In a recent article, the subject of using fasteners for composite components was discussed. The number of components for which composites are considered is increasing considerably, and in some race series their use is limited by regulations.

There are many areas in a Formula One engine, for example, where composites are expressly forbidden, but in production-based series, people are free to use composite components much more freely and so they Read more…

When we design a fastener, or select one for use, there are a number of points to consider. Not least among these is whether the fastener will last for the life of the engine, or certainly between planned services.

Where a fastener is cyclically loaded, we need to consider the effects of fatigue, and in this regard we need to pay special attention to design features. Where a bespoke engine is concerned, or where we are looking to increase markedly the output of an existing engine, it is very likely that we will have to look beyond the realm Read more…

The use of composite materials in racecars is not new; nor does it represent a particular novelty for race engines. The strength, stiffness and low density make them ideal for many components, both structural and decorative.

It is now pretty rare to find a race engine airbox, certainly on ‘formula’ cars, made from anything other than carbon-fibre reinforced polymer (CFRP) composites. It has also been used to good effect for plenums on turbocharged engines, on structural covers for race engines and in parts used specifically to increase the stiffness of the engine in order to provide a performance benefit to the vehicle as a whole. It is widely used for electrical boxes and cosmetic covers too. Read more…

We have, in previous articles, looked at the importance of correct pre-load for fasteners, and this is especially important where there are cyclic loads involved that might causes fatigue failures.

One of the more reliable ways in which we can tighten a fastener is to measure the extension or ’stretch’ of a given bolt or stud, and for a con rod, this is indeed the way that the vast majority of engine builders will work. Knowing the load versus extension relationship of the bolt means we can Read more…

Continuing the discussion of wire thread inserts in previous articles, this month I’ll consider ’solid’ types of insert. There are at least two varieties of ’solid’ inserts in common use, and these are used mainly for repairs and, less often, in situations where female thread strength is felt to be a problem and that without such an insert, the chances of thread stripping are high.

The ‘problem’ with solid inserts is that they can (and generally do) bias the distribution of load Read more…

In the previous article on thread inserts, Wayne Ward briefly discussed some of the reasons why people might choose to specify a thread insert and looked in a little detail on one of the types of insert which find common use in current racing engines. There is one further reason why a wire insert may be an advantage and that is in improving the fatigue life of the bolt installed therein, or of the female threaded component.

Previous articles that I have written on the subject Read more…

In previous articles on the subject of fasteners, we have dwelt very little on the subject of female threads, other than in the article talking of bespoke nuts. The other main situation where we will find female threads is where these have been machined into castings or into machined parts. Unless the rules forbid their use, it is likely that we will have chosen an aluminium block, or where we are designing bespoke parts, aluminium is a very popular material, either in its cast or wrought forms, owing to its low density. Where Read more…

There are a plethora of different kinds of nuts on the market, and many are aimed at the racing market. Most of these will have been designed originally for the aerospace sector, and here we benefit from the exceptional quality control that the aerospace industry demands. Despite this range of good quality proprietary parts being available to us, there are also a considerable number of racing engine manufacturers who have bespoke nuts manufactured to their own designs. These might be to fit into a particularly confined space, maybe to minimise the height of the nut, or perhaps to Read more…

In the recent Race Engine Technology magazine article on the subject of fasteners, Wayne Ward touched on the subject of locking nuts and locking thread inserts. There are a great many applications where the loss of a fastener is not critical to the operation of the system as a whole; indeed it is common to build in a certain level of redundancy into a bolted or riveted joint for loss or failure of fasteners and the accompanying loss of pre-load. Again, even in this situation, the physical loss of the fastener is again rarely critical. In this article we shall look at some of the implications of losing a fastener. Read more…

After having calculated bolt stiffness, or measured the load-deflection curve directly, the best way to calculate pre-load is to measure the extension of the bolt directly. This method is preferred for con rod bolts and all con rod and bolt suppliers generally recommend this method. The fasteners require design features to allow measurement with a special micrometer. This method is impossible for fasteners in blind holes. For large fasteners in blind holes the extension can be measured directly if there is sufficient access for other measuring equipment.

Ultrasonic methods are very accurate but don’t seem to Read more…