I've just made a batch of cider from 16kg (35 lbs) of apples. Based on various sources (example), I expected to extract about 8L (1.75 gal) of juice - however, I only managed to get about 4.5L (1 gal), which I feel is too little trade off for the cost of the apples, nevermind the time and effort.
My method: I first chopped the apples into quarters using a kitchen knife, then ran them through a fruit mill to create a pulp. The pulp was then pressed using a press (both the mill and press are similar to the ones depicted here - apologies for the link to a commercial site but I don't have pictures readily at hand).
One thing to note: I thought the flesh of the apples seemed a little drier than some juicy eating apples I've had before. I'm wondering how much a role the type of apple play in the conversion ratio. The apples I got were a mix of "seconds" from a local orchard, mostly eating apples that were discarded due to cosmetic issues.
What can I do to get more juice out of the apples? I'm open to all suggestions but have a preference for non-electric means. I'm aiming to get closer to the 2/1 (kg/l) ratio that seems to be achievable using standard methods.