From my research solid tines would have the opposite effect of what you are trying to accomplish... compacting the earth instead of loosening it, like sawdust said.
My thoughts on building a plug aerator was to use a 12" pipe instead of a spindle to mount the tines on. Then when the plug is pushed up through the tine it ends up inside the 12" pipe. Drill several holes in the pipe that the soil falls through while the plugs are tumbling. Put a fixed piece of angle iron inside the pipe to increase the tumbling action and encourage the plugs through the holes.
Or make something similar with a cage made out of 1/4" screen instead of the 12" pipe.
Aerated lawn without a bunch of lawn turds scattered all over!
Just a thought...