What oil for crankshaft bearings?

[jamespetts]

I know that, for lubricating inside the cylinders of a steam engine, a special steam oil is required which can withstand the heat and wetness of steam.

However, ought one use that same oil for the engine's crankshaft bearings, or is it too sticky, such that it would create unnecessary resistance? If so, what sort of oil should be used for the crankshaft bearings? (If it makes a difference, the engine in question is a Stuart Score, twin cylinder 3/4" x 3/4").

[havoc]

If the bearing can get wet from condense or so I use steam oil. Like for the bearing of an oscillator. Otherwise I use SAE30 non detergent oil. Don't use too thin oil. The small bearings of our engines do not turn at such speeds that a dynamic film can set up and the pressure is higher than expected so very thin oil can get pushed out.

[jamespetts]

Thank you for your advice. Do you think that the bearings of a Stuart Score would likely get wet in operation?

[albertsell]

Hello James,
I have been into locos and traction engines for more than 40 years and have always used SAE 90 or140 gearbox oil on every thing except the cylinder lubrication.I spent 25 years as a volenteer on the Ffestiniog Railway and the oil they used was of similar viscocity.I may also point out that the only bearing material I use on my engines is cast iron.
Bye Albert

[chameleonrob]

what about lathe slideway oil? its viscose but doesn't pick up dirt and turn it into grinding paste like some other thick oils.

rob

[havoc]

Do you think that the bearings of a Stuart Score would likely get wet in operation?

No idea as I don't know that engine at all, but since you have one you could find out I suppose.

I fear that slideway oil is a bit too thick. It is a rather special purpose oil after all, high pressure, cold use and slow motion.

[alanstepney]

On a small engine such as the ST 10, or Score, and assuming it is only running for demonstrations not to produce power, almost anythoing will do.
When new, and if the bearings are tight, 3 in1, and as everything loosens up, a straight SAE 30 or 40 is ideal.

However, to avoid buying anything special, a drop of whatever you put in your car will suffice.

[jamespetts]

Thank you, everyone, for your advice - it is, as always, much appreciated. Alan, to answer your query, after the initial running-in period (my engine is a new one), I will be running it attached to a load: the ultimate aim is to have it generating electricity, perhaps enough to power a small computer (and thus generate the delightful anachronism of a steam-powered computer).

I don't actually have a car, but I do have some rather interesting oil for my bicycle. It does not have a printed SAE rating, but the back of the bottle says this,

"Cross Country is a strong synthetic lubricant capable of withstanding extreme pressurs over extended re-lubrication intervals. Water and temperatures (-20F to +450F) will not adversely affect Cross Country. Extreme pressure additives provide a 4,600lb Falex rating. Anti-wear agents provide superior anti-friction protection to retard chainring, link pin and bushing wear in high stress applications. A special non-toxic polymer adheres to metal surfaces to repel water and prevent wash-off".

Does that seem suitable for a Score running under heavy load for extended periods?

[alanstepney]

I'm no oil expert, and someone with more knowledge may disagree, but I cant see anything wrong with that oil for that specific application.

My personal preference is for non synthetic, "straight" rather than multigrade oil, but that is more tradition than for any other reason.

You are using it in a total loss situation, but even so,the duty is quite light. Bearing pressures, and speed, are only a fraction of what they would be in an IC engine, for example.

Try what you have got.
The very worst thing that can happen is that the bearings will wear faster than you want them to, but even replacing them is not a major task.

[Shawki Shlemon]

I use gearbox oil 90 grade and when I buy the bottle ,I add one spoon of graphite powder and give it a shake and then use it in the oil cans for lubrication of all parts of the loco except the cylinders .I think its a personal choice .

[jamespetts]

alanstepney said:

My personal preference is for non synthetic, "straight" rather than multigrade oil, but that is more tradition than for any other reason.

I take the point about tradition: my bicycle oil, I suspect given what I have read here, would probably do the job, but would almost certainly not look and smell the part. Where could I find some old-fashioned pure mineral oil of the appropriate sort at a reasonable price?

Anyway, thank you everyone for your help again - I know that I can use the bicycle oil if I can't find anything more authentic :-)