"What's slicker - snot on ice, or a whetstone?  That's the difference between hydrodynamic and boundary lubrication."

~Cherry

Educate yourself - Lubricant Formulation & Regimes

Lubrication: Core Concepts

 

While there are numerous ways to formulate lubricants, everything comes down to minimizing friction and reducing wear.

 

Metal surfaces under a microscope look similar to sandpaper – even highly polished surfaces appear as jagged peaks and valleys, called ‘asperities’ - these are sometimes erroneously referred to as “pores”. Outside of specifically designed 'porous metals', metal generally does not have 'pores' in the common sense of the word, but it does have incredibly small surface asperities that do resemble the sandpaper analogy. These asperities are a tremendous source of friction when two surfaces rub together.  It’s virtually impossible to polish them out completely. When they come into contact, you get friction, which produces sometimes extreme heat, and reduces efficiency in a machine and causes wear. And that wear is the asperities breaking off. Combined, this causes machines to malfunction more often and break faster. Lubrication serves to help separate these surfaces, minimizing heat, prolonging their lifespan, and maximizing efficiency and reliability.

Oils are designd to suspend contaminant and flow - greases trap contaminant out, and stay put. Know the best use of each.

Formulation Basics

Lubricants can come as liquids, solids, and even gasses in some rare cases.  Any given industrial lubricant is almost always a mixture of liquids and solids.  Generally, they’re formed of a liquid ‘base stock’, to which much smaller amounts of solid are added in an ‘additive package’. The 'boundary lubricant' solids are slick, microscopic particles that adhere to friction surfaces with slight electrical charges, and can include derivatives of molybdenum, zinc, phosphorous, and many others.  Other additives provide beneficial properties to a given application beyond just lubrication, including cleansing, viscosity modification, anti-corrosion, and others. It's critical to understand that virtually all quality lubricants contain additives, for many reasons. If your firearms lubricant doesn't contain an additive package, there's a high likelihood it is simply repackaged industrial oil. Some on the market may have only one or two additives, and while this is better than nothing, it is also the tribological equivalent of a Model T.  

 

The process of combining these relatively simple additives is where proper tribological science and engineering come into play.  In concept it’s simple, and has been likened to baking a cake, but the science can be complicated.  As with baking, small differences in ‘ingredients’ can have big effects on the resulting product.  The wrong ingredients (or absence of key ingredients), can cause serious problems. Additionally, from the beginning, a lubrication engineer is going to develop a new lubricant with a specific kind of machine in mind, with various types of standardized ASTM tests available to assess viability and performance.

 

Despite the variables possible in creating a lubricant formulation, virtually every lubricant operates primarily under one of two general ‘lubrication regimes’ – hydrodynamic, and boundary.

Lubrication Regimes

Hydrodynamic lubrication is about fluid + motion. While there are variations of this regime, the core concept is similar to hydroplaning your car – you need to generate enough speed and/or fluid pressure between parts for those parts to essentially ride or 'float' on top of a fluid film. This fluid-film barrier between moving parts is generally the most effective way to lubricate any kind of machine, when possible.  When you can achieve hydrodynamic lubrication, many machines are able to go millions of cycles over their operational lifetime, with common car motors going over a billion rotations. 

 

Boundary Lubrication, or Boundary Film Lubrication, is the second lubrication regime, which generally witnesses two surfaces coming into contact, separated by a very thin film of friction-reducing solid material, such as Teflon or molybdenum, or specialized coatings, like titanium nitride or nickel boron.  Often, this is the ‘make do’ category of lubrication, when hydrodynamic separation cannot be achieved – when you can’t ‘hydroplane’ those parts.  When this inability to achieve hydrodynamic lift occurs, the peaks of metal asperities penetrate the fluid film, slam into each other, and break off against each other - and that's essentially what wear is in your guns. Broken off asperities. In concept, it's similar to what happens when your car leaves skid marks of broken-off rubber when you slam on the breaks.  Same concept, different scale. Yet this won't happen if your car is hydroplaning on a film of liquid water.

 

To understand how boundary lubrication generally works, think of a patch of black ice...pretend it's not frozen water for a second, but rather just one of dozens of types of solids that are incredibly slick - some of which do have friction levels around that of ice. At the microscopic level, molybdenum, Teflon, and other solids perform similarly to that patch of black ice, being far slicker than the substrate material beneath it. Different solid lubricants are selected for different applications, but the role of boundary lubrication is to have a slick contact surface resting between moving parts.

 

 

Mixed Regime - The reality of guns is that they operate in what’s called a ‘mixed regime’, where both hydrodynamic and boundary lubrication are needed. Guns, being unsealed machines with no pumps and a back-and-forth sliding motion, are literally impossible to keep in the hydrodynamic regime. During every cycle, they come to a complete stop at the beginning and end of travel, and their parts need to get back up to a certain speed again to achieve that 'lift off' and ride on the fluid film. Before they reach that speed - which is partially determined by the viscosity and volume of lubricant - they essentially grind along in the boundary regime. Without proper boundary lubricants, all you get is that 'whetstone effect'.  

 

But if you have the right mix of wet and boundary lubricants, it's like having a roadway largely paved in black ice, completely covered in oil. This is what CherryBalmz do. 

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