Motorsport Materials : Choosing the Appropriate Metal
Selecting materials for race vehicles should never focus on the most sophisticated options. Each material has its own unique qualities and the goal should be to select materials based on individual needs. Selecting the correct materials when building a weekend track car or running a club racing program can result in a machine that is reliable and does not break every other session.
Aluminum Alloys: The Workhorse Material
Aluminum is the most common choice for most fabrication work and for very good reasons. Brackets, mounting plates, and several structural elements are often built from the 6082-T6 grade, which is relatively easy to weld, machines well, and has a yield strength just over 290 mega pascals. This material is very common in suspension mounting points, seat frames, and roll cage gussets in all levels of motorsport.
For applications requiring even greater tensile strength, 7075-T6 aluminum is ideal. With a yield strength just over 500 MPa, it is nearly twice as strong as mild steel, and weighs ⅓ as much. It is used in suspension wishbones, pedal boxes, and any application requiring large load capacities (high strength) and low overall weight. The downside is that 7075 is more difficult to weld, so it is common for fabricators to machine it from solid billets or to use it in structures where welding is not needed.
Titanium: When Temperature and Weight Both Matter
Titanium Grade 5 (Ti-6Al-4V) is the most widely used titanium alloy for motorsport, and for good reason. It is very expensive (approximately 10 times as steel), but the weight savings may justify the expense in critical applications. Exhaust systems are the most common titanium applications. Titanium is particularly useful for maintaining strength at elevated temperatures. Other uses include fasteners, connecting rods, and valve spring where it’s light weight and good fatigue resistance is ideal.Titanium is strong and lightweight, but challenging to manufacture. While working with titanium, one needs to have the right tools. To weld titanium, one needs to do an inert gas purge to ensure no gas contamination. As a rule of thumb, use titanium in applications where its properties really provide benefits. Don’t use titanium wheel bolts just because they look better.
Steel: Still Relevant
Don’t just look for new materials to use. Aluminum and titanium do tend to look better but that doesn’t make them better. Even with the advent of new materials, mild steel still is the standard for roll cage design. Its still cheap, and has good crash protection. Most of the time, driveshafts and hub carriers are made of EN24T steel. Yes, steel is heavy, but in a lot of applications it just makes sense to use steel.
4130 chromoly steel is a good middle option. You can use thinner tubes because it is stronger than mild steel, and saves a lot of weight. single-seater chassis use chromoly tube frames a lot because the weight saving is significant.
Magnesium Alloys
Alloys such as AZ31 magnesium offer good weight savings as they are 35% lighter than aluminum. This means magnesium can be used in components such as gearbox casings, bellhousings, and some wheel designs, which helps reduce both rotating and reciprocating masses. The downside is magnesium corrodes quickly, especially in damp conditions, which means components will need to be coated and inspected regularly. This can be particularly annoying for weekend racers as the performance increases may not be worth the upkeep.
Choosing The Correct Material
When it comes to choosing materials there are a number of factors to take into consideration. First, is what the loads will be? High static loads are best suited with aluminum or steel, and if there are cyclical loads with the potential for fatigue, titanium is recommended. Secondly, consider the operating temperature. Titanium is required when temperatures exceed 300C. Third factor is how often you will need to repair or modify the part? Aluminum is great for components that will need adjustments as it easier to weld and machine.
Money is also a consideration. A club racer, when building a budget car, should do most of the fabrication work in aluminum and mild steel while titanium can be reserved for the exhaust and perhaps a few essential fasteners. A professional team going for championship points would be justified in using titanium for the wishbones and magnesium for the gearbox casings, as those weight savings would directly translate to faster lap times.
Sourcing Materials
Dynamic Metals is one of the specialist motorsport suppliers that understand the trade-offs and stock the most appropriate grades for racing. For the construction of safety-critical components, being able to supply materials with full traceability and certification is beneficial. Having the option of same-day or next-day delivery for in-stock materials means you can avoid the weeks of lead time that others impose when you need to fix damaged components from a crash or build new ones between race weekends.
Design your car according to the engineering requirements, not the latest trends. If you understand the engineering, spending money on the ‘fancy’ materials will be less important than using the right metal in the right place, which will make your car faster and more reliable.