Tin Compactor Design

Dunno why you want hydraulic. A simple lever should give plenty of grunt, specially if you design it so you can pull down with your body weight.
Del

What plans?

The're cheap....buy it....

http://www.ebay.co.uk/sch/i.html?_nkw=can+crusher

great for aluminum cans but not a hope in hell for steel food tins, tried it, got the broken bits to prove it.Need something the Mrs can use if needs be, and though I use a sledge hammer at the moment its a pain setting up the can, flattening it and collecting them. Ideal if I hopper feed the beast and it collects in a bin or bag below. Simple ram or a piston engine driven. Checked on YouTube lots of types but again mostly for aluminum.... Could even think of using a pipe, filling the pipe with tins, compacting the lot (mini baler) and the slug coming out the bottom?

For steel cans expecially, first squeezing the sides a bit by hand will ease the end-to-end compression.

"expecially"

Ebonics?

Hmm, I wonder what subconscious thing could have led to that....maybe too much expresso?

As the question has already been answered above, have you thought about switching to bagged cat and dog food?