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Geoff Theasby08/02/2012 17:03:27
613 forum posts
17 photos
My question is about bearings. I understand that we should not lubricate axleboxes from the top, as that is the centre of pressure, and they should be fed from the side or below. All OK.
However, in the case of stationary engines, or others where there is no standing weight from above, and depending on the direction of drive from the crankshaft, surely it is OK to lubricate from above, as the centre of pressure does not lie there. In reciprocating engines, thrust is applied at more or less 90 degrees plus or minus from the vertical, and with no standing weight, it should be OK to lubricate from above.
In doing so, it enables a small recess to be formed in the bearing, in which an oiler can be inserted, or a pool of oil laid, so as to feed to machine during its running. This will facilitate a short period of operation, such as my power hacksaw, or demonstration run, without complex oiling problems.
Am I right? Or, in which case, am I wrong?
Stub Mandrel08/02/2012 19:06:24
4315 forum posts
291 photos
1 articles
HI Geoff, I have seen plenty of stationary engine bearings with lubricators on top.
mgj08/02/2012 19:14:50
1017 forum posts
14 photos
My Little Samson is lubricated from above and that works fine. Even the bearings which carry an upthrust from the gears are also lubricated from above, and they are always good and oily. Equally Sweet Peas axleboxes are lubricated from above and they last very well.
If in doubt, turn a shallow groove in the bearing and then oil from whichever direction you want? Install an oil cup with a small hole, and a wick or felt pad, and the thing will last forever - if its big enough. If not the groove will act as a reservoir.

Geoff Theasby08/02/2012 20:05:20
613 forum posts
17 photos
Yes, all my stationary engines have oil cups or recesses in the top of the bearings, and they seem to work well.
I was questioning the received wisdom of doing so, if there was no downward thrust on the bearings.
It may be that axleboxes are a special case.
Geoff Theasby
John McNamara09/02/2012 00:00:17
1340 forum posts
126 photos
Hi All
As long as there is a passage for the lubricant to follow (The narrow bearing gap) Does not capillary action come into play?
Even a cotton wick will do. as used in many machines to direct oil to the area of need.
Ian S C09/02/2012 09:59:06
7468 forum posts
230 photos
Open crank IC engines, large and small are lubricated from the top, including a Ruston Hornsby HR6 that I have a bit to do with at a local museum, we have had a little trouble with lack of lubrication on the big end which is also supplied with oil when running via a slinger ring on the side of the crank, the oil for this comes from the oil pump. The big end bearing is white metal, and some were about 5/ 6" dia, and about 6" wide. Before starting the oil cup on top of the big end is filled befor starting. The main bearings are oiled from a well under the bearings by a ring running on the shaft, and dipping in the oil. The is an oil cup half way along the con rod, to oil the little end. Ian S C

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