That is a great looking generator you have there, great way to use what materials and tools you have on hand.

It is hard to tell from the pictures, but it looks like your magnets are mounted to a wood disc. Maybe you already have, but the magnets should be mounted to a steel disc with alternating poles adjacent to each other.

I have been playing with ferrous cores on the coils as well. I'm wondering if you took the coil/bolt assemblies you already have built and mount them to a steel ring say 1/8" to 1/4" thick if your output would increase.

The reason I say this is that each coil/bolt needs a good return path for the magnetic flux. So two adjacent coil/bolts on a steel ring would form a horseshoe pole that lines up with two permanant magnet poles on the rotor side. I'm thinking this may increase the magnetic flux cutting through your coils.

Just a thought, I'm still experimenting too!