Wednesday, June 1, 2011

Brass & Goggles: A Metallurgical Perspective

As mentioned in my wedding post, I mentioned Mr.ME and I are having a steampunk wedding. Consequently, we've spent a lot of time explaining what exactly that means. While there are many philosophical debates within the community, and some objections, two of the things almost everyone associates with steampunk are brass and goggles. However, most people don't really stop to think why.

It's right there in the name: steam. Consider the most common modern steam-powered device, quality espresso makers. They're typically made of one of three things: copper, brass and stainless steel. Steampunk is very focused on the Victorian era, which predates the development of stainless steel. Stainless steel is also rather more difficult to machine and form. Copper is also very common in steam applications due to its very high thermal conductivity, but pure copper is very soft.

This brings me to the second part: goggles. In a world where everything is powered by steam, you're then constantly surrounded by pressure vessels. Steam engines fundamentally transform thermal energy to mechanical energy via pressurized steam. In a world of pressure vessel, ruptures happen, and if they do, I'd like to be wearing goggles when it does. Furthermore, many of the preferred goggles are actually based on brazing or welding goggles, two of the more common processes for joining brass or copper.

Which brings me back to brass. In many ways, it's the optimal material for a world of steam and filigree. Being an alloy of copper and zinc, it retains many of copper's thermal properties. Good conductivity is important when using inefficient heat sources, such as wood and coal. Brass also has much better mechanical properties than pure copper, allowing vessels to operate at higher pressures, and gears to resist wear. It's corrosion resistant compared to the steels available at the time, and the melting point allows for castability. Adding small amounts of lead (as the Victorians likely would) can dramatically improve machinability. All in all, this makes for good steam powered machines.

Brass and goggles: not just because they look good.

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