What do I need to build a pendulum?

MonsterBot:
Yes–provided you don’t make the pendulum arm excessively long. Servo’s aren’t very fast so depending on the magnitude of the acceleration you want to measure, it may or may not provide the velocity you need.

That’s definitely a worry of mine, as the pendulum arm will be a bit over 2 feet long. I’ll make it out of aluminium so the weight won’t be increased a LOT, but I know the longer the arm is the more torque I’ll need.

MonsterBot:
I’ve never used the Servo Trigger but I don’t know that it has a timer to periodically toggle the direction automatically. Something like the example in the SFE video would work.

Please forgive me for being dumb, but could you link this SFE video you’re mentioning? I’m failing to find it.