Recycling stuff and hourglass accuracy

 Many online videos show how to make hourglasses using recycled plastic water bottles and clear light bulbs.  It seems all of these options, though laudable, use a horizontal discs to separate the two bottles' or bulbs' openings. The sand or other particle material loses momentum as it descends toward the hole since the angle of the container does not continue directly to the hole so the stuff just piles up on the horizontal surface surrounding the hole.

This is not necessarily a bad situation if the desired end result is a fun timing device. However, if accuracy is the goal then the pile up on the horizontal surface surrounding the hole is a problem. The weight of the sand initially pushes particles through the hole combined with gravity but since the piles can potentially vary in size with each turning of the device, the time it takes the sand to travel from the top to the bottom could be different, making the time inconsistent.