What's Shaking?

The first is a unique treatment branded XTreme Finishing. It involves placing parts concerned in a vibrating vat of special ceramic pellets and leaving them there for maybe 10 or 12 hours. When a component is removed it looks highly polished, but it isn't. To understand the transformation we need to know the difference between two fundamental types of surface finishes: anisotropic and isotropic.

Turning and grinding produce finishes that are anisotropic. This means the surface irregularities (properly called asperities) all run in the same direction. Such a surface is further classified as an example of a period process, meaning the asperities are all the same distance apart.

On the other hand, the asperities, on an isotropic surface finish have no discernable pattern ? they all run in different directions. XTreme Finishing leaves an isotropic finish.

All of this is relevant for lubricated surfaces because an isotropic surface allows oil to flow evenly in all directions. Conversely, anisotropic surfaces force the oil to flow in the same direction as the irregularities. At least as important as the direction of surface asperities is their size. Again, further explanation is required. Surface irregularities consist of high and low spots often referred to casually as peaks and valleys. Skew is the term used to describe the disposition of these peaks and valleys in relation to a mean line that represents the desired size of the component.

If, on average, the peaks are the same size as the valleys, the surface is said to have a skew of zero value. If the peaks are higher than the valleys, skew is said to be positive. It follows, then, that negative skew is characterised by valleys that are deeper than than the peaks are high. Negative skew is ideal for lubricated surfaces and combined with an isotropic finish it produces an ideal bearing surface. The XTreme Finishing process results in just this combination.

Clearances in engines are typically discussed in terms of measurements ranging from 0.001" to 0.003", but such measurements represent only static clearances. In service, the distance between working components can be much less than this depending on the conditions prevalent at any particular moment. The thickness of a oil film separating heavily loaded surfaces can be just 0.0001" (a "tenth") or even less. If an average human hair were scaled up to the width of this page an oil film under pressure would be about as thick as the average length of a word. So, if the two surfaces both had asperities that measured 0.00005" or greater, the peaks would break through the oil film and make contact. When this happens the peaks are sheared off creating heat (which is wasted energy) and metal particles that circulate with the oil.

A considerable part of the process of running in can consist of shearing between peaks on each surface. Yet racing cars don't usually have the luxury of long run-in periods under varying conditions of load. All the parts in a race engine or transmission have to run hard from the beginning of their service lives, and anything that will reduce temperatures and friction is a distinct advantage.

The originators of this process claim temperature reductions of up to 20 percent are possible between surfaces prepared using the X-Treme Finishing technique. It's a popular treatment with race teams overseas, including Formula 1; locally Guru Motorsport offers the service. Guru's owner, Rohan Ambrose, says his on-track testing confirms considerable temperature reductions.

It's not difficult to imagine that vibrating ceramic pellets would knock the peaks of a component over a period of 10 hours. In fact, this basic process in isolation is called vibratory honing and it's widely used by industry. But although it's a fundamental part of the XTreme Finishing process, there's more to XTreme than that. There are special chemicals involved that interact with the ceramic pellets and aid in the removal of the peaks while leaving the valleys untouched. The last part of the process leaves the extremely bright finish shown.

This all adds up to reduced temperatures, reduced wear and greater reliability. Basically, any performance part that's made from metal can pass through the process and benefit from it. Rear-end gear sets for V8 Supercars are popular as are cogs and other transmission components from performance transmissions. Valvetrain components like springs, retainers, valves and so on are being treated as well; so are cranks and reciprocating parts. Some people are putting just about everything through.

Demand has been so great, Guru is bringing in another machine to increase capacity.

If you'd like to know more about XTreme Finishing you can call Rohan Ambrose at Guru on +61 3 9782 5998