Porous Bearings

[275 GTB-4]

I have only average mechanical skills so please don't respond too technically!!

Has anyone heard of this term and what does it mean? I can't imagine oil actually impregnating the surface of a bearing shell. I heard the term used in conjunction with an old A-Series engine (yes the Austin/Morris/MG type!!)

[StuiE]

From r31skylineclub.com

The spigot bush needs to be soaked in oil over night prior to installing as the brass bush is porus and soaks in the lub which will stop the input shaft from freezing into it while spinning.

(this was talking about a manual conversion)

Brass can, so I'm guessing there is a possibility that other metals ca...or the bearing is made from brass, but I wouldn't think so.

[275 GTB-4]

Originally posted by gtr69
From r31skylineclub.com

(this was talking about a manual conversion)

Brass can, so I'm guessing there is a possibility that other metals ca...or the bearing is made from brass, but I wouldn't think so.

Thanks...I vaguely remember that about Brass, but for a Bearing Shell,

I would have thought the idea was to case harden or somehow otherwise (a type of chrome?)provide the inner face with a long wearing surface that would maintain a film of oil between it and the spinning crank jounal faces???

(obviously outta my depth here)

[tangoed sparky]

I think that older bearing types were a made of a metal called babbet/white metal or an aloy of containing it. It was some time ago that I did my motor vehicle engineering course so I might be wrong I do not know if it is porous. mabe a search on google might do the trick. Sorry I could not be of more help.

[graham bahr]

which bearing was it referring to? if its an transverse engine, it might of been referring to the bearing which both carries the clutch and slides over the end of the crank, from memory these had a phosfer bronze type bearing, which is slightly porous and would benifit from being soaked in oil prior to fitmant.

[Dave Brand]

What you're referring to is an 'Oilite' bush. They are made of a sintered bronze material, which is porous & oil-impregnated before installation. There are also similar bearings (can't remember the brand name) which are made of a similar material but PTFE-impregnated.

[275 GTB-4]

Originally posted by Dave Brand
What you're referring to is an 'Oilite' bush. They are made of a sintered bronze material, which is porous & oil-impregnated before installation. There are also similar bearings (can't remember the brand name) which are made of a similar material but PTFE-impregnated.

Dave thanks for that, I googled away and found numerous mentions to this type of bearing....you learn something everday!

Sadly, that is not what I am on about, a friends Austin Healey 1275 had "porous" main bearings (which had somehow become "porous") and that was the problem. He had to overhaul the crank and bearings before he could drive it again, hence the question re porosity!!!

[Dave Brand]

Originally posted by 275 GTB-4
Sadly, that is not what I am on about,

If I'd referred back to your original post rather than just replying to Graham's I'd have noticed that!

a friends Austin Healey 1275 had "porous" main bearings (which had somehow become "porous") and that was the problem. He had to overhaul the crank and bearings before he could drive it again, hence the question re porosity!!!

Interesting! Never heard of that one.....:confused:

[StephenRae]

If you replace the word porous with knackered then you are probably closer to the mark. Shell bearings provide the 'soft' surface, only a few microns thick, and the crank journal the 'hard' surface. Hopefully a few molecules of oil keep the two apart!

[zefarelly]

Originally posted by StephenRae
Hopefully a few molecules of oil keep the two apart!

except when your flat out through a right hander and a big orange light comes on reminding me the oil pressure gauge is going anticlockwise faster than the rev counter goes clockwise

[james_williams]

Phosphour Bronze (similar in colour to brass) is an example of a porous material. If you soak this in oil, especially under pressure, oil seeps into the 'pores' of the material and gives it a 'natural' lubricant. Often used where grease or oil causes problems and a lubricated joint is required.

[Dave Brand]

Originally posted by james_williams
Phosphour Bronze (similar in colour to brass) is an example of a porous material.

Close, but no cigar! Phoshor bronze in its natural state is not porous. Porous bearings (such as Oilite, which I referred to earlier) are made by sintering; metal powder is compacted in a press to produce blanks which are then heated to fuse the particles together to make a rigid bearing. Bearings may be impregnated before sintering with solid lubricants, such as graphite, PTFE, etc., or oil-impregnated after sintering.

Getting back to the original post, here's a quotation from 'Powder Metallurgy for Engineers' on the subject of steel-backed bearings, as used for mains & big ends:

>>Steel-backed Bearings

Bearings of this type are produced in very large quantities for all types of internal combustion engine. As the name implies, the bearing is of composite construction with two or three of these main components
a steel shell which serves to support the bearing during manufacture and in service;

a sintered lining applied to the shell and bonded to it during the manufacturing process; it may be porous or fully densified;

a surface layer which may be applied as an overlay to a fully dense layer or as an impregnant into a porous substrate.<<

[275 GTB-4]

Originally posted by Dave Brand
quotation from 'Powder Metallurgy for Engineers' on the subject of steel-backed bearings, as used for mains & big ends:

>>Steel-backed Bearings

Bearings of this type are produced in very large quantities for all types of internal combustion engine. As the name implies, the bearing is of composite construction with two or three of these main components
a steel shell which serves to support the bearing during manufacture and in service;

a sintered lining applied to the shell and bonded to it during the manufacturing process; it may be porous or fully densified;

a surface layer which may be applied as an overlay to a fully dense layer or as an impregnant into a porous substrate.<<

Well quite possibly the fully dense layer maaaan!! has like, whale, bin, worn away (liiike), exposin the soft porous underbelly which is the substrate??? (with apologies to the Young Ones)

[Dave Brand]

Originally posted by 275 GTB-4
Well quite possibly the fully dense layer maaaan!! has like, whale, bin, worn away (liiike), exposin the soft porous underbelly which is the substrate??? (with apologies to the Young Ones)

That, differently expressed , would be my guess.

[james_williams]

Dave,

Thanks for that additional information. I will add it to my knowledge database. Most informative

James