By Bertie Scott Brown, January 28, 2015
When a round wire lock, the spring-loaded device that retains the piston pin within the pin towers, comes out while the engine is racing, it releases a frenzy, a chain of events that most engine builders describe as catastrophic. It is an insecurity within the racing engine most dare not think of.
Recently, however, a Californian engineer shook the establishment, when he not only cured the curse but also devised an ingeniously simple method of installing and removing them.
Karl Ramm, who has been engineering racing pistons for almost twenty years, has devised a new style of wire lock: the Kramm-Lox®. Characterized by its 90 degree tang, which resides within the existing pick lock notch, the Kramm-Lox importantly will not spin. Equally appealing, this non-rotating lock requires no modifications to the traditional piston. Furthermore, Ramm was also the inspiration behind a tool (Patent Pending) that makes them easy to install and remove.
Also worth noting, the tool negates the danger of scratching the pin bore; it also removes the threat of eye injury, a comforting distinction from the notorious, flying spring-loaded locks! In addition, by keeping the wire lock stationary in the pin bore groove, the Kramm-Lox avoids other self-destructive traits.
If the traditional round wire lock rotates placing its gap at the top of the pin bore, particularly in high-revving long-stroke engines, the lock can distort and can pop out. The extreme jolt that occurs as the piston changes direction at the top of its stroke can momentarily change the shape of the lock. “I just started using Kramm-Lox,” says acclaimed Sprint car engine builder Mark Burch of Lincoln, Nebraska, “after a conventional lock partially worked its way out of the groove. We were fortunate to catch it in time.”
But in some cases the wire locks don’t jump out. “Instead,” comments engine builder Jon Kaase, “they beat-up the grooves—always at the bottom of the groove. The non-rotating Kramm-Lox has a ton of advantages.”
Significantly, round wire locks are created to be used in conjunction with a pin with chamfered ends. By design, the chamfered ends are bearing surfaces riding on the locks. The chamfered ends also act as a wedge that tends to force the locks outwards thus retaining them in their grooves. “
At the other end of the spectrum, high-revving motorcycle engines, some spinning as high as 15,000rpm, exhibit the same quirk or, alternatively, they spin the lock in the groove, cutting it deeper. If it continues to spin, the lock can virtually disappear and, ominously, the pin loses its retention.