Crankshafts that won’t break—and won’t break the bank.

The folks at Eagle Specialty Products have noticed a trend in the high-performance engine component market that relates to our theme of “cost versus performance” in crankshafts.

“People seem to take pride in how much money they’ve spent on their build even though there is no reason to have the parts they have,” said Alan Davis from the Southaven, Mississippi, manufacturer.

He noted someone bragging online about having “only the best parts in my engine,” and yet that person’s 6-liter V8 was making only a modest 800 horsepower.

“I mean, if you want to spend a lot of money, we will sell you whatever you want, but you really are wasting your money,” he said.

Instead, Davis and other contacts stressed, there are “mid-range” options for parts, including crankshafts, that won’t break in race conditions—and also won’t break the bank for racers.

First, Some Facts

Tom Molnar of Molnar Technologies in Kentwood, Michigan, has been building engine parts for more than 40 years, so he knows a thing or two about crankshafts. First, “all cranks bend,” he said. “I don’t care what you make them out of, I don’t care what you do to them, or who made them.”

Bending causes them to break, and the key is to understand how to reduce bending. He used the analogy of bending a paperclip back and forth: If you keep the bends smaller, it’ll take longer to break.

A second point from Molnar is remembering the formula for calculating kinetic energy in physics—mass times velocity squared—and how it applies to crankshafts.

“If you go from 2,000 rpm to 4,000 rpm, the forces on that crank don’t double, they quadruple,” he said. “These forces go up quickly, and if not dealt with can cause major problems.”

Molnar explained that it’s not simply rpm or “a horsepower number” that breaks crankshafts: “It’s cycles—cycles and load—not horsepower.”

Christoph Wachmann of Pankl, based in Austria, used Top Fuel to illustrate that engine life requirements of a particular race class should be considered when choosing a crankshaft. Top Fuel engines have limited full-load cycles from short runs down the drag strip compared to a circle track engine, but peak cylinder pressures are extremely high. With that, the crankshaft has to be even stronger.

“This type of ‘low-cycle fatigue’ requires a completely different approach in terms of choice of material, nitriding depths, and design versus the usual minimum 10 mio [million] cycle life target for most other race classes,” Wachmann said, “all of which add cost to the crankshaft.”

Also, when using thinner oils for friction reduction in highly competitive race classes, Wachmann noted that he uses a double-grind process—before and after deep nitriding—to improve cylindricity, reduce waviness of the pin and main journals, and increase surface hardness.

In a less competitive environment, Wachmann said he uses a shallower nitriding and moves to lapping or polishing rather than a second grind.

He offered two examples of customers who used the double-grind process and made other changes to solve engine problems.

One customer experienced multiple failures of the first crankshaft pin on a dual-plane V8 engine. “[He] switched to stronger, cleaner material and deeper nitride, and double grind. Problem solved,” Wachmann reported.

He acknowledged it was more expensive, “but at the same time saved a lot of hassle without engine failures.”

Another customer was experiencing bearing failures due to bad cylindricity and white layer remainders on the pins from the nitriding process. That customer switched to the double-grind process as well to solve the problem.

The old adage of pay me now or pay me later applies to race engines, as Wachmann explained. “Customers need to look at the global picture of total engine cost, cost of failure, cost of customer claims, cost per mile, etc. before deciding on the ‘best cost’ per component.”

Mid-level, Far-sighted

We found numerous examples of manufacturers who build mid-level crankshafts to satisfy customers seeking affordable performance...

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Sources

Callies Performance Products
callies.com

Crower Cams & Equipment Co.
crower.com

Dart Machinery
dartheads.com

Eagle Specialty Products
eaglerod.com

Howards Cams & Racing Components
howardscams.com

Lunati
lunatipower.com

Manley Performance Products
manleyperformance.com

Molnar Technologies
molnartechnologies.com

Pankl
pankl.com

Race Winning Brands
racewinningbrands.com