Follow this block by block section by section and it will work. If it doesn't work for you, try again. If it still doesn't work, don't bother asking me. I followed this exact video to make mine and it works 100%. It only works when tps is high. It will NOT duplicate anything when the tps is low.
Evidently some do work; mine does not work anymore, but I'm sure there are many designs, so check youtube.
Hi guys! This design works, but it is a bit slow. For 1.4.5 or 1.4.6 you have to put two layers of sand on top of the pistons, and then it will work. This causes it to work about 4 times as slow though, however you do get free sand!