Tech Articles

Gear Superfinishing: More Power, Less Friction

Isometric superfinishing of gears, including ring and pinion gears, is an increasingly popular and effective method to reduce friction and improve gear life.

Often taken for granted in most race cars, the ring and pinion is often used, abused, with little attention paid until a failure occurs. Regardless of the type of racing, the gears are exposed to a great deal of shock and severe loading, while also being expected to endure soaring temperatures for extended periods. Isotropic superfinishing can eliminate the rough surfaces that cause power-robbing friction and increase operating temperatures.

During circle track or road racing situations, the ring and pinion is heavily loaded each time the throttle is winged open as drivers exit the corners and then quickly unloaded during de-acceleration at the end of the straightaways. Drag race launches are even more abusive, particularly when the car in question features a high-horsepower engine combined with a hefty curb weight. Many drag racers are often required to use special, high-impact 9310 steel “pro” ring and pinion gears to achieve the necessary durability.

Regardless of the sanction or venue, racers are always in search of increased performance, but it seems higher speeds and acceleration often are won at the cost of reduced durability. One process that has proven to help both the performance and the durability of ring and pinion gears and quick-change gears is Isotropic Superfinishing (ISF), pioneered by REM Surface Engineering. Commonly performed on ring and pinion or quick-change gear sets, the process has proven equally successful upon transmission gears, slip yokes, and wheel bearings.

An industry leader in the field of metal surface engineering since 1965, REM initially became involved in the development of new and innovative finishing methods in the early 1980’s. The company followed by patenting the Chemical Accelerated Vibratory Finishing (CAVF) process in 1985.

Industry demands for the company’s CAVF process skyrocketed worldwide, particularly in the automotive and aviation markets, and they followed by trademarking ISF in 2002. REM recently developed the Rapid ISF Process specifically for the automotive market in the effort to help improve efficiency and delivery time.

Superfinishing a ring and pinion set, for example, removes the microscopic peaks created by the cutting and grinding associated with gear manufacturing, while the microscopic valleys remain untouched. Stress risers, which inadvertently occur during the manufacturing process and can lead to gear fracturing, are also eliminated during gear superfinishing. 

Superfinishing (ISF) completes this process in two steps:

The first step of ISF, referred to as the refinement stage, uses conventional vibratory finishing equipment and high density, non-abrasive ceramic media that are used in conjunction with chemical interaction. The chemicals provide a soft, thin conversion film of just one micron on the gear’s surface that allows the microscopic peaks to be removed during the process, while the valleys are untouched, resulting in a smooth microfinish.

The second and final step is referred to as the burnishing stage. This stage removes the conversion film from the gears, resulting in a polished, mirror-like finish and achieves a dramatically improved RA (Roughness Average), a calculated measurement of the microscopic peaks and valleys present in the gear’s surface finish.

The process does not affect the metallurgical, chemical or hardness properties of the gears, nor does it alter the dimensions as less than .0001” of material is typically removed. An added benefit is that the entire ISF process is non-hazardous and environmentally friendly.

The many benefits of ISF have resulted in an increased demand for off-the-shelf availability of processed gear sets and the aftermarket has overwhelmingly responded. PEM Racing offers a full line of Premium Lightweight series quick-change gears that are ISF finished in-house and ready to install, right out-of-the-box.

Leading gear manufacturer U.S. Gear recently debuted their Lightning series ISF-finished ring and pinion sets, while differential component specialist Mark Williams Enterprises offers Richmond Gear ring and pinion sets that are treated with the company’s Supra-Fin ISF superfinishing for an added cost.

Comparison of ring gear with Supra-Fin ISF superfinishing and standard ring gear.

 

Comparing the surface finish on an ISF/Supra-Fin superfinished ring gear (left) with a standard gear (right). Photo courtesy of Mark Williams Enterprises.

According to Randy Harrison, technical representative of PEM Racing, “ISF delivers a highly-polished look with an extremely smooth, non-directional surface finish, helping to reduce friction, contact, and wear, effectively improving performance and eliminating the need for break-in”. Harrison states that the process additionally helps improve oil retention and reduce operating temperatures. During initial development, REM performed testing using a T101 manual transmission that showed a six horsepower gain when substituting ISF processed gears for production gears.

Proven effective in laboratory RA studies, dyno-testing, and on-track analysis, ISF superfinishing has certainly become a viable, cost-effective option for racers that not only desire increased performance, but added durability and longevity as well.