but yea...if you can't afford to make a Cavendish Apparatus then you shouldn't be able to afford your computer, monitor, mouse, keyboard, desk, food, water, electricity, home....
I'll presume you meant the Foucault Pendulum, not the complex Cavendish Experiment.
The Foucault Pendulum is flawed because we must assume that there is zero effect in a room which could affect the pendula. If you've ever yawned and made your ears pop from within the room of a house you've equalized the pressure in your middle ear with the pressure of the room. The air pressure is always and perpetually changing in a room, however minutely. As you take a deep breath your jaw pulls on the muscles connected to the ear and the middle ear is opened to the outside environment. Through a manual yawn we can make the popping noise over and over again, attesting to the quickly changing pressures of a room.
Thus, being concluded that pressure is always changing, we all know that different surrounding pressures creates "wind" which is basically air particles moving from areas of high to low pressures. There are in fact slight imperceptible winds within the stillness of a room. And indeed, even without pressure changes, every motion of your body makes wind.
There is also a matter of which hand you use to drop the pendula and let it swing freely. From the issues I've looked at with inconsistent rotation it seems that some authors believe that the inconsistency or consistency in the direction of its rotation has statistical significance to the left or right handedness of the observer putting the pendula into motion. It is extraordinarily difficult to drop a pendula with zero angular velocity - maybe even impossible.
Here's an experiment any one of us can conduct: Construct a simple Foucault Pendulum in our bedroom from ceiling to floor and see if the pendua's motions are modified when is a door is opened, a window is opened, the temperature of the room is turned up or down, and if one uses his bad hand to put it into motion.