Lutetium-
Hack Chat Transcript, Part 2
10/19/2022 at 21:49 • 0 comments![]()
@Andy Pugh I was mainly talking gaseous - there are some air bearings and things like that, but like I said they're very niche.![]()
Please tell about bearings lube![]()
Okay, so then most of the solid lubricants act the same. If you look at the molecular structure of graphite, boron trifluoride, molybdenum disulphide, calcite or boron nitride, they all look mostly the same - sheets of atoms with low shear strength.![]()
Solid lubes are good for vacuum applications. Except graphite.![]()
Low shear sheets sounds very use-once?![]()
Boron trifluoride is a gas...?![]()
The choice of which one to use mainly comes down to the operating requirements. You see a lot of Moly used because it has very good oxidation stability - it even gets used in the space industry, where the oxidation stability is very important.![]()
in space, is it about oxidation stability, or about working even without water molecules like what graphite relies on?![]()
@Thomas Shaddack sorry that was a brain fart, I meant boron nitride. Specifically hexagonal boron nitride, because there are a few different isomers that don't have the same lubricating properties.![]()
yup, the cubic boron nitride is a diamond-class abrasive. (handy for ferrous metals that dissolve diamonds at high temperatures at contact zone.)![]()
Why is oxidation stability important in space? Are we talking about the atmospheres in crewed areas?![]()
So in space it's a bit weird - in low earth orbit you ironically need really good oxidation stability because there's not much oxygen up there, but the oxygen that is present is in atomic form. So not O2, just random highly reactive oxygen atoms looking for a friend.![]()
Or about low earth orbits where there are way too many single oxygen atoms, all eager to bond to something? (Yes, space corrosion IS a thing.)![]()
Obviously once you get above that, then you're in the clear -the main thing you need to deal with is temperature variation and like @Thomas Shaddack said, the lack of water that would help graphite work.![]()
In space applications, that an example where the solid lubricant is actually part of the machine surface - which is the same as moly coated piston rings. Generally it's sputtered onto the surface.![]()
I saw eg. plastics that are composites with solid lubricant particles embedded in polymer matrix. I also saw eg. electrodeposited nickel codeposited with teflon particles.![]()
Moly still gives you that really nice lubricity, but in piston rings it also helped with run in because moly is quite soft. We're starting to move away from moly rings because they're not durable enough for really high combustion pressure and sometimes they flake off, which means bad things for the engine.![]()
On the solid lubricants stuff, this video does a better job of visualising it: ![]()
Also if you're invested in piston rings and liners then I did this interview with a piston ring specialist: he goes into much more detail that I ever could about some of the new spray-bore technologies.![]()
So out of curiosity, what's the deal with dielectric grease? What's added to give it electrical properties? Or subtracted, I suppose.![]()
do you have video for bearings lubricant?![]()
Great question @Dan Maloney![]()
So - dielectrics are an interesting one - there's obviously a lot more interest in the topic now that EVs are starting to become a thing. Getting the dielectric properties right is about balancing the electrical properties of the base oil and additives.![]()
Could have also answers for improvising high voltage/transformer oil for high voltage hacking.![]()
As a general rule - the less polar, the less charge is carried. So PAOs and Group III minerals carry the least charge, esters and PAGs the most.![]()
And on the additives side, metallic additives (like ZDDP, calcium and magnesium detergents) carry charge but sulphur and nitrogen based ones don't.![]()
And, of course, those lovely PCBs![]()
With most dielectric greases, it's about marrying the conductivity to the intended application. If the grease doesn't carry any charge, that can be a bad thing because you get a buildup of static in the grease (or oil) over time, and once the voltage potential gets high enough, you'll get static discharge.![]()
But carrying too much charge will allow things to short. So there's some happy middle ground.![]()
if it's conductive it wouldn't be a dielectric grease. But there are static dissipation additives for fuels, to prevent sparks during transfer.![]()
Alrighty! Halfway though, hope everyone is feeling ok.![]()
There was a question about bearing lubricants.![]()
Aren't all lubricants bearing lubricants? Otherwise they are not lubricating?![]()
</pedant>![]()
Arcing can however do a job on the bearing races. I think I saw somewhere about failure of gyroscopes in space related to solar storms. The sparks can machine ragged pits into the races.![]()
Well, we usually only go for an hour, but keep going if you like!![]()
So bearing oils are relatively simple. Most of the time it's just a base oil (rolling element bearings love 100cSt) and then some rust and corrosion inhibitors. That's if you're just lubricating a bearing. Then you start adding things depending on the location of the bearing. So say if you're in a screw compressor - the oil acts as a seal for the lobes so you actually bump up the viscosity a little bit to optimize for that. If there's also some gears, you'll start to add more antiwear and EP additives.![]()
So yes @Andy Pugh you're absolutely right, most oil start off as just "bearing lubricants" and then we build up from there.![]()
@Dan Maloney okay! Why don't we do another 15 minutes then?![]()
Works for me!![]()
@Rafe I was actually coming at it from the other side, in that if there isn't a bearing (of some sort) then what you need isn't a lubricant.![]()
Greases. The different kinds, lithium, calcium... why are they different?![]()
do lubricant wears out?![]()
It's also about proritizing what we want to protect. If you look at an engine oil, you need to protect the bearings, pump, gears, chain, cams, lifters, etc. But we choose the viscosity based on the crankcase bearings because they're the most expensive (and annoying) to replace.![]()
Greases - great question.![]()
So, the different types of greases are different for a couple of reasons. Let's start with the soap-based ones. These are the lithium, calcium, and aluminium soaps.![]()
If you think of a soap (for your hands) it's designed to be water soluble, but attracted to oils. This way it can bind to the oils on your cutlery and wash them away.![]()
Grease soaps are the opposite - they're oil soluble, but with polar heads that are attracted to each other. That forms a matrix or web that holds the oil. People usually use the analogy of a sponge holding water - when you put a sponge under stress is releases water. Same thing with the thickeners - under load they release the lubricant, and the lube oil is the thing that is actually doing the lubricating.![]()
Okay, so why then are there different types? Mainly it's to do with other things like resistance to water washout and spray off, as well as high temperature performance.![]()
lithium is the most common because its a good "multipurpose" thing. Aluminium can be made to be food grade.![]()
Would that work also with some polymer matrix? Kind of like candle gel?![]()
Then there are the non-soaps. You've got polyurea for example - more stable at high temperatures because there's no metals to catalyse oxidation.![]()
They get used in a lot of high speed electric motors, and fill-for-life applications.![]()
There's also clays - which are really good at high temperatures. And then there's my personal favourite, the Calcium Sulphonates. Calcium sulphonates are cool because the thickener can also act as an additive - there's calcite particles that act as a solid lubricant, but they're also really good anticorrosion additives, plus you get good high temperature performance and water washout performance.![]()
Historically they've been rare because they were 3x more expensive that a lithium grease, but with lithium shortages around the world and the price of lithium going up, that difference is not more like 50>#/span###![]()
I was surprised to find how hard it was to get NLG3 grease. I suspect that NLG1, 000 and 6 are "how many tonnes should we make for you"?![]()
@Thomas Shaddack exactly - so the polyureas are polymer.![]()
So the di and trivalent ions are better as ionic "crosslinkers" for the grease?![]()
@Thomas Shaddack I think yes? But cross linking is also related to to "complexing". That's the difference between Lithium, and Lithium complex greases. Think of the soap molecules like the two long bits of a ladder - the complexing agent is the rungs. It really helps the stability of the grease under high shear and/or high temperature.![]()
@Andy Pugh yes NLGI 3 and up aren't very common.![]()
Alrighty, I think we're just about done!![]()
@Dan Maloney thanks so much for having me!![]()
You bet, this was great -- so many good questions!![]()
Hopefully everyone learned something!![]()
...and I have a new youtube channel to binge on.![]()
Thanks so much for taking time out to be with us today, I really appreciate it. And thanks everyone for attending!![]()
Thanks everyone!![]()
Great questions!![]()
Yes, definitely some great videos on Rafe's channel, I've been subbed for a while now.![]()
Thanks Rafe!![]()
Transcript coming up - thanks all! -
Hack Chat Transcript, Part 1
10/19/2022 at 21:48 • 1 comment![]()
Hi folks, let's get started! Welcome to the Hack Chat, I'm Dan, and Dusan and I will be moderating today for Rafe Britton as we talk about lubrication engineering![]()
Fun thing for solid lubricants. Hexagonal boron nitride vs tungsten disulfide, the latter is much more dense so you get much less volume of the powder at the same gram.![]()
My favorite spray can lube for the last couple years is CRC Power Lube![]()
Hi @Rafe! Welcome aboard![]()
Thanks @Dan Maloney - pleasure to be here everyone![]()
Thanks for the early morning sign on, too -- really appreciate it. Can you start us off with a little about yourself?![]()
Sure! My name is Rafe Britton and I'm a lubrication engineer out of Sydney, Australia (hence the early start). I spent 13 years at Mobil where I did one time drilling gas wells in various locations around the world before becoming part of the lubes team. So in the O&G world, I've been as far upstream and downstream as you can get.![]()
Hi Dan, Rafe, welcome everyone!![]()
Spent six years at mobil lubricants as a field engineer assisting industrial customers with technical problems, and now I'm out on my own doing the same thing as an independent consultant.![]()
So I now have the fortune of not having to sell any particular product :)![]()
Cool, didn't know you were on the exploration and production end of things too!![]()
Yeah!![]()
I really enjoy lubricants because it's this amazing blend of mechanical engineering, chemistry and physics. Plus it's applicable to anything that moves, so I get to work with alot of different industries.![]()
Did some work in clutched AWD systems... Lube was incredibly important.![]()
Makes the job really interesting. But anyway, that's my background. My specialty is mostly industrial lubricants, but know enough about engine oils to be dangerous.![]()
I believe mobil supplied some sort of tractor hydraulic oil we used in a few systems... had great Mu-V![]()
On that subject, what's the "magic" in the "traction fluid" in Rotrex superchargers (and, possibly, also Kopp Variators)?![]()
I'm also really keen to help educate people about lubricants and lubrication (which is why I'm here).![]()
Great question to start us off about tractor fluids!![]()
(I have a Variator and Kopp are insistent that anything but Shell Morlina SL10BL (or something a few letters away from that) will result in instant failure.![]()
Ok, so the trick with tractor fluids (from a formulation standpoint) is that a tractor fluid is pretty general purpose. As a rule - it's easy to formulate for a single application, but difficult when it might be used in many different applications. So with a tractor fluid, it often needs to act a little bit like a hydraulic fluid, a little like a gear oil, a little like a bearing oil, a little like a circulating oil.![]()
What the components of Motor Oil. Also what the difference between Gas eng oil and diesel oil?![]()
So with tractor fluids, the "magic" is threading the needle between the competing requirements of those different applications.![]()
@Rafe Also clutch cooling + friction additives![]()
it has to wear a lot of hats![]()
I am planning to build a spindle-speeder modelled after the Rotrex, but I was hoping not to have to seal it and/or supply pumped lubricant.![]()
Is there real difference between Oil for motorcycle and car?![]()
@EcPc - yes, sorry I forgot to mention that too. It's the same issue we're also having in the industry at the moment with EV fluids. In the interests of efficiency and weight savings, most have gone with a "wet motor" design in which the transmission and electric motor are lubricated by a single system. This is really challenging, because all the molecules we traditionally use to protect gear teeth are a family of sulphured olefins that eat copper windings for breakfast.![]()
What about corrosion protection? Graphite can cause galvanic corrosion of many metals, for example. Any such issues with "conventional" lubricants?![]()
So there's a lot of R&D going on at the moment to develop new molecules that can handle the lubrication of transmissions while not corroding the E-motor.![]()
And presumably bronze bushes in older engines?![]()
Corrosion protection is a good question too. So corrosion protection (and this relates to the question about engine oils) is the province of a couple of different lubricant components.![]()
Material compatibility in general, see the sulfur additives.![]()
In an engine oil - the byproducts of combustion are usually acidic compounds. Any oxidation of base oil / fuel produces organic acids, sulhpur combustion produces sulphuric acid, nitrogen produces nitric acid. So we use two different molecules - overused detergents to neutralise the acids, and nitrogen based corrosion inhibitors to form protective layers on metals.![]()
could you suggest oil type for "wet" motor?![]()
The inverse is mostly true in industrial oils - the corrosion inhibitors are usually slightly acidic because you don't need to deal with combustion byproducts. It's one of the main reasons that you shouldn't mix industrial and motor oils - as a general rule one is usually basic and the other is acidic.![]()
@Sergio Kviato I have heard that motorcycle oils are more likely to not mess up a wet clutch.![]()
As for the other components of an engine oil - engine oils are usually about 80-90% base oil. And then the additives are viscosity modifiers, detergents, dispersants, corrosion inhibitors, rust preventatives and antioxidants.![]()
...thought... could the tungsten/molybdenum disulfide solid lubricant play the role of the wear protection on the gear teeth? Is it sufficiently reactive under the high pressure condition to release the reactive sulfur, and sufficiently unreactive as solid-state thingy to ignore the copper components?![]()
With motorcycle oils, yes you need to take into account the fact that most have a clutch system in the same sump.![]()
@Andy Pugh I heard different story. That oil specification only matters, and motorcycle oil is just marketing thing.![]()
There are MC's with separate engine and transmission oils. General MC oil is made to handle both environments.![]()
And the difference with diesel oils is that they are generally a slightly higher viscosity (usually a 15W-40, but that's changing slowly) plus more detergents to handle the increased level of sulphur in the fuel relative to gasoline.![]()
And man, does diesel oil get black FAST!![]()
@Rafe you brought up base oil. Can you go a bit more into that?![]()
Lots of soot, I imagine![]()
I saw a question about solid lubricants. I'll do base oils first, and then solid lubricants.![]()
I've had an issue at work where the base oil changed, all add pacs were the same, all test specs changed but performance in our app changed![]()
test specs passed *![]()
Oh yes @Dan Maloney , lots of soot too! The dispersants are usually the additive that tries to take care of that.![]()
@Rafe Not so slowly, I work in Diesel engine development and we are speccing 0W30 at the moment![]()
@Andy Pugh that's awesome! Having said that over here in Aus, I still can't really get fleets on board with it. Even when the OEM calls for something thinner, they all replace it with 15W-40.![]()
(Actually, I think that's a "were" and we are back at 5W)![]()
Anyway, base oils.![]()
So, base oils are broadly divided into two categories - mineral and synthetic.![]()
What's ligher than 0W? Is it like wire gauges and we will have 00W and 000W?![]()
Mineral base oils are derived from crude, then refined. The viscosity fraction for lubricants is generally around the same size as diesel, but obviously in the case of some gear oils and such you go a little higher.![]()
There are four major types of mineral oils. There's naphthenic (mainly a fluid that gets very thin at high temperatures and therefore a great heat carrier) which mainly gets used in transformer oils, as well as a little bit in greases.![]()
The engine oils and industrial oils are mostly paraffinic lubricants. These are further split in Group I/II/III base oils. As the number goes up, you generally get less sulphur, more oxidation stability, and more viscosity index (which is the ability of the oil to hold it's viscosity at higher and higher temperatures)![]()
is that true, mineral oil molecule bigger than synthetic?![]()
In the industrial world, these are all called "mineral" oils. But in the motor oil world, Group III can legally be called "synthetic"![]()
big is relative. also count with shape (branching), and mutual interactions (polar vs nonpolar groups).![]()
(that's due to a dispute between Castrol and Mobil, which Castrol won). I actually did a video on that here: ![]()
YOU HAVE A YOUTUBE CHANNEL?!?!!![]()
https://www.youtube.com/c/LubricationExplained
Lubrication Explained
"23% (119 EJ) of the world's total energy consumption originates from tribological contacts. Of that 20% (103 EJ) is used to overcome friction and 3% (16 EJ) is used to remanufacture worn parts and spare equipment due to wear and wear-related failures." - Holmberg, K & Erdermir, A. (2017).
![]()
oh my god, i came late to the party![]()
sorry![]()
Ok - after that you've got the synthetics. The major type of synthetic is the polyalphaolefins (PAOs) which get their own category - Group IV. They get their own group because they far and away have the most use in the motor oil world, but you'll also see them a lot in industrial. They have high VI, and almost no polarity - which makes them separate from water really easily. They also last a long time due to great stability - the wind turbine gear oils can typically last 10 years without an oil change.![]()
...I want to live in a world where smart people discuss real stuff like tribology more commonly than pretend stuff like differences between Lacan and Wittgenstein...![]()
Then there's the esters - PAOs are so non polar that they typically can't dissolve most of the additives in lubricants. You need to mix in some ester to be able to dissolve them![]()
That's the main use for esters. However, the aviation jet oils are ALL polyol esters. This is a regulatory thing - the FAA mandates that all jet oils must be compatible with each other so a flight can't be brought down due to mixing of incompatible lubricants.![]()
Plus you also see some biodegradable esters in environmentally sensitive application (particularly stern tube lubricants in marine) as well as some compressor oils![]()
The downside of esters is that they both love water (they'll pull it out of the air) but are also sensitive to water) they break down into acids and alcohols in the presence of water.![]()
Stern tube - is that where the shafts exit the hull?![]()
Yes![]()
Then there's the polyalkylene glycols (PAGs). These are really good in applications like worm gear drive. The downside - they're incompatible with most seals, paints, and other lubricants on site.![]()
Yes @Dan Maloney![]()
The swelling of gaskets can be a royal bitch. Viton FTW.![]()
Now - a note of caution. Anything that isn't a Group I/II/III/IV is classed as Group V. That could mean the highest quality ester / PAG synthetic, or it could also mean vegetable oil.![]()
Within the (non group V) groupings of base oils is there allowance for much variation or is it pretty strictly the same chemical make up?![]()
So, for our 1916 Fire Engine with a worm drive, and nary a seal to be seen (barring a bit of felt) PAG would be great?![]()
Beware of vegetable oils. Lots of double bonds, lots of polymerization at the blink of an eye.![]()
So Group V effetely means nothing. It also includes specialty silicone oils, PFPE lubricants, white oils and pharmaceutical grade oils.![]()
@Andy Pugh yes, a PAG would usually do the trick. Traditional gear oils don't work in most worm drives, because those same sulphur additives we talked about earlier usually eat the yellow metal wheel (corrode).![]()
PAGs don't require those same additives.![]()
Why not?![]()
PAGs have a much higher lubricity, which can help to protect the worm and wheel even under the higher degree of sliding motion in that kind of gear drive.![]()
If the application still calls for a mineral oil, they'll usually use a "compounded" oil, which achieves the same thing through either the use of animal fats (tallow) or really high lubricity PIBs (polyisobutylene)![]()
That way you avoid having to use sulphur based additives.![]()
Tallow? What is its advantage/disadvantage?![]()
Tallow's disadvantages are basically the same as most of the other "naturally" derived oils. More double bonds makes them less oxidatively stable, so you get more oxidation and a shorter life out of them.![]()
Any more questions about base oils before we go on to solid lubricants?![]()
Tallow compared to vegetable oils should have very few double bonds. C16-C18 trialkyl glycerol, mostly. Would that fall into ester oils, sort of?![]()
I have heard that tallow is good for preventing galling when press-fitting parts. Unless you are Vegan, or various religions.![]()
I never saw a vegan metal part.![]()
Yes - so another disadvantage of most animal / vegetable oils is that the "fatty acid" is mostly an long chain acid combined with an alcohol (triglycerol) to form an ester. When they're exposed to water, they devolve back into acids and alcohols, which accelerates the oxidation process.![]()
I have heat-treated parts in Whale Oil. Leeds University had large stocks bought in the 50s. It works very well, and not using it up would have been even more wasteful.![]()
Let's do solids! And i have some questions about surface finish + lubricant interactions![]()
I am assuming that there isn't a section on gaseous lubricants?![]()
Alright - so sold lubricants. These are a really interesting category because it broaches both liquid lubricants, as well as surfaces. Think about Moly for example - sometimes it's a lube oil additive, but moly-coated piston rings are also common.![]()
@Andy Pugh it's a bit of a specialty application that I probably don't know enough about to talk intelligently on, sorry.![]()
Which one? Whales or Gases?![]()
Are gaseous lubricants even a thing?![]()
The basic purpose of solid lubricants as an oil additive, is to provide a very low-shear material that can act as a physical barrier between two metal surfaces under high load. As an example - think about the graphite in a pencil. The reason a pencil glides so nicely across paper is that graphite is comprised of individual graphene sheets that have low shear strength between each other. As you move the pencil, the individual sheets shear off and give you a ice, low friction glide.![]()
