When we come to describe a ‘traditional’ racecar con rod for a four-stroke engine, we would imagine a split rod with a bushed small end (or at least many of us would). The bushed small end has been with us for many decades, but the bushless steel con rod is becoming more popular, and bushless rods are a possibility in a number of other materials. As reported in the con rods ‘Focus’ article in Race Engine Technology (issue 48, August 2010), some rod suppliers have been supplying Read more…

The matter of how to positively locate the two halves of a conventional split con rod together is one to which there doesn’t appear to be a single solution that everyone has adopted. In terms of production cars, the approach of using a controlled fracture is now very popular, and is being applied to stronger grades of material.

Traditionally, racing rods have had their mating caps Read more…

In motorsport, the four-stroke engine is dominant in terms of numbers, and the vast majority of them use what we would describe as conventional shell bearings for both crankshaft main bearings and big ends. The most common method used to ensure proper location of these bearings and to prevent rotation is a combination of proper preload and tags (or tangs) which locate in precisely machined slots in the con rod big-end bore. This method is also that used by most production engines. There are alternative location features used in Read more…

There have been brief mentions in the pages of Race Engine Technology of the possibility of coating the big-end bore of con rods directly with the soft metal bearing coatings that we find on the surface of bearing shells. Further mentions have appeared in previous RET-Monitor articles on the subjects of coatings and con rods.

Many years ago, this was indeed the way it was done, with the bearings manually ’scraped’ by hand to achieve Read more…

The forces acting on the con rod are considerable, and the components to which they are attached are surprisingly flexible, although they may not appear so when you pick up a component such as crankshaft. The deflections of the crankshaft (bending and torsion) and the con rod (torsion) give rise to a tendency for there to be some axial force on the con rod trying to force it one way or the other parallel to the crankshaft axis. Read more…

There is a natural tendency for race engineers to try to improve the performance of engines - after all, this is precisely what many of us are paid to do. There are different ways to achieve this goal, but the primary focus for many of us is to increase the amount of energy converted from chemical energy in the fuel into kinetic energy. The rules impose various limits on us but, in general, if we are constrained on engine swept displacement as one of our development strategies, we will want to improve the breathing characteristics of the engine in order to admit and trap more fresh charge.

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After inventing the internal combustion engine, it became clear that man always wanted more power, not only for racing and record-breaking, but also for his road vehicles. Today we have road-going production motorcycles that are more powerful than their Grand Prix counterparts of 15 years ago.

The merits of using multiple cylinders are well known, and to make compact engines with larger numbers of cylinders, ‘vee’ engines are a good solution. Most Read more…

At the recent Autosport Show in England there was a lot to interest the motorsports enthusiast, but during the two trade days preceding the public show days, there is a simultaneous show, Autosport Engineering, where the latest developments in motorsports components are shown, manufacturing technologies are highlighted and much new technology is discussed. Many specialist engine component manufacturers from Europe and the US are represented here. Read more…

In the previous article on the subject of maintaining the accurate locations of the two parts of a split con rod design, we looked at dowel pins and ring dowels, and the relative merits of the two methods.

The subject of joint shear stiffness was raised, and it was noted that the ring dowel, having a greater cross-sectional area, provides more stiffness to the joint. A stiffer joint is more stable and less likely to suffer from joint face fretting wear. While the con rod bolt may not Read more…

In an article published in 2009, I looked at some of the design features of the joint face of a split con rod. One important requirement is that the two parts of the con rod - the ‘blade’ of the rod and its cap - must be positively and reliably located with respect to each other.

It is important that these location features are machined into the rod before the big-end bore is finished to size. This guarantees that when the rod is assembled and the Read more…