Scratchbuilding aluminum breathers (and other parts) without power tools!

Nothing looks more like metal than metal. Working with metal traditionally means power tools...a lathe, a mill etc. I inadvertently found a method for making realistic (to me, at least) breathers from aluminum welding rod with no power tools.

This technique is simple, but hard to explain - since it starts where it ends.

A needle file, some sandpaper and a utility knife blade are the only tools involved. A small ruler or dial caliper (digital is even better!) will help for making several of the same size. A piece of wood is also required. Use 1/8" aluminum welding rod to represent a 3" diameter breather.
Getting a domed end on the end of the rod is the first step:

Use the utility knife blade to cut the rod. Lay it on a piece of wood and roll the rod back and forth while pressing down firmly on the blade. Cutting the rod in this manner gives a nice "dome" to the cut end.
A bit of filing to smooth the ridges left from cutting, and some sanding (I use 400 or 600 grit) will leave a smooth, brushed finish with a nice dome to it.
The next step is to figure out how tall you want the finished part to be. I just "eyeball it", I haven't done any measurements, so I just go with what looks right. After you figure out where to make the cut, it's time to cut again.
The reason for rolling the rod across a piece of wood is that it allows the metal to deform, leaving a flared ridge at the cutting line. This is an important detail!!
Keep cutting all the way through the rod.

Be careful as the tiny piece you are cutting off could go flying into oblivion! It's happened to me more than once!

Simple, cost-effective and realistic! Looks high-tech too! The aluminum rod can also be used to form exhaust systems and rollcages, just be aware that it doesn't bend to an extremely tight radius, it will break.