 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Natural Science Forum / Physics / Acoustics / January 2006[Fwd: Re: Ball Bearing "Squeal"]
Lets try again. Ari Karjalainen wrote: > Angelo Campanella wrote: > >> Does any one know the origin of ball bearing "squeal". >> >> I have an ancient bench grinder that now makes a prolonged squeal as >> it winds down after being shut off. >> >> I have no idea what is the cause, nor do I have any idea as to how to >> lubricate it since the bearings are buried deep inside the motor >> housing, with a grinding wheel bolted to each end of the shaft. >> >> Ball bearings these days usually come with the advisory that they >> need no lubrication since they are lubricated for life (?!?!?!?!?). >> >> So, what's the sound source (5-10 kHz and higher)? >> >> What to do about it? >> >> Angelo Campanella >> > These relatively high frequencies are, to my understanding, called > bearing frequencies. These freqs are commonly caused by faults (like > spall) in the balls and/or inner and/or outer races. In the field of > maintenance there many handbooks and standards showing how to > calculate these (and other) frequencies for rotating machinery. Years > ago they could found on SFK web pages as well. > > In broader sense, in some applications squeal is caused by sliding > (friction) and "amplified" by (cylinder-like) structures. > > As a rule of thumb: For maintenance purposes don't drill anything! It > is most probably the fastest way to ruin the bearing. > > Since the grinder is old, i would expect that the bearings can > actually be replaced (or lubricated with correct grease). > > Hope this helps. Given some time i can find some formula as well. > > ari >> Angelo Campanella wrote: >>> So, what's the sound source (5-10 kHz and higher)? >> In broader sense, in some applications squeal is caused by sliding >> (friction) and "amplified" by (cylinder-like) structures. I figure that the sound source includes a rolling friction of the nature that a ball bearing in a toroidal race experiences. Such a ball cannot possibly roll with zero shear-friction. That means that ball (not roller) bearings must be lubricated or they shall die. Since I bought the grinder about 1960 (from Montgomery Ward), it might be near the end of the useful "life" of the ball bearings... The wheel stones are still usable, and the motor still seems OK. There's a lot to be said in favor of oilite (sintered bronze) bearings as the better alternative for light radial loads, due to this lubrication anomaly. >> As a rule of thumb: For maintenance purposes don't drill anything! It >> is most probably the fastest way to ruin the bearing. >> Since the grinder is old, i would expect that the bearings can >> actually be replaced (or lubricated with correct grease). I just have not worked up the courage to disassemble it since I still use it weekly. >> Hope this helps. Given some time i can find some formula as well. Formulas won't do much good if they only count rpm and radiuses. The real source may simply the ball-toroid mode cited. What I am looking for is some lore-advice as to how to lubricate them without complete disassembly at this time. Thanks for your interest, Angelo Campanella >> ari > (not roller) bearings must be lubricated or they shall die. Which is why ball bearing come in two versions, with seal and without seal. The seal is a good protection from dry dirt. There is likely to be a type number on the bearings, which should suffice to get the right ones, it is expectable to replace ball bearings and thus likely to be possible. > is some lore-advice as to how to lubricate them without complete > disassembly at this time. Oilzum or similar spray _lubricant_. Be aware of the electic motor caveat, mostly spray lubricants are best applied on a running machine, but it may be unwise if the spray fog will then enter the motor. The caveat may also be about the risk that the lubrication type will reduced required conductivity if it gets into the wrong places. > Angelo Campanella Kind regards Peter Larsen  Signature******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* >>(not roller) bearings must be lubricated or they shall die. > [quoted text clipped - 3 lines] > ones, it is expectable to replace ball bearings and thus likely to be > possible. And to continue Peter's comment a bit, in many applications the original not sealed bearing can be replaced with a new sealed one. Bearings can be sealed against moisture as well. clip, clip Replacing a ball bearing with a sliding one is not easy. I'm tempted to say, definitely not worth the trouble. BTW sintered bronze (or other self-lubricated materials) is not an anomaly, but engineering:) If the grinder has to be in use and can't be fixed or lubricated, avoid unnecessary shutdowns. BR, ari www.machineryacoustics.fi > If the grinder has to be in use and can't be fixed or lubricated, avoid > unnecessary shutdowns. OK. It's been squealing for the last few years... mainly during the last 10% of spin-down; really a juicy, aesthetic sort of squeal. One fine day, I will get serious and disassemble it all the way, and shoot up some WD-40, or rub in some grease, I think... Ang. C. Angelo, check the shaft for play due to excessive wear. If there is not much play then you can relubricate it, but if the play is excessive (you can feel it), then replace the bearings (both). There are several ways of relubing--the simplest is to use some turbine oil at the seal and rotate the bearing to work it in--this is predicated on the idea that the old grease has dried out and adding a superior liquid lubricant will reactivate the old grease and allow it to redistribute. Turbine oil is a wonderful lubricant on it own. I would never use WD40--too light weight light (it will evaporate) and no extreme pressure additives. Mike D >> If the grinder has to be in use and can't be fixed or lubricated, avoid >> unnecessary shutdowns. [quoted text clipped - 6 lines] > > Ang. C. > I would never use WD40--too light weight light (it will evaporate) But not until it has washed remaining grease away .... O;-) > Mike D Kind regards Peter Larsen Signature******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* > Angelo, check the shaft for play due to excessive wear. If there is not > much play then you can relubricate it, but if the play is excessive (you can [quoted text clipped - 4 lines] > grease and allow it to redistribute. Turbine oil is a wonderful lubricant > on it own. I have often wondered what the special properties of "turbine" oil might be. It just so happens that I have an old can of Turbine oil around... from the '60's, I think.. > I would never use WD40--too light weight light (it will evaporate) and no > extreme pressure additives. WD-40 is a popular "act of desperation". Thanks, Ang. C. >WD-40 is a popular "act of desperation". Does anyone know what WD-40 really is? It seems to have more uses than Windex in that Greek wedding movie. :-) One final thought. If you can't fix the bearings, maybe you can just replace the motor. A new motor comes with new bearings, and may not cost much more than bearings alone. Especially if you go to a place like Grainger's that a) has lots of motors in stock, and b) sells at wholesale to businesses only. Ken Plotkin > >WD-40 is a popular "act of desperation". > Does anyone know what WD-40 really is? It is a loosener, not a lubricant. To replicate most of its functionality use lamp kerosene, 5 to 10 percent bicycle or sowing machine oil, a bit of graphite powder perhaps, and probably a bit of molybdene bisuflide, aka molykote. Oilzum or the similar product from LK-lub is a true lubricant. To loosen a bolt: just use lamp kerosone and then a bit of oil. > One final thought. If you can't fix the bearings, maybe > you can just replace the motor. A new motor comes with > new bearings, The ease of this depends on the actual construction of the grinder - I can not recall having seen a physical description, if all parts are on one common axle then it is perhaps not quite easy. > Ken Plotkin Kind regards Peter Larsen Signature******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.