One that explains why people throw ball bearings into open gears, pull petty power trips, create computer viruses, establish frivolous red tape, give false directions, ect. SW |
#33
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Balancing a fan
On Sat, 15 May 2010 04:59:52 -0500, "Karl Townsend"
wrote the following: The team used a technique using oversensing and SVD (singular value decomposition) sometimes used in aerospace guidance & control systems. It worked! At least a dozen patents were spawned. Then politics and corporate infighting rendered the project stillborne. Reminds me of a company I used to work for. There's a reason I dropped the huge salary job and now farm for a living. An apple a day keeps the infighting politicians away? When the corporation bought the company I was working for, I bailed and started my own company rather than face, um, let's call them The Dilbertian Uncertainties. Like you, I'm very glad I did. Low pay, hard work, and total satisfaction. What's a guy not to like? -- Work and struggle and never accept an evil that you can change. -- Andre Gide |
#34
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Balancing a fan
Larry Jaques wrote: On Sat, 15 May 2010 04:59:52 -0500, "Karl Townsend" wrote the following: The team used a technique using oversensing and SVD (singular value decomposition) sometimes used in aerospace guidance & control systems. It worked! At least a dozen patents were spawned. Then politics and corporate infighting rendered the project stillborne. Reminds me of a company I used to work for. There's a reason I dropped the huge salary job and now farm for a living. An apple a day keeps the infighting politicians away? When the corporation bought the company I was working for, I bailed and started my own company rather than face, um, let's call them The Dilbertian Uncertainties. Like you, I'm very glad I did. Low pay, hard work, and total satisfaction. What's a guy not to like? I'm working on early retirement to subsistence farming and ignoring the imploding world myself... |
#35
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Balancing a fan
"Karl Townsend" wrote in message anews.com... I got so much help on my sprayer, I'm trying again... Full time investigation and part replacement has me working on this theory of the problem cause: The squirrel cage fan is out of balance. It is barely detectable because the fan has a 2" solid steel shaft and some serious pillow block bearings mounted solid to a beefy frame. At the resonate RPM, this imbalance feeds on the slack in the drive line. Any system upset causes the fan to become unstable and it lurches back and forth. I've called around and not found a place to dynamic balance something like this. Are there any home brew methods? Or other suggestions? Its built so solid I don't think I'm looking for a minor imbalance. Karl Get a couple of load cells and a digital storage scope, trigger from a signal once per revolution. Perhaps a vibration sensor at each pillow block would do the same thing? This probably isn't practical unless you already have the DSO. RogerN |
#36
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Balancing a fan
"DoN. Nichols" wrote in message ... On 2010-05-15, Stu Fields wrote: "DoN. Nichols" wrote in message ... [ ... ] I presume that you have tried static balancing the fan? If not, that would be a lot cheaper to try at least. [ ... ] Dynamic balance is a lot trickier to manage -- you need expensive tooling for that. [ ... ] Don: We have an example where a man made a jig to turn his tail rotor, a simple fan, from his helicopter, by an electric motor. He used a dial indicator and a graphical technique developed by the Russians, to determine the amount and location of the correcting weight. In theory it takes 4 spin ups to determine the amount and location to put the weight. Then a 5th spin up to verify. I've had some success with this method on a tail rotor of a helicopter that had a critical speed kind of close to the operating speed. That could make things rather exciting. :-) That is the good news. The bad news is even some Phds who specialize in vibrations can't explain why some of the steps are done. They revert back to "Well it does work". That is better than "It shouldn't work" at least. :-) O.K. But the rotor is similar to a standard room fan blade, rather than the squirrel cage blade, so the dynamic balance is not that far from the static balance. With a squirrel cage blower, whose length is similar to its diameter, the dynamic balance points can be very different from static balance, depending on luck. Enjoy, DoN. Given the geometry you mention, it sounds like a two plane balancing job similar to that used on the auto crankshafts or in the case of the Helicycle turbine engine the compressor and turbine wheels. (63,000 rpm) I watched several of those things being balanced and it does seem to require simultaneous balancing of both ends. It would seem that the Squirrel cage might require a two plane static balance by both balancing in the plane perpindicular to the rotation axis as well as the plane containing the rotation axis. That might be a first step in taking care of the rotational balance as well as the "rocking couple". I've seen a helicopter rotor carefully statically balanced span wise that needed no more span wise attention when run with the dynamic balancer. I certainly agree that balancing a spinning mass can often involve requiring the balancer to have the proper DNA and family history. |
#37
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Balancing a fan
"RogerN" wrote in message m... "Stu Fields" wrote in message ... "Roger Haar" wrote in Roger: You are dead right. On the Helicopter, the first move is to track the blades. aerodynamically. Out of track blades on the helo will cause a 1/rev vertical vibration that can confuse a balancing operation if the operator isn't paying attention. On our ship we put two different color grease pencil marks on each blade. When the rotor is spun to full speed, my wife takes a pole with the center cardboard tube from a paper towel roll attached to the top of the pole and carefully brings the paper towel roll in until it just ticks the blade ends. We get two different color tick marks of one blade is higher than the other. We adjust until we get just one color combined from the two. This doesn't guarantee good aerodynamic tracking at cruise speed on the helo since aerodyanic differences of the two blades can cause a "climbing" blade. Helps to have a fearless wife... I do something sort of similar on my R/C helicopters. I use 2 different color tape strips near the tip of each blade, hover the helicopter and look at it from the side, you can see if one color of tape is flying higher than the other. When the blades are out of track it causes a lot of vibration. RogerN With our bigger ships, a tracking tip light was invented where you install a red LED on one blade tip and a white LED on the other. The LEDs are pointed at the pilot. The first time I tried these, I was nervous about them coming off in flight and creating a hellatious vibration. While running up I noticed a red streak and a white streak and thought "This is Great". Then at flight rpm the lights disappeared. No vibration so they must have both left at the same time. Slowed back down and there the lights were again. Great design. Centrifugal force pulled the little battery away from the LED. Tremendous idea though. It eliminated the need for a passenger operating a strobe light to check track during cruising flite. One design used centrifugal force to turn the LEDs on... |
#38
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Balancing a fan
"Stu Fields" wrote in message ... "RogerN" wrote in message m... "Stu Fields" wrote in message ... "Roger Haar" wrote in Roger: You are dead right. On the Helicopter, the first move is to track the blades. aerodynamically. Out of track blades on the helo will cause a 1/rev vertical vibration that can confuse a balancing operation if the operator isn't paying attention. On our ship we put two different color grease pencil marks on each blade. When the rotor is spun to full speed, my wife takes a pole with the center cardboard tube from a paper towel roll attached to the top of the pole and carefully brings the paper towel roll in until it just ticks the blade ends. We get two different color tick marks of one blade is higher than the other. We adjust until we get just one color combined from the two. This doesn't guarantee good aerodynamic tracking at cruise speed on the helo since aerodyanic differences of the two blades can cause a "climbing" blade. Helps to have a fearless wife... I do something sort of similar on my R/C helicopters. I use 2 different color tape strips near the tip of each blade, hover the helicopter and look at it from the side, you can see if one color of tape is flying higher than the other. When the blades are out of track it causes a lot of vibration. RogerN With our bigger ships, a tracking tip light was invented where you install a red LED on one blade tip and a white LED on the other. The LEDs are pointed at the pilot. The first time I tried these, I was nervous about them coming off in flight and creating a hellatious vibration. While running up I noticed a red streak and a white streak and thought "This is Great". Then at flight rpm the lights disappeared. No vibration so they must have both left at the same time. Slowed back down and there the lights were again. Great design. Centrifugal force pulled the little battery away from the LED. Tremendous idea though. It eliminated the need for a passenger operating a strobe light to check track during cruising flite. One design used centrifugal force to turn the LEDs on... Perhaps you are refering to 'centrifugal reaction' ? ;)) Sorry, couldn't resist.... phil |
#39
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Balancing a fan
"Phil Kangas" wrote in message ... "Stu Fields" wrote in message ... "RogerN" wrote in message m... "Stu Fields" wrote in message ... "Roger Haar" wrote in Roger: You are dead right. On the Helicopter, the first move is to track the blades. aerodynamically. Out of track blades on the helo will cause a 1/rev vertical vibration that can confuse a balancing operation if the operator isn't paying attention. On our ship we put two different color grease pencil marks on each blade. When the rotor is spun to full speed, my wife takes a pole with the center cardboard tube from a paper towel roll attached to the top of the pole and carefully brings the paper towel roll in until it just ticks the blade ends. We get two different color tick marks of one blade is higher than the other. We adjust until we get just one color combined from the two. This doesn't guarantee good aerodynamic tracking at cruise speed on the helo since aerodyanic differences of the two blades can cause a "climbing" blade. Helps to have a fearless wife... I do something sort of similar on my R/C helicopters. I use 2 different color tape strips near the tip of each blade, hover the helicopter and look at it from the side, you can see if one color of tape is flying higher than the other. When the blades are out of track it causes a lot of vibration. RogerN With our bigger ships, a tracking tip light was invented where you install a red LED on one blade tip and a white LED on the other. The LEDs are pointed at the pilot. The first time I tried these, I was nervous about them coming off in flight and creating a hellatious vibration. While running up I noticed a red streak and a white streak and thought "This is Great". Then at flight rpm the lights disappeared. No vibration so they must have both left at the same time. Slowed back down and there the lights were again. Great design. Centrifugal force pulled the little battery away from the LED. Tremendous idea though. It eliminated the need for a passenger operating a strobe light to check track during cruising flite. One design used centrifugal force to turn the LEDs on... Perhaps you are refering to 'centrifugal reaction' ? ;)) Sorry, couldn't resist.... phil You're right. It is just a habit I've picked up reading Baumeister and Marks Mechanical Engineering Handbook where they refer to the definition of centrifugal force on page 3-25. Ir does remain a useful concept. |
#40
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Balancing a fan
Karl Townsend wrote:
Pete and Don, I also agree. I've said it CAN'T be the fan vibration for years. But I also can't find anything else wrong. And its not for a lack of trying. I'm about to pop $11,100 and trade it in for a new used one. Julie's not to keen on that idea, but only because we haven't got the money. Got a big electric motor? Can you borrow a VFD off something for an hour? It might be REALLY instructive to spin the thing up on electric power and see if the vibration shows up, or not. If you can't detect any vibration under electric power as you vary the RPM across the troublesome range, then I think that proves it is NOT an out-of-balance condition. That leaves speed pulsation from the IC engine as the cause of the problem. Some kind of coupling that softens the pulsations would be the fix. When the engine puts out these pulses, it slams the gear train from one side of the teeth to the other, and this is REALLY hard on all the parts. I still think that is what is going on in this case. Jon |
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