How do you measure yield? By 60% I mean 6L juice/10kg fruit. I haven,t heard of 85% yield with apples so I think you must be using a different measure - you could only get that sort of yield with a commercial belt or screw press.
Greg
Our measure is the same as yours. except we weighed the juice, as it's more realistic, so perhaps by your scale it's more like 75-80% because of the 7% difference in our measures.
We did it using a scratter, and a cheese press with drains between the cheeses, and a 20 tonne load cranked up untill the 4x2 timbers threaten to (and eventually do) snap.
Drain boards between the cheeses made a HEAP of difference. And the scratter - High speed mill, which breaks the cells by impact, not just cutting.
I'd LOVE to have a belt press, they work so efficiently and quickly.
The scratter, as I mentioned was poorly made, but this led to slow production more than low yield.
I've been convinced to build a scratter. Plans and photos will be provided when it's ready and proven (next apple season)
It's rather fancy and high quality, because of the commercial like yields we're going for, so I don't know how many ppl will be interested, but the cost is looking at about $300 so far. I'm prepared to spend up to $600.
I'll let you know.
regarding presses, the only difference between a hydraulic press and a screw press is the gearing in a screw press. But given a sufficiently wide cylinder and enough oil, the same pressures can be experienced.
Also: waiting a while for the juice to propperly slow down gives ~1% more yield
giving it 10 minutes to recover again, and then re-pressing gives another ~4% yeild.
(the measured value was 5% all up, I'm guessing 1% and 4% based on my visual recollection)
My hypothesis on this is that you squish all the juice out of the cheeses, but some juice gets squished into the pulp. Letting it rest means you have some very dry pulp and some wet, so the juice wicks into the dry pulp. when you press again, some of that juice is pressed out, and some pressed back in again. But the result is a higher yield - if you have the time to wait.