 A steel component exposed to an ASTM B117 salt fog environment test with the above coating systems. While Elisha MTC is 100% chromate-free, the heat-cured epoxy topcoat contains chromates. Overall, the system is approximately 95% chromate-reduced. |
Elisha Technologies Co. LLC's latest progress in surface engineering technology was driven by growing environmental concerns and an industrial mandate to eliminate chromate conversion coatings. The company's MTC (mineral tie-coat) process, debuting at the 2000 SAE International Off-Highway & Powerplant Congress & Exhibition, is formed through a patented electrolytic process that is chromate and phosphate free. The company claims it also outperforms its chromate competitors.
The MTC process forms a tightly adhering mineral in place of the surface oxide. The mineral layer, typically less than 1/1000th the thickness of a sheet of paper, will not affect the dimensions of tolerance-sensitive parts. The mineral layer can replace chromate for electro- or mechanical-plated zinc, as well as coatings for steel, stainless steel, zinc/aluminum alloys, and other metal or metallized parts. It is also beneficial when employed as an inorganic mineral tie-coat for improving the bond between metal and organic topcoats. The mineral can be topcoated with a range of commercial coatings such as silane, heat-cured epoxy, carbonate, alkyds, and water-based coatings.
Elisha's MTC process is similar in setup to electrogalvanization, but the company claims it is different in performance and environmental exposure. The process is accomplished by immersing a metallic (or an electrically conductive) component within an electrolyte containing water and a silicate solution. The electrolyte can be tailored by adding water-soluble additives. A current is passed through the electrolyte, allowing the component to be employed as the cathode. Under these conditions, the part's surface interacts or reacts with the electrolyte to form a mineral layer. Components and parts such as fasteners, rivets, bolts, and nuts can be processed in conventional barrel plating systems. Rack plating can process larger parts. Brush plating is an option for large surfaces or when immersion is not practical. Coil work is in development.
 Spot-heat sources were applied to the center of a CoolPoly panel (left) and a standard plastic panel (right) to demonstrate the difference in how each polymer handles the heat. |
Although plastics are the material of choice for many applications, standard plastics do not possess the needed conductivity to provide thermal solutions in an unmodified state. Heat build-up from microelectronic and other heat-generating functions that rely on plastic to conduct heat often leads to component failure. Thermally conductive polymers conduct heat away from a "hot spot," spreading it through a component to more efficiently dissipate the heat into the surrounding environment. The trend toward developing smarter, smaller, and lighter products has driven the development of these polymers forward.
Cool Polymers, Inc., a division of Chip Coolers, has developed CoolPoly, a thermally conductive polymer that the company claims will provide engineers with a plastic material for solving heat-transfer problems. According to the company, applications for the product include fluid/air or fluid/fluid heat exchangers, passenger interface components, electronic enclosures, electric motor encapsulation, coil bobbins, and sensors, among others. CoolPoly can replace metals and ceramics in some applications and replace commodity or engineering plastics in other applications.
CoolPoly is made through a patent-pending process that combines a base resin (most commodity and engineering plastics can be used) with proprietary fibrous and particulate-reinforcement fillers to tailor material properties to meet custom performance requirements. All fillers are non-metallic; some CoolPoly grades are based on carbonaceous and ceramic materials. Additional additives such as UV inhibitors, heat stabilizers, and lubricants can be used for specific applications.
In the attached figure, engineers at Cool Polymer applied spot-heat sources of 5 W to the center of a 76 x 76 x 3 mm (3 x 3 x 0.125 in) CoolPoly thermally conductive panel (left) and a standard plastic (polypropylene) panel (right) that, like most plastics, is a thermal insulator. The CoolPoly panel conducted the heat, generating a more isothermal profile, while the standard plastic panel created a hot spot. The maximum temperature difference on the CoolPoly panel from the center temperature to the outer edge temperature was 4°C (7.2°F), while the standard plastic produced a 24°C (43°F) difference. Additionally, the temperature at the edge of the standard plastic was equal to the ambient temperature, indicating that no thermal energy had been transferred to the edge.
 Dana Spicer's Model 53R300 axle was designed with a four-pinion gear system, distributing the load over four planetary gears instead of the traditional three. |
Dana Corp.'s Off-Highway Systems Group introduced late last year the Spicer Model 53R300 axle, designed to provide improved life and increased capacity for equipment applications in the construction, forestry, and underground mining markets. The new Spicer axle, an enhanced version of the existing Model 21D4354 axle, is designed with an advanced four-pinion planetary gear system that provides substantially improved life and strength. The new design distributes the load over four planetary gears instead of the traditional three-gear design on the 21D4354. The additional gear capacity was added using less space.
"The deeper 6.25:1 planetary reduces torque on the axle shaft, allowing for a lower numerical ring and pinion ratio at the same axle output torque," said Rick Honeyager, Product Engineering Manager, Spicer Off-Highway Products Division.
Other important features of the 53R300 axle include a larger spindle and hub spline for more torque capacity, a wider bump ring for improved rim support, a new sun gear coupler for deeper planet ratio, and an optional trunnion mount. Spicer now offers mining equipment manufacturer customers the trunnion mount option on its complete range of axles from 8165 to 49,900-kg (18,000 to 110,000-lb) carry capacities.
"The engineering development of this new axle demonstrates our commitment to providing the most reliable, durable, and robust products and systems for our customers and their end-user customers," said Bernie May, Axle Product Manager, Spicer Off-Highway Products Division.
As a further product improvement, the seals of the Model 53R300 have been removed, thus eliminating leak paths, which reduces downtime and maintenance costs on the integrated pin planet carrier. The larger bearing with increased spread accommodates wider track and tire ranges with less sensitivity to side loads, resulting in increased bearing life.
