[modeleng] Re: Lubricating oils

Jesse,

I picked up all 8 books as a set when I purchased them on Ebay, and in 
perfect condition. I did notice later, that they showed up on ebay as 
individuals, but would have been expensive to buy like that.

As for oil draining from stationary bearings...... Yes you, and Audel, are 
absolutely correct. But the drainage rate is dependant on 3 factors. 
Temperature of the oil, size of the drainage oriface, and, time. In our 
close tollerance bearings, compared with a 6" bearing with a free running 
fit giving (for heavy loads) of 10 thou' clearance, drainage is very slow 
and is unlikely to lose enough oil to stop boundary film lubrication in the 
time it takes to refuel, unload passengers, take on water, chat up the 
passenger kid's aunty etc. Yes, I was terrible when I was single. I had a 
built in compass the would point me at every single woman within 100 
yards.....

As most of you will know (from reading this lists postings) that I am 
getting ready to build a Juliet as a teaching instrument for my eldest son 
as he builds one. Going through the original articles in the ME magazine, 
has shown several areas of poor engineering. This is in the area of bearing 
surfaces and materials. LBSC wrote the articles for the complete novice, so 
I was not expecting high tech bearings. Or was I? Perhaps I was, as why else 
am I going to change them. Things like crank pins, eccentrics, cross head 
guides, expansion links, die blocks, and valve gear pins, will now be 
hardened and polished high tensile steel. Modern hardening steels are 
relatively inexpensive (compared to LBSC's time), easily obtainable, and 
easily heat treated at home. The advantages of making these small changes, 
show up over the long term as they will wear (as will their matching 
componants) at around 10%, or less, of those materials originally selected.
This works because the difference in the materials becomes greater. Look at 
the bearings in your cars engine. They are really soft compared to the crank 
shaft. An even better example is the cam shaft and it's bearings. Hardened 
steel on (what is essentially) white metal bearings. Your camshaft wears at 
a much lower rate than the crank shaft, and not just because it is turning 
slower, but because the difference between the dissimilar metals is greater.
The use of a bronze bush, is to be able to carry a larger load on the 
bearing than a softer material can accomodate without deformation, at the 
same size. The softer material will give you a better bearing, but must be 
much larger to take the same load without going out of round. GM will work 
Ok on polished mild steel pins/shafts etc, just.... PB is designed for 
polished hardened steel pins ONLY. It will destroy a mild steel pin at the 
same time as wearing itself. But when used on a really hard material, will 
last a very long time. GM also prefers hardened steel pins.

Bearing wear occurs due to 2 main factors.
1) bearing being overloaded and deforming. This happens to the softer of the 
2 materials first. The case 2 takes over.
2) foreign bodies. Foreign bodies can be any thing from dirt, soot, dust, to 
bearing material particals. These items behave in 2 ways. Firstly, if they 
are small and/or sharp enough (dust, soot, and bearing fragments) they 
become embedded in the softer material of the bearing and then act as a lap 
on the harder surface. This then accellorates the process as it removes more 
of the harder material, which in turn also becomes embedded in the softer 
material and hence wears away the pin/shaft. Secondly, if they are large 
and/or blunt they act as grinding paste and wear away the softer material at 
a faster rate than they do the hard material.

This is why really hard pins/shafts with PB bushes is favoured as a plain 
bearing. The PB is hard and strong enough to withstand high loads and some 
abbrasion. While the really hard pin/shaft is highly resistant to lapping 
when polished. If unpolished, small pieces will be torn from the surface of 
the pin/shaft and be embedded into the PB to ask as a lap.

There is one last factor for the selection of bronze on hardened steel.... 
Coefficient of friction. Bronze has a very low coefficient of friction, and 
so has hardened and polished steel.


Oh dear..... It looks like I digressed a bit here..... Sorry Gents. I seem 
to have digressed to giving the lecture "bearings 102", so I'll leave it 
there.


Cheers,

Phill.




----- Original Message ----- 
From: "Jesse Livingston" <fernj1@xxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Thursday, June 04, 2009 9:27 PM
Subject: [modeleng] Re: Lubricating oils


> As I am sure our resident ME Phill knows, oil will drain from a stationary
> bearing or at least that is what my 1921 Audel's manual says.
>
> Phill, did you ever get the entire 8 books in that Audel's series you 
> found
> on ebay?  If you are only missing #8, don't worry as it deals with
> electricity and not steam.
>
> Jesse in rainy Troy, TN USA
>
>> Ron,
>>
>> With really small bearings, you can take advantage of the excess 15W40.
>> The
>> basic rule is, the bigger the bearing (diameter) the thicker the oil. The
>> smaller the bearing the thinner the oil. This is because the surface
>> speeds
>> are generally in the same range, but the clearances are shrinking as the
>> bearing decreases in size. As the clearances decrease, and the RPM
>> increases
>> to maintain the surface speed, the shear stress of the oil becomes
>> greater,
>> and hence the pwer being absorbed also increases. This is counteracted to
>> some degree by the heat generated by this process, which thins the oil,
>> but
>> not enough unless it is over heated. If the bearing is turning slowly,
>> then
>> you are often better of using a thicker oil. Very few 3.5" and 5" gauge
>> loco's are driven at scale RPM. This is partly due to the scale effect of
>> miniaturization. Basically, properties don't change, just the quantities.
>> Therefore, things like the expansion rate of steam is the same, 
>> regardless
>> of the size of the engine. THEORETICALLY, a miniature staem loco, can go
>> just as fast as the prototype. Unfortunately, they can't due to 
>> ballancing
>> dynamics, mass stability, etc. etc. They just fly of the track, before
>> they
>> come anywhere near reaching thier potential. Which brings us back to the
>> RPM
>> of operation. At 3/4" scale, the scale opperating speed is 1/16 of the
>> full
>> size. So assuming you are racing around the track at 5 mile an hour, 
>> which
>> is pretty typical for what I have seen, then you are doing a scale speed
>> of
>> 90 miles an hour..... Hmmmm..... I doubt whether many full sized shunting
>> engines did that speed...... Full size speed here, was 50 miles per hour
>> for
>> goods services. That makes a scale speed of 3.125 miles per hour. That's 
>> a
>> pretty slow walking speed.... If you are operating at full size RPM,
>> approximately 300 RPM, then you are better of using a thicker oil than a
>> thin one. The boundry film pressures are lower at 300 RPM than at 600 
>> RPM.
>> and hence the thinner oil used for 600 RPM will not generate enough
>> pressure
>> in the boundary layer to keep the 2 components apart. That's when wear
>> starts.....
>>
>> Slideway oil is good stuff, on your machinery. But, not always for
>> everything else. Take the tacking agent for example. It "tacks" the oil,
>> only after it has stood still for a while. It has no useful effect while
>> the
>> bearings are moving. If you let it sit and "tack off" and then start
>> moving
>> the bearing again, it imeadiately reverts to it's normal liquid nature
>> until
>> it stand still for a while again. So the tacking agent can make clean-up
>> after running harder. But the other aditives are excellent, for our use,
>> as
>> long as they don't get to hot. I know that most of the tacking agent 
>> don't
>> like heat.
>>
>> I hope that gives you all more food for thought.
>>
>>
>> Cheers,
>>
>> Phill.
>>
>>
>> ----- Original Message ----- 
>> From: "Ron Head" <ronald.head@xxxxxxxxxxxxxx>
>> To: <modeleng@xxxxxxxxxxxxx>
>> Sent: Thursday, June 04, 2009 1:32 AM
>> Subject: [modeleng] Re: Lubricating oils
>>
>>
>>> Some interesting replies so far!
>>> The preference seems to lean towards heavier oils, perhaps with a
>>> tackiness additive.  I was surprised to hear that some folk use steam 
>>> oil
>>> for everything!
>>>
>>> I've always been reluctant to use motor oil in anything other than a car
>>> engine, as I don't know what effect the detergents have on bronzes etc.
>>> Mind you, my current car is a diesel which uses the most expensive
>>> synthetic oil imaginable, so I've got plenty of surplus 15W40 doing
>>> nothing!
>>>
>>> I also have some Mobil Febis K68 slideway oil in my shop, which I use on
>>> my lathe bed.  This has a tackiness additive, so it might be suitable 
>>> for
>>> motion....who knows?  Anybody tried it?
>>>
>>> Regards
>>> Ron
>>> MODEL ENGINEERING DISCUSSION LIST.
>>>
>>> To UNSUBSCRIBE from this list, send a blank email to,
>>> modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the 
>>> subject
>>> line.
>>
>>
>> --------------------------------------------------------------------------------
>>
>>
>>
>> No virus found in this incoming message.
>> Checked by AVG - www.avg.com
>> Version: 8.5.339 / Virus Database: 270.12.52/2153 - Release Date: 
>> 06/03/09
>> 18:00:00
>>
>> MODEL ENGINEERING DISCUSSION LIST.
>>
>> To UNSUBSCRIBE from this list, send a blank email to,
>> modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject
>> line.
>
>
> --------------------------------------------------------------------------------
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.5.339 / Virus Database: 270.12.52/2152 - Release Date: 06/03/09
> 05:53:00
>
> MODEL ENGINEERING DISCUSSION LIST.
>
> To UNSUBSCRIBE from this list, send a blank email to,
> modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject 
> line.


--------------------------------------------------------------------------------



No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 8.5.339 / Virus Database: 270.12.52/2153 - Release Date: 06/03/09 
18:00:00

MODEL ENGINEERING DISCUSSION LIST.

To UNSUBSCRIBE from this list, send a blank email to, 
modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.

Other related posts: