Bicycle lubricant

Abstract

A bicycle chain lubricant that may be applied as a coating on a bicycle chain is a crystalline solid at ambient temperatures, yet when the chain is in motion the forces around internal components locally transforms the coating to a lubricous fluid. This increases chain efficiency in the drive train and reduces ware by limiting water and dirt access to chain internal components.

Claims

1. A crystalline solid lubricant composition consisting essentially of molybdenum disulphide dispersed in a paraffinic oil-paraffin wax matrix, wherein: the concentration of paraffin wax is greater than or equal to 50% by weight; the concentration of paraffinic oil is less than or equal to 30% by weight; and the concentration of molybdenum disulphide is 10% to 20% by weight.

2. The crystalline solid lubricant composition of claim 1, wherein the concentration of paraffin wax is 50% to 60% by weight.

3. The crystalline solid lubricant composition of claim 1, wherein: the concentration of paraffin wax is 60% to 70% by weight; and the concentration of paraffinic oil is less than or equal to 20% by weight.

4. The crystalline solid lubricant composition of claim 1, wherein: the concentration of paraffin wax is 70% to 80% by weight; and the concentration of paraffinic oil is less than or equal to 10% by weight.

5. The crystalline solid lubricant composition of claim 1, wherein: the concentration of paraffin wax is 75% to 85% by weight; and the concentration of paraffinic oil is less than or equal to 5% by weight.

6. A chain drive component comprising: a chain; and the crystalline solid lubricant composition of claim 1 coating the chain.

7. The chain drive component of claim 6, wherein the crystalline solid lubricant composition has a solidification temperature greater than or equal to 15° C. and less than 25° C.

8. The chain drive component of claim 6, wherein the crystalline solid lubricant composition has a solidification temperature greater than or equal to 25° C. and less than 35° C.

9. The chain drive component of claim 6, wherein the crystalline solid lubricant composition has a solidification temperature greater than or equal to 35° C. and less than 42° C.

10. The chain drive component of claim 6, wherein the crystalline solid lubricant composition has a solidification temperature greater than or equal to 42° C.

11. A method of lubricating a bicycle chain, the method comprising: determining a maximum ambient temperature in which the bicycle is to be operated; and lubricating the bicycle chain with the crystalline solid lubricant composition of claim 1, wherein the crystalline solid lubricant composition has a solidification temperature 5° C. or more above the maximum ambient temperature.

12. The method of claim 11, wherein the concentration of paraffin wax in the crystalline solid lubricant composition is 50% to 60% by weight.

13. The method of claim 11, wherein: the concentration of paraffin wax in the crystalline solid lubricant composition is 60% to 70% by weight; and the concentration of paraffinic oil in the crystalline solid lubricant composition is less than or equal to 20% by weight.

14. The method of claim 11, wherein: the concentration of paraffin wax in the crystalline solid lubricant composition is 70% to 80% by weight; and the concentration of paraffinic oil in the crystalline solid lubricant composition is less than or equal to 10% by weight.

15. The method of claim 11, wherein: the concentration of paraffin wax in the crystalline solid lubricant composition is 75% to 85% by weight; and the concentration of paraffinic oil in the crystalline solid lubricant composition is less than or equal to 5% by weight.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a phase diagram for the oil-wax-MoS.sub.2 compound, with temperature and shear stress on vertical axes plotted against MoS.sub.2 concentration by weight on the horizontal axis. The oil-wax ratios are 20%:65%. The cloud point boundary denotes the phase transition between liquid solution and shear-thinning fluid phase, and the solidification boundary denotes the phase transition between shear-thinning fluid phase and microcrystalline solid.

(2) FIG. 2 is a phase diagram for an oil-wax mixture, with temperature and shear stress on vertical axes plotted against the oil to wax ratio on the horizontal axis. Three phases are represented: liquid solution, shear-thinning fluid and crystalline solid.

(3) FIG. 3 is a phase diagram for a wax-MoS.sub.2 mixture, with no oil present, with temperature and shear stress on vertical axes plotted against MoS.sub.2 concentration by weight on the horizontal axis. Three phases are represented: liquid solution, shear-thinning fluid and crystalline solid. The eutectic MoS.sub.2 concentration (14%) is denoted by the dashed vertical line.

(4) FIG. 4 is a phase diagram for an oil-wax-MoS.sub.2 mixture, with temperature and shear stress on vertical axes plotted against MoS.sub.2 concentration by weight on the horizontal axis. The cloud point boundary is shown for mixtures having oil content of 0% to 29%. The eutectic MoS.sub.2 concentration (14%) is denoted by the dashed vertical line.

DETAILED DESCRIPTION

(5) The following detailed description should be read with reference to the drawings, in which identical reference numbers refer to like elements throughout the different figures. The drawings, which are not necessarily to scale, depict selective embodiments and are not intended to limit the scope of the invention. The detailed description illustrates by way of example, not by way of limitation, the principles of the invention.

(6) The inventor has discovered that a mixture of three components: petroleum oil (oil), paraffin wax (wax) and MoS.sub.2, form a resultant compound that has three possible phases depending on temperature and pressure; specifically, a crystalline solid, shear thinning gel suspension, or liquid solution, as represented in FIG. 1. It has been observed that the phase transition between the crystalline solid to shear thinning fluid to liquid occurs with increases in shear stress or temperature.

(7) The compound formulation is designed to be crystalline solid at 5° C. or greater above the maximum ambient temperatures that the chain is expected to experience. The inventor has determined that the ratio of oil to wax by weight changes the solidification temperature. For example, a 1:3 oil-wax compound solidifies at about 25° C., whereas a change in ratios to a 1:7 oil-wax ratio raises the solidification temperature to about 35° C. FIG. 2 reports the temperature and shear stress dependence of phase with respect to the ratio of oil to wax.

(8) At temperatures above 65° C. the oil-wax compound can be regarded as a solution in which the long chain alkanes (wax) are dissolved by the short chain alkanes (oil). It is important to note that below the cloud point temperature the solution becomes saturated and solid crystals precipitate that are a mixture of long and short chain alkanes, this is the beginning of the shear thinning fluid phase. As the temperature is lowered further the size of these crystals grows, increasing the viscosity of the compound. There is not a well-defined boundary from “mushy” low viscosity liquid to a high viscosity semi-solid, both are in the fluid-phase. Once the solidification temperature is reached the compound is a crystalline solid with no diffusion of molecules.

(9) The inventor has examined the oil-wax compound from the perspective of stress at constant ambient temperature. At rest the compound is a crystalline solid. As shear stress is increased above the solidification strain, weak intramolecular and intra-crystalline bonds are readily broken, and viscosity is reduced allowing flow. As the shear increases the large crystals are reduced in size along with a rapid decrease in viscosity. At high strains, the oil-wax compound is a highly lubricious with a shear thinning fluid phase where the crystals are small, eventually beyond the cloud point strain the compound is a liquid solution.

(10) The inventor investigated many additives to the oil-wax mixture, including powders of graphene, C.sub.60 buckminsterfullerenes, graphite, PTFE and MoS.sub.2. MoS.sub.2 was unique in that it bonds at a crystalline level with the wax and oil, whereas the other additives were just impurities remaining chemically distinct. Specifically, MoS.sub.2 affected the crystalline composition and physical characteristics of the compound. A mixture of MoS.sub.2 with wax (no oil present) revealed a eutectic temperature which was lower than the melting points of MoS.sub.2 and wax. The phase diagram is shown in FIG. 3. The inventor also determined the eutectic concentration of MoS.sub.2 to be about 14% by weight.

(11) In another aspect, the MoS.sub.2 concentration changed the characteristics of the crystals formed in the shear-thinning fluid phase of the oil-wax-MoS.sub.2 compound. With a concentration of less than the eutectic concentration, long waxy light grey crystals formed on the surface, whereas above the eutectic concentration the crystals formed were dark grey, small, and dense. As the temperature was decreased the crystals grew in size and number with a corresponding increase in viscosity.

(12) Even in the solid phase there is a difference in the mixture texture below and above the eutectic concentration. Below the eutectic concentration the mixture is a predominantly waxy crystalline solid with some grey coloration and is smooth to the touch. Above the eutectic concentration the structure is believed to be principally dark grey nanoclusters of MoS.sub.2 surrounded by wax crystals and is textured (not smooth) to the touch.

(13) In another aspect, the performance of the mixture as a lubricant has been tested over a variety of MoS.sub.2 concentrations. The minimal friction performance is in close proximity to the eutectic concentration of MoS.sub.2, in the range of 10%-20% MoS.sub.2.

(14) The inventor also studied fluorinated hydrocarbon waxes as they have a high melting point because of the stronger intramolecular bonding caused by the fluorine atoms. The fluorinated wax-MoS.sub.2 compound has a much smaller temperature and strain range for the shear thinning fluid phase and the solid phase is more brittle and has less adherence to the metal chain. Standard alkane oil-wax-MoS.sub.2 had dramatically better performance over the fluorinated hydrocarbon chains which proved to not be durable.

(15) In another aspect, the inventor compared the use of paraffinic oil verses petroleum oil, in the performance of oil-wax-MoS.sub.2. Both worked, although the paraffinic oil-wax-MoS.sub.2 compound had a more defined boundary at the solidification point, it also was less glossy to the touch and collected less dirt in mountain bike applications. Hence paraffinic oil is preferred.

(16) For application of the oil-wax-MoS.sub.2 compound to a bicycle chain the compound is heated to the liquid solution at temperatures above 65° C., allowing the oil, wax and MoS.sub.2 component to become a single solution. A clean bicycle chain is then immersed in the solution for several minutes to allow all internal component of the chain to be coated with the solution. The coating process is enhanced with some chain link movement while submersed. The chain is removed from the solution and allowed to cool, drying the coating on the chain. The chain is placed on the bike and ready for use.

(17) The inventor has verified that if the solidification temperature is about 5° C. above the maximum ambient temperature that the chain will experience then the exterior surfaces of the oil, wax and MoS.sub.2 coating will be solid during operation of the chain. Dirt, mud, and water that may land on the coated chain does not attach. The coating is also hydrophobic, so water and mud are repelled. As the chain moves, the dirt, mud, and water slide off. The chain performance has low friction as the internal components are lubricated by internal portions of the coating which turn to a lubricous gel under shear stress. Dirt does not gain access to the internal components because of the tight gaps that are mostly filled with the solid coating. Water and mud are repelled again because of the hydrophobic nature of the coating and the shear thinning fluid phase occupies the full internal working space of the chain. At the points of contact between the chain rollers and the sprockets in the drive train there are high shear forces. The coating thins in these areas but the MoS.sub.2 is burnished into the chain and the sprocket surfaces creating a dry lubricant for these surfaces.

(18) The inventor notes that utilizing a bike chain with an oil, wax and MoS.sub.2 coating as disclosed herein but having a solidification temperature lower than the operating temperature of the chain, for example a solidification temperature of 22° C. in 30° C. ambient temperatures, will result in the entire coating being in the shearing thinning fluid phase including the exterior of the chain. Dirt that comes into contact with the exterior of the chain with a fluid on the surface will attach rather than be shed, just like for an oil-based fluid chain lubricant. The external dirt will be abrasive to the external rollers and sprockets. As such, this is not a preferred embodiment. Such a chain should be cleaned after use just like with use of a fluid lubricant.

(19) A preferred embodiment in elevated temperature is to utilize a chain coating formulated with a higher solidification temperature. For the example with 30° C. ambient temperature, a coating with a solidification temperature of 35° C. or more would be utilized. The oil-wax-MoS.sub.2 compound would have an oil composition of 10% or less.

(20) In another aspect, in circumstances in which the maximum ambient temperature is about 38° C., 5% or less oil is recommended in the coating compound. The optimal performance with lowest friction was determined to be at the eutectic concentration of MoS.sub.2. FIG. 4 reports the temperature dependence of the cloud point around the eutectic point for a variation of oil concentration. As the oil content is increased, there is a decrease in the depth of the temperature dip associated with the eutectic point. When there was 1:2 oil-wax ratio, the cloud point is relative flat. The character of the compound transitioning from waxy to dry crystalline still occurs around the original eutectic point of 14% MoS.sub.2.

(21) These three regions were examined by the inventor: MoS.sub.2 (>20%) rich compound has a dull appearance, lumpy texture, on the bike virtually no dirt accumulation on the surface, chain performance was good but about 6% friction loss for over 200 miles. Further, some chain noise could be heard in sideways chain movement suggesting the internal component were not fully lubricated. MoS.sub.2 (<10%) low compound has a shiny-gloss appearance, smooth texture, on the bike dirt attached to the exterior surface, high chain performance with about 3% friction loss, but after about 50 miles of dust trails the loss increased to over 10%. MoS.sub.2 (10-20%) eutectic region is a good balance between the rich and low MoS.sub.2 compounds. It has a gun metal satin appearance, smooth texture, on the bike virtually no dirt accumulation on the exterior surface, high chain performance with about 3% friction loss that persisted for several 100 miles.

(22) Table 1 below reports optimal coating compound compositions for different ambient temperature ranges, illustrating the effect of oil content.

(23) TABLE-US-00001 TABLE 1 Maximum Ambient Solidification Temperature Temperature Paraffinic Oil MoS.sub.2 Paraffin Wax <38° C. >42° C.  ≤5% 10-20% ≥75-85% <30° C. >35° C. ≤10% 10-20% ≥70-80% <20° C. >25° C. ≤20% 10-20% ≥60-70% <10° C. >15° C. ≤30% 10-20% ≥50-60%

(24) Typically, for the oil-paraffin-MoS.sub.2 compounds disclosed herein the coating durability on dry road condition is over 1000 miles before the chain needs to be ultrasonically cleaned and the coating reapplied. In wet conditions this is shortened to about 800 miles. In dry mountain biking conditions, the durability is about 500 miles, and again in muddy and wet conditions this is reduced to about 300 miles.

(25) The long-term wear characteristics of the drive train and the chain are incredibly durable, with no drive train wear on road bikes with over 20,000 miles and mountain bikes with 10,000 miles. The chain is still in specification but is replaced after 5,000 miles for the mountain bikes and 10,000 miles for road bikes.

(26) The inventor determined the bike chain power loss for the oil-paraffin-MoS.sub.2 compounds to that for standard commercial bike chain lubricants based on light petroleum oil, petroleum jelly, PTFE in solvent, wax in solvent, paraffin wax, PFTE in wax with the latter two being applied in molten form. This was done by measuring for each bike chain lubricant the average power required to maintain 9.0 mph on an incline of 7% for 3 miles. The results are report in Table 2, below. The paraffin wax compounds are the highest performing, with the oil-wax-MoS.sub.2 compound being the most efficient.

(27) TABLE-US-00002 TABLE 2 Bike Chain Lubricant Average Power Δ Power Light Petroleum Oil 253.4 W 3.2 W Petroleum Jelly 253.2 W 3.0 W PTFE in Solvent 252.8 W 2.6 W Wax in Solvent 252.6 W 2.4 W Paraffin Wax 251.0 W 0.8 W Paraffin Wax + 250.8 W 0.6 W PTFE Paraffinic Oil + 250.2 W 0.0 W Paraffin Wax + MoS.sub.2

(28) To put the results of Table 2 in perspective, a benefit of the oil-paraffin-MoS.sub.2 lubricant compound over commercial lubricants is increased power to the wheels of up to 3 W. This difference in power could provide the winning benefit of over 30 seconds in a one hour race.

(29) To summarize, the advantages of the oil-paraffin-MoS.sub.2 lubricant compound over commercially available lubricants are: The chain has an external coating that remains solid and repellant to dirt, water and mud. The internal components of the chain transform the lubricant compound to a lubricous gel under shear stress. Durable coat that lasts for at least a month of riding, with no maintenance. Low drivetrain component wear. Low friction loss for the lifetime of the coating.

(30) This disclosure is illustrative and not limiting, Further modifications will be apparent to one skilled in the art in light of this disclosure and are intended to be fully in the scope of the appended claims.