your question is not that simple, as the parameters and the radial clearances for journal bearing, you are asking for involves with so many aspects before one can derive the same.
the main ones are: loading on bearing, the shaft diameter, speed of the shaft, type of loading, the shaft span, is it a overhung type or supported at both ends of the shaft? the working temperature etc.
whether there is any axial movement of the shaft, the nature of lubrication, which type of bearing you would be useing, plain white metal layer type like used in autocar engines, etc.
there are a number of bearing manufacturers: such as Glaciar Bearings of UK, Kingsbury of USA, Orian of USA and many more. the manufacturers as given above do provide the methodology for selecting the correct size and type of journal bearings, like its dimensions-length, breadth, whether plain, collered, with lubrication hole and its radial clearances required (between bearing bush and rotating shaft) and also fit tolerances for mounting it in bearing hub (assuming that journal bearing is not going to rotate). here the journal bearing may be in one piece or in two halves depending upon the the application suitability etc.
there are cases where journal bearing (of one piece) can be rotating along with the shaft but at much slower speed (and not locked at all as described earlier). in such case, it will have radial clearance (max/min), at both inside and outside of the journal bearing. in such case a suitable lubrication arrangement will also be required. hope this will start you off for the above. good luck.
if you are looking for an engineering solution to your problem, than there isn't any short and quick answer to it. you must go through a proper method and get a long term solution for it. I always believed that engineering is based on logical reasoning and following it through till you get an answer for it. it is an advise to you.
Hi enqr amjadali. There is no simple calculation for this one as bearing manufacteres specify different clearences fo their bearings only. So my advice is to contact the company who supplied the bearings. I have fitted many bearings from 6mm shafts to 600mm shafts and usually the company will supply you with the right clearence when you buy the bearings. It also depends on what type of bearing you intend to use, ball, roller, neddle, and if it is annular, conical or thrust bearing. Spencer.
Generally, I've found that journal bearings are designed with the intention of the lubricant film, that forms between the shaft and the bearing, intended to see the brunt of the work and that there is actually no contact at all between the shaft and the bearing. Since you mentioned a forced lubrication system, and lubricating rings, I would have to assume that this is also the philosophy behind this design as well.
The gap or fit between the bearing and the shaft, in addition to all the excellent reasons mentioned previously by chittaranjan, is also dependant upon the physical characteristics of the lubrication you are using. Too small of a gap will prevent the lubricant polymer chain from entering the gap whereas too large of a gap will prevent the lubricant from forming a fluid-dynamic load supporting barrier.
Not being skilled in Tribology myself, I'd recommend contacting your lubricant manufacture, they'll be able to give you some excellent advice.
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Formula for Journal Bearing Clearance?
Re: Formula for Journal Bearing Clearance?
