Construction materials

[Paul Copioli]

Aluminum sheet metal is the ThunderChickens' preferred choice of material / configuration.

A couple of things to consider when weighing the steel vs. aluminum design choice.

1. Aluminum is ~ 1/3 the weight of steel

2. 6061 -T6, 6063 -T6, etc. aluminum is >1/2 the strength of your average steel. The exceptions are your alloy steels like 4140, 4150, etc.

3. Manufacturing constraints. If you calculate that a steel tube only needs to be 1/64" thick to be strong enough for your design, chances are you will not be able to use such a thin walled tube due to manufacturing limitations. So, by definition, your steel tube will be over designed due to the fact that you had to select a more readily available tube size. Aluminum, for example would need to be twice as thick (almost), but that still is pushing it for availability (1/32"). The aluminum would be over designed, too; but the weight penalty is much, much less.

4. Part geometry is more important than material selection. How your part handles the external load is much more important than what material you should use. In most cases on FIRST robots, we have more material than in we need in some places and less than we need in others. That single phenomenon is the leading cause of robot failures.

I can tell you this from an industrial point of view: Aluminum is the preferred material for housings, cases, etc. for economical, environmental, and cost reasons. Gears, shafting, and anywhere that needs small space, but high loads will usually be steel or titanium.

Composites are at a whole different level that I will leave to the spacecraft and aircraft people.


-Paul