Thinking about crossheads, it seems to me that we’d like to have an oil that gets a little bit more viscous when it experiences less shear: when it is supporting a bearing that is changing from hydrodynamic behavior to hydrostatic behavior (midstroke at the con-rod top end or TDC and BDC on the guide shoes); and transition back when the behavior goes the other way. Newtonian fluids wont do that, and dilatant fluids make it much worse. So I’m wondering about pseudoplastic fluids. I got a book on tribology from the library, but it doesn’t go into any detail except to show the following graph.
Since the speed of the bearing surfaces relative to each other is also changing, I don’t know how useful this representation is. Based on what I’ve gleaned from the Internet, pseudoplastic fluids are often those which contain polymers, and polymers are an additive to some lube oils… but I haven’t been able to find anyone who says, “Polymers are added to lube oils in order to give them pseudoplastic fluid characteristics to cope with the change from hydrodynamic bearing support to hydrostatic bearing support.”
I’m wondering if you all could let me pick your brains on the topic, or direct me to better resources than I have thusfar been able to find.
Yeah, I think so too. You want to resist changing the viscosity with temperature, of course… but I don’t think the temp of the LO has time to change much in the 1 or so seconds that it takes to go from say BDC to midstroke. Anyway, a constant viscosity is maybe ok, but I think it’d be better if it increased a little. Maybe it’d be better for starting, too, to have it be a little bit more supportive before things are up to speed: they say that’s when most of the wear happens. Shoot me down, Chiefs.
When designing any material, especially material in motion, engineers incorporate the best technology available at the time to prolong the life of the material. They also consider cost. Therefore the recommended lubricant may not be the best the design engineers have in mind but he/she knows they are dealing with practical application. Sure a tribologist could formulate a lubricant to serve your scenario but the cost has to be weighed against the benefits. Also what is the large scale development cost of this new lubricant, is the market sustainable if we can even find someone to make it? Would it extend the life on the machine 10000 hours, 100000 hours? If so how does the extra cost in lubricant compare to replacing parts? In the end engineering has as much to do with economics as practical function.
I don’t know. I was kinda hoping that LO already does this thing. and they just weren’t telling us. for some reason… >.> <.< #Cyptopseudoplastics But even if it would be expensive, cheaper ways are often found once the idea is out there. Or maybe its not expensive: maybe it can be made out of recovered microplastics or recycled starbucks cups or something. Not all materials advancements require rarefied intergalactic unicorn farts as a consumable. Anyways, until someone looks to see if this idea is loony toons or not, putting a price on it is like trying to shoot a mouse in a cowshed on a moonless night with a derringer.
So I asked someone who’s opinions I respect a lot. He was interested in the idea, but he pointed out the obvious thing that I was missing: LO sometimes needs dilatant qualities and other times needs psuedoplastic properties. It needs to be dilatent when it is feeling shocks, for example when the combustion starts then all of the running gear below that piston feels a sudden down force… so that cornstarch slurry quality would be nice. So maybe newtonian fluids are the best that we can do. Or maybe someone can make a LO that follows the green line?
What shall we call that? Biphasic Semi-Newtonian? I mean, after all, as the man says, “This is a distinct advance on the standard nivelsheave in that no drammock oil is required after the phase detractors have remissed.” Amiright, Cookie? (@CookingatSea)
With apologies to Mary Poppins…
Psuedoplastic anti-friction boundary lubrication.
Even though the sound of it is something quite atrocious.
If you say it loud enough, you’ll always sound precocious.
Psuedoplastic anti-friction boundary lubrication!