So, I built this hopper clock as part of a bigger build that I'm working on but that's gonna take me a while and I really like this clock so I wanted to post it. The way it works is fairly simple. You need at least enough items in the hoppers to give a comparator output one signal strength greater than the comparator in front of the barrel. For example, with one item in each barrel, their comparators will give a signal strength of one so the hoppers will have to have at least enough items to give a signal strength of two for the clock to run. After that, more items can be added to the hoppers to make the clock run faster. The more items you add to the barrels, the slower the clock can run.
The bigger version adds the ability to change the clock speed automatically so you can use one clock to create multiple different delays. The light blue redstone line is a comparator output from the dropper, if you want to use it.

The build is at /tp 69 69 69