[modeleng] Re: Lubricating oils

Thanks for that Phil, interesting indeed - now I know what to do if I'm 
ever confronted by one! Perhaps all aftermarket spigot bushes are 
sintered? Dunno, as I've never bought one.
Phill Smith wrote:
> TEL,
>
> Unlucky I would say...... <GRIN>
>
> I've come across quite a few. Why did they put the sintered bushes in when 
> they could have put a readily available sealed ball race in, beats me. 
> Thinking about it, the engines that I have found them in everytime, was in 
> Landrovers. And in both (really old) bedford trucks that I changed the 
> clutches on for my uncle, after my cousins learnt to drive....... I couldn't 
> tell you if the sintered bushes were original on the Bedfords, but they are 
> on the Landrovers (Series 2A & 3, Discovery/defender until the end of the 
> 300 series engine). A few others were mix and match.
>
> Straight PB works great, as long as it gets a good bit of grease on 
> assembly. They don't last as long as the Sintered bushes though. Only 
> because they run out of lubricant sooner. The "new" standard Landrover 
> fitting proceedure is to soak in clean engine oil until the oil has soaked 
> through. Remove form oil, and wipe clean with a rag. Push it into place, and 
> then insert the removal tool (eg spare spigot shaft) all the way in and push 
> it to one side, and roll it around the bush once or twice while keeping the 
> pressure on as you roll. This expands the ends of the bush to lock it into 
> place. (Unfortunately, it also ruins the porosity at the ends in the process 
> and increases the diameter on the ends. An alternative could be to locktite 
> it in place and then oil it.) Grease the bush before fitting the shaft. The 
> oil in the sintered bush will keep the grease alive for many years. Why the 
> "NEW" fitting proceedure? Because the bushes aren't made to have the same 
> interferance fit any more, and this prevents it form coming loose.
>
>
> Cheers,
>
> Phill.
>
> ----- Original Message ----- 
> From: "TEL" <tel47@xxxxxxxxxxx>
> To: <modeleng@xxxxxxxxxxxxx>
> Sent: Friday, June 05, 2009 5:49 PM
> Subject: [modeleng] Re: Lubricating oils
>
>
>   
>> Geez Phil, with all the engines I've pulled down over the years, and
>> that's considerably more than a few, I've never come across a sintered
>> spigot bush. Just lucky? I've made plenty of replacement bushes with
>> plain old bearing store PB tho', and with a light greasing on assembly
>> they last for years.
>> Phill Smith wrote:
>>     
>>> G'Day Jesse,
>>>
>>> I'm glad that at least one person enjoyed my rant on bearings. I hope all
>>> will forgive my typo's and misspelt words, as my spell checker in Outlook
>>> Express has died again, and this time I'm not going to waste my time 
>>> trying
>>> to fix it.
>>>
>>> As for being refered to as "Dr Phill".... I think I have seen a couple of
>>> minutes of that show, and don't know if it is a complement or not....
>>> <LAUGH>
>>>
>>> Ok, lets answer your questions...
>>>
>>> Sintered bronze bearings came about as a solution to an age old problem. 
>>> The
>>> problem is, lubricating bearings that are damn near imposible to get to, 
>>> and
>>> are imposible to set up remote oiling for. One of the most obvious
>>> situations is for the spigot bearing mounted in the flywheel of your 
>>> car's
>>> engine. The sucess of the sintered bronze bearing is because it is 
>>> porous.
>>> It is made by granulating bronze to a small size, then putting it into a
>>> former and heating it only just enough to melt the surfaces of the 
>>> granuels.
>>> This enables them to bond together and still retain it's porous nature. 
>>> The
>>> porousity enables the bearing to retain oil for lubrication, for very 
>>> long
>>> periods of time. Ten to fifteen years is not not unusual an unusual life 
>>> for
>>> a sintered bronze bush. The porous nature of the sintered structure also
>>> permits the foreign bodies to be lodged out of the way from being in 
>>> contact
>>> with the shaft.
>>> The problems with sintered bronze are as large as the benefits. It is 
>>> very
>>> soft, so is easily deformed, when compared to a normal plain bronze bush.
>>> Once they start to compress, the access for the lubricant is restricted, 
>>> and
>>> they start to wear dramatically due to both lack of lubrication, and, the
>>> embedded foreign bodies are no longer tucked away, but are now 
>>> protruding.
>>> The softness of these bearings limits the loads that can be placed upon 
>>> them
>>> to less than a 1/3 of that permisible with a standard plain bearing. The
>>> other problem with sintered metals, is that the surface of every granual 
>>> has
>>> an oxide layer. This layer, in the harder sintered bronze materials, can
>>> cause bluntening of your tooling if you try to machine it. They also 
>>> require
>>> hardened steel pins/shafts to be used, otherwise the oxides will wear the
>>> shaft.
>>> Sintered metals are not designed to be machined. This is because the 
>>> forces
>>> involved in machining cause compression of the grain structure and 
>>> smearing
>>> of the grains across the pores. If you must machine it, use very sharp
>>> tooling with a positive rake with light cuts and fine feeds, as this will
>>> help reduce the problems caused by machining.
>>>
>>> Next question..... Anyone? <GRIN>
>>>
>>>
>>> Cheers,
>>>
>>> Phill.
>>>
>>>
>>> ----- Original Message ----- 
>>> From: "Jesse Livingston" <fernj1@xxxxxxxxxxx>
>>> To: <modeleng@xxxxxxxxxxxxx>
>>> Sent: Friday, June 05, 2009 2:09 AM
>>> Subject: [modeleng] Re: Lubricating oils
>>>
>>>
>>>
>>>       
>>>> Blimey Dr.Phill,
>>>>
>>>> That was a good lecture on bearing materials and I enjoyed and was
>>>> intellectualized by it .  I assume that by PB you mean phosphor bronze 
>>>> and
>>>> not powdered bronze like "Oilite®".  Sometimes I worry about the 
>>>> powdered
>>>> "sintered" bronze bushes I have used as the material seems to dull HSS
>>>> tool
>>>> bits for some reason.  I know it holds oil well , but still I wonder if 
>>>> it
>>>> is not abrasive to some extent.  You left that material out of your
>>>> lecture
>>>> professor so would you mind elaborating on the subject?
>>>>
>>>> Oh, congratulations on having the entire set of Audel's Mechanics and
>>>> Engineers Guide from 1921.  My set shows considerable wear as my father
>>>> probably used them when he was attending Mississippi State A & M 
>>>> college,
>>>> plus I use them extensively when designing new projects for magazine
>>>> articles.  The covers are in pretty fair shape, but the index pages are
>>>> loose in some volumes.
>>>>
>>>> Jesse in still drizzly Troy, TN USA
>>>>
>>>> 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.
>>>>
>>>>
>>>> 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
>>>>
>>>> This email was cleaned by emailStripper, available for free from
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>>>>
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>>>>         
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